Bone morphogenetic protein 7 mediates stem cells migration and angiogenesis: therapeutic potential for endogenous pulp regeneration

International Journal of Oral Science ARTICLE www.nature.com/ijos OPEN Bone morphogenetic protein 7 mediates stem cells migration and angiogenesis: therapeutic potential for endogenous pulp regeneration 1234567890();,: Cheng Liang1, Qingqing Liang1, Xun Xu1, Xiaojing Liu1, Xin Gao1, Maojiao Li1, Jian Yang1, Xiaotao Xing1, Haisen Huang1, Qi Tang1, Li Liao 1 ✉ and Weidong Tian1 ✉ Pulp loss is accompanied by the functional impairment of defense, sensory, and nutrition supply. The approach based on endogenous stem cells is a potential strategy for pulp regeneration. However, endogenous stem cell sources, exogenous regenerative signals, and neovascularization are major difficulties for pulp regeneration based on endogenous stem cells. Therefore, the purpose of our research is to seek an effective cytokines delivery strategy and bioactive materials to reestablish an ideal regenerative microenvironment for pulp regeneration. In in vitro study, we investigated the effects of Wnt3a, transforming growth factor-beta 1, and bone morphogenetic protein 7 (BMP7) on human dental pulp stem cells (h-DPSCs) and human umbilical vein endothelial cells. 2D and 3D culture systems based on collagen gel, matrigel, and gelatin methacryloyl were fabricated to evaluate the morphology and viability of h-DPSCs. In in vivo study, an ectopic nude mouse model and an in situ beagle dog model were established to investigate the possibility of pulp regeneration by implanting collagen gel loading BMP7. We concluded that BMP7 promoted the migration and odontogenic differentiation of h-DPSCs and vessel formation. Collagen gel maintained the cell adhesion, cell spreading, and cell viability of h-DPSCs in 2D or 3D culture. The transplantation of collagen gel loading BMP7 induced vascularized pulp-like tissue regeneration in vivo. The injectable approach based on collagen gel loading BMP7 might exert promising therapeutic application in endogenous pulp regeneration. International Journal of Oral Science (2022)14:38 INTRODUCTION Dental tissue damage and loss impair oral and general health. Recently, the tissue engineering strategy has been introduced for dental tissue regeneration or bone regeneration.1,2 Many studies have been conducted in the fields of pulp-dentin regeneration and periodontal tissue regeneration. Root canal therapy (RCT) removes the dental pulp suffering severe infection in the mature teeth, which would make the teeth lose nutrition and become fragile.3 Regenerative endodontics procedures (REPs) such as revascularization promote the continued growth of immature roots but resulted in restorative responses rather than physiological pulp tissue regeneration.4 There are growing appeals for pulp regeneration strategy in the clinic.5 Stem cells residing in the dental tissues share the self-renewal and differentiation capacities, which provides a chance for physiological pulp regeneration. The approach triggering the migration and regenerative potentials of endogenous dental stem cells seemed to be a promising choice for clinical translation of pulp regeneration.6 The pulp regeneration based on endogenous stem cells undergoes stem cell migration, proliferation, and odontogenic differentiation. The oriented migration and differentiation of quiescent stem cells surrounding the root apex is the key point, which can be initiated and controlled by exogenous signaling molecules.7 Recently, in an in situ large animal model, ; https://doi.org/10.1038/s41368-022-00188-y Wnt3a, as a developmental signal, induced neo-dentin-like tissue regeneration in the root canal.8 Though the dentin-pulp-like tissue produced excessive mineralization, this finding suggested the possibility of pulp regeneration through reconstructing the regenerative microenvironment with developmental signals in the root canal. During tooth development, a cascade of molecular events including the Wnt, transforming growth factor-beta (TGF-β), and bone morphogenetic protein (BMP) pathways are precisely activated.9 Wnt molecules promote cell growth and osteo/ odontoblastic differentiation10 and mediate stem cell selfrenewal and tooth morphogenesis.11,12 Previous studies have reported that Wnt3a increased mesenchymal stem cell (MSC) proliferation and decreased apoptosis13 and modulated the tertiary dentin formation.14 Compared with Wnt3a, Wnt5a may exert different roles in different tissue-derived cells. One research has reported that wnt5a negatively regulated dental papilla cell proliferation and migration.15 But another research has reported that Wnt5a negatively regulated palate tissue cell proliferation but induced cell migration during palate development.16 Moreover, overexpression of Wnt10a decreased odontoblastic differentiation-related gene expression of dentine sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP-1).17 TGF-β molecules have similar bio-activities and play critical roles in 1 State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases & Engineering Research Center of Oral Translational Medicine, Ministry of Education & National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, China Correspondence: Li Liao () or Weidong Tian () Received: 1 December 2021 Revised: 17 June 2022 Accepted: 19 June 2022 Bone morphogenetic protein 7 mediates stem cells migration and. . . Liang et al. 2 epithelial-mesenchymal interactions and odontoblast maturation.18 TGF-β1 can promote odontoblastic differentiation by upregulating the expression of DSPP and DMP-1.19,20 Moreover, TGF-β1 regulates cell proliferation via Smad2/3 signaling during the tail regeneration in Xenopus tropicalis tadpoles21 and promotes the viability and proliferation of bone marrow-derived MSCs.22 And TGF-β1 and TGF-β2 both induced the synthesis of the collagen matrix in pulp fibroblasts.20 The BMPs play an important role in cell migration and angiogenesis,23,24 and mediate early tooth morphogenesis and mineralization.25 BMP2 and BMP4 display similar potential for osteo/odontogenic differentiation.26 But intense inflammation, ectopic bone formation, osteoclastmediated bone resorption, and inappropriate adipogenesis have been reported in the high-dose application of BMP2.27,28 BMP7 promoted the survival and proliferation of kidney cells and showed great potential for kidney tissue engineering.29 Meanwhile, BMP7 promoted proliferation and tube formation in human umbilical vein endothelial cells (HUVECs).30,31 Though these molecules share the potential on influencing the proliferation, migration, and differentiation abilities in many types of cells,32 the functions of inducing the endogenous stem cell have not been described during pulp regeneration. In light of these foundations of knowledge, we consider Wnt3a, TGF-β1, and BMP7 as candidate molecules for endogenous pulp regeneration. A suitable scaffold is necessary to facilitate the migration, residence, s (...truncated)