# Abstract

 

## Background Few clinical trials have investigated the safety and efficacy of mesenchymal stem cells for the management of post-traumatic osteoarthritis. The objectives of this pilot study were to determine the safety and tolerability and to explore the efficacy of a single intra-articular injection of allogeneic human mesenchymal precursor cells (MPCs) to improve clinical symptoms and retard joint structural deterioration over 24 months in patients following anterior cruciate ligament (ACL) reconstruction. 

## Methods In this phase Ib/IIa, double-blind, active comparator clinical study, 17 patients aged 18--40 years with unilateral ACL reconstruction were randomized (2:1) to receive either a single intra-articular injection of 75 million allogeneic MPCs suspended in hyaluronan (HA) (MPC + HA group) (*n* = 11) or HA alone (*n* = 6). Patients were monitored for adverse events. Immunogenicity was evaluated by anti-HLA panel reactive antibodies (PRA) against class I and II HLAs determined by flow cytometry. Pain, function, and quality of life were assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and SF-36v2 scores. Joint space width was measured from radiographs, and tibial cartilage volume and bone area assessed from magnetic resonance imaging (MRI). 

## Results Moderate arthralgia and swelling within 24 h following injection that subsided were observed in 4 out of 11 in the MPC + HA group and 0 out of 6 HA controls. No cell-related serious adverse effects were observed. Increases in class I PRA >10% were observed at week 4 in the MPC + HA group that decreased to baseline levels by week 104. Compared with the HA group, MPC + HA-treated patients showed greater improvements in KOOS pain, symptom, activities of daily living, and SF-36 bodily pain scores (*p* < 0.05). The MPC + HA group had reduced medial and lateral tibiofemoral joint space narrowing (*p* < 0.05), less tibial bone expansion (0.5% vs 4.0% over 26 weeks, *p* = 0.02), and a trend towards reduced tibial cartilage volume loss (0.7% vs --4.0% over 26 weeks, *p* = 0.10) than the HA controls. 

## Conclusions Intra-articular administration of a single allogeneic MPC injection following ACL reconstruction was safe, well tolerated, and may improve symptoms and structural outcomes. These findings suggest that MPCs warrant further investigations as they may modulate some of the pathological processes responsible for the development of post-traumatic osteoarthritis following ACL reconstruction. 

## Trial registration ClinicalTrials.gov ([NCT01088191](#)) registration date: March 11, 2010﻿ 

## Electronic supplementary material The online version of this article (doi:10.1186/s13075-017-1391-0) contains supplementary material, which is available to authorized users. # Results 

## Baseline characteristics of study participants The baseline characteristics of the study participants are shown in Table [2](#). There were no significant differences between the two groups in terms of age, gender, body mass index, tibial cartilage volume, tibial bone area, joint space width, tibial cartilage volume, or bone area. Apart from the KOOS activities of daily living (ADL) scores for the HA injected individuals, both groups exhibited KOOS baseline scores that were below the cut-off scores for individuals with physical problems associated with injured knees \[[7](#)\]. However, participants in the MPC + HA group reported worse KOOS pain (*p* = 0.02), symptoms (*p* < 0.001), ADL score (*p* = 0.047), and SF-36v2 bodily pain (*p* = 0.01) score than the HA-alone group at baseline. No significant differences in baseline characteristics were observed between completers and non-completers at 6, 12, and 24 months of follow-up as shown in Fig. [1](#) (Additional files [1](#), [2](#) and [3](#): Tables S1--S3). ::::table-wrap

::: caption
Baseline characteristics of study participants
:::

```
                                                                        MPC + HA (*n* = 11)   HA alone (*n* = 6)   *p**
```

