bluuebunny/crossref_metadata_2025 huggingface dataset:
Viability of fibroblast‐seeded ligament analogs after autogenous implantation
Authors: Bellincampi Lisa D. , Closkey Robert F. , Prasad Rajiv , Zawadsky Joseph P. , Dunn Michael G.
Published: February 2005

Fibroblast‐seeded collagen scaffolds or ligament analogs are potentially useful for reconstruction of the anterior cruciate ligament of the knee. To provide lasting benefits, the seeded cells must survive implantation within the harsh synovial environment of the knee joint. Our objective was to determine the in vivo fate of autogenous fibroblast‐seeded ligament analogs as a function of fibroblast source (anterior cruciate ligament or skin), implantation site (knee joint or subcutaneous space), and time after implantation (1,2, 4, 6, or 8 weeks). Before implantation, fibroblasts were labeled with PKH26‐GL, a fluorescent membrane dye. Immediately after retrieval of the implant, the viability of the labeled seeded cells was assessed under a fluorescent microscope. Viable seeded fibroblasts remained attached to the collagen fibers within the ligament analogs for at least 4 weeks (skin fibroblasts) or 6 weeks (anterior cruciate ligament fibroblasts) after implantation. A larger number of viable seeded cells were consistently observed in the subcutaneous space than in the knee joint. Scaffold resorption prevented observation at the 8‐week time period. Fibroblast‐seeded ligament analogs remained viable for prolonged periods in the knee joint and therefore have the potential to influence the formation and remodeling of neoligament tissue after reconstruction of the anterior cruciate ligament.
Comparison of mRNA levels for matrix molecules in normal and disrupted human anterior cruciate ligaments using reverse transcription‐polymerase chain reaction
Authors: Lo Ian K. Y. , Marchuk Linda L. , Hart David A. , Frank Cyril B.
Published: February 2005

Midsubstance samples of anterior cruciate ligaments from seven normal human cadaver knees (16–50 years old) were harvested and compared with midsubstance pieces of scarred anterior cruciate ligaments from 30 patients (15–40 years old). RNA was isolated from each ligament, and the expression of type‐I collagen, type‐III collagen, biglycan, decorin, lumican, and tissue inhibitor of metalloproteinase‐1 was evaluated by quantitative reverse transcription‐polymerase chain reaction with use of β‐actin as the housekeeping gene. Data for injured ligaments were further compared statistically as a function of time after injury to better define patterns of cellular expression over time. Our hypothesis was that injured ligaments would show minimal cellular activity and decreasing activity over time. The results revealed that both normal and injured anterior cruciate ligaments contain cells that express mRNA for all molecules studied. However, cells in Injured ligaments express much higher, but still proportional, quantities of message for type‐I collagen and, type‐III collagen (p < 0.000001) and higher quantities of biglycan (p < 0.02) and tissue inhibitor of metalloproteinase‐1 (p < 0.0003) than do cells in normal anterior cruciate ligaments. These levels remained elevated for longer than 1 year after injury. Linear regression analysis showed biglycan expression correlated with time from injury (r2 = –0.69; p = 0.007). These results collectively demonstrate that injured human anterior cruciate ligaments contain cells that express scar‐like molecules and that the injured ligaments are likely continuing to remodel matrix over time. Furthermore, they suggest that human anterior cruciate ligaments have not failed to heal due to the failure of scar formation per se. The quality and quantity of this scar remain questionable; however, the possibility of its enhancement as a healing strategy for human anterior cruciate ligaments cannot be dismissed.
Analysis of optimal range of socket orientations in total hip arthroplasty with use of computer‐aided design simulation
Authors: Seki Makoto , Yuasa Nobuhiro , Ohkuni Kyoko
Published: February 2005

A three‐dimensional computer‐aided design model of a total hip replacement was used to study the effects of anteversion and abduction of the acetabular component and anteversion and varus‐valgus an‐gulation of the femoral component on the range of hip flexion and extension that could be obtained without component impingement. Impingement of the component was defined as impingement between the neck of the femoral component and the edge of the acetabular component. To achieve an angle of hip flexion greater than 90° and an extension angle greater than 30° without component impingement, the optimal angulations were found to be between 1 and 30° of anteversion and 30 and 50° of abduction of the acetabular component, as well as 10° of anteversion of the femoral component. When the valgus angulation of the femoral component was reduced from 7 to 0°, the allowable range of flexion without impingement increased under the. same conditions of acetabular‐component orientation and femoral‐component anteversion. Significant inverse correlations were found between the anteversion angle of the acetabular component and both the lumbar lordosis angle and the sacrohorizontal angle.
Computer model to predict subsurface damage in tibial inserts of total knees
Authors: Sathasivam S. , Walker P. S.
Published: February 2005

