Pulp necrosis arrests root development in injured immature permanent teeth, which may result in tooth loss. However, dental pulp regeneration and promotion of root development remains challenging. We show that implantation of autologous tooth stem cells from deciduous teeth regenerated dental pulp with an odontoblast layer, blood vessels, and nerves in two animal models. These results prompted us to enroll 40 patients with pulp necrosis after traumatic dental injuries in a randomized, controlled clinical trial. We randomly allocated 30 patients to the human deciduous pulp stem cell (hDPSC) implantation group and 10 patients to the group receiving traditional apexification treatment. Four patients were excluded from the implantation group due to loss at follow-up (three patients) and retrauma of the treated tooth (one patient). We examined 26 patients (26 teeth) after hDPSC implantation and 10 patients (10 teeth) after apexification treatment. hDPSC implantation, but not apexification treatment, led to regeneration of three-dimensional pulp tissue equipped with blood vessels and sensory nerves at 12 months after treatment. hDPSC implantation increased the length of the root (P < 0.0001) and reduced the width of the apical foramen (P < 0.0001) compared to the apexification group. In addition, hDPSC implantation led to regeneration of dental pulp tissue containing sensory nerves. To evaluate the safety of hDPSC implantation, we followed 20 patients implanted with hDPSCs for 24 months and did not observe any adverse events. Our study suggests that hDPSCs are able to regenerate whole dental pulp and may be useful for treating tooth injuries due to trauma.

Extracellular vesicles (EVs) derived from living cells play important roles in donor cell-induced recipient tissue regeneration. Although numerous studies have found that cells undergo apoptosis after implantation in an ischemic-hypoxic environment, the roles played by the EVs released by apoptotic cells are largely unknown. In this study, we obtained apoptotic vesicles (apoVs) derived from human deciduous pulp stem cells and explored their effects on the dental pulp regeneration process. Our work showed that apoVs were ingested by endothelial cells (ECs) and elevated the expression of angiogenesis-related genes, leading to pulp revascularization and tissue regeneration. Furthermore, we found that, at the molecular level, apoV-carried mitochondrial Tu translation elongation factor was transported and regulated the angiogenic activation of ECs via the transcription factor EB-autophagy pathway. In a beagle model of dental pulp regeneration in situ, apoVs recruited endogenous ECs and facilitated the formation of dental-pulp-like tissue rich in blood vessels. These findings revealed the significance of apoptosis in tissue regeneration and demonstrated the potential of using apoVs to promote angiogenesis in clinical applications.

Objectives: Pulp regeneration brings big challenges for clinicians, and vascularization is considered as its determining factor. We previously accomplished pulp regeneration with autologous stem cells from deciduous teeth (SHED) aggregates implantation in teenager patients, however, the underlying mechanism needs to be clarified for regenerating pulp in adults. Serving as an important effector of mesenchymal stem cells (MSCs), exosomes have been reported to promote angiogenesis and tissue regeneration effectively. Here, we aimed to investigate the role of SHED aggregate‐derived exosomes (SA‐Exo) in the angiogenesis of pulp regeneration.Materials and Methods: We extracted exosomes from SHED aggregates and utilized them in the pulp regeneration animal model. The pro‐angiogenetic effects of SA‐Exo on SHED and human umbilical vein endothelial cells (HUVECs) were evaluated. The related mechanisms were further investigated.Results: We firstly found that SA‐Exo significantly improved pulp tissue regeneration and angiogenesis in vivo. Next, we found that SA‐Exo promoted SHED endothelial differentiation and enhanced the angiogenic ability of HUVECs, as indicated by the in vitro tube formation assay. Mechanistically, miR‐26a, which is enriched in SA‐Exo, improved angiogenesis both in SHED and HUVECs via regulating TGF‐β/SMAD2/3 signalling.Conclusions: In summary, these data reveal that SA‐Exo shuttled miR‐26a promotes angiogenesis via TGF‐β/SMAD2/3 signalling contributing to SHED aggregate‐based pulp tissue regeneration. These novel insights into SA‐Exo may facilitate the development of new strategies for pulp regeneration.

