BONE MARROW DERIVED FIBROBLASTS AND THEIR ROLE IN TISSUE REPAIR AND FIBROSIS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. There has been no change in the scope of this project. It remains focused on tissue repair, with a particular emphasis on fibrosis. Excessive fibrosis is the prominent histological features of many human systemic diseases such as idiopathic and secondary pulmonary fibrosis, myelofibrosis, endomyocardial fibrosis, sclerosing cholangitis, hepatic fibrosis, cirrohsis and fibrous thyroiditis. Another important dimension is the fibrosis that occurs with tumors. Overall, the fibrosis in many conditions results in a severe, and in most cases, irreversible loss of organ function. The fatal outcome of many of these conditions can be directly attributed to the fibrotic process. Recent data has suggested that marrow derived cells can significantly contribute to the fibroblasts both in normal regeneration process and also in excessive fibrosis in pathological conditions. Many of the investigators believe that the stromal component of the marrow is responsible for these marrow derived fibroblasts. However our recent data shows that cells with hematopoietic characteristics are able to produce fibroblasts in the injured skin. Our hypothesis is that fibroblasts in the scar tissue and also in skin models of excessive fibrosis are originate from the hematopoietic component of bone marrow. The current study will be undertaken to investigate whether the increase in fibroblasts at the site of pathogenic fibrosis originated from transplanted hematopoietic donor cells or they are mostly coming from the residing fibroblasts in the adjacent tissue. We are also planning to establish a hierarchical model of differentiation for tissue fibroblast by identifying differentiation markers from marrow stem cells to fully differentiated fibroblasts. We have proposed the following specific aims for this project: 1) To characterize a specific subgroup of marrow cells that is able to contribute to tissue fibroblasts in the scar tissue. To induce fibrosis, we will use three well defined model of tissue fibrosis, ie. bleomycin injury, graft versus host disease, and TSK mice; 2) To characterize the role of marrow derived fibroblasts in comparison to their endogenous counterparts in each specific model of tissue fibrosis. We will determine whether marrow derived fibroblasts, both quantitatively and qualitatively, contribute to the fibrosis process. A main component of the proposed work is that FSP1-GFP, ColA2-LacZ mice will be used as functional models to identify the differentiation of marrow cells to fibroblasts. 3) To identify the developmental steps in the process of differentiation of bone marrow derived fibroblasts. Donor derived fibroblast cells residing in the recipient scar tissue will be isolated and analyzed by gene microarray and the results will be compared to the marrow cells from which they were derived and also de novo fibroblasts from the same scar. The genes identified by this method will be confirmed with a combination of real time-PCR, immunofluorescent and flow cytometry techniques, the progeny and lineages of these cells. Emphasis will be placed on establishing an immunophenotypic profile for marrow derived fibroblasts. The progressive loss/addition of cell surface markers during fibroblast maturation will be monitored, as it is done with the step-wise maturation of other populations of marrow cells, such as B or T lymphocytes. 4) The role of marrow derived fibroblasts in the fibrosis observed in tumors. During tenure of this grant we plan to look very early on tumors from lung, melanoma, and lymph nodes.