Hypoxia modulates the differentiation potential of stem cells of the apical papilla (SCAP)

Introduction: Stem cells from the apical papilla (SCAP) are a population of mesenchymal stem cells likely involved in regenerative endodontic procedures, and of potential use as therapeutic agents in other tissues. In these situations, SCAP are exposed to hypoxic conditions either within a root canal devoid of an adequate blood supply or in a scaffold material immediately after implantation. However, the effect of hypoxia on SCAP proliferation and differentiation is largely unknown. Therefore, the objective of this study was to evaluate the effect of hypoxia on SCAP fate. Methods: SCAP were cultured under normoxia (21%O2) or hypoxia (1%O2), in basal or differentiation media. Cellular proliferation, gene expression, differentiation and protein secretion were analyzed by live imaging, qRT-PCR, cellular staining and ELISA, respectively. Results: Hypoxia had no effect on SCAP proliferation, but it evoked the upregulation of genes specific for osteogenic differentiation (RUNX2, ALP, TGF β1), neuronal differentiation (CNP, SNAIL, NSE, GDNF, NT3), and angiogenesis (VEGFA, VEGFB). Hypoxia also increased the sustained production of VEGFa by SCAP. Moreover, hypoxia augmented the neuronal differentiation of SCAP in presence of differentiation exogenous factors as detected by the up-regulation of NSE, VEGFB and GDNF and the expression of neuronal markers (PanF and NeuN). Conclusion: This study demonstrates that hypoxia induces spontaneous differentiation of SCAP into osteogenic and neurogenic lineages while maintaining the release of the pro-angiogenic factor VEGFa. This highlights the potential of SCAP to promote pulp-dentin regeneration. Moreover, SCAP may represent potential therapeutic agents for neurodegenerative conditions due to their robust differentiation potential