Harnessing developmental processes for tissue engineering represents a promising yet challenging approach to regenerative medicine. Tooth avulsion is among the most serious traumatic dental injuries, whereas functional tooth regeneration remains uncertain. Here, we established a strategy using decellularized tooth matrix (DTM) combined with human dental pulp stem cell (hDPSC) aggregates to simulate an odontogenesis-related developmental microenvironment. The bioengineered teeth reconstructed by this strategy regenerated three-dimensional pulp and periodontal tissues equipped with vasculature and innervation in a preclinical pig model after implantation into the alveolar bone. These results prompted us to enroll 15 patients with avulsed teeth after traumatic dental injuries in a pilot clinical trial. At 12 months after implantation, bioengineered teeth led to the regeneration of functional teeth, which supported continued root development, in humans. Mechanistically, exosomes derived from hDPSC aggregates mediated the tooth regeneration process by upregulating the odontogenic and angiogenic ability of hDPSCs. Our findings suggest that odontogenic microenvironment engineering by DTM and stem cell aggregates initiates functional tooth regeneration and serves as an effective treatment for tooth avulsion.

Inflammation plays a crucial role in triggering regeneration, while inadequate or chronic inflammation hinders the regenerative process, resulting in refractory wounds. Inspired by the ideal regeneration mode in lower vertebrates and the human oral mucosa, realigning dysregulated inflammation to a heightened and acute response provides a promising option for refractory wound therapy. Neutrophils play important roles in inflammation initiation and resolution. Here, a hybrid biomaterial is used to stimulate transiently heightened inflammatory responses by precise tempospatial regulation of neutrophil recruitment and apoptosis. The hybrid biomaterial (Gel@fMLP/SiO₂‐FasL) is constructed by loading of formyl‐met‐leu‐phe (fMLP) and FasL‐conjugated silica nanoparticles (SiO₂‐FasL) into a pH‐responsive hydrogel matrix. This composition enables burst release of fMLP to rapidly recruit neutrophils for heightened inflammation initiation. After neutrophils act to produce acids, the pH‐responsive hydrogel degrades to expose SiO₂‐FasL, which induces activated neutrophils apoptosis via FasL‐Fas signaling triggering timely inflammation resolution. Apoptotic neutrophils are subsequently cleared by macrophages, and this efferocytosis activates key signalings to promote macrophage anti‐inflammatory phenotypic transformation to drive regeneration. Ultimately, Gel@fMLP/SiO₂‐FasL successfully promotes tissue regeneration by manipulating inflammation in critical‐sized calvarial bone defects and diabetic cutaneous wound models. This work provides a new strategy for refractory wound therapy via inducing transiently heightened inflammatory responses.

The interplay between bacteria and their host influences the homeostasis of the human immune microenvironment, and this reciprocal interaction also affects the process of tissue damage repair. A variety of immunomodulatory commensal bacteria reside in the body, capable of delivering membrane vesicles (MVs) to host cells to regulate the local immune microenvironment. This research revealed, for the initial time, the significant enhancement of mucosal and cutaneous wound healing by MVs secreted by the human commensal Lactobacillus reuteri (RMVs) through modulation of the inflammatory environment in wound tissue. Local administration of RMVs reduces the proportion of pro‐inflammatory macrophages in inflamed tissues and mitigates the level of local inflammation, thereby facilitating the healing of oral mucosa and cutaneous wounds. The elevated oxidative stress levels in activated pro‐inflammatory macrophages can be modulated by RMVs, resulting in phenotypic transformation of macrophages. Furthermore, 3‐hydroxypropionaldehyde present in RMVs can decrease the mitochondrial permeability of macrophages and stabilize the mitochondrial membrane potential, thereby promoting the conversion of macrophages to an anti‐inflammatory phenotype. This study pioneers the significance of commensal bacterial MVs in tissue injury repair and presents a novel concept for the repair of tissue damage.