Schwann Cells Contribute to Alveolar Bone Regeneration by Promoting Cell Proliferation

Early infiltrating NKT lymphocytes attenuate bone regeneration through secretion of CXCL2

Trauma rapidly mobilizes the immune response of surrounding tissues and activates regeneration program. Manipulating immune response to promote tissue regeneration shows a broad application prospect. However, the understanding of bone healing dynamics at cellular level remains limited. Here, we characterize the landscape of immune cells after alveolar bone injury and reveal a pivotal role of infiltrating natural killer T (NKT) cells. We observe a rapid increase in NKT cells after injury, which inhibit osteogenic differentiation of mesenchymal stem cells (MSCs) and impair alveolar bone healing. Cxcl2 is up-regulated in NKT cells after injury. Systemic administration of CXCL2-neutralizing antibody or genetic deletion of Cxcl2 improves the bone healing process. In addition, we fabricate a gelatin-based porous hydrogel to deliver NK1.1 depletion antibody, which successfully promotes alveolar bone healing. In summary, our study highlights the importance of NKT cells in the early stage of bone healing and provides a potential therapeutic strategy for accelerating bone regeneration.

Interaction between immuno-stem dual lineages in jaw bone formation and injury repair

The jawbone, a unique structure in the human body, undergoes faster remodeling than other bones due to the presence of stem cells and its distinct immune microenvironment. Long-term exposure of jawbones to an oral environment rich in microbes results in a complex immune balance, as shown by the higher proportion of activated macrophage in the jaw. Stem cells derived from the jawbone have a higher propensity to differentiate into osteoblasts than those derived from other bones. The unique immune microenvironment of the jaw also promotes osteogenic differentiation of jaw stem cells. Here, we summarize the various types of stem cells and immune cells involved in jawbone reconstruction. We describe the mechanism relationship between immune cells and stem cells, including through the production of inflammatory bodies, secretion of cytokines, activation of signaling pathways, etc. In addition, we also comb out cellular interaction of immune cells and stem cells within the jaw under jaw development, homeostasis maintenance and pathological conditions. This review aims to eclucidate the uniqueness of jawbone in the context of stem cell within immune microenvironment, hopefully advancing clinical regeneration of the jawbone.

Periplaneta americana extract promotes hard palate mucosal wound healing via the PI3K/AKT signaling pathway in male mice

OBJECTIVES

This study aimed to investigate the effect of Periplaneta americana extract, a traditional Chinese medicine, on hard palate mucosal wound healing and explore the underlying mechanisms.

DESIGN

Hard palate mucosal wound model was established and the effects of Periplaneta americana extract on hard palate mucosal wound healing were investigated by stereomicroscopy observation and histological evaluation in vivo. Human oral keratinocytes and human gingival fibroblasts, which play key roles in hard palate mucosal wound healing, were selected as the main research cells in vitro. The effects of Periplaneta americana extract on cell proliferation, migration, and collagen formation were determined by cell counting kit-8 (CCK-8) assay, Transwell assay, and Van Gieson staining. The underlying mechanism was revealed by RNA sequencing, and results were verified by western blot assay.

RESULTS

Stereomicroscopy observation and H&E staining confirmed that Periplaneta americana extract accelerated the healing rate of hard palate mucosal wound (p < 0.001) in vivo. Transwell assay and Van Gieson staining assay showed that Periplaneta americana extract promoted the migration and collagen formation of human oral keratinocytes (p < 0.001) and human gingival fibroblasts (p < 0.001) in vitro. Mechanistically, RNA sequencing and western blot assay demonstrated that Periplaneta americana extract promoted hard palate mucosal wound healing via PI3K/AKT signaling, and the beneficial effects of Periplaneta americana extract were abrogated by the PI3K inhibitor LY294002.

CONCLUSIONS

Periplaneta americana extract shows promising effects for the promotion of hard palate mucosal wound healing and may be a novel candidate for clinical translation.

IFT80 promotes early bone healing of tooth sockets through the activation of TAZ/RUNX2 pathway

Intraflagellar transport (IFT) proteins have been reported to regulate cell growth and differentiation as the essential functional component of primary cilia. The effects of IFT80 on early bone healing of extraction sockets have not been well studied. To investigate whether deletion of Ift80 in alveolar bone-derived mesenchymal stem cells (aBMSCs) affected socket bone healing, we generated a mouse model of specific knockout of Ift80 in Prx1 mesenchymal lineage cells (Prx1Cre ;IFT80f/f ). Our results demonstrated that deletion of IFT80 in Prx1 lineage cells decreased the trabecular bone volume, ALP-positive osteoblastic activity, TRAP-positive osteoclastic activity, and OSX-/COL I-/OCN-positive areas in tooth extraction sockets of Prx1Cre ; IFT80f/f mice compared with IFT80f/f littermates. Furthermore, aBMSCs from Prx1Cre ; IFT80f/f mice showed significantly decreased osteogenic markers and downregulated migration and proliferation capacity. Importantly, the overexpression of TAZ recovered significantly the expressions of osteogenic markers and migration capacity of aBMSCs. Lastly, the local administration of lentivirus for TAZ enhanced the expression of RUNX2 and OSX and promoted early bone healing of extraction sockets from Prx1Cre ; IFT80f/f mice. Thus, IFT80 promotes osteogenesis and early bone healing of tooth sockets through the activation of TAZ/RUNX2 pathway.

Role of the Peripheral Nervous System in Skeletal Development and Regeneration: Controversies and Clinical Implications

PURPOSE OF REVIEW

This review examines the diverse functional relationships that exist between the peripheral nervous system (PNS) and bone, including key advances over the past century that inform our efforts to translate these discoveries for skeletal repair.

RECENT FINDINGS

The innervation of the bone during development, homeostasis, and regeneration is highly patterned. Consistent with this, there have been nearly 100 studies over the past century that have used denervation approaches to isolate the effects of the different branches of the PNS on the bone. Overall, a common theme of balance emerges whereby an orchestration of both local and systemic neural functions must align to promote optimal skeletal repair while limiting negative consequences such as pain. An improved understanding of the functional bidirectional pathways linking the PNS and bone has important implications for skeletal development and regeneration. Clinical advances over the next century will necessitate a rigorous identification of the mechanisms underlying these effects that is cautious not to oversimplify the in vivo condition in diverse states of health and disease.