Mesenchymal stem cell regeneration and differentiation after anti inflammatory drug exposure

Abstract: Traumatic and degenerative pathologies of the musculoskeletal system are common and often involve injuries of multiple mesenchymal tissues including bone, cartilage, tendons and ligaments. Medical intervention is frequently initiated to relieve pain, restore biomechanical function, with aim to return to the desired level of activity as soon as possible. Oral or locally administered symptomatic pain relief has been used for a very long time, with little or no consideration of the long-term consequences on regeneration or optimizing healing properties of the synovial joint. Commonly used drugs are non-steroid-anti-inflammatory drugs (NSAIDS), aswell as locally injected glucocorticoids, administred peri- or intra articular when oral analgetics are insufficient. The focus of this thesis was to deeper explore the impact of short time exposure of two commonly used anti-inflammatory drugs i.e diclofenac (DF) and triamcinolone acetonide (TA) on mesenchymal stem cell (MSC) viability, differentiation capacity and trancriptomic output. Effect of tenogenic inducing growth factor GDF-7 on MSC differentiation was also assessed. The results of a murine model system showed the significantly reduced growth of MSCs exposed to TA and DF in therapeutical concentrations, in a concentration- and time dependent manner, however the growth inhibitory effect of DF was significantly reduced only in high concentrations. MSCs exposed to GDF-7 showed increased expression of tenogenic marker tenomodulin. Concomitant exposure of MSCs to GDF-7 and TA increased adipogenesis unpremeditatedly in a time dependent manner. Further studies were performed on primary human bone marrow MSC growth (hBM-MSC) where TA exerted a time- and dose dependent negative impact on hBM-MSCs. In addition, TA impaired cell cycle regulation and DNA replication, increased apoptotic/late-apoptotic cells significantly in TA-exposed cells. Differentiation assays after TA exposure revealed upregulation of osteoblastic marker RUNX2, but no significant difference after osteoblastic differentiation of hBM-MSCs exposed to TA or control. Adipogenesis was spontaneously induced by TA and could be confirmed both molecular and functional and TA clearly impaired chondrogenic differentiation demonstrated by molecular- and functional assays. The anti-inflammatory glucocorticoid stimulus on hBM-MSCs was verified with impaired inflammatory response. TA also reduced hBM-MSC activation, pointing to several functional mechanisms altered in the MSC immunoresponse to TA. In concusion, the results from this thesis raise the awareness of unpremeditated negative trophic effects of the synovial joint tissue when treating with the anti- inflammatory drugs triamcinolone acetonide and diclofenac, aiming at relieving pain. The side-effects are significant, impairing regeneration and chondrogenesis while promoting adipogenesis.