Background: Bone marrow-derived mesenchymal stem cells (BMSCs) are a widely researched adult stem cell population capable of differentiation into various lineages. Because many promising applications of tissue engineering require cell expansion following harvest and involve the treatment of diseases and conditions found in an aging population, the effect of donor age and ex vivo handling must be understood in order to develop clinical techniques and therapeutics based on these cells. Furthermore, there currently exists little understanding as to how these two factors may be influenced by one another.

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Schwann cells (SCs) in animals exist in different developmental stages or wound repair phases, distinguished mainly by the expression of SC-specific markers. No study has yet determined SC state under in vitro culture conditions, and the specific markers expressed in SC are obscure as well. In this study, we harvested sciatic nerves from newborn mice and isolated SCs by an enzyme-digestion method, then we examined the expression profiles of ten markers (S100, p75NTR, Sox10, Sox2, GAP43, NCAM, Krox20, Oct6, MBP, and MPZ) at both the RNA and protein levels in in vitro mouse SCs and speculated their relation with in vivo SC stages. We assayed RNA and protein levels of SC specific markers by immunofluorescence, Western Blot, and real-time quantitative RT-PCR. The results show that the expression of most markers (S100, p75NTR, GAP43, NCAM, Krox20, Oct6, MBP and MPZ) was not detectable in all of early stage cultured SCs. The expression of transcription factors Sox10 and Sox2 was, however, detectable in all SCs. After 8 days, the positive expression rate of all markers except GAP43 and Oct6 was almost 100%.These results indicates Sox10 is a necessary marker for SC identification, while S100 is not reliable. SCs cultured in vitro express Sox2, P75NTR, NCAM, GAP43, Oct6, and MPZ, suggesting that they are similar to in vivo undifferentiated iSCs or dedifferentiated iSCs after nerve injury.

Dentin‐pulp complex regeneration is a promising alternative treatment for the irreversible pulpitis caused by tooth trauma or dental caries. This process mainly relies on the recruitment of endogenous or the transplanted dental pulp stem cells (DPSCs) to guide dentin‐pulp tissue formation. Platelet‐derived growth factor (PDGF), a well‐known potent mitogenic, angiogenic, and chemoattractive agent, has been widely used in tissue regeneration. However, the mechanisms underlying the therapeutic effects of PDGF on dentin‐pulp complex regeneration are still unclear. In this study, we tested the effect of PDGF‐BB on dentin‐pulp tissue regeneration by establishing PDGF‐BB gene‐modified human dental pulp stem cells (hDPSCs) using a lentivirus. Our results showed that PDGF‐BB can significantly enhance hDPSC proliferation and odontoblastic differentiation. Furthermore, PDGF‐BB and vascular endothelial growth factor (VEGF) secreted by hDPSCs enhanced angiogenesis. The chemoattractive effect of PDGF‐BB on hDPSCs was also confirmed using a Transwell chemotactic migration model. We further determined that PDGF‐BB facilitates hDPSCs migration via the activation of the phosphatidylinositol 3 kinase (PI3K)/Akt signaling pathway. In vivo, CM‐DiI‐labeled hDPSCs were injected subcutaneously into mice, and our results showed that more labeled cells were recruited to the sites implanted with calcium phosphate cement scaffolds containing PDGF‐BB gene‐modified hDPSCs. Finally, the tissue‐engineered complexes were implanted subcutaneously in mice for 12 weeks, the Lenti‐PDGF group generated more dentin‐like mineralized tissue which showed positive staining for the DSPP protein, similar to tooth dentin tissue, and was surrounded by highly vascularized dental pulp‐like connective tissue. Taken together, our data demonstrated that the PDGF‐BB possesses a powerful function in prompting stem cell‐based dentin‐pulp tissue regeneration. Stem Cells Translational Medicine 2017;6:2126–2134