Background and Objectives Balance between matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) ensures maintenance of healthy cartilage, whereas weighted damaging effects of the enzymes leads to the development of osteoarthritis (OA). To develop the adipose tissue derived stem cell (ASC) therapy in OA, we were seeking to evaluate paracrine and chondroprotective properties of the cells in recovering the homeostasis between MMPs/TIMPs in the joint.

Methods To determine the effects of ASCs on OA cartilage, we performed short (3 & 7 days) and long (21 day) in vitro ASC cocultures with articular cartilage explants (CE). To further reproduce the OA conditions, cocultures were also stimulated with IL-1β. Production of TIMPs, MMPs, and factors, related to inflammation or chondrogenesis, was analysed in coculture supernatants by ELISA. CE were further processed for RT-qPCR and immunohistochemical analysis.

Results ASC produced TIMP-1, -2 and -3, as well as gelatinases MMP-2 and -9 at the levels similar to those of CE. Gelatinases MMP-2 and -9 degrade denatured collagens, including type I. Cocultures with ASC resulted in up-regulation of COL1A1 gene. Although the increase in collagen type I production is generally considered as a sign of fibrosis, its enhancement has also been demonstrated during cartilage development, and might reflect early events of the repair. No or low production of MMP-1, MMP-3, and MMP-13 was determined in supernatants of ASC, whereas CE produced them abundantly. Noteworthy, cocultures with the cells resulted in significant suppression of MMP-13 on days 3 & 7, and in particular, day 21, as compared to CE alone at the both, mRNA and protein level.

Stimulation with IL-1β differentially modulated production of various MMPs and TIMPs by ASCs and CE, however the effects of ASC seem to further be beneficial.

Histological examination showed a tendency to extracellular matrix improvement in the osteoarthritic CE cocultured with ASC, further supporting chondroprotective effects of those cells in the both, presence or absence of IL-1β.

Conclusions Production of TIMPs and gelatinases, associated with the increase in collagen I production in CE by ASC suggest their active participation in cartilage turnover, encompassing stimulation of remodelling processes. Absence of MMP-1, -3 or -13 production implies safety of the use of ASC for intraarticular clinical applications. Down-regulation of MMP13 in CE indicates possible antihypertrophic effects of ASC. Taken together, results of our study suggest beneficial properties of ASC in prevention of cartilage from degradation during OA, even in the presence of IL-1β.