Two designs of total knee replacements were analysed to determine how the geometry of their bearing surface would affect the susceptibility of their ultra high molecular weight polyethylene tibial inserts to delamination. Orientations of the femoral components on the tibial surfaces were calculated with use of rigid body analysis for discrete intervals during the stance phase of gait. For each successive orientation, finite element analysis was used to compress the components together to determine the stresses in the tibial inserts. A damage function analogous to strain energy density was defined to account for the accumulated amplitudes, and frequencies of the maximum shear stress cycles and hence to predict fatigue failure. The damage function was applied to each polyethylene element in the tibial insert, and the highest value calculated for each design was its damage score. One knee had a damage score more than three times less than that of the other because of lower stresses and because the contact points moved in the medial‐lateral as well as anterior‐posterior directions during internal‐external rotation. The femoral and tibial components of this knee had lage outer frontal radii and close conformity in the frontal plane. We propose that this method, which accounts for the motions and stresses endured during walking, makes different predictions regarding the likelihood of delamination compared with the predictions made by conventional static compression tests performed when the knee is in a neutral position.
Chemotherapy and P‐glycoprotein expression in chondrosarcoma
Authors: Terek Richard M. , Schwartz Gary K. , Devaney Kenneth , Glantz Lisa , Mak Solida , Healey John H. , Albino Anthony P.
Published: February 2005

Chondrosarcomas are alleged to be resistant to chemotherapy. A retrospective review of our experience primarily with dedifferentiated chondrosarcomas treated with chemotherapy was performed to re‐evaluate the efficacy of chemotherapy for this tumor. There were 18 patients: 14 stage IIB and four stage III. Seventeen patients had dedifferentiated chondrosarcoma. The median age at diagnosis was 57 years. Fourteen of the patients underwent wide excision of the tumor, two underwent amputation, and two had no surgery. The femur and the pelvis were the most common locations of the primary tumor. Chemotherapy for 11 of the patients consisted of cisplatin and doxorubicin. Survival was analyzed with the Kaplan‐Meier method; the median survival was 12 months. The hypothesis that chondrosarcomas express P‐glycoprotein was tested. Expression of P‐glycoprotein was evaluated by immunostaining with use of the C494 and C219 antibodies on 41 benign and malignant cartilage tumors, six of which were from the patients in the chemotherapy group. Immunostaining revealed that 37 of 41 cartilage tumors expressed P‐glycoprotein. The rate of survival of patients with high‐grade chondrosarcoma treated with chemotherapy is poor. P‐glycoprotein expression is common in benign and malignant cartilage lesions. The lack of response to chemotherapy may be related to the expression of P‐glycoprotein.
Blood supply of the achilles tendon
Authors: Ahmed I. M. , Lagopoulos M. , McConnell P. , Soames R. W. , Sefton G. K.
Published: February 2005

The Achilles tendon is one of the most common sites of injury and rupture as a result of overuse. Evidence suggests that the pathogenesis of rupture could involve the pattern of its blood supply. With use of angiographic and histological techniques, the blood supply of the Achilles tendon was investigated in 12 human cadaveric specimens. Angiography confirmed Mayer's 1916 finding that the blood supply to the tendon is from three areas: the musculotendinous and osseotendinous junctions and the paratenon, with the posterior tibial artery providing the major contribution. However, qualitative and quantitative histological analyses in this study showed that the Achilles tendon has a poor blood supply throughout its length, as determined by the small number of blood vessels per cross‐sectional area, which do not in general vary significantly along its length. In light of these findings, it is suggested that poor vascularity may prevent adequate tissue repair following trauma, leading to further weakening of the tendon.
Pyridinoline in relation to ultimate stress of the patellar tendon during healing: An animal study
Authors: Chan Barbara P. , Fu S. C. , Qin L. , Rolf C. , Chan K. M.
Published: February 2005

The ultimate stress of the central one‐third of the patellar tendon was studied in a gap wound‐healing model in the rat. The specimens were also analyzed for collagen and nonreducible crosslinks, as measured by hydroxyproline and pyridinoline content, respectively. Thirty days after injury, the ultimate stress of the healing patellar tendon was restored to an average of 71% of the control value and remained constant over time. The pyridinoline content of the healing tendon was twice the control value by 30 days after injury and reached a plateau; however, the hydroxyproline content did not change significantly over time. Stepwise regression analysis demonstrated that pyridinoline was a better biochemical marker for ultimate stress than was hydroxyproline. The current study provides insights into the functional behaviour of the healing patellar tendon by establishing the relationship between the two biochemical components and the ultimate stress of the healing patellar tendon. This study also suggests the possibility of using pyridinoline content as an indirect marker of the ultimate stress because in vivo assessment is impossible.
Finite‐element modeling of trabecular bone: Comparison with mechanical testing and determination of tissue modulus
Authors: Ladd Anthony J. C. , Kinney John H. , Haupt David L. , Goldstein Steven A.
Published: February 2005

