ISOLATION OF STEM CELLS FOR THE KIDNEY AND EXPERIMENTAL TRIAL FOR THE REGENERATIVE MEDICINE

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Using transgenic rats which express GFP (Green Fluorescent Protein) throughout the body, we established chimeric rats which carry GFP(+) cells in all progeny of bone marrow. This system allowed us to find that bone marrow-derived cells contributed to the regeneration of mesangial cell in a self limiting acute glomerulonephritis model. We also showed that bone mar row cells were able to differentiate into mesangial cells in vitro. Both in vivo and in vitro, Platelet-derived growth factor-B was critical for the generation of bone marrow-derived mesangial cells. We also established a method to purify precursor cells/stem cells for mesangial cells from crude bone marrow preparation by using an unwoven mesh filter system. We purified side population (SP) cells from adult rat kidneys, and characterized them. In short, we proved that SP cells were not the stem cells for mesangial cells or tubular epithelial cells even though they clearly existed in the kidney. In order to find genes which are critical for the nephrogenesis, we compared a set of RNA obtained from neonatal rat kidneys to another set of RNA obtained from adult rat kidneys. By the suppression subtractive hybridization method, we found that retinaldehyde dehydrogenase type 2 (RALDH2) was highly enriched in the comma-shaped body and S-shaped body, and that RALDH2 was upregulated during the differentiation of glomerular epithelial cells. We also developed a new method which allows us to purify RNA from the nephrogenic zone of neonatal rat kidneys. Our extensive analysis revealed that the local concentration of retinoic acid that is produced by RALDH2 plays a critical role to repair injured podocytes, and that retinoic acid directly regulates the transcription of nephrin. Our further analysis about RALDH2 and other newly identified genes are under way.