ABSTRACT
INVESTIGATORS: Rhima Coleman, PhD (PI) is an Associate Professor of Biomedical Engineering focused on
genetic engineering of stem cells for the treatment of joint pathology. Tristan Maerz, PhD (Co-PI) is an Assistant
Professor of Orthopaedic Surgery with expertise in PTOA pathophysiology and synovial inflammation.
RESEARCH CONTEXT: Persistent intra-articular inflammation is a recognized driver of joint pathology during
post-traumatic osteoarthritis (PTOA) progression. Mesenchymal stem/multipotent stromal cells (MSCs) possess
potent anti-inflammatory properties, and MSC-derived chondrocytes (MdChs) have shown promise as a
regenerative intra-articular treatment. Successful implementation of MdChs as a cellular therapy is currently
hindered by rapid hypertrophic maturation of MdChs driven by the transcription factor RUNX2, which is
exacerbated by cytokines known to be enriched in the PTOA joint. We have genetically engineered MdChs to
autonomously suppress RUNX2 (sRX2-MdChs), and, therefore, chondrocyte hypertrophy, which supports
cartilage formation, even under inflammation. Critically, our preliminary data also indicate that the secretome of
these genetically modified cells markedly reduce the local pro-inflammatory environment by inducing
repolarization of pro-inflammatory macrophages (M1) into the anti-inflammatory (M2) phenotype.
OBJECTIVE: To test the disease-modifying and anti-inflammatory efficacy of genetically engineered RUNX2-
suppressing MdChs as a cellular treatment in a murine model of PTOA.
SPECIFIC AIMS: 1). Demonstrate that a single sRX2-MdCh injection blocks pathological inflammation and
PTOA progression following joint injury. 2). Characterize the mechanisms that mediate the autocrine and
paracrine effects of the sRX2-MdChs secretome on cartilage formation and the anti-inflammatory cellular
crosstalk between sRX2-MdChs and macrophages in vitro.
RESEARCH PLAN: In Aim 1, we will employ a noninvasive murine joint injury model of PTOA to test the anti-
inflammatory and PTOA-mitigating effects of a single sRX2-MdCh injection following injury. Male and female
mice will be randomized to 1) sRX2-MdChs; 2) Scramble-MdChs; 3) Unmodified/WT MSCs; or 4) Vehicle. We
will use a multifaceted set of live, in vivo and ex vivo outcomes to assess joint pain, intra-articular inflammation
and protease activity, bone remodeling, and articular cartilage damage to assess PTOA severity. We will track
intra-articular retention of injected cells via live fluorescent monitoring of luciferase activity and a near-infrared
tag. In Aim 2, we will test the hypothesis that the observed autocrine and paracrine effects of the sRX2-MdCh
secretome are mediated by IL-4 and assess the mechanism by which IL-4 effects MdCh cartilage formation and
M1-to-M2 macrophage polarization.
