Interaction between circadian gene Bmal1 and adipogenic regulator PPARγ in UVB-exposed mesenchymal stem cells

Background: Mesenchymal stem cells (MSCs), including adiposederived MSCs (ADMSCs) and bone marrow-derived MSCs (BMMSCs), are multipotent cells essential for tissue repair, with strong self-renewal and differentiation abilities.Bmal1 is a core component of the circadian cycle and plays a regulatory role in stem cell specialization; PPAR links adipogenesis to the circadian rhythm by epigenetically regulating Bmal1.Ultraviolet B (UVB) radiation influences circadian processes by modulating the expression of growth factors and cytokines in MSCs.Aims: This study investigated how UVB affects adipogenesis and circadian-system-related gene transcription in ADMSCs and BMMSCs.Methods: MSC viability post-exposure was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis.Cells were cultured in adipogenesis medium and stained with Oil Red O at multiple time points.UVB-treated MSCs were maintained under differentiation-inducing conditions for 28 days, and gene expression was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR).Results: Viability assays identified 25 mJ/cm as the optimal UVB dose.Flow cytometry confirmed the enhanced expression of MSC markers (CD54, CD90, and CD29) and low expression of hematopoietic markers (CD45, CD106, and MHC class II).Oil Red O staining revealed gradual lipid accumulation, beginning on day 14 and forming mature droplets by day 28.qRT-PCR indicated a significant increase in PPAR expression in adipogenic differentiation groups and Bmal1 expression post-UVB exposure. zetDayanak: Ya dokusundan elde edilen mezenkimal kk hcreler (ADMKH) ve kemik iliinden elde edilen mezenkimal kk hcreler (KMKH) dhil olmak zere mezenkimal kk hcreler (MKH), gl z yenilenme ve farkllama kapasiteleri sayesinde doku onarmnda nemli rol oynayan multipotent hcrelerdir.Bmal1 proteini, gnlk hcresel biyolojik sreleri dzenleyen sirkadiyen dngnn temel bileenlerinden biridir ve basklanmasnn kk hcrelerin farkllama kapasitesini deitirdii bilinmektedir.PPAR ise adipojenik farkllama ile sirkadiyen ritim arasnda balant kurarak Bmal1'in epigenetik dzenlenmesinde rol oynamaktadr.Ultraviyole B (UVB) radyasyonunun, MKH'lerde byme faktrleri ve sitokin ekspresyonunu etkileyerek sirkadiyen ritim zerinde