Biology subjects

Dyment, N.

Publications and source records attributed to Dyment, N..

8 recordsLinked to original sources

bioRxiv2026

Impaired loading following denervation elicits dynamic, differential growth trajectories of musculoskeletal tissues

Physical forces dictate the function and maintenance of adult musculoskeletal tissues. Yet, the impact of biophysical cues on the growth and maturation of these tissues, especially dense connective tissues, remains unclear. Here, we investigated the effects of neonatal mechanical loading on early postnatal growth of the musculoskeletal tissues of the lower limb, with particular focus on the Achilles tendon. We performed sciatic nerve resection (SNR) on one-day-old mice to denervate the hamstrings and distal hindlimb muscles. Sciatic Nerve Resection resulted in severe and sustained alterations in gait, accompanied by an altered transcriptional landscape in distal musculoskeletal tissues, with marked reductions in bone and tendon growth and smaller, fibrotic hindlimb musculature. Sciatic nerve resection impaired cumulative growth in the Achilles tendon, shifting cell proliferation and matrix-driven growth trajectories and altering mechanotransduction gene programs toward inflammation and matrix catabolism with age. This work highlights the essential role of mechanical loading in driving mechanosignaling and postnatal growth trajectories in musculoskeletal tissues of the developing limb, with implications for overall musculoskeletal health in adulthood.

bioengineering↗

bioRxiv2026

Expansion Microscopy reveals changes in cellular and extracellular structures between healthy and perturbed tendons

Tendons transmit mechanical forces between muscles and bones through their highly aligned, collagen-rich extracellular matrix. When damaged, resident cells help restore this matrix. However, in tendinopathies, this repair response fails, leading to loss of proper tendon function. How altered mechanical states reshape tendon cell and matrix architecture remains poorly understood because existing methods do not readily capture tendon structure across relevant length scales. Here, we combine Fluorescent Labeling of Abundant Reactive Entities (FLARE) with Expansion Microscopy (ExM) to visualize cellular and extracellular structures in native tendon tissue. FLARE-ExM resolves the dense fibrillar matrix across multiple tendon types, including elastic fibers and glycan-rich cellular protrusions. In a tendon resection model, acute loss-of-tension was associated with increased fibril width and expansion of carbohydrate- and protein-rich regions. In ruptured human Achilles tendon, FLARE-ExM revealed extracellular disorganization and disrupted cellular architecture. These results establish FLARE-ExM as a useful approach for studying how mechanical perturbation remodels tendon architecture across physiological and disease contexts.

physiology↗

bioRxiv2026

Age-Dependent Chromatin Remodeling Drives Inflammatory Dysregulation in Tendon Cells

Aging impairs tissue function and tolerance to cellular stress by reprogramming the behavior of resident cells. With global increases in lifespan, the prevalence of chronic and degenerative musculoskeletal disorders, including tendon degeneration, continues to rise; however, effective interventions to counteract age-related decline remain limited. Here, we investigate how a central age-associated stressor, inflammation, differentially modulates tendon cell behavior derived from young and mature-aged donors. Using super-resolution microscopy to resolve nanoscale chromatin organization in conjunction with epigenomic and transcriptomic profiling, we identify age-dependent regulatory mechanisms that govern inflammatory responsiveness. Mature-aged tendon cells exhibit exaggerated pro-inflammatory and catabolic responses across chromatin, gene expression, and protein signaling levels, characterized by enhanced TNF receptor organization, elevated accessibility at pro-inflammatory regulatory elements, and robust induction of matrix-degrading enzymes. Notably, the AP-1 transcription factor family emerges as a central age-dependent regulator, displaying distinct motif accessibility patterns that bias mature tenocytes toward inflammatory and degenerative transcriptional programs. Taken together, our findings demonstrate that age-dependent epigenetic priming amplifies inflammatory sensitivity and constrains reparative gene regulation in mature tendon cells. This work provides a mechanistic framework linking chromatin remodeling to tendon degeneration and holds potential to identify epigenetic and transcriptional pathways as potential targets for rejuvenation strategies in aging musculoskeletal tissues.