______________________________________________________________________

Age, years 26.0 (3.6) 26.9 (10.3) 0.85
Females, number (%) 3 (27) 2 (33) 0.79
Body mass index, kg/m^2^ 25.1 (3.1) 25.1 (4.6) 1.00
Interval between ACL injury and reconstruction, days 76.5 (54.3) 61.7 (34.8) 0.56
Interval between ACL reconstruction and intra-articular injection, days 48.5 (14.0) 47.8 (8.3) 0.92
KOOS\
Pain 69.1 (11.7) 84.2 (11.9) 0.02
Symptoms 59.7 (10.8) 83.9 (11.7) \<0.001
Activities of daily living 82.1 (11.0) 92.8 (6.4) 0.047
Sport and recreation function 29.7 (17.6) 40.0 (14.1) 0.47
Knee-related quality of life 40.9 (19.8) 50.0 (16.8) 0.36
SF-36 physical component score 41.3 (4.7) 45.9 (5.8) 0.11
Physical functioning 41.0 (6.2) 43.7 (1.7) 0.31
Role limitation: physical 40.0 (7.0) 42.6 (8.1) 0.51
Bodily pain 42.3 (8.6) 53.5 (5.4) 0.01
General health perception 55.2 (6.6) 55.4 (7.9) 0.95
Joint space width, mm\
Medial tibiofemoral compartment 4.36 (0.55) 4.97 (0.63) 0.06
Lateral tibiofemoral compartment 5.38 (0.62) 5.67 (0.52) 0.36
Knee structure measured from MRI\
Medial tibial cartilage volume, mm^3^ 2456 (397) 2627 (476) 0.44
Lateral tibial cartilage volume, mm^3^ 3291 (401) 3548 (847) 0.51
Medial tibial plateau bone area, mm^2^ 2299 (337) 2187 (182) 0.46
Lateral tibial plateau bone area, mm^2^ 1472 (202) 1415 (193) 0.58

Data are reported as mean (SD) or number (%)

\*For difference between two groups using independent samples *t* test
or chi-squared test where appropriate

*ACL* anterior cruciate ligament, *KOOS* Knee Injury and Osteoarthritis
Outcome Score, *MRI* magnetic resonance imaging:::: 

## Adverse events The incidence of adverse events was graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCICTCAE) and is summarised in Table [3](#). No participants experienced treatment-related or treatment-emergent serious adverse events that resulted in death, treatment discontinuation, or study termination over the course of the study. ::::table-wrap
::: caption
Incidence of adverse events
:::

```
                                                      MPC + HA (*n* = 11)   HA alone (*n* = 6)
```

______________________________________________________________________

Total number of adverse events 94 39
Non-serious, *n* (%) 92 (97.9) 39 (100.0)
Serious, *n* (%) 2 (2.1)^#^ 0 (0.0)
Adverse events by system organ class\*, *n* (grade)\
Musculoskeletal and connective tissue disorders 11 (2) 6 (1)
General disorders and administration site conditions 3 (2) 1 (1)
Injury, poisoning, and procedural complications 2 (1) 2 (1)
Infections and infestations 1 (1) 1 (1)
Respiratory, thoracic, and mediastinal disorders 1 (1) 0
Immune system disorders 2 (2) 1 (2)

- Graded according to the National Cancer Institute Common Terminology
  Criteria for Adverse Events (NCICTCAE)

^#^ Non-treatment related:::: In the MPC + HA group, increases in class I PRA >10% were observed in 5 out of 6 patients at week 4, in 5 out of 7 patients at week 36, in 2 out of 7 patients at week 78, and in 1 out of 6 patients at week 104. In the HA-alone group, only 1 out of 4 patients had increases in class I PRA >10% at week 4, and this level was maintained through to week 104. None of the study participants exhibited clinically significant abnormalities in haematology or blood chemistry laboratory results over the course of the study. No major changes in vital signs were reported following injection of the test substances, nor were there notable changes from baseline in the physical examination data. No ectopic tissue formation was noted from the blinded MRI evaluations. 

## Serious adverse events Two serious adverse events, fracture of the humerus and infective bursitis, were reported for patients in the MPC + HA group after week 52. These were not considered to be treatment related. 

## Effect of MPCs on knee pain, function, and quality of life over 24 months There was an improvement from baseline in both groups for all the KOOS dimensions over 24 months (Fig. [2](#), Additional file [4](#): Table S4). However, significant differences between treatment groups were observed for KOOS symptoms and pain at 18 months (both *p* = 0.03) and 24 months (*p* = 0.04 and 0.02, respectively), and for ADL at 18 months (*p* = 0.04), all in favour of patients who were injected with the MPC + HA preparation (Fig. [2](#), Additional file [4](#): Table S4). There was also an improvement over 24 months in both groups for all SF-36 physical components except for general health perception (Fig. [2](#), Additional file [5](#): Table S5). However, statistically significant differences between treatments were only observed for bodily pain at 6, 12, and 24 months (*p* = 0.02, 0.05, and 0.03, respectively), where injection with the MPH + HA preparation was found to be more beneficial than HA alone (Fig. [2](#), Additional file [5](#): Table S5). <figure> <p><img src="" /></p> <figcaption>Change from baseline in <strong>a–c</strong> Knee Injury and Osteoarthritis Outcome Score (<em>KOOS</em>) (pain scores (<strong>a</strong>), symptom scores (<strong>b</strong>), and activities of daily living (<em>ADL</em>) scores (<strong>c</strong>)), and <strong>d</strong> SF-36 physical component scores over 24 months (mean and 95% confidence interval shown). \*<em>p</em> \<﻿ 0.05﻿ <em>HA</em> hyaluronan, <em>MPC</em> mesenchymal precursor cell</figcaption> </figure> 

