Man Bone Marrow Of Flk-1 ~ + Mesenchymal Stem Cell Resistance To Dna Damage Material Effect

Mesenchymal stem cells(MSCs) are multipotential cells that can be isolated from various of human tissues such as bone marrow, adipose tissue, muscle, brain and dermis of mammalian[1-6].They are able to be expensively expended in vitro and differentiate into osteocytes, chondrocytes, adipocytes, myocytes and even neural cells under appropriate conditions[7-11]. Recently, more and more attentions are paid to MSCs for their potential roles in treatment of varieties of diseases including neural degenerative disorder, osteogenesis imperfecta and acute myocardial infarction[12-14].Moreover, their unique immunologic characteristics such as low immunogenicity make MSCs excellent candidate for application in dealing with autoimmunologic diseases and GVHD after haemopoietic stem cells transplantation[15-16].After conventional bone marrow transplantation (BMT), the majority of hMSCs in bone marrow seem to be of recipient origin[17,18], suggesting that hMSCs are not sensitive to the chemotherapy-induced damage, this assumption is further supported by the study of Li and co-workers that in vitro cultured hMSCs are resistant to a panel of chemotherapeutic drugs, especially at clinical dose commonly used in BMT patients receiving intensive chemotherapy[19].In this paper, we found that in vitro cultured Flk-1+hMSC showed a significant resistance for cisplatin, vincristine and etoposide compared to sensitive tumor cell lines, particularly at apoptosis-inducing doses. The phenotype and differentiation potential or senescence index of Flk-1+hMSC were not altered by genotoxic treatment at clinically relevant conditions in vitro; chemotherapeutic treatments did result in an over-expression of p53 protein but this increase is not accompany with the appearance of cell apoptosis; because human tumor suppressor p53 is the key regulator in determining the cell response(cell cycle arrest and apoptosis) to the induction of DNA damage substances[20],so we propose that there may be other factors involved in this process. p73,a member of p53 family, is similar to p53 in configuration and functions[21],it can also induce apoptosis response dependent or independent of p53 and probably is a potent inducer of cell death and a determinant of chemotherapeutic response[22,24].Based on these evidences, in this paper we try to connect human p73 protein with the sensitivity of Flk-1+hMSCs to DNA damage agent cisplatin and we found that in comparison to cancer cell line K562, the endogenous expression p73 was not altered by the treatment of chemotherapeutic agents, probably indicating that the expression level of p73 was correlate with the different response of cells to the chemotherapeutic agents and exogenous expressed p73 can enhance the sensitivity of Flk-1+ hMSCs to the DNA damage agent cisplatin, and we also got the fact that the increased apoptosis contribute to the increased sensitivity and Bax or p21 may involved in this process. Recently,adipose-derived mesenchymal stem cells become a favorable tool for tissue engineering and cell therapy due to ease of acquisition, relative abundance, and multilineage potential.So it is very important to understand the Molecular and cellular behavior of these cells before they can be used for clinical application safely an effectively.RNA interference (RNAi) technology is a powerful tool for gene function reseach. Short 19-mer double-stranded RNA molecules can effectively trigger post-transcriptional dsRNA-dependent gene silencing (PTGS) and, consequently, inhibit the expression of sequence-specific endogenous gene product. In these paper we used retrovius vector to introduce shRNA oligonucletide RNAi sequence target for p73 mRNA into proliferating adipose-derived Flk-1+ mesenchymal stem cells and showed whether the inhibition of endogenous p73 protein could influence the differention potential of mesenchymal stem cells into neural cells.We found that the shRNA oligonucletides can inhibit the expression of p73 protein with high effection and specificity at the level of transcription and translation. The inhibition of p73 protein could change the differentiation potential of Flk-l+mesenchymal stem cells when they were under the neural induction condition.This probably suggest that p73 protein might play important roles in differentiation potential of Flk-1+ mesenchymal stem cells into neural cells.