The effect of vitamin D on the expression of the calcium-sensing receptor in colonic organoids

Resumen del póster presentado 21st Workshop on Vitamin D, celebrado en Barcelona (España) del 16 al 19 de mayo de 2018.The calcium-sensing receptor (CaSR) is a heterotrimeric G protein-coupled receptor that regulates Ca2+ homeostasis in the blood. lt is suggested that the CaSR, in synergism with vitamin O, controls proliferation, differentiation and apoptosis of intestinal cells, and protects intestinal integrity preventing the development of colorectal cancer. However, the CaSR is down-regulated during tumorigenesis. We hypothesized that CaSR expression is linked to differentiation, and substances inducing differentiation, like vitamin O, would restare its expression. Therefore, we tested whether inducing differentiation of murine colonic organoids and treating them with 1 ,25-dihydroxyvitamin 03 (1 ,25-03) will re-establish CaSR expression. We have shown previously that vitamin O was able to induce CaSR expression in vivo, in normal colonic mucosa of m ice. In the present study we used a 30 in vitro culture system, by generating normal organoids from murine colonic crypts. We induced lineage-specific differentiation of the organoids either into enterocytes or goblet cells by altering the composition of the culturing media in combination with 100 nM 1,25-03. We assessed CaSR expression by RT-qPCR and immunofluorescence assays, testing also specific differentiation markers such as FABP2 for enterocytes and MUC2 for goblet cells. Our data showed that the CaSR was not expressed in the undifferentiated organoids cultured in stem cell media, where even the differentiation markers were barely detectable. 1,25-03 enhanced CaSR expression in organoids differentiated towards enterocytes, while in goblet cell-like condition CaSR expression remained undetectable. Our results not showed that CaSR is preferentially expressed in differentiated enterocytes and also that 1 ,25-03 further enhanced its expression. We conclude that 1 ,25-03 is not able to induce CaSR expression in undifferentiated colonic stem cells. However, 1 ,25-03 enhances CaSR expression during enterocyte-specific differentiation. Further studies with more samples and the employment of human specimens, in particular tumor biopsies, will help us to clarify the role of 1 ,25-03 on CaSR expression during colonic differentiation and carcinogenesis.Peer Reviewe