Effects of canine myoblasts expressing human cartilage-derived morphogenetic protein-2 on the repair of meniscal fibrocartilage injury

The aim of the present study was to explore the effects of human cartilage-derived morphogenetic protein-2 (hCDMP-2)-expressing canine myoblasts on the repair of meniscal fibrocartilage injury. Purified canine myoblasts were infected with lentiviruses carrying an empty vector or the hCDMP-2 gene. The following four experimental groups were established to study the in vivo meniscal repair in a canine model of meniscal injury: Group A, suture only; group B, suture with the addition of the recombinant hCDMP-2 on a polylactic acid/polyglycolic acid (PLA/PGA) scaffold; group C, a PLA/PGA scaffold with canine myoblasts carrying the empty vector; and group D, a PLA/PGA scaffold with canine myoblasts expressing hCDMP-2. Samples of the regenerated tissue were extracted at weeks 3, 8 and 12 post-repair and analyzed by morphological observation, immunohistochemistry (IHC) and quantitative analysis. At week 12 post-repair, the scaffold material had completely dissolved in the control groups and no changes were observed at the injured area, while regenerated tissue was observed in group D only. Hematoxylin and eosin and Safranin-O staining techniques further revealed cartilage lacunae and fibers present at the red-red zone of the repaired tissue, while cartilage lacunae without fibers were observed at the white-white zone in group D. In addition, IHC studies demonstrated that collagen I and II, and the S-100 protein were expressed at the red-red and the white-white zones of the repaired tissue in group D. It was concluded that purified canine myoblasts expressing the hCDMP-2 gene were able to promote meniscal fibrocartilage healing by regenerating fibrocartilage-like tissue. The tissue in the red-red zone was regenerated more rapidly than that in the white-white zone. Further studies are required to identify the best way to combine hCDMP-2 growth factor with myoblasts for use in the clinic due to the limitations regarding the clinical use of lentiviral infections.