Transplantation of mesenchymal stem cells (MSCs) is effective in decelerating
disc degeneration in small animals; much remains unknown about this new
therapy in larger animals or humans.
Fas-ligand (FasL), which is only found in tissues with isolated immune privilege, is expressed in IVDs, particularly in the nucleus pulposus (NP). Maintaining the FasL level is important for IVD function. This study evaluated whether MSC
transplantation has an effect on the suppression of
disc degeneration and preservation of immune privilege in a canine model of
disc degeneration. Mature beagles were separated into a normal control group (NC), a MSC group, and the
disc degeneration (nucleotomy-only) group. In the MSC group, 4 weeks after nucleotomy, MSCs were transplanted into the degeneration-induced discs. The animals were followed for 12 weeks after the initial operation. Subsequently, radiological, histological, biochemical, immunohistochemical, and RT-PCR analyses were performed. MSC
transplantation effectively led to the regeneration of degenerated discs. FACS and RT-PCR analyses of MSCs before
transplantation demonstrated that the MSCs expressed FasL at the genetic level, not at the
protein level. GFP-positive MSCs detected in the NP region 8 weeks after
transplantation expressed
FasL protein. The results of this study suggest that MSC
transplantation may contribute to the maintenance of IVD immune privilege by the differentiation of transplanted MSCs into cells expressing FasL.