Biology subjects

Hokugo, A.

Publications and source records attributed to Hokugo, A..

4 recordsLinked to original sources

bioRxiv2026

Single-cell RNA sequencing reveals collagen interactions between detached osteoclasts and activated fibroblasts in granulation tissue surrounding sequestra in medication-related osteonecrosis of the jaw

ObjectivesMedication-related osteonecrosis of the jaw (MRONJ) is a rare but serious complication of anti-resorptive agents used for osteoporosis and bone metastasis. As the global population ages, the number of patients with MRONJ continues to rise. Resorptive osteoclasts firmly attached to bone surfaces cannot be detected using single-cell RNA-Seq (scRNA-Seq); however, we hypothesized that multinucleated giant and detached osteoclasts (DetOCs) can be detected by this method. This study aimed to characterize DetOCs with scRNA-seq. Materials and MethodsscRNA-Seq and immunohistochemistry staining was performed on granulation tissues surrounding sequestra from four patients with MRONJ and radicular cysts, a common odontogenic infectious disease with normal bone metabolism. ResultsscRNA-Seq and immunohistochemistry staining revealed that DetOCs were detected exclusively in the granulation tissues of MRONJ. These DetOCs expressed well-known osteoclast markers as well as COL27A1. Subcluster analysis revealed that SPP1+ TREM2+ macrophages differentiated into DetOCs and expressed several types of collagens. Immunostaining confirmed the expression of COL27A1 not only in DetOCs in MRONJ but also in osteoclasts in mandibular cancer. CellChat analysis revealed interactions mediated by collagen signaling pathways between DetOCs, myeloid cells, and activated fibroblasts. ConclusionsWe successfully characterized DetOCs and identified a distinctive microenvironment involving DetOCs and activated fibroblasts in the granulation tissues surrounding sequestra in MRONJ. Clinical RelevanceIdentification of DetOCs and their unique interaction with activated fibroblasts in MRONJ lesions provides novel insight into the pathophysiology of sequestrum formation, suggesting potential therapeutic targets to ameliorate MRONJ.

immunology↗

bioRxiv2024

Silicon Nitride Induces Osteoconduction Via Activated Mitochondrial Oxidative Phosphorylation and Neovascularization

Silicon nitride (Si3N4: SiN) is a thermodynamically stable ceramic material with excellent mechanical properties, and wear and corrosion resistance for industrial applications. SiN has been proposed for orthopedic and dental implant applications owing to its enhanced osteoconduction. However, the biological mechanisms underlying SiN-induced bone formation have not been fully elucidated. In this study, SiN significantly increased in vitro mineralization of human bone marrow mesenchymal stromal cells (BM-MSC) and in vivo peri-implant bone volume in mouse femurs compared to conventionally used titanium (Ti) implants. RNA sequencing of BM-MSC cultured on SiN disks revealed that functional gene clusters associated with mitochondrial oxidative phosphorylation were significantly elevated. SiN in an aqueous solution has been shown to release ammonium/ammonia, which may provide a source for glutamine-dependent energy production, and BM-MSC upregulated the expression of a key enzyme, glutamate-ammonia ligase under osteogenic conditions. Additionally, SiN increased the expression of functional gene clusters involved in vascular formation. The upregulation of HIF1a in vitro and increased VEGFR3-positive blanching vascular structures in vivo implied that SiN induced neovascularization. This study revealed an important mechanism through which SiN stimulated osteoconduction by unique glutamine-driven mitochondrial oxidative phosphorylation and established oxygen and nutrient supply by neovascularization, leading to stable osseointegration.

bioengineering↗

bioRxiv2023

Mouse gingival single-cell transcriptomic atlas: An activated fibroblast subpopulation guides oral barrier immunity in periodontitis

Periodontitis, one of the most common non-communicable diseases, is characterized by chronic oral inflammation and uncontrolled tooth supporting alveolar bone resorption. Its underlying mechanism to initiate aberrant oral barrier immunity has yet to be delineated. Here, we report a unique fibroblast subpopulation activated to guide oral inflammation (AG fibroblasts) identified in a single-cell RNA sequencing gingival cell atlas constructed from the mouse periodontitis models. AG fibroblasts localized beneath the gingival epithelium and in the cervical periodontal ligament responded to the ligature placement and to the discrete application of Toll-like receptor stimulants to mouse maxillary tissue. The upregulated chemokines and ligands of AG fibroblasts linked to the putative receptors of neutrophils in the early stages of periodontitis. In the established chronic inflammation, neutrophils together with AG fibroblasts appeared to induce type 3 innate lymphoid cells (ILC3s) that were the primary source of interleukin-17 cytokines. The comparative analysis of Rag2-/- and Rag2{gamma}c-/-mice suggested that ILC3 contributed to the cervical alveolar bone resorption interfacing the gingival inflammation. We propose that AG fibroblasts function as a previously unrecognized surveillant to initiate gingival inflammation leading to periodontitis through the AG fibroblast-neutrophil-ILC3 axis.

pathology↗

bioRxiv2021

Therapeutic downregulation of neuronal PAS domain 2 (Npas2) promotes surgical skin wound healing

Attempts to minimize scarring remain among the most difficult challenges facing surgeons, despite the use of optimal wound closure techniques. Previously, we reported improved healing of dermal excisional wounds in circadian clock neuronal PAS domain 2 (Npas2)-null mice. In this study, we performed high-throughput drug screening to identify a compound that downregulates Npas2 activity. The hit compound (Dwn1) suppressed circadian Npas2 expression, increased murine dermal fibroblast cell migration, and decreased collagen synthesis in vitro. Based on the in vitro results, Dwn1 was topically applied to iatrogenic full-thickness dorsal cutaneous wounds in a murine model. The Dwn1-treated dermal wounds healed faster with favorable mechanical strength and developed less granulation tissue than the controls. The expression of type I collagen, Tgf{beta}1, and -smooth muscle actin was significantly decreased in Dwn1-treated wounds, suggesting that hypertrophic scarring and myofibroblast differentiation are attenuated by Dwn1 treatment. NPAS2 may represent an important target for therapeutic approaches to optimal surgical wound management.

bioengineering↗