Biology subjects

Bahney, C. S.

Publications and source records attributed to Bahney, C. S..

8 recordsLinked to original sources

bioRxiv2025

Deep behavioral phenotyping tracks functional recovery following tibia fracture in mice

IntroductionAn estimated 178 million fractures occur worldwide each year, with lower limb fractures in particular showing a high incidence of poor healing, and these often lead to reduced mobility and chronic pain. Bone healing and the ability to bear weight are closely tied to the mechanical stability of the fracture site. Although fracture stabilization is a well-established factor modulating the rate and extent of bone repair, there is a notable gap in non-destructive technologies that can rapidly and objectively quantify functional recovery in preclinical settings. We consider this to be a significant limiting factor in translational studies directed at improving fracture healing. Here, we describe a novel behavioral phenotyping approach that enables rapid quantification of post-fracture weightbearing and kinematic metrics in freely behaving mice. Our goal is to identify and characterize metrics most indicative of fracture-induced behavioral impairment and to use these metrics to quantify how functional recovery is altered in mice with pin stabilized versus non-stabilized fractures. We also use this approach to explore whether sex is a significant contributor to functional recovery. MethodsMale and female adult C57BL6/J received a mid-shaft tibial fracture that was either left unstabilized or fixed with an intramedullary pin. Non-fractured naive mice served as controls. Behavioral recordings of freely moving mice were acquired prior to fracture and then throughout the time course of healing, from 5 to 35 days post fracture (DPF). To track mice and analyze changes in paw pressure and kinematic behaviors after fracture, we then applied a novel machine learning-enabled behavioral phenotyping analysis. ResultsIn this study, we demonstrate that severity of the behavioral phenotype is more significant in mice with unstabilized fractures when compared to mice with pin-stabilized fractures. Pin stabilization generally allowed increased weightbearing and produced smaller changes in kinematic metrics. Interestingly, we observed only minor sex specific differences in fracture-induced behavioral impairments and recovery. Our analysis also revealed that functional recovery is more complex than is a set of individual parameters viewed in isolation. In fact, unique behavioral parameters identified different time windows for functional recovery. Therefore, we developed a comprehensive, unified graph theoretic metric of fracture recovery that encompasses all behavioral parameters quantified. Using this unified metric, we confirmed the increased severity of the fracture phenotype in unstabilized versus pin stabilized mice and identified a clear time window of functional recovery, for both fracture groups. DiscussionOur findings demonstrate how this novel comprehensive behavioral phenotyping approach, which combines machine learning and graph theory, makes it possible to rapidly quantify longitudinal changes in mice after fracture. This approach enables us to determine functional recovery patterns based on a unified behavioral metric of healing. Our data and methodology form a foundation for future mechanistic experiments focused on understanding biological or mechanical variables that influence functional healing and will also enable more rapid testing of various strategies to accelerate bone healing.

animal behavior and cognition↗

bioRxiv2025

Chronic degenerative failure of salivary glands can be reversed through restoring mitochondrial function

Chronic degenerative wounds are often deemed irreparable, directing research efforts to focus predominantly on acute tissue injury regeneration while leaving endogenous repair mechanisms for chronically damaged tissues largely unexplored. In this study, we demonstrate that non-healing, severely degenerated salivary gland tissues can be fundamentally restored through first-line treatment with muscarinic agonists. This approach rescues tissue structure and function, returning it to a homeostatic-like state, and reactivates endogenous regeneration processes to drive new cell expansion that persists for months post-treatment. Furthermore, neuromimetic activation profoundly depletes radiation-induced DNA damage and re-establishes the nerve-acinar relationship, ultimately restoring the tissues physiological capacity to maintain homeostasis, even in the absence of treatment. We show that full recovery of organ function, comparable to uninjured controls, is primarily mediated by the re-differentiation of aberrantly de-differentiated epithelial acinar cells and the restoration of mitochondrial function via a muscarinic-calcium signaling pathway. These findings challenge the prevailing notion that chronic organ degeneration is irreversible and propose a readily testable therapeutic strategy for epithelial restoration with potential applications across a spectrum of chronic injuries.

cell biology↗

bioRxiv2024

Murine Progeria Model Exhibits Delayed Fracture Healing with Dysregulated Local Immune Response

