Leptin receptor (LepR)-positive cells are key components of the bone marrow hematopoietic microenvironment, and highly enrich skeletal stem and progenitor cells that maintain homeostasis of the adult skeleton. However, the heterogeneity and lineage hierarchy within this population has been elusive. Using genetic lineage tracing and single-cell RNA sequencing, we found that Lepr-Cre labels most bone marrow stromal cells and osteogenic lineage cells in adult long bones. Integrated analysis of Lepr-Cre-traced cells under homeostatic and stress conditions revealed dynamic changes of the adipogenic, osteogenic, and periosteal lineages. Importantly, we discovered a Notch3 + bone marrow sub-population that is slow-cycling and closely associated with the vasculatures, as well as key transcriptional networks promoting osteo-chondrogenic differentiation. We also identified a Sca-1 + periosteal sub-population with high clonogenic activity but limited osteo-chondrogenic potential. Together, we mapped the transcriptomic landscape of adult LepR + stem and progenitor cells and uncovered cellular and molecular mechanisms underlying their maintenance and lineage specification.
Highlights d Osteolectin interacts with Fap and inhibits its protease activity d Genetic deletion of Fap ameliorates bone loss in aged mice d Pharmacological inhibition of Fap attenuates ovariectomyinduced osteoporosis d Osteolectin inhibits Fap to promote mineralization during zebrafish development
RATIONALE: Myocardial infarction (MI) elicits cardiac fibroblast activation and ECM (extracellular matrix) deposition to maintain the structural integrity of the heart. Recent studies demonstrate that Fap (fibroblast activation protein)—a prolyl-specific serine protease—is an important marker of activated cardiac fibroblasts after MI. OBJECTIVE: This study aims to test whether Fap is a critical regulator of cardiac repair after MI and to uncover the underlying cellular and molecular mechanisms for better treatment of MI. METHODS AND RESULTS: We found that Fap is upregulated in patient cardiac fibroblasts after cardiac injuries, while plasma Fap is downregulated and functions as a prognostic marker for cardiac repair. Genetic or pharmacological inhibition of Fap in mice significantly improved cardiac function after MI. Histological and transcriptomic analyses showed that Fap inhibition leads to increased angiogenesis in the peri-infarct zone, which promotes ECM deposition and alignment by cardiac fibroblasts and prevents their overactivation, thereby limiting scar expansion. Mechanistically, we found that BNP (brain natriuretic peptide) is a novel substrate of Fap that mediates postischemic angiogenesis. Fap degrades BNP to inhibit vascular endothelial cell migration and tube formation. Pharmacological inhibition of Fap in Nppb (encoding pre-proBNP) or Npr1 (encoding the BNP receptor)-deficient mice showed no cardioprotective effects, suggesting that BNP is a physiological substrate of Fap. CONCLUSIONS: This study identifies Fap as a negative regulator of cardiac repair and a potential drug target to treat MI. Inhibition of Fap stabilizes BNP to promote angiogenesis and cardiac repair.
Unlike long bones, jawbone development is mainly accomplished by intramembranous ossification resulting from the differentiation of periosteal progenitor cells. However, the spatiotemporal ontogeny of periosteal progenitor cells during jawbone development and repair remains elusive. In this study, we mapped the transcriptional landscape of the human jawbone periosteum at single-cell resolution and identified a cathepsin K (Ctsk)+ periosteal subset. Lineage tracing analysis indicated that Ctsk-Cre–labeled periosteal cells could make contributions to jawbone development. However, different from the periosteal-specific location of Ctsk+ cells in long bone, we also identified Ctsk+ stromal cells in jawbone marrow and implied the heterogeneity of jawbone Ctsk+ hierarchy. In further analysis of the periosteal progenitor cell subset of heterogeneous Ctsk+ hierarchy, we identified a unique Ctsk+Ly6a+ subset of cells. The additional marker Ly6a helped to further confine the progenitor subset to the jawbone periosteum and was nearly undetectable in the bone marrow. Defects in the jawbone could activate the migration and osteogenic differentiation of Ctsk+Ly6a+ cells. Local ablation of Ctsk+ cells by diphtheria reduced the number of Ctsk+Ly6a+ cells and delayed the repair of the bone defect. Taken together, we identify a novel periosteal osteogenic progenitor subset that is active in jawbone osteogenesis and healing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.