Biology subjects

Mauck, R.

Publications and source records attributed to Mauck, R..

14 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

Reprogramming Dedifferentiation Regulatory Networks Preserves Human Chondrocyte Phenotypes

Chondrocyte-based cartilage repair strategies such as autologous chondrocyte implantation (ACI) require extensive in vitro expansion to obtain clinically relevant cell numbers. However, this expansion step progressively drives chondrocyte dedifferentiation, reducing matrix-forming capacity and contributing to variable repair outcomes. To better understand this process, we used single-nucleus multiome profiling (snRNA-Seq + snATAC-Seq) to define the transcriptional and chromatin accessibility programs underlying human chondrocyte dedifferentiation during expansion. Multiome integration across passages revealed a continuous dedifferentiation trajectory accompanied by coordinated remodeling of gene expression and chromatin accessibility, identifying chromatin destabilization as an early regulatory event during phenotype loss. Guided by these regulatory signatures, we screened available small-molecule inhibitors targeting candidate pathways and found that Fludarabine most consistently preserved chondrocyte identity during early expansion. Fludarabine was associated with suppression of STAT1-related programs and early stabilization of the chromatin landscape prior to broader transcriptional recovery. Functionally, treated cells demonstrated enhanced matrix-forming capacity in chondrogenic pellet culture and significantly increased nascent protein synthesis in 3D hydrogel culture, with biosynthetic output approaching unexpanded controls by day 21. Together, these findings identify chromatin stability as a key regulatory determinant of expansion-associated chondrocyte dedifferentiation and establish a pharmacologic strategy to preserve chondrocyte functional potency during cell manufacturing for cartilage repair.

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

Mechano-activation of synovial fibroblasts and macrophages during OA progression in the dynamically stiffening synovial microenvironment

ObjectiveDuring osteoarthritis (OA) progression, the synovial membrane undergoes profound structural and compositional remodeling and fibrosis. We sought to elucidate how evolving synovial microenvironmental mechanics during fibrotic remodeling influence cell behavior and drive the progression of synovial pathology. MethodsSkeletally-mature male C57BL/6J mice were subjected to destabilization of the medial meniscus (DMM). To control for surgical confounders, both sham-operated and unoperated mice were included, with evaluation at 4- and 8-weeks. Synovial micromechanics were quantified via atomic force microscopy (AFM). Single-cell RNA sequencing (scRNA-seq), RNA fluorescence in situ hybridization (FISH), and flow cytometry were employed to investigate cellular heterogeneity, spatial organization, and crosstalk within fibrotic and non-fibrotic synovial niches. ResultsProgressive fibrotic remodeling and marked matrix stiffening were observed in DMM-operated synovium but absent in sham- and un-operated controls. While both sham and DMM joints mounted an acute stromal and immune response to surgery, these changes resolved over time in sham conditions but persisted in DMM synovium. During disease progression, distinct functional subsets of synovial fibroblasts and immune cells emerged, with mechanosignalling pathways and distinct immune cell-fibroblast crosstalk robustly activated within DMM-induced fibrotic microenvironments. ConclusionThis study demonstrates the complex cellular dynamics and crosstalk that differentiate the evolution of the pathological synovial response in the fibrotic DMM condition relative to surgical sham controls. Our findings highlight mechanotransduction as a central mechanism driving OA synovial pathogenesis and underscore the utility of the DMM model as a platform to dissect the molecular underpinnings of synovial fibrosis.

bioengineering↗

bioRxiv2026

Hyperactive BMP and Mechanosignaling Remodel Chromatin to Drive Aberrant Osteogenesis in FOP