bioengineering↗

bioRxiv2025

Maternal exercise rescues fetal akinesia-impaired joint and bone development

Fetal movements exert mechanical forces that shape the developing skeleton. Conditions that impair fetal movements can cause skeletal defects, but interventions are limited. Here, we show that maternal wheel running exercise regulates fetal skeletal development in mice. In wild-type fetuses, maternal exercise stimulated joint and bone morphogenesis. We reasoned that these effects occurred through either indirect maternofetal communication or direct mechanical stimulation of the fetus. Maternal exercise did not alter placental measures of nutrient transport. However, in the Splotch-delayed (Spd) mouse model of fetal akinesia, which features intact maternofetal communication but lacks fetal movements, maternal exercise substantially rescued fetal akinesia-impaired joint and bone development and prevented disuse-induced resorption of the deltoid tuberosity. Further, direct mechanical stimulation of Spd limbs explanted from systemic factors similarly stimulated joint morphogenesis. Together, these findings identify maternal exercise as a regulator of fetal skeletal development, providing a platform for studying skeletal developmental mechanobiology and suggesting potential therapeutic applications for fetuses with impaired movement.

developmental biology↗

bioRxiv2025

Prg4+ fibro-adipogenic progenitors in muscle are crucial for bone fracture repair

Clinically, compromised fracture healing often occurs at sites with less muscle coverage and muscle flaps can provide the necessary healing environment for appropriate healing in severe bone loss. However, the underlying mechanisms are largely unknown. Here, we established a mouse reporter model for studying muscle cell contribution to bone fracture repair. Analyzing skeletal muscle scRNA-seq datasets revealed that Prg4 marks a fibro-adipogenic progenitor (FAP) subpopulation. In mice, Prg4+ cells were specifically located in the skeletal muscle, but not at the periosteum or inside cortical bone. These cells expressed FAP markers, responded to muscle injury, and became periosteal cells under normal and muscle injury conditions. Fracture fragmented muscle fibers, rapidly expanded Prg4+ FAPs at the injury site and promoted their migration into the fracture site. Later, they gave rise to many chondrocytes, osteoblasts, and osteocytes in the outer periphery of callus next to muscle. In repaired bones, the descendants of Prg4+ FAPs were detected as mesenchymal progenitors in the periosteum and osteocytes at the prior fracture site. A second fracture activated those cells and stimulated them to become osteoblasts in the inner part of callus. Importantly, ablation of Prg4+ FAPs impaired fracture healing and functional repair. In an intramembranous bone injury model (drill-hole), Prg4+ FAPs became periosteal cells, but their contribution to bone defect repair was significantly less than in fractures. Taken together, we demonstrate the critical role of FAPs in endochondral bone repair and uncover a novel mechanism by which mesenchymal progenitors transform from muscle to cortical bone. Significance statementFracture healing is often impaired in areas with less muscle coverage, but the mechanisms behind this are poorly understood. In this work, we uncovered a critical role of specific muscle cells, known as Prg4+ fibro-adipogenic progenitors (FAPs), in bone regeneration. Using mouse models, we show that these muscle-resident mesenchymal progenitors expand after bone injury, migrate to the fracture site, transform into various bone cells in the fracture callus, and eventually become bone surface progenitors after the bone is healed. This finding highlights the importance of muscle cells in endochondral fracture repair and reveals a novel crosstalk mechanism between muscle and bone tissues. Future studies targeting these muscle progenitor cells could develop new treatments for delayed and nonunion fractures.

cell biology↗

bioRxiv2023

YAP and TAZ couple osteoblast precursor mobilization to angiogenesis and mechanoregulated bone development