We combined three techniques—mechanical testing, three‐dimensional imaging, and finite‐element modeling—to distinguish between the contributions of architecture and tissue modulus to mechanical function in human trabecular bone. The objectives of this study were 2‐fold. The first was to assess the accuracy of micromechanical modeling of trabecular bone using high‐contrast x‐ray images of the trabecular architecture. The second was to combine finite‐element calculations with mechanical testing to infer an average tissue modulus for the specimen. Specimens from five human L1 vertebrae were mechanically tested along the three anatomic axes. The specimens were then imaged by synchrotron x‐ray tomography, and the elastic moduli of each specimen were calculated from the tomographic image by finite‐element modeling. We found that 23‐μm tomographic images resolved sufficient structural detail such that the calculated anisotropy in the elastic modulus was within the uncertainties of the experimental measurements in all cases. The tissue modulus of each specimen was then estimated by comparing the calculated mean stiffness of the specimen, averaged over the three anatomical directions, with the experimental measurement. The absolute values of the experimental elastic constants could be fitted, again within the uncertainties of the experimental measure‐ments, by a single tissue modulus of 6.6 GPa, which was the average tissue modulus of the five specimens. These observations suggest that a combination of mechanical testing, three‐dimensional imaging, and finite‐element modeling might enable the physiological variations in tissue moduli to be determined as a function of age and gender.
Can the sagittal lumbar curvature be closely approximated by an ellipse?
Authors: Janik Tadeusz J , Harrison Donald D. , Cailliet Rene , Troyanovich Stephan J. , Harrison Deed E.
Published: February 2005

For the sagittal lumbar curvature, existing spinal models are based only on the anthropomorphic radiographic characteristics of one individual, or, at best, of only a few individuals. This raises questions of applicability of the modeling results to clinical situations. Because spinal coupling and loads on spinal tissues have been shown to be functions of the initial static posture, a rigorously derived neutral lumbar lordosis would be important for clinicians and spine researchers. This study presents modeling of the sagittal lumbar spine in the shape of an ellipse. Vertebral body and disc heights, derived from digitized lateral lumbar radiographs of 50 normal subjects, were used to create an ellipse along the posterior body margins from the inferior of T12 to the superior sacralbase. Additional data to create an elliptical lumbar model were determined from a least‐squares analysis of passing ellipses through the digitized posterior body points. This confirmed that an elliptical model closely fit the lumbar curvature with a least‐squares error of 1.2 mm per digitized point. The elliptical model is approximately an 85° portion of a quadrant. The semi‐major and semi‐minor axes, a and b, are parallel to the posterior body margin of T12 and parallel to the inferior body endplate of T12, respectively, with a semi‐minor to semi‐major radio of b/a = 0.39. The elliptic model has a height‐to‐' length ratio of H/L = 0.963. where height is the vertical distance from inferior T12 to superior SI and length is the arc length along George's line (along the posterior longitudinal ligament) from T12 to SI.
Bone marrow cells produce soluble factors that inhibit osteoclast activity
Authors: Ninomiya James T. , Bi Yanming , Banks Michael A. , Lavish Sandra A. , Goldberg Victor M. , Greenfield Edward M.
Published: February 2005

Cytokines that stimulate bone resorption are produced by cells found in bone marrow. However, marrow cells produce multiple factors, some of which may be inhibitors of osteoclast differentiation or activity. Thus, it is not possible to predict a priori whether the mixture of factors produced by marrow cells will have a net stimulatory or inhibitory effect on bone resorption. In this study, we showed that the net effect of whole marrow is to inhibit osteoclast activity induced by parathyroid hormone. Fractionation of the marrow revealed that the inhibitory activity was in the marrow fluid. However, conditioned media obtained from marrow cell cultures also inhibited osteoclast activity. Thus, it is likely that the inhibitory factors are produced in vivo by cells residing in the marrow. These inhibitory factors may represent a physiological regulatory process that plays an important role in maintaining the balance between bone resorption and formation. Because we have previously shown that interleukin‐6 is one of the cytokines that parathyroid hormone induces in osteoblastic cells to stimulate osteoclast activity, one potential mechanism by which the marrow‐derived inhibitory factors might act is by preventing this production of interleukin‐6. However, we found that the marrow cell‐conditioned media do not inhibit the production or activity of interleukin‐6. Thus, the inhibitory factors appear to block osteoclast activity through a mechanism that does not involve interleukin‐6. Taken together, these results demonstrate the importance of factors that inhibit bone resorption and emphasize that the presence of cytokines that stimulate bone resorption in conditions such as osteoporosis and orthopaedic implant loosening should be interpreted with caution unless evidence exists demonstrating their functional importance.
Intermittent pneumatic compression of legs increases microcirculation in distant skeletal muscle
Authors: Liu Kang , Chen Long‐En , Seaber Anthony V. , Johnson Glenn W. , Urbaniak James R.
Published: February 2005

