Growth differentiation factor 5 improves meniscal healing in a pilot study on rats.

PURPOSE: Meniscus injuries are common, but failed repairs remain an issue. The aim of this study was to demonstrate, in an in vivo rat model, the ability of growth differentiation factor 5 (GDF5) to improve meniscal tear healing. METHODS: Eight Lewis rats (four females and four males) underwent radial tear of the medial meniscus on the right knee. There were two post-operative treatments: the GDF5 group (n = 4) received 0.1 mg/mL of GDF5, and the saline group (n = 4) a saline injection. The eight left knees were the control without surgery. Sacrifice was six weeks post-operatively. The GDF5 and saline groups were compared according to histology and meniscus healing score (MHS) in different zones: red-red (R-R), red-white (R-W) and white-white (W-W). RESULTS: In the R-R zone, the median [interquartile range, IQR] MHS was 2.5 [2-3] in the GDF5 group and 2 [1.25-2] in the saline group (p = 0.200), and in the W-R zone it was 2 [2-2.75] for GDF5 and 1 [1-1.75] for saline (p = 0.047). There was no difference in the W-W zone (median MHS under one; p = 0.686). Regardless of groups, median [IQR] MHS in R-R (2 [2-2.75]) and R-W zones (2 [1-2]) were significantly higher (p < 0.001) than in the W-W zone (0 [0-1]). MHS intraclass correlation coefficient inter-observer was 0.88 and intra-observer was 0.90. CONCLUSIONS: GDF5 increases meniscal healing, especially in the R-W zone, although the W-W zone remains challenging. GFD5 is a promising factor for improving meniscus healing. The small sample size and absence of biomechanical evaluation are limitations that warrant caution when interpreting these findings. Further studies with larger sample sizes in larger animal models, combined with meniscal repair, are required to confirm these preliminary results. STUDY DESIGN: Animal laboratory study. LEVEL OF EVIDENCE: Level V, animal study.