Biology subjects

Little, C. B.

Publications and source records attributed to Little, C. B..

4 recordsLinked to original sources

bioRxiv2023

Recommendations For a Standardized Approach to Histopathologic Evaluation of Synovial Membrane in Murine Models of Experimental Osteoarthritis

BackgroundSynovial pathology has been linked to osteoarthritis (OA) pain in patients. Microscopic grading systems for synovial changes in human OA have been described, but a standardized approach for murine models of OA is needed. We sought to develop a reproducible approach and set of minimum recommendations for synovial histopathology in mouse models of OA. MethodsCoronal and sagittal sections from male mouse knee joints subjected to destabilization of medial meniscus (DMM) or partial meniscectomy (PMX) were collected as part of other studies. Stains included Hematoxylin and Eosin (H&E), Toluidine Blue (T- Blue) and Safranin O/Fast Green (Saf-O). Four blinded readers graded pathological features (hyperplasia, cellularity, and fibrosis) at specific anatomic locations in the medial and lateral compartments. Inter-reader reliability of each feature was determined. ResultsThere was acceptable to very good agreement between raters. After DMM, increased hyperplasia and cellularity and a trend towards increased fibrosis were observed 6 weeks after DMM in the medial locations, and persisted up to 16 weeks. In the PMX model, cellularity and hyperplasia were evident in both medial and lateral compartments while fibrotic changes were largely seen on the medial side. Synovial changes were consistent from section to section in the mid-joint area mice. H&E, T-blue, and Saf-O stains resulted in comparable reliability. ConclusionsTo allow for a standard evaluation that can be implemented and compared across labs and studies, we recommend using 3 readers to evaluate a minimum set of 3 pathological features at standardized anatomic areas. Pre-defining areas to be scored, and reliability for each pathologic feature should be considered.

pathology↗

bioRxiv2023

Loss of Grem1-articular cartilage progenitor cells causes osteoarthritis.

Osteoarthritis (OA), which carries an enormous disease burden across the world, is characterised by irreversible degeneration of articular cartilage (AC), and subsequently bone. The cellular cause of OA is unknown. Here, using lineage tracing in mice, we show that the BMP-antagonist Gremlin 1 (Grem1) marks a novel chondrogenic progenitor (CP) cell population in the articular surface that generates joint cartilage and subchondral bone during development and adulthood. Notably, this CP population is depleted in injury-induced OA, and with age. OA is also induced by toxin-mediated ablation of Grem1 CP cells in young mice. Transcriptomic analysis and functional modelling in mice revealed articular surface Grem1-lineage cells are dependent on Foxo1; ablation of Foxo1 in Grem1-lineage cells led to early OA. This analysis identified FGFR3 signalling as a therapeutic target, and injection of its activator, FGF18, caused proliferation of Grem1-lineage CP cells, increased cartilage thickness, and reduced OA pathology. We propose that OA arises from the loss of CP cells at the articular surface secondary to an imbalance in progenitor cell homeostasis and present a new progenitor population as a locus for OA therapy.

cell biology↗

bioRxiv2022

Understanding the effects of mesenchymal stromal cell therapy for treating osteoarthritis using an in vitro co-culture model

Osteoarthritis (OA) is a leading cause of chronic pain and disability, for which there is no cure. Mesenchymal stromal cells (MSCs) have been used in clinical trials for treating OA due to their unique functions to send paracrine anti-inflammatory and trophic signals. Interestingly, these studies have shown mainly short-term effects of MSCs in improving pain and joint function, rather than sustained and consistent benefits. This may reflect a change or loss in the therapeutic effects of MSCs after intra-articular injection. This study aimed to unravel the reasons behind the variable efficacy of MSC injections for OA using an in vitro co-culture model. Osteoarthritic human synovial fibroblasts (OA-HSFs) exposed to MSCs showed short-term downregulation of pro-inflammatory and pro-catabolic genes, but the MSCs showed upregulation of pro-inflammatory genes and impaired ability to undergo osteogenesis and chondrogenesis in the presence of OA-HSFs. Moreover, short-term exposure of OA-HSFs to MSCs was insufficient for inducing sustained changes to their diseased behaviour. These findings suggest MSCs may not provide long-term effects in correcting the OA joint environment due to adopting the diseased phenotype of the surrounding tissues, which have important implications in the future development of effective stem cell-based OA treatments with long-term therapeutic efficacy.

cell biology↗

bioRxiv2017

Cartilage microRNA dysregulation during the onset and progression of mouse osteoarthritis overlaps with patient disease candidates

To explore the role of microRNAs in osteoarthritis (OA), we conducted microRNA expression profiling on micro-dissected tibial cartilage and subchondral bone in a mouse model of OA produced by medial meniscus destabilization (DMM). DMM mice had characteristic cartilage degeneration, subchondral bone sclerosis and osteophyte formation. While subchondral bone showed no microRNA dysregulation, 139 microRNAs were differentially expressed in DMM cartilage at 1 and/or 6 weeks after OA initiation. To prioritize OA-candidates, dysregulated microRNAs with human orthologues were filtered using paired microRNA:mRNA expression analysis to identify those with corresponding changes in mRNA target transcripts in the DMM cartilage. An important cohort overlapped with microRNAs identified in human end-stage OA. Comparisons with microRNAs dysregulation in DMM mouse cartilage where aggrecan cleavage was genetically-ablated demonstrated that all were independent of aggrecan breakdown, earmarking these as important to the critical stages of OA initiation. Our comprehensive analyses identified high-priority microRNA candidates that have potential as human OA-biomarkers and therapeutic targets.\n\nSUMMARYKung et al. conducted global analysis of microRNA dysregulation in joint tissues of a well-established mouse osteoarthritis model. Stringent filtering against human microRNA orthologues, integrated mRNA target analysis and comparison with published studies on human end-stage osteoarthritis identified microRNA candidates of potential clinical relevance.

cell biology↗