Intermittent pneumatic compression has been established as a method of clinically preventing deep vein thrombosis, but the mechanism has not been documented. This study observed the effects of intermittent pneumatic compression of legs on the microcirculation of distant skeletal muscle. The cremaster muscles of 80 male rats were exposed, a specially designed intermittent pneumatic‐compression device was applied to both legs for 60 minutes, and the microcirculation of the muscles was assessed by measurement of the vessel diameter in three categories (10–20, 21–40, and 41–70 μm) for 120 minutes. The results showed significant vasodilation in arterial and venous vessels during the application of intermittent pneumatic compression, which disappeared after termination of the compression. The vasodilation reached a maximum 30 minutes after initiation of the compression and could be completely blocked by an inhibitor of nitric oxide synthase, NG‐monomethyl‐L‐arginine (10 μmol/min). A 120‐minute infusion of NG‐monomethyl‐L‐arginine, beginning coincident with 60 minutes of intermittent pneumatic compression, resulted in a significant decrease in arterial diameter that remained at almost the same level after termination of the compression. The magnitude of the decrease in diameter in the group treated with intermittent pneumatic compression and NG‐monomethyl‐L‐arginine was comparable with that in the group treated with NG‐monomethyl‐L‐arginine alone. The results imply that the production of nitric oxide is involved in the positive influence of intermittent pneumatic compression on circulation. It is postulated that the rapid increase in venous velocity induced by intermittent pneumatic compression produces strong shear stress on the vascular endothelium, which stimulates an increased release of nitric oxide and thereby causes systemic vasodilation.
Effect of seeding duration on the strength of chondrocyte adhesion to articular cartilage
Authors: Schinagl Robert M. , Kurtis Melissa S. , Ellis Kristi D. , Chien Shu , Sah Robert L.
Published: February 2005

Chondrocyte adhesion to cartilage may play an important role in the repair of articular defects by maintaining cells in positions where their biosynthetic products can contribute to the repair process. The objective of this in vitro study was to determine the effect of the duration of seeding time on the ability of chondrocytes to resist detachment from cartilage when subjected to mechanical perturbation (fluid‐induced shear stress). Suspensions of adult bovine articular chondrocytes were prepared from primary, high‐density monolayer cultures and infused into a parallel‐plate shear‐flow chamber where they settled onto 50‐μm‐thick sections of bovine articular cartilage at a density of approximately 20,000 cells/cm2. The chondrocytes were seeded and allowed to attach to the cartilage surface for specific durations (5‐40 minutes) in medium including 10% serum at 22°C, after which the cells were exposed to fluid flow‐induced shear stresses (6‐90 Pa). The fraction of detached cells at each shear stress was calculated from microscopic images. Shear stress was applied for 1 minute because this lenght of time was sufficient to induce steady‐state cell detachment. Increasing the duration of cell seeding led to a more firm attachment of chondrocytes to cartilage. After 9 minutes of seeding, 50% cell detachment was induced by gravitational force alone. After 40 minutes of seeding, 50% detachment required 26 Pa of shear stress. Extrapolation of the data to account for the effect of repeated applications of cell suspensions to an individual cartilage substrate indicated that for a freshly prepared cartilage section, 50% detachment was induced by gravity after 25 minutes of seeding and by 2.3 Pa of shear stress after 40 minutes of seeding. The increase in resistance to shear stress‐induced cell detachment with increasing seeding duration suggests that it may be beneficial to allow chondrocytes to stabilize in the absence of applied load for some time after chondrocyte transplantation for cartilage repair in vivo.
Callus formation and fixation rigidity: A fracture model in rats
Authors: Probst A. , Jansen H. , Ladas A. , Spiegel H. U.
Published: February 2005

To produce different amounts of callus in rats. we devised a procedure to fix leg fractures using intramedullary nails that differ in bending rigidity. We inserted a silicone cannula into the intact diaphysis of the tibia of rats that had already been killed and then fractured the tibia by a three‐point bending technique. The fracture was stabilised by insertion of either a stainless‐steel or polypropylene nail into the silicone cannula. Biomechanical testing showed that the initial stiffness of the fractures differed between the two nail types by a factor of 16. In vivo, 16 Wistar rats were operated on by the same technique to study the formation of callus. Four weeks after fracture, the size of the callus differed significantly between the steel‐nailed and polypropylene‐nailed fractures. In conclusion, mechanically differing internal fixation devices led to different callus responses in rats when all other factors were kept equal.
Effect of serum proteins on osteoblast adhesion to surface‐modified bioactive glass and hydroxyapatite
Authors: El‐Ghannam A. , Ducheyne P. , Shapiro I. M.
Published: February 2005

Previous studies indicate that modification of the surface of porous bioactive glass promotes osteoblast function. We hypothesize that bone formation on treated bioactive glass is due to the selective adsorption of serum attachment proteins. To test this hypothesis, we examined the profile of proteins adsorbed to treated bioactive glass and compared these proteins with those adsorbed to untreated bioactive glass and porous hydroxyapatite. Porous bioactive glass was treated with Tris‐buffered electrolyte solution to generate a calcium phosphate‐rich surface layer and then immersed in tissue‐culture medium containing 10% serum. Proteins adsorbed to the ceramic surfaces were analyzed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and Western blot analysis. Porous hydroxyapatite bound a higher amount of total protein than did the other substrates. However, surface‐modified porous bioactive glass adsorbed more fibronectin than did hydroxyapatite. The effect of serum‐protein adsorption on osteoblast adhesion to bioactive glass and hydroxypatite was also evaluated. Cell adhesion to porous bioactive glass that was either surface‐modified and serum‐treated was significantly greater than to porous bioactive glass that was either surface‐modified or serum‐treated. Furthermore, cell adhesion to porous bioactive glass treated to form the dual layer of calcium phosphate and serum protein was significantly higher than adhesion to porous hydroxyapatite with adsorbed serum protein. Results of the study strongly suggest that adsorption of serum fibronectin to the surface of modified porous bioactive glass coated with calcium phosphate may be responsible for enhanced osteoblast adhesion.
Experimental acute hematogenous osteomyelitis in mice. II. Influence of Staphylococcus aureus infection on T‐cell immunity
Authors: Yoon K. S. , Fitzgerald R. H. , Sud S. , Song Z. , Wooley P. H.
Published: February 2005

