Immunomodulatory properties and in vivo osteogenesis of human dental stem cells from fresh and cryopreserved dental follicles

Abstract

In our previous study, dental follicle tissues from extracted wisdom teeth were successfully cryopreserved for use as a source of stem cells. The goals of the present study were to investigate the immunomodulatory properties of stem cells from fresh and cryopreserved dental follicles (fDFCs and cDFCs, respectively) and to analyze in vivo osteogenesis after transplantation of these DFCs into experimental animals. Third passage fDFCs and cDFCs showed similar expression levels of interferon-γ receptor (CD119) and major histocompatibility complex class I and II (MHC I and MHC II, respectively), with high levels of CD119 and MHC I and nearly no expression of MHC II. Both fresh and cryopreserved human DFCs (hDFCs) were in vivo transplanted along with a demineralized bone matrix scaffold into mandibular defects in miniature pigs and subcutaneous tissues of mice. Radiological and histological evaluations of in vivo osteogenesis in hDFC-transplanted sites revealed significantly enhanced new bone formation activities compared with those in scaffold-only implanted control sites. Interestingly, at 8 weeks post-hDFC transplantation, the newly generated bones were overgrown compared to the original size of the mandibular defects, and strong expression of osteocalcin and vascular endothelial growth factor were detected in the hDFCs-transplanted tissues of both animals. Immunohistochemical analysis of CD3, CD4, and CD8 in the ectopic bone formation sites of mice showed significantly decreased CD4 expression in DFCs-implanted tissues compared with those in control sites. These findings indicate that hDFCs possess immunomodulatory properties that involved inhibition of the adaptive immune response mediated by CD4 and MHC II, which highlights the usefulness of hDFCs in tissue engineering. In particular, long-term preserved dental follicles could serve as an excellent autologous or allogenic stem cell source for bone tissue regeneration as well as a valuable therapeutic agent for immune diseases.