Systemic transplantation of stem cells from human exfoliated deciduous teeth (SHED) is used to treat systemic lupus erythematosus (SLE)–like disorders in MRL/lpr mice. However, the mechanisms underlying the SHED-based therapy remain unclear. In this study, we hypothesized that trophic factors within SHED-releasing extracellular vesicles (SHED-EVs) ameliorate the SLE-like phenotypes in MRL/lpr mice. SHED-EVs were isolated from the culture supernatant of SHED. SHED-EVs were treated with or without RNase and systemically administered to MRL/lpr mice. Subsequently, recipient bone marrow mesenchymal stem cells (BMMSCs) isolated from SHED-EV–administered MRL/lpr mice were examined for the in vitro and in vivo activity of hematopoietic niche formation and immunoregulation. Furthermore, the recipient BMMSCs were secondarily transplanted into MRL/lpr mice. The systemic SHED-EV infusion ameliorated the SLE-like phenotypes in MRL/lpr mice and improved the functions of recipient BMMSCs by rescuing Tert mRNA-associated telomerase activity, hematopoietic niche formation, and immunoregulation. The secondary transplantation of recipient BMMSCs recovered the immune condition and renal functions of MRL/lpr mice. The RNase treatment depleted RNAs, such as microRNAs, within SHED-EVs, and the RNA-depleted SHED-EVs attenuated the benefits of SHED-EVs in MRL/lpr mice. Collectively, our findings suggest that SHED-secreted RNAs, such as microRNAs, play a crucial role in treating SLE by targeting the telomerase activity of recipient BMMSCs.

BackgroundStem cells from apical papilla (SCAP) are a subpopulation of mesenchymal stem cells (MSCs) isolated from the apical papilla of the developing tooth root apex of human teeth. Because of their osteogenic/dentinogenic capacity, SCAP are considered as a source for bone and dentin regeneration. However, little is understood about the molecular mechanism of osteogenic/dentinogenic differentiation of SCAP. Phosphoinositide 3 kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) signal pathway participates in regulating the differentiation of various cell types, such as MSCs. In this study, we examined the role of the PI3K-AKT-mTOR signal pathway in the osteogenic/dentinogenic differentiation of SCAP. Moreover, we challenge to fabricate scaffold-free SCAP-based spheroidal calcified constructs.MethodsSCAP were pretreated with or without small interfering RNA for AKT (AKT siRNA), PI3K inhibitor LY294402, and mTOR inhibitor rapamycin and were cultured under osteogenic/dentinogenic differentiation to examine in vitro and in vivo calcified tissue formation. Moreover, SCAP-based cell aggregates were pretreated with or without LY294402 and rapamycin. The cell aggregates were cultured under osteogenic/dentinogenic condition and were analyzed the calcification of the aggregates.ResultsPretreatment with AKT siRNA, LY294402, and rapamycin enhances the in vitro and in vivo calcified tissue-forming capacity of SCAP. SCAP were fabricated as scaffold-free spheroids and were induced into forming calcified 3D constructs. The calcified density of the spheroidal constructs was enhanced when the spheroids were pretreated with LY294402 and rapamycin.ConclusionsOur findings indicate that the suppression of PI3K-AKT-mTOR signal pathway plays a role in not only enhancing the in vivo and in vitro osteogenic/dentinogenic differentiation of SCAP, but also promoting the calcification of scaffold-free SCAP-based calcified constructs. These findings suggest that a suppressive regulation of PI3K-AKT-mTOR signal pathway is a novel approach for SCAP-based bone and dentin regeneration.Electronic supplementary materialThe online version of this article (10.1186/s13287-018-1077-9) contains supplementary material, which is available to authorized users.

Background: Systemic transplantation of stem cells from human exfoliated deciduous teeth (SHED) recovers bone loss in animal models of osteoporosis; however, the mechanisms underlying this remain unclear. Here, we hypothesized that trophic factors within SHED-releasing extracellular vesicles (SHED-EVs) rescue osteoporotic phenotype. Methods: EVs were isolated from culture supernatant of SHED. SHED-EVs were treated with or without ribonuclease and systemically administrated into ovariectomized mice, followed by the function of recipient bone marrow mesenchymal stem cells (BMMSCs) including telomerase activity, osteoblast differentiation, and sepmaphorine-3A (SEMA3A) secretion. Subsequently, human BMMSCs were stimulated by SHED-EVs with or without ribonuclease treatment, and then human BMMSCs were examined regarding the function of telomerase activity, osteoblast differentiation, and SEMA3A secretion. Furthermore, SHED-EV-treated human BMMSCs were subcutaneously transplanted into the dorsal skin of immunocompromised mice with hydroxyapatite tricalcium phosphate (HA/TCP) careers and analyzed the de novo bone-forming ability. Results: We revealed that systemic SHED-EV-infusion recovered bone volume in ovariectomized mice and improved the function of recipient BMMSCs by rescuing the mRNA levels of Tert and telomerase activity, osteoblast differentiation, and SEMA3A secretion. Ribonuclease treatment depleted RNAs, including microRNAs, within SHED-EVs, and these RNA-depleted SHED-EVs attenuated SHED-EV-rescued function of recipient BMMSCs in the ovariectomized mice. These findings were supported by in vitro assays using human BMMSCs incubated with SHED-EVs. Conclusion: Collectively, our findings suggest that SHED-secreted RNAs, such as microRNAs, play a crucial role in treating postmenopausal osteoporosis by targeting the telomerase activity of recipient BMMSCs.

No abstract

Background: Systemic transplantation of stem cells from human exfoliated deciduous teeth (SHED) induces bone regeneration in animal models of osteoporosis; however, the mechanisms underlying this remain unclear. Here, we hypothesized that trophic factors within SHED-releasing extracellular vesicles (SHED-EVs) rescue osteoporotic phenotype.Methods: EVs were isolated from culture supernatant of SHED. SHED-EVs were treated with or without ribonuclease and systemically administrated into ovariectomized mice, followed by the measurement of bone regenerative function of recipient bone marrow mesenchymal stem cells (BMMSCs) including Tert expression. Subsequently, human BMMSCs were stimulated by SHED-EVs with or without ribonuclease treatment, and then human BMMSCs were examined osteogenic function in vitro and telomerase activity. Furthermore, SHED-EVs treated human BMMSCs were subcutaneously transplanted into dorsal skin of immunocompromised mice with hydroxyapatite tricalcium phosphate (HA/TCP) careers and analyzed the de novo bone forming ability.Results: We revealed that systemic SHED-EV-infusion recovered bone volume in ovariectomized mice and improved osteogenic function of recipient BMMSCs by rescuing the mRNA levels of Tert and telomerase activity. Ribonuclease treatment depleted RNAs, including microRNAs, within SHED-EVs and these RNA-depleted SHED-EVs attenuated SHED-EV-triggered bone regeneration and telomerase-mediated osteogenesis in the ovariectomized mice. These findings were supported by in vitro osteogenic assays using human BMMSCs incubated with SHED-EVs.Conclusion: Collectively, our findings suggest that SHED-secreted trophic factors, specifically microRNAs, play a crucial role in treating postmenopausal osteoporosis by targeting the telomerase activity of recipient BMMSCs.