A murine model of acute hematogenous osteomyelitis was used to study the immune response following Staphylococcus aureus infection and to examine the hypothesis that the bacteria may modify T‐cell responses due to the production of bacterial enterotoxins with mitogenic or superantigenic activity. Lymphnode T cell‐receptor expression was assessed with use of flow cytometry and reverse transcription‐polymerase chain reaction techniques, and increased apoptosis (programmed cell death) in T‐cell subsets was monitored. The expression and levels of circulating cytokines and T‐cell cytokines within tissues surrounding the damaged area of the proximal tibia were also investigated. Analysis of T‐cell receptors in experimental osteomyelitis revealed two distinct patterns of T‐cell evolution during the disease. Certain T‐cell subsets (Vβ2, Vβ3, Vβ9, and Vβ10) were activated and expanded during the first 24 hours after infection; they reached maximum levels 6 days after infection, followed by a return to pre‐infection levels. In contrast, other T‐cell subsets (Vβ11, Vβ12, Vβ13, Vβ14, and Vβ16) contracted during the first 24 hours after infection, followed by expansion to a maximum level 9 days after infection. Activation and proliferation of T‐cell subsets (notably Vβ14 T cells) was followed by apoptosis, suggesting that staphylococcal bone infection caused superantigenic‐like effects on the mouse immune system. Analysis of cytokine responses in local tissue revealed that the T‐cell cytokines interleukin‐2 and interferon‐γ showed a late and relatively short activation pattern compared with the inflammatory cytokines interleukin‐1, interleukin‐6, and tumor necrosis factor‐α. The results suggest that Staphylococcus aureus bone infection may undermine the antibacterial immune response through downregulation of T‐cell immunity and immune‐cytokine production, which could increase the severity of the systemic infection and local osseous destruction that occur with acute hematogenous osteomyelitis.
Stiffness and muscle function with age and reduced muscle use
Authors: Brown Marybeth , Fisher Jonathan S. , Salsich Gretchen
Published: February 2005

Changes in passive muscle stiffness with age and disuse were assessed in male Fischer‐344 and Brown Norway rats. Three groups of rats were studied: young (approximately 7 months old), old (approximately 33 months old), and old that had undergone 2 weeks of hindlimb unweighting, a model of reduced muscle use. Four hindlimb muscles were examined: the soleus (postural), plantaris (locomotor), extensor digitorum longus (nonpostural), and peroneus longus (nonpostural). Supramaximal stimuli elicited peak tetanic tensions throughout the available range of motion (amount of muscle elongation before the maximal attainable contractile or tetanic tension is obtained) for each muscle, permitting the creation of length‐tension curves. Passive tension (amount encountered at each millimeter of change in muscle length) was also recorded throughout the available range of motion and was unchanged with aging and unchanged or reduced with hindlimb unweighting; muscle stiffness remained unchanged under both conditions. Passive tension, however, accounted for a greater proportion of total tension with age and particularly with hindlimb unweighting. A significant loss in muscle range of motion, resulting in a leftward shift in the length‐tension curve, occurred with aging in only the plantaris. Hindlimb unweighting resulted in a marked loss in muscle range for all four muscles studied, suggesting that the remaining muscle force was constrained to a very small arc. Significant declines in muscle mass and peak contractile tension, associated with age and hindlimb unweighting, were observed for all four muscles.
Localization and expression of cartilage oligomeric matrix protein by human rheumatoid and osteoarthritic synovium and cartilage
Authors: Cesare Paul E. Di , Fang Carrie , Leslie Michael P. , Valle Craig J. Della , Gold Julie M. , Tulli Hermina , Perris Roberto , Carlson Cathy S.
Published: February 2005

