Dental Follicle Cells Rescue the Regenerative Capacity of Periodontal Ligament Stem Cells in an Inflammatory Microenvironment

Aims: Periodontal ligament stem cells (PDLSCs) are one of the best candidates for periodontal regeneration. Their function could be impaired in periodontitis microenvironment. Dental follicle cells (DFCs), serving as precursor cells and mesenchymal stem cells, have intimate connection with PDLSCs. However, it is still unknown whether DFCs could provide a favorable microenvironment to improve the proliferation and differentiation capacity of PDLSCs from healthy subjects (HPDLSCs) and patients diagnosed with periodontitis (PPDLSCs). Methods: HPDLSCs, PPDLSCs and DFCs were harvested and identified using microscopic and flow cytometric analysis. Then, the coculture systems of DFCs/HPDLSCs and DFCs/PPDLSCs were established with 0.4 mu m transwell, in which all the detection indexs were obtained from HPDLSCs and PPDLSCs. The expression of stemness-associated genes was detected by real-time PCR, and the proliferation ability was assessed using colony formation and cell cycle assays. The osteogenic differentiation capacity was evaluated by real-time PCR, western blot, ALP activity, Alizarin Red S staining and calcium level analysis, while the adipogenic differentiation capacity was determined by real-time PCR and Oil Red O staining. The cell sheet formation in vitro was observed by HE staining and SEM, and the implantation effect in vivo was evaluated using HE staining and Masson's trichrome staining. Results: PPDLSCs had a greater proliferation capability but lower osteogenic and adipogenic potential than HPDLSCs. DFCs enhanced the proliferation and osteogenic/adipogenic differentiation of HPDLSCs and PPDLSCs to different degrees. Moreover, coculture with DFCs increased cell layers and extracellular matrix of HPDLSCs/PPDLSCs cell sheets in vitro and improved periodontal regeneration by HPDLSCs/PPDLSCs in vivo. Conclusions: Our data suggest that the function of PPDLSCs could be damaged in the periodontitis microenvironment. DFCs appear to enhance the self-renewal and multi-differentiation capacity of both HPDLSCs and PPDLSCs, which indicates that DFCs could provide a beneficial microenvironment for periodontal regeneration using PDLSCs.