Phenotypic dissection of the mouse Ren1d knockout by complementation with human renin

Advances in use of mouse models to study the renin-angiotensin system

The renin-angiotensin system (RAS) is a highly complex hormonal cascade that spans multiple organs and cell types to regulate solute and fluid balance along with cardiovascular function. Much of our current understanding of the functions of the RAS has emerged from a series of key studies in genetically-modified animals. Here, we review key findings from ground-breaking transgenic models, spanning decades of research into the RAS, with a focus on their use in studying blood pressure. We review the physiological importance of this regulatory system as evident through the examination of mouse models for several major RAS components: angiotensinogen, renin, ACE, ACE2, and the type 1 A angiotensin receptor. Both whole-animal and cell-specific knockout models have permitted critical RAS functions to be defined and demonstrate how redundancy and multiplicity within the RAS allow for compensatory adjustments to maintain homeostasis. Moreover, these models present exciting opportunities for continued discovery surrounding the role of the RAS in disease pathogenesis and treatment for cardiovascular disease and beyond.

Culture in 10% O2 enhances the production of active hormones in neuro-endocrine cells by up-regulating the expression of processing enzymes

To closely mimic physiological conditions, low oxygen cultures have been employed in stem cell and cancer research. Although in vivo oxygen concentrations in tissues are often much lower than ambient 21% O₂ (ranging from 3.6 to 12.8% O₂), most cell cultures are maintained at 21% O₂ To clarify the effects of the O₂ culture concentration on the regulated secretion of peptide hormones in neuro-endocrine cells, we examined the changes in the storage and release of peptide hormones in neuro-endocrine cell lines and endocrine tissues cultured in a relatively lower O₂ concentration. In both AtT-20 cells derived from the mouse anterior pituitary and freshly prepared mouse pituitaries cultured in 10% O₂ for 24 h, the storage and regulated secretion of the mature peptide hormone adrenocorticotropic hormone were significantly increased compared with those in cells and pituitaries cultured in ambient 21% O₂, whereas its precursor proopiomelanocortin was not increased in the cells and tissues after being cultured in 10% O₂ Simultaneously, the prohormone-processing enzymes PC1/3 and carboxypeptidase E were up-regulated in cells cultured in 10% O₂, thus facilitating the conversion of prohormones to their active form. Similarly, culturing the mouse β-cell line MIN6 and islet tissue in 10% O₂ also significantly increased the conversion of proinsulin into mature insulin, which was secreted in a regulated manner. These results suggest that culture under 10% O₂ is more optimal for endocrine tissues/cells to efficiently generate and secrete active peptide hormones than ambient 21% O₂.