Epigenetic modulation of mesenchymal stem cells as therapeutic interventions for osteoarthritis
Osteoarthritis (OA) is an inflammatory and degenerative joint and cartilage disease affecting millions of adults worldwide. It is an unmet clinical need still lacking effective treatments except for pain management and surgical procedures to maintain joint movement, thus. Mesenchymal stem cells (MSCs) have emerged with promising potential for cell-based articular cartilage repair, as they secrete a variety of chemokines and cytokines that aid in repair and restoration of degraded tissue, and counteracting inflammation. Such chondro-regenerative and immunomodulatory potential make MSCs ideal therapeutic candidates for treating OA. However, clinical and translational studies on cartilage repair have used heterogenous MSC populations with varying differentiation abilities yielding inconsistent healing outcomes.
Given that chromatin states in MSCs are distinct during undifferentiated (euchromatin) and differentiated (heterochromatin) states, we hypothesize that epigenetic modulation of MSC chromatin with small molecules can trigger specific transcriptional responses towards achieving desired cellular phenotypes facilitating tissue regeneration. We also hypothesize that variable heterochromatin states and associated signaling pathways influence secretion of bioactive trophic factors critical for healing. Based on these hypotheses, we propose a novel epigenetic modulation strategy for enhancing and maintaining the chondro-regenerative potential of MSCs.
Preliminary data indicate that cytoskeletal actin modifications with Cytochalasin D (CytoD) initiated robust osteogenic differentiation concomitant with suppression Polycomb chromatin regulator Enhancer of Zeste Homolog 2 (EZH2) which controls heterochromatin formation, while independently upregulating RUNX2. Samsonraj also observed that combination of CytoD or melatonin with EZH2-selective inhibitor, GSK126, promoted synergistic osteogenic effects. The overall objective is to epigenetically precondition MSCs to improve both chondrogenic differentiation and secretion of trophic factors to facilitate cartilage regeneration. We seek to achieve this goal by working on two specific aims:
Aim 1: Determining effects of epigenetic drugs on MSC chondrogenesis and secretome. The feasibility of this approach has been previously tested with two epigenetic small molecule combinations (CytoD-GSK126 and melatonin-GSK126) in evaluating their effects on MSC differentiation. We will assess individual and synergistic effects of curcumin, a histone deacetylase (HDAC) inhibitor, in combination with melatonin and CytoD, on adipose MSC proliferation, differentiation and secretome. Chromatin immunoprecipitation (ChIP) and secretome profiling for chondrogenic factors and anti-inflammatory cytokines will be performed. These results will demonstrate the effects of epigenetic preconditioning on in vitro MSC chondrogenesis.
Aim 2: Assessment of MSC efficacy in rat osteochondral defect model. In vivo efficacy in mediating cartilage regeneration will be assessed on an established rat osteochondral defect model wherein epigenetically modified MSCs will be delivered in fibrin and healing assessed by analyzing knee joints for gene expression, repair scoring, histomorphometry, and micro-computed tomography 8 weeks post-administration of MSCs. Results will demonstrate the safety and efficacy of MSCs in treating cartilage defects.
Study outcomes will lead to development of a novel grade of epigenetically modulated MSCs with improved potency for treating osteoarthritis. Our innovative cell-bioengineering strategy circumvents the need to genetically modify MSCs and represents a new line of investigation not been previously funded. Faculty on this proposal have not collaborated previously. Procedures involving animals will be performed as per approved IACUC protocols.
- Stem cells
- Mesenchymal Stem Cells
- Osteochondral defect
- Regenerative Medicine