ABSTRACTO_ST_ABSBackgroundC_ST_ABSBone fracture is one of the most globally prevalent injuries, with an estimated 189 million bone fractures occurring annually. Delayed union or nonunion occurs in up to 15% of fractures and involves the interruption or complete failure of bone continuity following fracture. Preclinical testing is essential to support the translation of novel strategies to promote improved fracture repair treatment, but there is a paucity of small animal models that recapitulate clinical attributes associated with delayed fracture healing. This study explores whether the Zmpste24-/- (Z24-/-) knockout mouse model of Hutchinson-Gilford progeria syndrome presents with delayed fracture healing. Leveraging the previously characterized Z24-/- phenotype of genomic instability, epigenetic changes, and fragility, we hypothesize that these underlying alterations will lead to significantly delayed fracture healing relative to age-matched wild type (WT) controls. MethodsWT and Z24-/- mice received intramedullary fixed tibia fractures at [~]12 weeks of age. Mice were sacrificed throughout the time course of repair for the collection of organs that would provide information regarding the local (fracture callus, bone marrow, inguinal lymph nodes) versus peripheral (peripheral blood, contralateral tibia, abdominal organs) tissue microenvironments. Analyses of these specimens include histomorphometry, CT, mechanical strength testing, protein quantification, gene expression analysis, flow cytometry for cellular senescence, and immunophenotyping. ResultsZ24-/- mice demonstrated a significantly delayed rate of healing compared to WT mice with consistently smaller fracture calli containing higher proportion of cartilage and less bone after injury. Cellular senescence and pro-inflammatory cytokines were elevated in the Z24-/- mice before and after fracture. These mice further presented with a dysregulated immune system, exhibiting generally decreased lymphopoiesis and increased myelopoiesis locally in the bone marrow, with more naive and less memory T cell but greater myeloid activation systemically in the peripheral blood. Surprisingly, the ipsilateral lymph nodes had increased T cell activation and other pro-inflammatory NK and myeloid cells, suggesting that elevated myeloid abundance and activation contributes to an injury-specific hyperactivation of T cells. ConclusionTaken together, these data establish the Z24-/- progeria mouse as a model of delayed fracture healing that exhibits decreased bone in the fracture callus, with weaker overall bone quality, immune dysregulation, and increased cellular senescence. Based on this mechanism for delayed healing, we propose this Z24-/- progeria mouse model could be useful in testing novel therapeutics that could address delayed healing. The Translational Potential of this ArticleThis study employs a novel animal model for delayed fracture healing that researchers can use to screen fracture healing therapeutics to address the globally prevalent issue of aberrant fracture healing.

molecular biology↗

bioRxiv2022

Wireless Measurements Using Electrical Impedance Spectroscopy to Monitor Fracture Healing

There is an unmet need for improved, clinically relevant methods to longitudinally quantify bone healing during fracture care. Here we develop a smart bone plate to wirelessly monitor healing utilizing electrical impedance spectroscopy (EIS) to provide real-time data on tissue com-position within the fracture callus. To validate our technology, we created a 1-mm rabbit tibial defect and fixed the bone with a standard veterinary plate modified with a custom-designed housing that included two impedance sensors capable of wireless transmission. Impedance magnitude and phase measurements were transmitted every 48-hours for up to 10-weeks. Bone healing was assessed by X-ray, CT, and histomorphometry. Our results indicated the sensors successfully incorporated into the fracture callus and did not impede repair. Electrical impedance, resistance, and reactance increased steadily from weeks 3 to 7--corresponding to the transition from hematoma to cartilage to bone within the fracture gap--then plateaued as the bone began to consolidate. These three electrical readings significantly correlated with traditional measurements of bone healing and successfully distinguished between union and not healed fractures, with the strongest relationship found with impedance magnitude. These results suggest that our EIS smart bone plate can provide continuous and highly sensitive quantitative tissue measurements throughout the course of fracture healing to better guide personalized clinical care.

bioengineering↗

bioRxiv2022

Long-term functional regeneration of radiation damaged salivary glands through delivery of a neurogenic hydrogel

Salivary gland acinar cells are severely depleted after radiotherapy for head and neck cancer, leading to loss of saliva and extensive oro-digestive complications. With no regenerative therapies available, organ dysfunction is irreversible. Here using the adult murine system, we demonstrate radiation-damaged salivary glands can be functionally regenerated via sustained delivery of the neurogenic muscarinic receptor agonist, cevimeline. We show that endogenous gland repair coincides with increased nerve activity and acinar cell division that is limited to the first week post-radiation, with extensive acinar cell degeneration, dysfunction and cholinergic denervation occurring thereafter. However, we discovered that mimicking cholinergic muscarinic input via sustained local delivery of a cevimeline-alginate hydrogel was sufficient to regenerate innervated acini and retain physiological saliva secretion at non-irradiated levels over the long-term (> 3 months). Thus, we reveal a novel regenerative approach for restoring epithelial organ structure and function that has significant implications for human patients. TeaserNovel application of an injectable neurogenic-based hydrogel for restoring the structure and function of radiation-damaged tissue.

