Physiology of Retinal Pericytes

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DESCRIPTION (provided by applicant): Our long-range objective is to elucidate the pathophysiological mechanisms that disrupt microvascular function early in the course of diabetic retinopathy. A vital function lost soon after the onset of diabetes is the autoregulatory control of the retinal microcirculation. The resulting inefficiency in the distribution of blood flow compromises the function, and eventually, the viability of retinal neurons, glia and vascular cells. At present, a critical gap in our understanding of how diabetes alters microvascular function is the limited knowledge of the mechanisms by which local vasoactive signals regulate capillary perfusion in the retina. Our proposed studies are based on a new working hypothesis. Namely, voltage changes induced by vasoactive signals that act at distal capillary sites must be transmitted electrotonicly via gap junction pathways to proximal pericytes. This intercellular transmission is necessary because proximal, but not distal, pericytes contain the contractile apparatus necessary to regulate the diameter of the microvascular lumen. Using dual perforated-patch recordings and other techniques, we will compare intercellular communication within pericyte-containing microvessels freshly isolated from retinas of control and diabetic rats. To address the mechanisms by which diabetes disrupts distal-to-proximal communication within the retinal microvasculature, the specific aims of our proposed studies will test the hypotheses that (1) in diabetes a disruption of electrotonic transmission between retinal pericytes compromises the transduction mechanism by which a vasoactive signal acting at a distal capillary site elicits a contraction or relaxation of the proximal portion of a pericyte-containing microvessel, (2) PKC-beta isoforms play a critical role in the mechanism by which gap junction pathways are disrupted in microvessels of the diabetic retina and (3) ET/A endothelin receptors mediate disruption of intercellular communication within diabetic microvessels. Over the long-term, elucidating the mechanisms by which diabetes disrupts the ability of local vasoactive signals to regulate capillary perfusion will facilitate the development of new strategies to ameliorate, and hopefully, prevent sight-threatening complications of this disease.