HIF-1α Overexpression Using a Protein Transduction Domain to Increase the Osteogenic Potential of SHED

Abstract

Background: Hypoxia-Inducible Factor 1 (HIF-1) alpha (HIF-1α) is known to be expressed in hypoxia and affects stemness and bone differentiation. Protein Transduction Domains (PTDs) safely and effectively deliver proteins into cells. This study combined HIF-1α delta Oxygen-Dependent Degradation Domain–Transcription Modulation Domain (ntHIF-1α-ΔODD-TMD) with the PTD and then used it to treat Stem cells from Human Exfoliated Deciduous teeth (SHED) to determine its effect on stemness and bone differentiation. Methods: The SHED were treated using PDT-conjugated ntHIF-1α-ΔODD-TMD, and its effects on STRO-1 expression, cytotoxicity, stemness-related gene expression, and osteogenic differentiation were confirmed. These were also transferred to 5-week-old mice in order to confirm the effects in vivo after recellularization of SHED treated using ntHIF-1α-ΔODD-TMD on decellularized tooth specimens. After 9 weeks, they were sacrificed to confirm the expression of genes related to bone differentiation and angiogenesis. Results: ntHIF-1α-ΔODD-TMD increased the expression levels of STRO-1, HIF-1α-related genes, and stemness-related genes in SHED. Osteogenic differentiation was also increased both in vitro and in vivo. Conclusion: These results suggest that ntHIF-1α-ΔODD-TMD maintains or increases the stemness of SHED and also increases the osteogenic potential. SHED have previously been found to have excellent proliferative but low differentiation capacities compared with other cells. However, properly using ntHIF-1α-ΔODD-TMD increases the osteogenic potential of SHED, indicating the potential of using SHED as a useful source for hard-tissue regeneration.