The Development of the Model Mice Having the System that Easily Measuring their Pancreatic Islet Beta Cell Mass

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To quantify the islet beta cell mass, we tried to develop the noninvasive and easily measurable system. We designed a beta cell model, which constitutively secrete an artificial reporter molecule, reflecting the beta cell mass, to be measured with conventional methods. First of all, we have constructed three types of artificial fusion proteins. One has the human albumin signal sequence with the human C-peptide (Alb-hc), another two types of constructs both have the mice IgK signal sequence fused with human C-peptide cDNA (hCPR tandem) while the one has also YFP cDNA (hCPR/YFP). We have determined those proteins expression and secretion outside of cultured cell lines (Cos7, HEK293), meaning these signal peptides play the role as the secreting signal in vivo. Besides we could detect and measure those fusion proteins with the human C-peptide ELISA kit, these reporter molecules are apparently easy to be measured.As the further investigation, we will import those reporters into MIN6 cells, mouse beta cell line, and prove those expression in it and secretion. It is important to confirm whether those reporters secretion is constitutive or not. We have to determine the alteration of those reporters secretion independent of several conditions (glucose stimulation etc.) so that we will be able to use these reporters to calculate beta cell mass.After establishing transgenic mice imported those fusion genes, we are making hybrid mice between these mice and other diabetic mice. These hybrid mice will demonstrate the alteration of beta cell mass till the onset of diabetes mellitus. Along with the elucidation of the mechanism of the diabetes onset or progression, this noninvasive beta cell mass quantifying system will contribute to developing the new drugs to inhibit beta cell mass reduction or to the advancing of beta cell regenerative therapy.