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder in which a recurrent ACVR1 (R206H) mutation drives progressive heterotopic ossification (HO). While aberrant BMP hypersensitivity has been studied, how this mutation enforces a persistent pro-osteogenic state remains unclear. Here, we combined super-resolution stochastic optical reconstruction microscopy (STORM), transposase-accessible chromatin with sequencing (ATAC-Seq), and RNA sequencing (RNA-Seq) to investigate how Acvr1R206H remodels chromatin to promote osteogenic transcriptional programs. Mutant mouse embryonic fibroblasts (MEFs) exhibited globally decondensed chromatin and increased accessibility at developmental and osteogenic loci enriched for HOX, TEAD, and RUNX motifs. Integration of ATAC-Seq and RNA-Seq data identified transcriptional networks primed for osteochondrogenic gene expression, including ossification, extracellular matrix organization, and cell adhesion pathways, consistent with enhanced BMP-SMAD and mechanotransduction activity. Time-course experiments revealed heightened responses to BMP ligands in Acvr1R206H/+ MEFs compared to wild-type, highlighting ligand hypersensitivity. Importantly, pharmacological modulation showed that chromatin alterations were dynamic and reversible: activation of Rho/ROCK in wild-type cells reproduced the mutant chromatin state, while inhibition of Rho/ROCK or BMP-SMAD signaling restored condensation to wild-type levels in mutant cells. Together, these findings establish that Acvr1R206H enforces a pro-osteogenic chromatin landscape through convergent BMP-SMAD and Rho/ROCK signaling, predisposing progenitors to aberrant differentiation trajectories. Our study reframes FOP as a disorder of persistent, but reversible, chromatin states and identifies novel therapeutic opportunities to restore mesenchymal cell homeostasis and prevent pathological bone formation. Significance StatementFibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder in which a mutation in ACVR1/ALK2 drives progressive heterotopic ossification. However, how this mutation enforces a persistent pro-osteogenic state is unclear. Here, we show that the Acvr1R206H mutation remodels chromatin architecture and accessibility through hyperactive BMP-SMAD and Rho/ROCK signaling, activating transcription factor networks that drive osteochondrogenic gene expression. These chromatin changes are dynamic and reversible with targeted pathway inhibition, revealing therapeutic potential to restore mesenchymal cell plasticity and prevent pathological bone formation.

bioengineering↗

bioRxiv2025

O-SNAP: A comprehensive pipeline for spatial profiling of chromatin architecture

We present O-SNAP (Objective Single-Molecule Nuclear Architecture Profiler), a comprehensive pipeline for the automated extraction, comparison, and classification of nuclear features from single-molecule localization microscopy (SMLM) data. O-SNAP quantifies 144 interpretable, biologically grounded spatial features describing chromatin organization or histone mark distributions at nanoscale resolution. The pipeline includes modules for pairwise comparison of features using volcano plots, feature set enrichment analysis, robust feature selection and classification of cell states, and pseudotime trajectory inference. We validate O-SNAP across diverse biological contexts, including fibroblast-to-stem cell reprogramming, tendon disease, histone variant sensitivity to oxidative stress, and chondrocyte de-differentiation, demonstrating its ability to detect subtle changes in nanoscale chromatin organization across diverse biological transitions.

biophysics↗

bioRxiv2024

Engineering kidney developmental trajectory using culture boundary conditions

Kidney explant cultures are traditionally carried out at air-liquid interfaces, which disrupts 3D tissue structure and limits interpretation of developmental data. To overcome this limitation, we developed a 3D culture technique using hydrogel embedding to capture morphogenesis in real time. We show that 3D culture better approximates in vivo-like niche spacing and dynamic tubule tip rearrangement, as well as in vivo-like presentation of branching defects under perturbations to glial cell-derived neurotrophic factor (GDNF)-REarranged during Transfection (RET) tyrosine kinase signaling. We find that the concentration of the embedding matrix influences the number of nephrons per ureteric bud (UB) tip and the spacing between tips. To isolate the effect of specific material properties on explant development, we introduce engineered acrylated hyaluronic acid hydrogels that allow independent tuning of stiffness and adhesion. We find that sufficient stiffness and adhesion are both required to maintain kidney shape. Matrix stiffness has a "Goldilocks effect" on the nephron per UB tip balance centered at [~]2 kPa, while higher matrix adhesion increases nephron per UB tip ratio. Our technique captures large-scale, in vivo-like tissue morphogenesis in 3D, providing a platform suited to contrasting normal and congenital disease contexts. Moreover, understanding the impact of boundary condition mechanics on kidney development benefits fundamental renal research and advances the engineering of next-generation kidney replacement tissues.

developmental biology↗

bioRxiv2024

Learning on a Limb: An outreach module to engage high school students in orthopaedics

Orthopaedic researchers need new strategies for engaging diverse students. Our field has demonstrated noticeable gaps in racial, ethnic, and gender diversity, which inhibit our ability to innovate and combat the severe socioeconomic burden of musculoskeletal disorders. Towards this goal, we designed, implemented, and evaluated Learning on a Limb, an orthopaedic research outreach module to teach diverse high school students about orthopaedic research. During the 4-hr module, students completed hands-on activities to learn how biomechanical testing, microcomputed tomography, cell culture, and histology are used in orthopaedic research. Over three years, we recruited 32 high school students from the Greater Philadelphia Area to participate in Learning on a Limb. Most participants identified as racial/ethnic or gender minorities in orthopaedic research. Using pre/post-tests, we found that students experienced significant learning gains of 51 percentage points from completing Learning on a Limb. In addition to teaching students about orthopaedic research, post-survey data demonstrated that participating in Learning on a Limb strongly influenced students interest in orthopaedic research. Several students acted on this interest by completing summer research experiences in the McKay Orthopaedic Research Laboratory at the University of Pennsylvania. Learning on a Limb instructors also benefited by having the opportunity to "pay it forward" to the next generation of students and build community within their department. Empowering institutions to host modules like Learning on a Limb would synergistically inspire diverse high school students and strengthen community within orthopaedic departments to ultimately enhance orthopaedic research innovations.

