Toll-benzeri reseptörlerin mezenkimal kök hücre farklılaşmasına ve immünmodülasyonuna katkıları

Mesenchymal stem cells (MSC) are pluripotent progenitor cells harboringunique characteristics along with several stem cell features such as lineagedependent differentiation and self-renewal capacity. MSCs are known to induceimmunomodulatory activity and homing capacity to damaged tissue sites. Suchdiverse capabilities of MSCs make them distinct from adult stem cells and can beharnessed in several therapeutic applications.Toll-like receptors (TLR) can recognize conserved microbial byproducts andare mainly expressed by innate immune system cells as well as epithelial orendothelial cells. Recent findings suggest that in vitro generated MSCs express someof these pathogen recognition receptors. In our view, to broaden the breath of thetherapeutic potential, TLR mediated activation of MSCs and demonstrate its impacton differentiation and immunomodulatory activity is critical.First, bone marrow-derived MSCs were generated and characterized via theirsurface marker expression by FACS (CD90, CD106 and CD45) at protein level andtheir message transcripts by RT-PCR (CD11b, CD29, CD34, CD45, CD71, CD73,CD90 and CD166). The most abundant marker was found to be CD90 over severalpassages. Following determination of TLR expression profile by RT-PCR,contribution of TLR ligands addition (TLR2, TLR3, TLR7 and TLR9) to MSCsduring adipogenic or osteogenic differentiation was studied. TLR3 was found to bethe most abundant type over several passages. The adipogenic differentiation ofrMSCs was found to be facilitated in the presence of TLR2 TLR3 and TLR7 ligands.Additionally, changes in the adipogenic and osteogenic markers (LPL, PPAR-g foradipogenesis, and ALP, OC-1, RUNX for osteogenesis) were analyzed by RT-PCR.While adipogenic markers upregulated osteogenic markers were downregulated inresponse to TLR ligand treatment.The final part of this study was performed with mouse mesenchymal stemcells. In order to define the immunostimulatory/immunosuppressive potential ofmouse MSCs, immunomodulatory character of MSCs were examined in the presenceor absence of mouse spleen cells. Our data suggested that when mMSCs are primedwith TLRL, a pro-inflammatory cascade as evidenced by increased IL-6 and IFN-?secretion is initiated either alone or in co-culture with splenocytes.In conclusion, TLR priming of MSCs augments their differentiation primarilyinto adipogenesis, and mainly these cells are immunostimulatory.