Research On The Mechanisms Of Flk-1~+ Mesenchymal Stem Cells Differentiation

Stem cell research is one of the most fascinating areas of biology today.In our lab, Flk-1~+CD31~-CD34~-MSCs could be isolated and purified from various fetal or adult tissues,which have been proven with extensive clone-forming and expansion capacity and the potential to differentiate into cells of all three layers,including hematopoietic differentiation,although at a very low frequency.Small non-coding RNAs(sRNA) study is also one of the most fascinating areas recently.MicroRNAs,as the most famous sRNAs,have been demonstrated to have important foles in development,cell proliferation,differentiation,apoptosis,cell cycle progression,tumorigenesis and many other physiological or pathological processes.In the first part of this study,we aims to find the highly functional sRNAs during the differentiation of bone marrow derived Flk-1~+CD31~-CD34~- MSCs(BMSCs) to hematopoietic cells.The results indicted that sRNA ZK-249,a newly identified short hairpin RNA(shRNA) could enhance the hematopoietic differentiation of BMSCs. BMSCs transduced with ZK-249 can differentiate into hematopoietic stem cells (HSCs) more efficiently and their descendant multipotent progenitor cells that have the capacity of further differentiating into blood cells in vitro.On transplantation into sublethally irradiated NOD/SCID mice,transduced human BMSCs engrafted and differentiated into all hematopoietic lineages including lymphocytes and myelocytes. Furthermore we find that this new shRNA alters BMSC fate by repressing the translation of EID1.Thus our findings establish a model that the endogenous shRNA can confer definitive tropism to BMSCs and unveil an intrinsic roadmap for programming hematopoiesis-related genes in HSCs. In the second part,adipose tissue-derived MSCs(ADAS) were induced to differentiate into endothelial cells,neural cells and epithelial cells respectively.And then mRNA microArray and sRNA microArray were used to detect the differential expression profiles of mRNA and sRNA.The results showed that the major signaling pathways involved in the "stemness" and differentiation of ADAS to three layers are TGFβ,Wnt,BMP4 and Notch pathways.The role of TGFβand Wnt pathways is to maintain the stemness of ADAS,and the other pathways mainly to enhance the differentiation.Comparing to the mRNA level,sRNA alterations during the differentiation of ADAS are more the phenomena than elucidation due to the limit understanding of sRNA function.The sRNAs altering during the differentiation are classified into several categories,for example,the down-regulation sRNAs in all the three layers differentiation are listed together,which are proposed to be associated with the "stemness" of ADAS.In addition,all the sRNAs＜30nt were cloned and sequenced,which provides the sRNA expression patterns of ADAS.And by alignment with the microRNA database,the microRNA expression profiles in ADAS were acquired as well as several novel sRNA requiring the further identification.