Culture-expanded mesenchymal stromal cell therapy: does it work in knee osteoarthritis? A pathway to clinical success

Abstract

Osteoarthritis (OA) is a degenerative multifactorial disease with concomitant structural, inflammatory, and metabolic changes that fluctuate in a temporal and patient-specific manner. This complexity has contributed to refractory responses to various treatments. MSCs have shown promise as multimodal therapeutics in mitigating OA symptoms and disease progression. Here, we evaluated 15 randomized controlled clinical trials (RCTs) and 11 nonrandomized RCTs using culture-expanded MSCs in the treatment of knee OA, and we found net positive effects of MSCs on mitigating pain and symptoms (improving function in 12/15 RCTs relative to baseline and in 11/15 RCTs relative to control groups at study endpoints) and on cartilage protection and/or repair (18/21 clinical studies). We examined MSC dose, tissue of origin, and autologous vs. allogeneic origins as well as patient clinical phenotype, endotype, age, sex and level of OA severity as key parameters in parsing MSC clinical effectiveness. The relatively small sample size of 610 patients limited the drawing of definitive conclusions. Nonetheless, we noted trends toward moderate to higher doses of MSCs in select OA patient clinical phenotypes mitigating pain and leading to structural improvements or cartilage preservation. Evidence from preclinical studies is supportive of MSC anti-inflammatory and immunomodulatory effects, but additional investigations on immunomodulatory, chondroprotective and other clinical mechanisms of action are needed. We hypothesize that MSC basal immunomodulatory "fitness" correlates with OA treatment efficacy, but this hypothesis needs to be validated in future studies. We conclude with a roadmap articulating the need to match an OA patient subset defined by molecular endotype and clinical phenotype with basally immunomodulatory "fit" or engineered-to-be-fit-for-OA MSCs in well-designed, data-intensive clinical trials to advance the field.

Keywords: Cell therapy; MSC; Osteoarthritis; RCT; mesenchymal stromal cell.

Fig. 1

PRISMA flow diagram of the literature selection process. PubMed search string “((((((MPC) OR (Mesenchymal stem cell)) OR (MSC)) OR (ASC)) OR (Mesenchymal stromal cell)) AND (Osteoarthritis) + Clinical Trial + RCT”

Fig. 2

Clinical and preclinical evidence of mesenchymal stromal cell mechanisms of action on immunomodulation and chondroprotection in knee osteoarthritis. Solid arrows are used to demonstrate mechanisms for which there is supporting clinical evidence: dashed arrows indicate the relationship between immunomodulatory and chondroprotective mechanisms supported by preclinical evidence. MSC mesenchymal stromal cell, CQAs critical quality attributes, OA osteoarthritis

Fig. 3

Levers for enabling successful mesenchymal stromal cell trials in osteoarthritis - Four aspects that need to be addressed to enable successful patient outcomes. PROMs patient-reported outcome measures, CPPs critical process parameters, CQAs critical quality attributes, MSCs mesenchymal stromal cells, OA osteoarthritis