gms | German Medical Science

Objectives: Osteoarthritis (OA) is a complex immunologic disease. Current surgical and non-surgical concepts to treat OA only result in symptom-modifying effects. However, there is no disease-modifying therapy available. Extracellular vesicles released by mesenchymal stem/stromal cells (MSC-EV) are promising agents to positively influence joint homeostasis in osteoarthritic surroundings. Nevertheless, functional phenotypic differences of different MSC populations can influence the therapeutic potential of specific EV preparations. The aim of this study was to investigate the influence of characterized MSC-EVs on the chondrogenesis in a 3D chondrocyte pellet culture model. To analyze the therapeutic potential of MSC-EVs in a standardized inflammation model with the pro-inflammatory cytokine tumor necrosis factor alpha (TNF α ) was used.

Methods: Bovine articular chondrocytes were cultured and transferred into pellet culture at passage 3. TNF α(20ng/ml), human MSC-EV preparations (MSC-EV batches 41.5_i1, 84_i; 2x 105 cell equivalent), EVs from human platelet lysate (hPL) or the combination of cytokine and EVs were supplemented. To assess the effect of MSC-EVs in the chondrocyte inflammation model after 14 days, DNA, glycosaminoglycan (GAG), total collagen, IL-6 and NO release were quantified, and gene expression of anabolic (collagen 2, aggrecan, COMP, PRG 4), catabolic (MMP 3, MMP 13), dedifferentiation (collagen 1), hypertrophy (collagen 10) and inflammation (IL-8) markers were analyzed; histological evaluation was performed using safraninO/ fast green staining and immunohistochemistry of collagen 1 and 2. Apoptosis was analyzed by immunolabeling of anti-active caspase 3. For statistical evaluation non-parametric tests were chosen with a significance level of p<0.05.

Results and conclusion: TNF αsupplementation resulted in catabolic stimulation with increased levels of NO and IL 6, upregulation of catabolic gene expression and downregulation of anabolic markers. These findings were supported by a decrease of matrix differentiation (collagen 2) and increased apoptosis. Supplementation of EVs resulted in an upregulation of the chondrogenic marker PRG 4. All EV preparations significantly enhanced GAG retention per pellet. On the other hand, catabolic markers (MMP 3, MMP 13) and IL-8 were upregulated by MSC-EV 41.5i1. On protein level, IL-6 and NO release was increased by MSC-EV 41.5_i1. Histologic and immunohistochemical evaluation demonstrated a higher differentiation potential of MSC-EV 84_i.

TNF αhas a negative influence on chondrogenesis of chondrocyte pellets. MSC-EVs can positively influence chondrocyte matrix production in pro-inflammatory surroundings, but can also stimulate inflammation. In this study, MSC-EV 41.5_i1 enhanced inflammation, whereas MSC-EV 84_i had a higher chondrogenic potential. MSC-EVs present heterogenous inter-donor and intra-preparation properties. Further investigation to identify an MSC-EV preparation for OA treatment needs to be addressed.