Endochondral ossification requires coordinated mobilization of osteoblast precursors with blood vessels. During adult bone homeostasis, vessel adjacent osteoblast precursors respond to and are maintained by mechanical stimuli; however, the mechanisms by which these cells mobilize and respond to mechanical cues during embryonic development are unknown. Previously, we found that deletion of the mechanoresponsive transcriptional regulators, YAP and TAZ, from Osterix-expressing osteoblast precursors and their progeny caused perinatal lethality. Here, we show that embryonic YAP/TAZ signaling couples vessel-associated osteoblast precursor mobilization to angiogenesis in developing long bones. Osterix-conditional YAP/TAZ deletion impaired endochondral ossification in the primary ossification center but not intramembranous osteogenesis in the bone collar. Single-cell RNA sequencing revealed YAP/TAZ regulation of the angiogenic chemokine, Cxcl12, which was expressed uniquely in vessel-associated osteoblast precursors. YAP/TAZ signaling spatially coupled osteoblast precursors to blood vessels and regulated vascular morphogenesis and vessel barrier function. Further, YAP/TAZ signaling regulated vascular loop morphogenesis at the chondro-osseous junction to control hypertrophic growth plate remodeling. In human cells, mesenchymal stromal cell co-culture promoted 3D vascular network formation, which was impaired by stromal cell YAP/TAZ depletion, but rescued by recombinant CXCL12 treatment. Lastly, YAP and TAZ mediated mechanotransduction for load-induced osteogenesis in embryonic bone.

developmental biology↗

bioRxiv2022

Csf1 from marrow adipogenic precursors is required for osteoclast formation and hematopoiesis in bone

Colony stimulating factor 1 (Csf1) is an essential growth factor for osteoclast progenitors and thus an important regulator for bone resorption. It remains elusive which mesenchymal cells synthesize Csf1 stimulating osteoclastogenesis. We recently identified a novel mesenchymal cell population, marrow adipogenic lineage precursors (MALPs), in bone. Single cell RNA- sequencing indicated specific expression of Csf1 in MALPs, which is further increased during aging. To investigate its role, we constructed Csf1 CKO mice using Adipoq-Cre. These mice showed increased femoral trabecular bone over time, but their cortical bone appeared normal. In comparison, depletion of Csf1 in the entire mesenchymal lineage using Prx1-Cre led to a more striking high bone mass phenotype, suggesting that additional mesenchymal subpopulations secrete Csf1. TRAP staining revealed diminished osteoclasts in the femoral secondary spongiosa region of Csf1 CKOAdipoq mice, but not at the chondral-osseous junction nor at the endosteal surface of cortical bone. Moreover, Csf1 CKOAdipoq mice were resistant to LPS-induced calvarial osteolysis. Bone marrow cellularity, hematopoietic progenitors, and macrophages were also reduced in these mice. Taken together, our studies demonstrate that MALPs are a critical player in controlling bone remodeling and hematopoiesis.

cell biology↗

bioRxiv2020

Bone marrow adipogenic lineage precursors (MALPs) promote osteoclastogenesis in bone remodeling and pathologic bone loss

Bone is maintained by coupled activities of bone-forming osteoblasts/osteocytes and bone-resorbing osteoclasts and an alternation of this relationship can lead to pathologic bone loss such as in osteoporosis. It is well known that osteogenic cells support osteoclastogenesis via synthesizing RANKL. Interestingly, our recently identified bone marrow mesenchymal cell population--marrow adipogenic lineage precursors (MALPs) that form a multi-dimensional cell network in bone--was computationally demonstrated to be the most interactive with monocyte-macrophage lineage cells through highly and specifically expressing several osteoclast regulatory factors, including RANKL. Using an adipocyte-specific Adipoq-Cre to label MALPs, we demonstrated that mice with RANKL deficiency in MALPs have a drastic increase of trabecular bone mass in long bones and vertebrae starting from 1 month of age but that their cortical bone is normal. This phenotype was accompanied by diminished osteoclast number and attenuated bone formation at the trabecular bone surface. Reduced RANKL signaling in calvarial MALPs also abolished osteolytic lesions after lipopolysaccharide (LPS) injections. Furthermore, in ovariectomized mice, elevated bone resorption was partially attenuated by RANKL deficiency in MALPs. In summary, our studies identified MALPs as a critical player in controlling bone remodeling during normal bone metabolism and pathological bone loss in a RANKL-dependent fashion.

cell biology↗