Conclusions
The higher regenerative potential of pulp SP cells may be due to potent trophic factors, including CXCL14 and MCP1, which promote migration and angiogenesis.
Methods
The tooth root transplantation in an ectopic site model was used for investigation of the regenerative potential and trophic effects in vivo. Either pulp CD31(-) SP cell populations (1×10(6) cells) at the third to fourth passage or 5 μg/ml of CM from dental pulp, bone marrow, and adipose stem cells from four different individuals were injected into the root with collagen TE. Each root was transplanted subcutaneously in 5-week-old severe combined immunodeficiency mice. Each root with surrounding tissue was harvested for histology on days 7, 21, and 28 and for Western blot analysis and real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis on day 28. Furthermore, the trophic factors responsible for the regenerative potential were identified as the upregulated genes present in pulp CD31(-) SP cells when compared with the genes in both bone marrow and adipose CD31(-) SP cells by using microarray analysis, real-time RT-PCR, and Western blot analysis.
Results
Transplantation of pulp CM yielded increased volume of pulp regeneration, more bromodeoxyuridine (BrdU)-positive migrated cells, and fewer caspase 3-positive cells in the regenerated pulp compared with the others. Pulp CM also demonstrated significantly increased cell migration, anti-apoptosis, and angiogenesis in C2C12 cells. Higher expression of CXCL14 and MCP1 in pulp SP cells suggested candidate trophic factors. The stimulatory effects on both migration and angiogenesis of CXCL14 and MCP1 were demonstrated in vitro. In the regenerated tissue, BrdU-positive migrated cells expressed CXCR4 and CCR2, receptors for CXCL14 and MCP1, respectively. Conclusions: The higher regenerative potential of pulp SP cells may be due to potent trophic factors, including CXCL14 and MCP1, which promote migration and angiogenesis.