## Effect of MPCs on tibial cartilage volume change over 24 months There was no significant difference in annual change in medial or lateral tibial cartilage volume between the MPC + HA and HA-alone groups over 6, 12, and 24 months (Table [4](#)). However, the MPC + HA group tended to have a reduced rate of medial tibial cartilage volume loss compared with the HA-alone group over the first 6 months of the study (0.7% vs --4.0%, *p* = 0.10) (Table [4](#)). ::::table-wrap
::: caption
Annual percentage change from baseline in tibial cartilage volume over
24 months
:::

```
              MPC + HA      HA alone      *p**
```

______________________________________________________________________

Medial tibia\
6 months 0.7 (5.9) --4.0 (3.9) 0.10
12 months 0.3 (6.3) --2.4 (3.1) 0.36
24 months --1.4 (4.2) --3.3 (5.3) 0.54
Lateral tibia\
6 months --1.4 (5.3) --2.7 (4.4) 0.65
12 months --4.7 (3.4) --2.6 (2.5) 0.25
24 months --3.7 (3.4) --0.8 (3.5) 0.22

Data are reported as mean (SD)

- For difference between two groups using independent samples *t* test

*HA* hyaluronan, *MPC* mesenchymal precursor cell:::: 

## Effect of MPCs on tibial bone expansion over 24 months The rate of total tibial bone expansion in the MPC + HA group showed a significantly decrease compared with the HA-alone group over the first 6 months post-treatment (0.5% vs 4.0%, *p* = 0.02) (Table [5](#)). The trend was maintained over the subsequent 12 and 24 months (both *p* = 0.09). ::::table-wrap
::: caption
Annual percentage tibial bone expansion from baseline over 24 months
:::

```
                       MPC + HA      HA alone    *p**
```

______________________________________________________________________

Medial tibial plateau\
6 months 0.8 (3.9) 4.2 (3.4) 0.13
12 months --1.9 (4.0) 1.5 (3.6) 0.17
24 months 0.1 (1.7) 0.8 (0.9) 0.43
Lateral tibial plateau\
6 months 0.4 (4.2) 3.6 (3.6) 0.17
12 months --0.2 (4.0) 1.9 (2.8) 0.35
24 months --1.8 (2.6) 1.2 (3.5) 0.16
Total tibial plateau\
6 months 0.5 (2.4) 4.0 (2.3) 0.02
12 months --1.2 (2.8) 1.7 (2.0) 0.09
24 months --0.7 (1.5) 1.0 (1.1) 0.09

Data are reported as mean (SD)

- For difference between two groups using independent samples *t* test

*HA* hyaluronan, *MPC* mesenchymal precursor cell:::: 

## Effect of MPCs on tibiofemoral joint space width over 24 months Radiological assessments of the mean joint space width of patients when expressed as individual changes from baseline revealed a greater increase in the MPC + HA group than the HA-alone group at 12, 18, and 24 months post-administration (Fig. [3](#), Additional file [6](#): Table S6). In the medial compartment, injection with MPC + HA resulted in a greater joint space width increase compared with the HA-alone group at 18 months (*p* = 0.03) and 24 months (*p* = 0.07) (Fig. [3](#), Additional file [6](#): Table S6). In the lateral compartment, joint space width increased relative to baseline in the MPC + HA group but declined in the HA-alone group. This resulted in significant differences between treatment at 12 months (*p* = 0.01), 18 months (*p* = 0.03), and 24 months (*p* = 0.04) (Fig. [3](#), Additional file [6](#): Table S6). <figure> <p><img src="" /></p> <figcaption>Change from baseline in tibiofemoral joint space width over 24 months (﻿medial joint space width (<strong>a</strong>) and lateral joint space width (<strong>b</strong>)) (mean and 95% confidence interval shown). <em>HA</em> hyaluronan, <em>MPC</em> mesenchymal precursor cell</figcaption> </figure>


Extracted trial result:
Outcome: Knee Injury and Osteoarthritis Outcome Score improvement (continuous)
Intervention: Allogeneic mesenchymal precursor cells
Comparator: Control
Intervention group size: 11
Comparator group size: 6
Notes: Numerical values in figure.