Biology subjects

Blackler, G.

Publications and source records attributed to Blackler, G..

3 recordsLinked to original sources

bioRxiv2024

Metabolic Stress Accelerates Dysregulated Synovial Macrophage-Fibroblast Communication and Htra1 Overproduction in Osteoarthritis

Biomechanical and metabolic factors increase the risk for osteoarthritis (OA) by causing supraphysiological stresses on joint tissues. Chronic exposure to these stresses contributes to failure of the joint organ system, resulting in pain and loss of function for patients with OA. The synovium is vital for joint organ health but during OA, synovial inflammation and damage are associated with worse outcomes including pain. Unfortunately, the separate and combined effects of metabolic and biomechanical stresses on synovial tissues are not well understood. In this study, metabolic syndrome (MetS) was associated with worse knee pain in patients with early-stage knee OA, suggesting that metabolic stress may act on synovial tissues during early-stage OA, exacerbating outcomes. In a rat model of experimental knee OA, the combined effects of biomechanical and metabolic stresses induced worse knee pain, cartilage damage, and synovial inflammation than biomechanical stress alone. Further, single-cell RNA sequencing of synovial macrophages and fibroblasts identified earlier metabolic (glycolytic and respiratory) shifts, neurogenesis, dysregulated communication, and cell activation when metabolic and biomechanical stresses were combined. Lastly, using a direct contact co-culture system, we showed that metabolic stress alters macrophage-fibroblast communication leading to increased expression of Htra1, a pathogenic protease in OA. This study identifies novel mechanisms that may represent amenable therapeutic targets for patients experiencing MetS and OA. One-sentence summary: Metabolic stress may cause worse outcomes in OA through dysregulated synovial cell communication that activates synovial fibroblasts and increases Htra1 production.

physiology↗

bioRxiv2023

Synovial macrophage activation mediates pain experiences in experimental knee osteoarthritis

It has been suggested that synovial macrophages mediate nociceptive signals in knee osteoarthritis (OA) but the underlying mechanisms are unknown. Our objectives were to investigate the role of synovial macrophages and their activation via signal transducer and activator of transcription (STAT) signaling in mediating OA pain experiences. We induced experimental OA in rats via knee destabilization surgery and then performed RNA sequencing analysis in sorted synovial macrophages to identify signaling pathways associated with macrophage activation. Next, we repeated intra-articular injections of liposomal clodronate to deplete macrophages, or liposomal inhibitors of STAT1 or STAT6 to block macrophage activation, and tested the effects on local and distal mechanical pain sensitivity. We also assessed synovitis, cartilage damage, and synovial macrophage infiltration with histopathology and immunofluorescence, and crosstalk between liposomal drug-treated synovium and articular chondrocytes in co-culture. Most enriched signaling pathways in activated OA macrophages involved STAT signalling. Macrophage depletion and STAT6 inhibition led to marked, sustained improvements in mechanical pain sensitivity and synovial inflammation compared to controls, but macrophage depletion caused increased synovial fibrosis and vascularization. In contrast, STAT1 and STAT6 inhibition in macrophages did not worsen synovial or cartilage pathology. In crosstalk assays, macrophage STAT1-inhibited synovium caused the greatest increases in the expression of anabolic and catabolic chondrocyte genes and sulphated glycosaminoglycan secretion in chondrocytes. Our results suggest that synovial macrophages play a key role in mediating pain experiences in experimental knee OA, and that selectively blocking STAT6 in synovial macrophages may reduce OA-related pain without accelerating joint tissue damage. (248/250) One Sentence SummarySelective drug targeting to synovial macrophages improves pain experiences in surgical joint destabilization-induced experimental rodent knee OA. (145/150)

physiology↗

bioRxiv2021

Genetic deletion of interleukin-15 is not associated with major structural changes following experimental post-traumatic knee osteoarthritis in rats

Post-traumatic Osteoarthritis (PTOA) is a degenerative joint disease, leading to articular cartilage breakdown, osteophyte formation, and synovitis, caused by an initial joint trauma. Pro-inflammatory cytokines increase catabolic activity and may perpetuate inflammation following joint trauma. Interleukin-15 (IL-15), a pro-inflammatory cytokine, is increased in OA patients, although its roles in OA pathophysiology are not well characterized. IL-15 levels appear to correlate to self-reported pain levels, and polymorphisms in the IL-15 receptor alpha gene correlate to a 1.5-fold increase in OA symptoms. This could be due to IL-15 effects on the activity of proteinases, such as matrix metalloproteinases (MMP) -1, -3, and -7. Here we utilized Il15 deficient rats to examine the role of IL-15 in PTOA pathogenesis in an injury-induced model of OA. OA was surgically induced in Il15 deficient rats and control wild-type rats to compare PTOA progression. Semi-quantitative scoring of the articular cartilage, subchondral bone, osteophyte size, and synovium was performed by two blinded observers. Analyses of articular cartilage damage, subchondral bone damage, and osteophyte formation revealed no significant difference between Il15 deficient rats and wild-type rats following PTOA-induction. Similarly, synovitis scoring across 6 parameters found no significant difference between genetic variants. Overall, IL-15 does not appear to play a key role in the development of structural changes in this surgically-induced rat model of PTOA.

genetics↗