Synovium and cartilage from patients with osteoarthritis or rheumatoid arthritis were analyzed for expression of cartilage oligomeric matrix protein. Immunostaining of synovium with antiserum to cartilage oligomeric matrix protein demonstrated positive staining in both diseases. In osteoarthritis, there was positive staining within the synovial cells and immediately subjacent connective tissue, with less intense staining in the deeper connective tissue. In rheumatoid arthritis, there was less intense staining within the synovial cells and marked intense staining in the deeper connective tissue. In situ hybridization performed with an antisense digoxigenin‐labeled riboprobe to human cartilage oligomeric matrix protein confirmed the presence of cartilage oligomeric matrix protein mRNA in the cells of the synovial lining in both types of synovium. Quantitative polymerase chain reaction with a cartilage oligomeric matrix protein MIMIC demonstrated increased cartilage oligomeric matrix protein mRNA in rheumatoid cartilage and synovium as compared with osteoarthritic cartilage and synovium, respectively; mRNA levels in rheumatoid synovium were similar to those from osteoarthritic chondrocytes. As a result of the high expression of cartilage oligomeric matrix protein from rheumatoid synovium, inflammatory synovium should be considered as a potential tissue source of cartilage oligomeric matrix protein in any investigation of biological markers of cartilage metabolism. The upregulated expression of cartilage oligomeric matrix protein in inflammatory tissues suggests its in vivo regulation by cytokines.
Enhanced repair of extensive articular defects by insulin‐like growth factor‐I‐laden fibrin composites
Authors: Nixon Alan J. , Fortier Lisa A. , Williams Janice , Mohammed Hussni
Published: February 2005

Stem cells indigenous to the cancellous spaces of the bone bed in an acute injury provide an important source of pluripotent cells for cartilage repair. Insulin‐like growth factor‐I facilitates chondrogenesis of bone marrow‐derived stem cells in long‐term culture and may enhance chondrogenesis in healing cartilage lesionsin vivo. This study examined the impact of insulin‐like growth factor‐I, gradually released from fibrin clots polymerizedin situ, on the recruitable stem‐cell pool in a full‐thickness critical cartilage defect model. Twelve full‐thickness 15‐mm cartilage lesions in the femoropatellar articulations of six young mature horses were repaired by an injection of autogenous fibrin containing 25 μg of human recombinant insulin‐like growth factor‐I or, in control joints, fibrin without the growth factor. All horses were killed at 6 months, and cartilage repair tissue and surrounding cartilage were assessed by histology, histochemistry, types I and II collagen immunohistochemistry, types I and II collagenin situhybridization, and matrix biochemical determinations. White tissue filled grafted and control lesions, with the growth factor‐treated defects being more completely filled and securely attached to the subchondral bone. A moderately improved chondrocyte population, more columnar cellular organization, and better attachment to the underlying bone were evident on histological evaluation of growth factor‐treated defects. Type‐II procollagen mRNA was abundantly present in the deeper half of the treated sections compared with moderate message expression in control tissues. Immunolocalization of type‐II collagen showed a preponderance of the collagen in growth factor‐treated lesions, confirming translation of type‐II message to protein. Composite histologic healing scores for treated defects were significantly improved over those for control defects. DNA content in the cartilage defects was similar in treated and control joints. Matrix proteoglycan content was similar in treated and control defects and lower in the defects than in the intact surrounding and remote cartilage of the treated and control joints. The proportion of type‐II collagen significantly increased in growth factor‐treated tissues. Fibrin polymers laden with insulin‐like growth factor‐I improved the histologic appearance and the proportion of type‐II collagen in healing, full‐thickness cartilage lesions. However, none of the biochemical or morphologic features were consistent with those of normal articular cartilage.
Low‐intensity ultrasound stimulates proteoglycan synthesis in rat chondrocytes by increasing aggrecan gene expression
Authors: Parvizi Javad , Wu Chi‐Chuan , Lewallen David G. , Greenleaf James F. , Bolander Mark E.
Published: February 2005

We evaluated the effect of low intensity‐pulsed ultrasound stimulation on rat chondrocytes in vitro using two different 1.0‐MHZ ultrasound signals with spatial and temporal average intensities of 50 or 120 mW/cm2. The pulses had a duration of 200 microseconds and were repeated every millisecond, with corresponding average peak‐pressure amplitudes of 230 or 360 kPa, respectively. Cells were stimulated one, three, or five times for 10 minutes each day starting the third day after plating. One group of cells was exposed to sham ultrasound as a control. The cultures were evaluated for cell proliferation (by [3H]thymidine incorporation and DNA measurement), steady‐state mRNA levels of α1(I) and α1(II) procollagens and aggrecan (by Northern blotting), and proteoglycan synthesis (by [35S]sulfate incorporation). The results revealed that ultrasound causes increases in the level of aggrecan mRNA (p < 0.05) and in proteoglycan synthesis (p < 0.03) after three and five treatments. Expression of mRNA for α1(II) procollagen increased over time, but ultrasound had no stimulatory effect. Expression of mRNA for α1(I) procollagen was initially low and remained unchanged with time. Although cell proliferation increased with time in both groups, there was no statistically significant difference between the cultures treated with ultrasound and the controls (p = 0.1). The in vitro results support our previous in vivo findings that low‐intensity ultrasound stimulates aggrecan mRNA expression and proteoglycan synthesis by chondrocytes, which may explain the role of ultrasound in advancing endochondral ossification, increasing the mechanical strength of fractures, and facilitating fracture repair.
Mechanical modulation of growth for the correction of vertebral wedge deformities
Authors: Mente Peter L. , Aronsson David D. , Stokes Ian A. F. , Iatridis James C.
Published: February 2005

