CBX7 Rejuvenates Late Passage Dental Pulp Stem Cells by Maintaining Stemness and Pro-angiogenic Ability

Background: Ever-growing tissue regeneration causes pressing need for large population of stem cells. However, extensive cell expansion eventually leads to impaired regenerative potentials. In this study, chromobox protein homolog 7 (CBX7) was overexpressed to rejuvenate late passage dental pulp stem cells (DPSCs-P9). Methods: The recruitment of copper ions (Cu 2+ )-activated hypoxia-inducible factor-1α (HIF-1α) to the CBX7 gene promoter was confirmed by chromatin immunoprecipitation assay. Functions subsequent to Cu 2+ -induced or recombinant overexpression of CBX7 on proliferation, multipotency, odontoblastic differentiation and angiogenesis were investigated in vitro , while murine subcutaneous transplantation model was used to further detect the effects of Cu 2+ -induced CBX7 overexpression in vivo . Results: Our data displayed that CBX7 overexpression maintain proliferation and multipotency of DPSCs-P9 almost as strong as those of DPSCs-P3. Both gene level of odontoblast-lineage markers and calcium precipitation were nearly the same between CBX7 overexpressed DPSCs-P9 and normal DPSCs-P3. Moreover, we also found upregulated expression of vascular endothelial growth factor in DPSCs-P9 with CBX7 overexpression, which increased the number of capillary-like structures and migrating co-cultured human umbilical vein endothelial cells as well. These findings indicate CBX7 as an effective factor to rejuvenate late passage stem cells insusceptible to cell expansion. Cu 2+ has been proved to achieve CBX7 overexpression in DPSCs through the initiation of HIF-1α-CBX7 cascade. Under Cu 2+ stimulation since P3, DPSCs-P9 exhibited ameliorated regenerative potential both in vitro and in vivo . Conclusion: Long-term stimulation of Cu 2+ to overexpress CBX7 could be a new strategy to manufacture large population of self-renewing stem cells.