IN EXPERIMENTAL RAT DIABETES TRANSCRIPTION FACTOR MAFA IS SYNTHESIZED IN DIFFERENTIATED PANCREATIC ISLET CELLS AND DOES NOT SERVE AS A MARKER OF PROGENITOR CELLS

Abstract

Different transcription factors, which are synthesized at different stages of cell differentiation, are often considered markers of p-cell precursors. One of these transcription factors is MafA, the role of which is not fully understood. According to one hypothesis, it activates insulin gene expression in the differentiating p-cells. According to another, this factor is only necessary for the regulation of insulin secretion by already differentiated p-cells. In favor of the latter hypothesis, we showed that MafA is not expressed in the immature p-cells during the prenatal development of the human pancreas. In order to finally determine whether MafA is a marker of differentiating cells or it is synthesized in already mature p-cells the aim of our investigation was the analysis of dynamical changes of MafA-positive cell population and C-kit-positive endocrinocyte precursors in Langerhans islets during experimental diabetes in rats. The study was performed on male Wistar rats (250-300g body weight) which were intraperitoneally injected with alloxan. Animals were sacrificed 1,2, 7, 14, 21 days of the experiment for the morphological analysis of pancreas. Paraffin sections of pancreas were stained immunohistochemically with antibodies against MafA, C-kit, insulin and glucagon. The maximum number of MafA-positive cells in the islets was found during normal prenatal development of pancreas. At all stages of the experimental diabetes the number of MafA-positive cells in the islets decreased, wherein the number of insulin-positive cells in the islets increased by the end of the first and third weeks of the experiment. It was also established that in experimental diabetes, changes in populations of MafA- and C-kit-positive cells occur in different ways. Thus, the results of our research showed that MafA cannot be considered as a marker of progenitor cells and is expressed only in the mature cells of the Langerhans islets, that confirms our previous data obtained during the study of prenatal development of human pancreas.