1Ectopic fibrogenesis induced by transplantation of adipose-derived progenitor cellsuspension immediately after lipoinjection.

Authors:Kotaro Yoshimura, M.D.,1 Katsujiro Sato, M.D.,2 Noriyuki Aoi, M.D.,1 Masakazu Kurita,M.D.,3 Hirotaka Suga, M.D.,1 Keita Inoue, M.D.,1 Hitomi Eto, M.D.,1 Toshitsugu Hirohi,M.D.,4 Kiyonori Harii, M.D.3

Adipose tissue has its own tissue-specific progenitor cells, a subpopulation of which has
been shown to have multipotency and called adipose stem cells or adipose-derivedmesenchymal stem cells (1, 2). During a clinical trial in which soft tissue is augmented
by transplantation of progenitor-enriched adipose tissue (cell-assisted lipotransfer, orCAL), we have encountered incidence of an unexpected complication: local ectopic
subcutaneous fibrogenesis. Patients participating in the trial did so under informed
consent approved by individual review boards.
CAL was designed based on the finding that aspirated fat tissue contains many fewer
vessels and adipose progenitor cells than intact fat tissue. This may explain thetendency of transplanted aspirated fat to atrophy during the first six months
post-transplantation (3). In the relevant clinical trial, the stromal vascular fraction(SVF) comprising 10-40% adipose progenitor cells was freshly isolated from aspirated
fat via collagenase digestion and transplanted together with aspirated fat tissue grafts(4).
In 146 cases, SVF cells were used as a cell pellet, mixed with and attached to aspirated
fat tissue grafts before injecting into fatty and muscular layers of breast mounds. On
the other hand, in 2 cases, SVF cells isolated from 600 ml aspirated fat were separately
injected as a cell suspension in 60ml of saline into both breast mounds (30 ml per side)
immediately after conventional lipoinjection. Although grafted fat survived well andfibrogenesis in the breasts or surrounding tissues was not seen in the former group,
fibrous tissue formation was observed in both cases of the latter group 3 months aftertreatment. In the two cases, breast mounds were somewhat hard to the touch;inspection by CT scan detected unexpected fibrosis in the subcutaneous fat layers. Inthe thinner patient of the two (Figure 1), fibrous tissue approximately 10 mm thick had
formed on the sternum and caused anterior elevation of the skin, which was treated2with local injections of triamcinolone acetonide at 6 and 8 months. Furthermore,
lymphadenopathy was seen at the left abdominal wall and the left inguinal region at 3months and gradually disappeared by 12 months.
Fibrogenesis results from persistent inflammation, in which tissue remodeling andrepair processes are impaired and injured cells are replaced not with cells of the same
type but with connective or scar tissue (5). As fibrogenesis was seen only when SVF cells
were injected separately as a cell suspension, a non-physiological environment in which
adherent adipose progenitors cells are suspended in saline solution may give rise to theunexpected differentiation and migration of the cells. After large-volume lipoinjection,
tissue injury, edema, hemorrhage and local inflammation are commonly seen, andtransplanted adipose progenitor cells are temporarily placed in and stimulated by anischemic and inflammatory microenvironment.
These findings provide some insights into a therapeutic strategy for future cell-based
therapies involving adherent stem/progenitor cells. Previous experimental studies
demonstrated that transplanted bone marrow-derived mesenchymal stem cells
differentiated into myofibroblasts and contributed to liver fibrosis after acute or chronic
liver injury (6,7). In cell-based therapies using adherent mesenchymal stem cells, thepossibility of unfavorable behaviors such as differentiation into myofibroblasts should
be taken into account, even if the cells are derived from adult tissue and have not been
substantially manipulated. It may be a resolution to adhere adipose-derived adherent
stem/ progenitor cells to cells, tissue, extracellular matrix, or biological scaffold before
administration to avoid their unexpected behaviors.

3References
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3

Matsumoto D, Sato K, Gonda K, et al. Cell-assisted lipotransfer: supportive use ofhuman adipose-derived cells for soft tissue augmentation with lipoinjection. TissueEng 2006; 12: 3375.
4Yoshimura K, Sato K, Aoi N, Kurita M, Hirohi T, Harii K. Cell-assisted lipotransfer
for cosmetic breast augmentation: supportive use of adipose-derived stem/stromalcells. Aesth Plast Surg 2008; 32: 48.

5Wynn T. Cellular and molecular mechanisms of fibrosis. J Pathol 2008; 214: 199.

6Russo FP, Alison MR, Bigger BW, et al. The bone marrow functionally contributes toliver fibrosis. Gastroenterology. 2006; 130: 1807.

7

di Bonzo LV, Ferrero I, Cravanzola C, et al. Human mesenchymal stem cells as atwo-edged sword in hepatic regenerative medicine: engraftment and hepatocyte
differentiation versus profibrogenic potential. Gut 2008; 57: 223.

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Figure Legend
Figure 1.
CT scan images taken before (Pre) and 3, 6, 12, and 36 months after treatment (3m, 6m,12m, and 36m).
Normal mammary glands and the thin fatty layers around them are visible beforetreatment. Substantial fibrosis had occurred, both diffusely in the transplanted fat
surviving around the mammary glands and in the subcutaneous layer over the sternum,at 3 months. The fibrotic mass over the sternum was treated twice with local injectionsof triamcinolone acetonide at 6 and 8 months and dissipated, but diffuse fibrosis in thebreasts remains at 36 months.