Biology subjects

Howser, S. C.

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

4 recordsLinked to original sources

bioRxiv2026

Thrombospondin-2 deficiency primes the synovial joint for aberrant tissue remodeling and injury response

ObjectiveThis study investigates joint injury-induced angiogenesis and the effects of genetic deficiency of thrombospondin-2 (TSP2), an anti-angiogenic factor, in joint homeostasis and post-traumatic osteoarthritis (PTOA). MethodWe utilized a murine non-invasive anterior cruciate ligament rupture (ACLR) model of PTOA and mined published synovial transcriptomics datasets to investigate injury-induced synovial angiogenesis. Spatial transcriptomics and flow cytometry of TSP2-GFP reporter mice were used to assess injury-induced thrombospondin-2 and its cellular origins in synovium. Global TSP2 knockout mice (TSP2-KO) were used to assess the effect of TSP2 deficiency on early and late stages of PTOA development via molecular imaging of inflammation and angiogenesis, histopathology, micro-computed tomography, Raman spectroscopy, and synovium bulk RNA-sequencing. ResultsIntra-articular angiogenesis peaked at 7d post-ACLR and declined but remained elevated above baseline at 28d post-ACLR. We identified synovial crosstalk between endothelial cells and sublining fibroblasts as a key driver of angiogenesis and source of thrombospondin-2 signaling, with TSP2 primarily upregulated in sublining fibroblasts. TSP2-KO mice exhibited increased peri-articular inflammation at 7d post-ACLR and inferior bone quality. Histopathology revealed greater PTOA severity but paradoxically lower synovitis in TSP2-KOs. Additionally, aberrant structural remodeling of the entire knee joint was observed in uninjured and ACLR TSP2-KO limbs. The uninjured TSP2-KO synovial transcriptome demonstrated elevated immune, fibrotic, and angiogenic activation; however, TSP2-KO and WT synovial transcriptomes partially converged upon injury. ConclusionTSP2 is essential for joint homeostasis and trauma response. Global TSP2 deficiency causes premature OA and worsened PTOA, suggesting that therapeutic targeting with TSP2 mimetic could be used to prevent OA.

physiology↗

bioRxiv2025

Spatial transcriptomic profiling of decalcified murine musculoskeletal samples via Xenium Prime 5K

Successful generation of high-quality spatial transcriptomics data from murine musculoskeletal tissues has been impeded by the challenge of preserving RNA integrity through the harsh tissue processing steps required for histological sectioning. In particular, the need to thoroughly fix and decalcify mineralized tissues has proven problematic. We detail a comprehensive sample processing pipeline for three common murine musculoskeletal tissue samples, enabling high-quality transcript detection via imaging-based spatial transcriptomics using the Xenium Prime 5K platform from 10x Genomics. Our protocol outlines methodological details for transcardiac perfusion, fixation, decalcification, paraffin processing, and a sample co-embedding strategy facilitating anatomically consistent and simultaneous sectioning of multiple samples onto the spatial transcriptomics slide. Rigorous quality control demonstrates high-quality tissue-specific outcomes across intact knee joints, tibiae, and lumbar spines from adult mice. Our pipeline enabled 70-91% high-quality transcripts across synovium, meniscus, patellar tendon, articular cartilage, subchondral bone, cortical bone, bone marrow, muscle, fracture callus, and dorsal root ganglion tissues. The average number of detected transcripts varied markedly between tissue types - soft tissues such as synovium, patellar tendon, muscle, bone marrow, and callus exhibited ~200 - 400 transcript per cell; mineralized tissues such as subchondral bone, meniscus, and cortical bone exhibited ~ 13 - 150 transcripts per cell; highly active neuronal tissues such as dorsal root ganglion neurons yielded 750 - 1100 transcripts per cell. Canonical cell markers within each tissue confirmed successful identification and representation of key cell types. Through rigorous sample quality assessment at multiple stages of processing, this protocol yields high-quality RNA transcript detection while preserving critical anatomical context and will serve as a valuable tool enabling spatial transcriptomic profiling of intact musculoskeletal tissue samples. Lay summarySpatial transcriptomics is a powerful scientific tool that characterizes genetic coding material ("transcripts") of specific cell types in their native anatomical context. However, successfully applying this tool to musculoskeletal tissues has been challenging because preserving transcript integrity in these tissues requires additional care. The authors of this publication developed a specialized method for preparing tissue samples from mice that works with the spatial transcriptomics platform, 10x Genomics Xenium Prime 5K. This protocol improves sample quality while preserving high-quality genetic information in various mouse musculoskeletal tissues, making it easier to explore their functions. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=168 SRC="FIGDIR/small/693132v1_ufig1.gif" ALT="Figure 1"> View larger version (87K): org.highwire.dtl.DTLVardef@4c4389org.highwire.dtl.DTLVardef@e607bcorg.highwire.dtl.DTLVardef@5f957org.highwire.dtl.DTLVardef@34ce27_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2025