This study tested the following hypotheses: (a) a vertebral wedge deformity created by chronic static asymmetrical loading will be corrected by reversal of the load asymmetry; (b) a vertebral wedge deformity created by chronic static asymmetrical loading will remain if the load is simply removed; and (c) vertebral longitudinal growth rates, altered by chronic static loading, will return to normal after removal of the load. An external fixator was used to impose an angular deformity (Cobb angle of 30°) and an axial compression force (60% body weight) on the ninth caudal (apical) vertebra in two groups of 125‐week‐old Sprague Dawley rats. This asymmetrical loading was applied to all rats for 4 weeks to create an initial wedge deformity in the apical vertebra. The rats from group I (load reversal) then underwent 1 week of distraction loading followed by 4 weeks of asymmetrical compressive loading with the imposed 30° Cobb angle reversed. The rats from group II (load removal) had the apparatus removed and were followed for 5 weeks with no external loading. Weekly radiographs were obtained and serial fluorochrome labels were administered to follow vertebral wedging. After the initial 4‐week loading period, the combined average wedge deformity that developed in the apical vertebra of the animals in both groups was 10.7 ± 4.4°. The group that underwent load reversal showed significant correction of the deformity with the wedging of the apical vertebra decreasing to, on average, 0.1 ± 1.4° during the 4 weeks of load reversal. Wedging of the apical vertebra in the group that underwent load removal significantly decreased to 7.3 ± 3.9° during the first week after removal of the load, but no significant changes in wedging occurred after that week. This indicated a return to a normal growth pattern following the removal of the asymmetrically applied loading. The longitudinal growth rate of the apical vertebra also returned to normal following removal of the load. Vertebrae maintained under a load of 60% body weight grew at a rate that was 59.4 ± 17.0% lower than that of the control vertebrae, whereas after vertebrae were unloaded their growth averaged 102.4 ± 31.8%. These findings show that a vertebral wedge deformity can be corrected by reversing the load used to create it and that vertebral growth is not permanently affected by applied loading.
Quantitative determination of joint incongruity and pressure distribution during simulated gait and cartilage thickness in the human hip joint
Authors: von Eisenhart R. , Adam C. , Steinlechner M. , Müller‐Gerbl M. , Eckstein F.
Published: February 2005

The objective of this study was to provide quantitative data on hip‐joint incongruity and pressure during a simulated walking cycle and on articular‐cartilage thickness in the same set of specimens. Using a casting technique in eigth specimens of the human hip (age: 18‐75 years), we determined the width of the joint space (incongruity) required at minimal load for contact at four phases of the gait cycle. The pressure distribution, measured with pressure‐sensitive film, was determined at physiologic load magnituded on the basis of in vivo measurements of hip‐joint forces. Cartilage thickness was assessed with A‐mode ultrasound. At minimal loading, the average maximum width of the joint space ranged from 1.1 to 1.5 mm in the acetabular roof, with the contact areas located ventro‐superiorly and dorso‐inferiorly throughout the gait cycle. At physiological loading, the width decreased and the contact areas covered the complete articular surface during midstance and heel‐off but not during heel‐strike or toe‐off. The pressure distribution was inhomogeneous during all phases, with average maximum pressures of 7.7 ± 1.95 MPa at midstance. The cartilage thickness varied considerably throughout the joint surfaces; maxima greater than 3 mm were found ventro‐superiorly. These data can be used to generate and validate computer models to determine the loadsharing between the interstitial fluid and the solid proteoglycan‐collagen matrix of articular cartilage, the latter being relevant for the initiation of mechanically induced cartilage degeneration.
Effects of sintered bovine bone on cell proliferation, collagen synthesis, and osteoblastic expression in MC3T3‐E1 osteoblast‐like cells
Authors: Matsumoto Takuji , Kawakami Mamoru , Kuribayashi Koichi , Takenaka Toru , Minamide Akihito , Tamaki Tetsuya
Published: February 2005

To determine the function of biomaterials on osteoblasts, we studied the effects of two different biomaterials, sintered bovine bone (true bone ceramic) and hydroxyapatite‐related material, on DNA and collagen synthesis and osteoblastic expression in osteoblast‐like cells in vitro. Osteoblasts cultured with true bone ceramic exhibited greater increases in DNA and collagenous protein synthesis and alkaline phosphatase activity than those cultured with hydroxyapatite. Furthermore, expression of mRNA for type‐I collagen and osteocalcin, as assessed by reverse transcription‐polymerase chain reaction, was higher in cultures grown on true bone ceramic or hydroxyapatite than in those grown with glass fragments, and levels of gene expression in true bone ceramic and hydroxyapatite cultures were at almost the same level. These findings indicate that osteoblasts cultured with true bone ceramic increase their activity, suggesting that true bone ceramic may be a more favorable substrate than hydroxyapatite for growth and differentiation of osteoblast‐like cells.
Integrin subunits responsible for adhesion of human osteoblast‐like cells to biomimetic peptide surfaces
Authors: Rezania Alireza , Healy Kevin E.
Published: February 2005