scientific communication and education↗

bioRxiv2023

Microinterfaces in bicontinuous hydrogelsguide rapid 3D cell migration

Cell migration is critical for tissue development and regeneration but requires extracellular environments that are conducive to motion. Cells may actively generate migratory routes in vivo by degrading or remodeling their environments or may instead utilize existing ECM microstructures or microtracks as innate pathways for migration. While hydrogels in general are valuable tools for probing the extracellular regulators of 3D migration, few have recapitulated these natural migration paths. Here, we developed a biopolymer-based (i.e., gelatin and hyaluronic acid) bicontinuous hydrogel system formed through controlled solution immiscibility whose continuous subdomains and high micro-interfacial surface area enabled rapid 3D migration, particularly when compared to homogeneous hydrogels. Migratory behavior was mesenchymal in nature and regulated by biochemical and biophysical signals from the hydrogel, which was shown across various cell types and physiologically relevant contexts (e.g., cell spheroids, ex vivo tissues, in vivo tissues). Our findings introduce a new design that leverages important local interfaces to guide rapid cell migration.

bioengineering↗

bioRxiv2023

Acute repair of meniscus root tear partially restores joint displacements as measured with MRI and loading in a porcine knee

The meniscus serves important load-bearing functions and protects the underlying articular cartilage. Unfortunately, meniscus tears are common and impair the ability of the meniscus to distribute loads, greatly increasing the risk for developing osteoarthritis. Therefore, surgical repair of the meniscus is a frequently performed procedure; however, this repair does not always prevent osteoarthritis. This is hypothesized to be due to altered joint loading post injury and repair, where the functional deficit of the meniscus prevents it from performing its role of distributing forces. However, many studies of meniscus function required opening the joint, which alters kinematics. The objective of this study was to use novel MRI methods to image the intact joint under axial load and measure the acute meniscus and femur displacements in an intact joint, after a meniscus root tear, and after suture repair in the porcine knee, a frequently used in vivo model. We found that anterior root tear led to large meniscus and femur displacements under physiological axial loading, and that suture anchor repair reduced these displacements, but did not fully restore intact joint kinematics. After tear and repair, the anterior region of the meniscus moved posteriorly and medially as it was forced out of the joint space under loading, while the posterior region had small displacements as the posterior attachment acted as a hinge about which the meniscus rotated in the axial plane. This technique can be applied to evaluate the effect of knee injuries and to develop improved repair strategies to restore joint kinematics.

bioengineering↗

bioRxiv2022

Rapid Restoration of Cell Phenotype and Matrix Forming Capacity Following Transient Nuclear Softening

The dense extracellular matrix of connective tissues impedes cell migration and subsequent matrix formation at sites of injury. We recently employed transient nuclear softening via histone deacetylase inhibition with trichostatin A (TSA) treatment to overcome the stiff nuclear impediments to cell migration through dense tissues and electrospun matrices. Despite these positive findings, the long-term implications of transient nuclear softening on cell transcriptional phenotype and matrix formation capacity are unknown. To address this, we investigated the influence of transient TSA treatment on porcine meniscal cell behavior, beginning with the efficacy and reproducibility of transient TSA treatment on histone acetylation and chromatin remodeling in vitro and cell migration through native meniscus tissue. Within 3 days after cessation of transient TSA treatment, histone acetylation and chromatin remodeling returned to control levels. Following TSA treatment, endogenous cell migration through native meniscus tissue increased greater than 3-fold compared to controls. Importantly, meniscal cells completely restored their transcriptional phenotype and maintained their capacity to respond transcriptionally and functionally to a secondary pro-matrix stimuli (i.e., transforming growth factor {beta}3) within 7 days after cessation of TSA treatment. Towards translation, we also showed the feasibility of biomaterial-delivered TSA to increase endogenous cell migration to a wound edge ex vivo. Together, this work defines the efficacy, reproducibility, safety, and feasibility of future translational approaches for nuclear softening to treat dense connective tissue injuries.