cell biology↗

bioRxiv2021

Localized delivery of β-NGF via injectable microrods accelerates endochondral fracture repair

Currently, there are no biological approaches to accelerate bone fracture repair. Osteobiologics that promote endochondral ossification are an exciting alternative to surgically implanted bone grafts, however, the translation of osteobiologics remains elusive because of the need for localized and sustained delivery that is both safe and effective. In this regard, an injectable system composed of hydrogel-based microparticles designed to release osteobiologics in a controlled and localized manner is ideal in the context of bone fracture repair. Here, we describe poly (ethylene glycol) dimethacrylate (PEGDMA)-based microparticles, in the form of microrods, engineered to be loaded with beta nerve growth factor ({beta}-NGF) for use in a murine tibial fracture model. In-vitro studies demonstrated that protein-loading efficiency is readily altered by varying PEGDMA macromer concentration and that {beta}-NGF loaded onto PEGDMA microrods exhibited sustained release over a period of 7 days. In-vitro bioactivity of {beta}-NGF was confirmed using a tyrosine receptor kinase A (Trk-A) expressing cell line, TF-1. Moreover, TF-1 cell proliferation significantly increased when incubated with {beta}-NGF loaded PEGDMA microrods versus {beta}-NGF in media. In-vivo studies show that PEGDMA microrods injected into the fracture calluses of mice remained in the callus for over 7 days. Importantly, a single injection of {beta}-NGF-loaded PEGDMA microrods resulted in significantly improved fracture healing as indicated by significant increases in bone volume, trabecular connective density, and bone mineral density and a significant decrease in cartilage despite a remarkably lower dose ([~]111 fold) than the {beta}-NGF in media. In conclusion, we demonstrate a novel and translational method of delivering {beta}-NGF via injectable PEGDMA microrods to improve bone fracture repair.

bioengineering↗

bioRxiv2020

β-catenin Signaling Regulates Cell Fate Decisions at the Transition Zone of the Chondro-Osseous Junction During Fracture Healing

Chondrocytes within the fracture callus transform into osteoblasts during bone regeneration, but the molecular mechanisms regulating this process are unknown. Wnt ligands are expressed within the fracture callus, and hypertrophic chondrocytes undergoing transformation to osteoblasts exhibit nuclear localization of {beta}-catenin, indicating active Wnt signaling in these cells. Here, we show that conditional knock out (cKO) of {beta}-catenin in chondrocytes inhibits the transformation of chondrocytes to osteoblasts, while stabilization of {beta}-catenin in chondrocytes accelerates this process. After cKO, chondrocyte-derived cells were located in the bone marrow cavity and upon re-fracture formed cartilage. Lineage tracing in wild type mice revealed that in addition to osteoblasts, chondrocytes give rise to stem cells that contribute to repair of subsequent fractures. These data indicate that Wnt signaling directs cell fate choices of chondrocytes during fracture healing by stimulating transformation of chondrocytes to osteoblasts, and provide a framework for developing Wnt-therapies to stimulate repair.

developmental biology↗

bioRxiv2018

Smart bone plates can monitor fracture healing

One Sentence SummaryElectrical impedance measurements using microscale sensors implanted in two mouse fracture models tracked longitudinal differences between individual mice with proper healing and mice experiencing poor healing, laying the groundwork for translation to the clinic through integration into fracture fixation implants (i.e. instrumented bone plates).\n\nAbstractThere are currently no standardized methods for monitoring fracture healing. While histological studies can clearly identify the tissues found in the four stages of repair, in practice surgeons rely on X-ray, which is only useful at later stages of healing after mineralization has occurred. As electrical impedance spectroscopy (EIS) has previously been used to distinguish tissue types during healing, we hypothesized that microscale sensors embedded in the fracture callus could track the changing tissue with high sensitivity. Using in vivo mouse fracture models, we present the first evidence that microscale instrumented implants provide a route for post-operative fracture monitoring. In this study, we implanted sensors in mouse long bone fractures fixed with either external fixators or bone plates. EIS measurements taken across two electrodes implanted in the fracture gap were able to track longitudinal differences between individual mice with proper healing and mice experiencing poor healing. We additionally present an equivalent circuit model that combines the EIS data in order to classify healing states of fractures. Lastly, we show that EIS measures are strongly correlated with standard {micro}CT measures of healing and that these correlations validate clinically-relevant operating frequencies for implementation of this technique. The data from these two models demonstrate that this technique can be translated to the clinic through integration into current fracture management strategies such as bone plating, providing physicians with quantitative information about the state of a fracture to guide clinical decision-making for patients.

bioengineering↗