Advancement of a lead small molecule gp130 modulator for improving outcomes in joint fibrosis

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Project summary/abstract Fibrosis is a pathological wound healing characterized by excessive deposition of disorganized collagen (COL) fibers by differentiated fibroblasts known as myofibroblasts that often originate from fibro-adipogenic progenitors (FAPs). Arthrofibrosis is a fibrotic disorder that occurs specifically in joints and is often attributed to surgical procedures or injury in which an excessive scar tissue response leads to restriction of joint motion and pain. Arthrofibrosis (AF) significantly decreases quality of life for patients and treatment options are currently limited to surgery and general anti-inflammatories. Various signaling cascades are activated during arthrofibrosis including IL-6/gp130 inflammatory signaling. IL-6 is involved in the development of chronic fibrosis, and IL-6 deficiency in mice results in fewer fibrotic changes after tissue injury. In addition, IL-6 is responsible for upregulation of TGF-β1, which is the primary driver of fibrosis and fibrogenic transition of FAPs. Another IL-6 family member, oncostatin M (OSM), has also been implicated in various stages of the fibrotic process including inflammation and activation of fibroblasts. During chronic inflammation, FAPs in the synovial capsule and infrapatellar fat pad differentiate into fibrogenic cells that generate scar tissue, limiting normal joint function. Our group has previously shown that modulation of IL-6/gp130 signaling with small molecules stimulated defect repair with superior hyaline tissue and prevented deposition of fibrocartilaginous matrix during wound healing in a full- thickness rat osteochondral defect model. However, the effects of gp130 modulators have never been studied in arthrofibrosis. We have now synthesized a library of novel analogs with different functional properties from the prototypic original molecule. Based on previously analyzed signaling properties in human mesenchymal progenitors and compelling in vivo data in a mouse model of pulmonary fibrosis, we have chosen CX-159 to progress forward. Thus, we hypothesize that modulating gp130 signaling with CX-159 early in the process of injury-induced arthrofibrosis may prevent and/or halt the processes that lead to arthrofibrosis. Here we will define the optimal concentration of CX-159 that blocks fibrosis in the presence of IL-6 cytokines and/or TGF-β1. We will evaluate the fibrotic biomarker profile (COLI, COLIII) via qPCR and ELISA, and differentiation of human and rat FAPs to myofibroblasts will be assessed via immunocytochemistry staining for α-SMA/COLI and Picrosirius Red staining for COL I/COLIII. We will then evaluate CX-159 in an established rat model of AF. Joint range of motion and contracture will be evaluated using a validated apparatus we first published, coupled with behavioral outcomes and immunohistological analysis of the synovium to assess AF. The overall goal of the proposed study is to develop an effective pharmacological therapeutic approach for reducing the progression of post-traumatic arthrofibrosis.