Activation of KYN-AHR axis impairs the chondrogenic and chondroprotective effects of human umbilical cord-derived mesenchymal stem cells on osteoarthritis

Abstract

Background: It has been proved that intra-articular injection of mesenchymal stem cells (MSCs) could alleviate cartilage damage of osteoarthritis (OA) via differentiating into chondrocytes or protecting inherent cartilage. However, how OA articular microenvironment could affect MSCs’ chondrogenic and chondroprotective efficiency has yet to be fully demonstrated. Tryptophan (Trp) metabolites, most of which are endogenous ligand for aryl hydrocarbon receptor (AHR), are abnormally increased in synovial fluid (SF) of OA patient. In this study, the effects of kynurenine (KYN), one of the most important metabolites of Trp, were evaluated on the chondrogenic and chondroprotective effects of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs). Methods: hUC-MSCs were cultured with conditioned medium containing different proportions of OA SF, then AHR activation, proliferation and chondrogenesis of hUC-MSCs were measured. In order to determine whether the chondrogenic differentiation of hUC-MSCs were regulated by AHR, hUC-MSCs were stimulated with KYN before detecting their chondrogenesis. In vitro AHR-konck down hUC-MSCs stable cell line (shAHR-UC-MSC) was generated using lentivirus transfection. Moreover, the chondroprotective effiency of shAHR-UC-MSC was determined in OA rat model.Results: OA SF could activate AHR signaling in hUC-MSCs in a concentration-dependent manner and inhibit the chondrogenic differentiation and proliferation ability of hUC-MSCs. Similar results were observed in hUC-MSCs stimulated with KYN in vitro. AHR knockdown could remarkably eliminate the suppression effects of KYN on hUC-MSCs’ chondrogenic differentiation and proliferation ability. Notably, hUC-MSCs with AHR knockdown exhibited superior therapeutic effiency in OA rat upon intra-articular injection. Conclusion: Taken together, this study indicates that OA articular microenvironment is not conducive to the therapeutic effect of hUC-MSCs, which is related to the activation of the AHR pathway by tryptophan metabolites, thus impairs the chondrogenic and chondroprotective effects of hUC-MSCs. AHR might be a promising modification target for further improving the therapeutic efficacy of hUC-MSCs on treatment of cartilage-related diseases such as OA.

Recent advances in mesenchymal stem/stromal cells (MSCs)‐based approaches for osteoarthritis (OA) therapy

“…In coculture conditions, human UC-MSCs can affect the expression profile of the OA patients' derived chondrocytes. The UC-MSCs downregulated MMP-13, collagen type X α1 chain, and COX-2 expression in OA chondrocytes and potentiated their proliferation (Chang et al, 2022). OA chondrocytes also can stimulate the expression of type II collagen (Col2), SRY-box transcription factor 9 (SOX-9), and aggrecan in UC-MSCs and thus improve their chondrogenesis (Wang, et al, 2018).…”