Acute immune modulation with poly-salicylic acid particles ameliorates pain and structural damage in post-traumatic osteoarthritis

Joint inflammation is a hallmark of post-traumatic osteoarthritis (PTOA) progression and a recognized driver of articular destruction and symptoms. Despite its known pathological role, inflammation has not been successfully targeted to treat PTOA. With the hypothesis that blocking the acute influx of systemically-derived immune cells can mitigate injury-induced inflammation and downstream PTOA disease severity, we targeted immune cell recruitment via systemically-administered poly salicylic acid (PolySA) particles. This formulation targets immune cells in circulation, namely neutrophils and monocytes, to inhibit their vascular extravasation into injured tissue. Employing a murine joint injury model, we show that PolySA particles reduced neutrophil and monocyte recruitment to the synovium by >50% when administered acutely after injury. Sex-specific therapeutic effects of PolySA emerged 7d post-ACLR, whereby female knee joints exhibited increased cathepsin activity and alleviation of knee hyperalgesia. Despite also observing reduced immune cell recruitment in male mice treated with PolySA, therapeutic effects were entirely absent in males. RNAseq of female synovium revealed a transcriptomic signature indicative of accelerated immune resolution and matrix remodeling in PolySA-treated female mice. Analyses at a timepoint of established disease showed that PolySA-treated female mice exhibited sustained pain alleviation, reduced osteophyte formation, and decreased histopathological PTOA and synovitis severity scores. Together, these findings indicate that blocking acutely-recruited immune cells to the local joint microenvironment via systemic PolySA particle treatment is a promising therapeutic for PTOA prevention by reprogramming early injury-induced inflammation.

bioengineering↗

bioRxiv2025

CXCL16 mediates nociception and inflammation in murine post-traumatic osteoarthritis

This study investigates the role of the chemokine CXCL16 and its receptor, CXCR6, in post-traumatic osteoarthritis (PTOA) and joint nociception, highlighting the potential of targeting the CXCL16-CXCR6 axis for therapeutically managing joint inflammation and pain. Following joint injury in mice, the CXCL16-CXCR6 signaling axis is activated in synovium, driven by synovial fibroblasts and macrophages. Human OA synovium also exhibited increased CXCL16 and CXCR6 gene expression. CXCL16 stimulated a pro-inflammatory response in fibroblasts and macrophages, contrasting with an anti-inflammatory response observed in mesenchymal progenitor cells. In mice, repeated intra-articular CXCL16 injections induced histological synovitis and sex-dependent activation of inflammatory and fibrotic transcriptional programs in synovium. Repeated CXCL16 joint injections also induced knee hyperalgesia, which was mitigated by co-administration of the CXCR6 antagonist, ML339. A single intra-articular injection of CXCL16 induced acute knee hyperalgesia as early as 30 minutes post-injection, which was completely abrogated by ML339 co-treatment, suggesting direct CXCL16 binding to nociceptor-expressed CXCR6. In a murine PTOA model, systemic CXCR6 antagonism with ML339 alleviated knee hyperalgesia and altered circulating immune cell profiles. Direct stimulation of mouse dorsal root ganglion-derived nociceptive neurons with CXCL16 induced rapid calcium signaling, which was abolished by co-treatment with ML339. These findings establish CXCL16 as a regulator of joint inflammation and identifies the CXCL16-CXCR6 binding mechanism as key in mediating pain-related behaviors and nociceptor activation, offering a therapeutic target for PTOA-related inflammation and pain management. One Sentence SummaryCXCL16 regulates synovial inflammation and mediates joint nociception via CXCR6, highlighting its potential as a therapeutic target for post-traumatic osteoarthritis.

physiology↗