Proceedings of The Physiological Society
University College Dublin (2009) Proc Physiol Soc 15, PC149
Pericyte-mediated regulation of vasa recta capillaries in situ.
C. Crawford1, C. Sprott1, T. Desai1, R. J. Unwin2, S. S. Wildman1, C. M. Peppiatt-Wildman1
1. Urinary System Physiology Unit, The Royal Veterinary College, London, United Kingdom. 2. Centre for Nephrology, University College London, London, United Kingdom.
Pericytes have been shown to control capillary diameter in situ, in whole retina and in the CNS (1). Pericytes occur at regular intervals on renal medullary vasa recta capillaries and are known to constrict isolated perfused descending vasa recta (2). Here we aim to (i) identify renal pericytes on vasa recta capillaries in live kidney slices, (ii) establish kidney slices as a viable model and (iii) investigate the role of pericytes in the regulation of vasa recta capillaries in situ. Freshly isolated live kidney slices were labeled with calcein, propidium iodide and Hoechst and imaged using confocal imaging techniques to confirm viability of kidney slices (n=3). Pericytes and vasa recta capillaries were labeled with fluorescently conjugated NG2 (neural-glial 2) and IB4(isolectin B4), respectively and pericyte location along vasa recta capillaries was confirmed in the medulla of kidney slices by confocal imaging techniques (n=10). Video imaging techniques were utilized to identify pericytes along vasa recta capillaries in live kidney slices and to investigate whether pericytes regulate the diameter of vasa recta capillaries in response to vasoactive agents in adult rat kidney slices. Kidney slices (200µm) were obtained from adult Sprague Dawley rats (killed by cervical dislocation). Here we show for the first time, pericyte-mediated constriction of vasa recta in situ, in live kidney slices. Superfusion of Angiotensin-II (Ang-II 100nM) resulted in an average constriction of vasa recta capillaries at pericyte sites of 29.26+4.67% (mean+s.e.m,n=14). This was significantly greater than at non-pericyte sites (p<0.001, Student’s t test) where capillary diameter changes were 7.56+1.98%, (mean+s.e.m,n=14.). Noradrenaline (10nM) also evoked a significantly greater vasoconstriction of vasa recta at pericyte sites (20.77+5.05%, mean+s.e.m,n=7) than at non-pericyte sites (7.63+2.04%, mean+s.e.m, p<0.05, Student’s t test). The nitric oxide donor S-nitroso-N-acetyl-l,l-penicillamine (SNAP 100µM) evoked a significantly greater vasodilation of vasa recta at pericyte sites (14.05+3.52%, mean+s.e.m,n=12) than that at non-pericyte sites (4.23+1.62%, mean+s.e.m, p<0.05, Student’s t test). Superimposing SNAP on Ang II significantly decreased (p<0.05, Student’s t test) the Ang II-evoked constriction (i.e. it dilated the vessel) by 84% (n=4) of the preconstricted diameter at the pericyte but had no effect elsewhere. The techniques described here establish kidney slices as a viable model which can be used to investigate the role of in situ pericytes in the regulation of vasa recta. We have identified pericytes along vasa recta capillaries in the renal medulla and have presented data that shows vasa recta pericytes, like CNS pericytes, constrict vasa recta capillaries and may play a role in regulation of blood flow in the renal medulla.
Where applicable, experiments conform with Society ethical requirements