We have identified the integrin subunits responsible for the initial adhesion of human osteoblast‐like cells to peptide‐modified surfaces. Biomimetic peptide surfaces containing homogenous RGD (Arg‐Gly‐Asp), homogenous FHRRIKA (Phe‐His‐Arg‐Arg‐Ile‐Lys‐Ala), and a mixed ratio of FHRRIKA:RGD (25:75) were used to assess integrin‐mediated adhesion. The RGD and FHRRIKA peptides were selected from the cellbinding and putative heparin‐binding domains of bone sialoprotein. A panel of monoclonal antibodies against human α1, α2, α3, α4, α5, β1, αv, and αβ3 was used to identify the subunits most dominant in mediating short‐term (10 or 30 minutes) and long‐term (4 hours) cell adhesion to the peptide surfaces. Anti‐α2, anti‐β1, and anti‐αv significantly (p < 0.05) diminished cell attachment to homogenous RGD surfaces following 30 minutes of incubation. After 4 hours of incubation on RGD‐grafted surfaces, immunostaining of these integrin subunits revealed discrete localization of the αv subunit at the periphery of the cell (similar to focal contact points), whereas the α2 and β1 subunits stained very diffusely throughout the cell. A radial‐flow apparatus was used to determine the effect of anti‐integrin antibodies on strength of cell detachment following 10 minutes of incubation on peptide‐grafted surfaces. The strength of detachment from surfaces containing RGD was significantly reduced (p < 0.05) in the presence of anti‐α2, anti‐αv, or anti‐β1 compared with controls (presence of preimmune mouse IgG). None of the antibodies significantly influenced cell attachment to homogenous FHRRIKA‐grafted surfaces. These results demonstrate that initial (30 minutes) attachment of human osteoblast‐like cells to homogenous RGD surfaces was mediated by the collagen receptor α2β1 and the vitronectin receptor αvβ3, whereas only the vitronectin receptor governed longer term (longer than 30 minutes) adhesion (localization to focal contacts). The importance of distinct integrins in mediating the attachment of bone cells to RGD‐immobilized surfaces indicates a strategy for engineering orthopaedic implants with a built‐in surface specificity for cell adhesion.
Computer model of endochondral growth and ossification in long bones: Biological and mechanobiological influences
Authors: Stevens Sheila S. , Beaupré Gary S. , Carter Dennis R.
Published: February 2005

Endochondral growth and ossification, the processes by which cartilage increases in size and is replaced by bone, are affected by biological factors such as intrinsic genetic makeup and systemic chemical agents. In addition, these processes are affected by epigenetic mechanical factors: they may be accelerated in regions of intermittent high shear stress and decelerated in regions of intermittent high hydrostatic pressure. Previous models of bone development have not incorporated both biological and mechanobiological influences on endochondral growth and ossification. We have implemented a finite element analysis to model a developing bone rudiment from 8 weeks of gestational development to approximately 2 years after birth. As a function of time, we calculated a maturity index that reflects the progression of a region of cartilage through the endochondral ossification sequence of proliferation, hypertrophy, mineralization, and replacement by bone. We calculated a specific growth rate for each region of cartilage and estimated overall longitudinal growth of the rudiment. Regions of cartilage replaced by bone were remodeled. The results from the maturity index can be compared with distributions of proliferative, hypertrophic, and mineralized cartilage seen on histology at various stages in development. The results of the simulation predicted prenatal and postnatal developmental events, including formation of a secondary ossific nucleus, a layer of articular cartilage, and a growth plate. Our results demonstrate the necessity to include biological and mechanobiological influences when endochondral growth and ossification are considered.
Effect of local density changes on the failure load of the proximal femur
Authors: Oden Z. Maria , Selvitelli David M. , Bouxsein Mary L.
Published: February 2005

Hip fracture among the elderly is a large and growing public health issue. Presently, all therapies approved for treatment and prevention of osteoporosis involve pharmacological agents that act systemically. In this study, we evaluated the feasibility of preventing osteoporotic hip fractures with local, rather than systemic, therapy. Our hypothesis is that local therapy to increase bone density may be as effective as systemic therapy in reducing fracture risk. Thus, the goal of this investigation was to use finite element analyses to study the effect of a localized increase in bone density on the strength of an osteopenic, human femur. Finite element predictions of the failure load were made after increasing the bone density within small regions in the proximal femur. The outcome variable from these analyses was the predicted load required to break a femur in a simulated fall to the side with impact on the greater trochanter. Increasing the density by 25% relative to baseline values in a small region (0.86 cm3) of the femoral neck increased the predicted failure load by 6.2%. The same density increase in a much larger region (4.92 cm3) increased the failure load by 15%. Inclusion of more than one region of increased density provided little additional benefit. In comparison, when the density of the entire femur was increased by 5% relative to baseline values, the predicted failure load increased by 5.4%. These findings suggest that agents capable of inducing increased bone density in small regions of the proximal femur have the potential to reduce the risk of hip fracture.