genomics↗

bioRxiv2022

Anti-Inflammatory Tension-Activated Repair Patches Improve Repair After Intervertebral Disc Herniation

Conventional treatment for intervertebral disc herniation alleviates pain but does not repair the annulus fibrosus (AF), resulting in a high incidence of recurrent herniation and persistent disfunction. The lack of repair and the acute inflammation that arise after injury further compromises the disc and can result in disc-wide degeneration in the long term. To address this clinical need, we developed tension-activated repair patches (TARPs) for annular repair and the local delivery of bioactive anti-inflammatory factors. TARPs transmit physiologic strains to mechanically-activated microcapsules (MAMCs) embedded within, which activate and release encapsulated biomolecules in response to physiologic loading. Here, we demonstrate that the TARP design modulates implant biomechanical properties and regulates MAMC mechano-activation. Next, the FDA-approved anti-inflammatory molecule, interleukin 1 receptor antagonist, Anakinra, was loaded in TARPs and the effects of TARP-mediated annular repair and Anakinra delivery was evaluated in a model of annular injury in the goat cervical spine. TARPs showed robust integration with the native tissue and provided structural reinforcement at the injury site that prevented disc-wide aberrant remodeling resulting from AF detensioning. The delivery of Anakinra via TARP implantation improved the retention of disc biochemical composition through increased matrix deposition and retention at the site of annular injury. Anakinra delivery additionally attenuated the inflammatory response associated by scaffold implantation, decreasing osteolysis in adjacent vertebrae and preserving disc cellularity and matrix organization throughout the AF. These results demonstrate the translational and therapeutic potential of this novel TARP system for the treatment of intervertebral disc herniations. One Sentence SummaryTension-activated repair patches delivering bioactive anti-inflammatory factors improve healing in an in vivo goat cervical disc injury model.

bioengineering↗

bioRxiv2021

Marked differences in local bone remodeling in response to different marrow stimulation techniques in a large animal

Marrow stimulation, including subchondral drilling and microfracture, is the most commonly performed cartilage repair strategy, whereby the subchondral bone plate is perforated to release marrow-derived cells into a cartilage defect to initiate repair. Novel scaffolds and therapeutics are being designed to enhance and extend the positive short-term outcomes of this marrow stimulation. However, the translation of these newer treatments is hindered by bony abnormalities, including bone resorption, intralesional osteophytes, and bone cysts, that can arise after marrow stimulation. In this study, three different marrow stimulation approaches -- microfracture, subchondral drilling, and needle-puncture - were evaluated in a translationally relevant large animal model, the Yucatan minipig. The objective of this study was to determine which method of marrow access (malleted awl, drilled Kirschner wire, or spring-loaded needle) best preserved the underlying subchondral bone. Fluorochrome labels were injected at the time of surgery and 2 weeks post-surgery to capture bone remodeling over the first 4 weeks. Comprehensive outcome measures included cartilage indentation testing, histological grading, microcomputed tomography, and fluorochrome imaging. Our findings indicated that needle-puncture devices best preserved the underlying subchondral bone relative to other marrow access approaches. This may relate to the degree of bony compaction occurring with marrow access, as the Kirschner wire approach, which consolidated bone most, induced the most significant bone damage with marrow stimulation. This study provides basic science evidence in support of updated marrow stimulation techniques for preclinical and clinical practice.

bioengineering↗

bioRxiv2020

Identification of Gli1 as a progenitor cell marker for meniscus development and injury repair

Meniscal tears are associated with a high risk of osteoarthritis but currently have no disease-modifying therapies. Using Gli1-CreER tdTomato mice, we found that Gli1+ cells contribute to the development of meniscus horns from 2 weeks of age. In adult mice, Gli1+ cells resided at the superficial layer of meniscus and expressed known mesenchymal progenitor markers. In culture, meniscal Gli1+ cells possessed high progenitor activities under the control of Hh signal. Meniscus injury at the anterior horn induced a quick expansion of Gli1+ cells. Normally, the tissue healed slowly, leading to cartilage degeneration. Ablation of Gli1+ cells further hindered this repair process. Strikingly, intra-articular injection of Gli1+ meniscal cells or an Hh activator right after injury accelerated the bridging of the interrupted ends and attenuated signs of osteoarthritis. Taken together, our work identified a novel progenitor population in meniscus and proposes a new treatment for repairing injured meniscus and preventing osteoarthritis.

developmental biology↗