Glomerularendothelialcellsplaypivotalrolesinthemaintenanceofthenormalstructureandfunction of the healthy glomerulus, and also in the development of glomerular injury in kidney diseases. However, our knowledge of the mechanisms that constantly maintain and regenerate the glomerular endotheliumafterinjuryhavebeenlimited,duetotheinaccessibilityofthiscelltypeandlackofinvivo researchtechnologies.Ourlaboratoryhasrecentlydevelopednoveltransgenicmousemodelsandan intravital imaging approach using serial multiphoton microscopy (MPM) of the same glomerulus over several days-weeks to quantitatively visualize and track the fate and function of the same single glomerularendothelialcellsintheintactlivingkidney.Thistechnicaladvanceprovidedvisualclueson thedevelopmentofclonalendothelialcellclustersattheglomerularvascularpoleinresponsetodietary saltrestrictionandvarioustypesonglomerularinjury,andsuggesteditscontrolbythejuxtaglomerular apparatus (JGA). In addition, the foundation of this proposal is our recent preliminary findings which suggestedthatmaculadensa(MD)cellsoftheJGAarenovelchieforganizersandmasterregulators of glomerular remodeling in the adult kidney. Gene profiling showed that MD cells produce novel secretedtissueremodelingfactorsthatactinaparacrinefashiononresidentprogenitorcells.Oneof thetopnewMDgenesresponsibleforthisnewglomerularremodelingprogramwasidentifiedasCCN1 (alsoknownasCyr61),codingforasecretedangiogenicproteinthatisknowntotargetendothelialcells aswellasothercelltypes.OurmainhypothesisisthatMDcells,viaWntsignaling-mediatedsynthesis andsecretionofangiogenicproteinsincludingCCN1,aremajorparacrineregulatorsoftheglomerular endothelium. This project will use comprehensive experimental approaches including in vitro cell culture, new transgenic mouse models, fluorescently tagged cell lineages, cell fate tracking, in vivo diseasemodelsandserialMPMtoinvestigatetheangiogenicrole,mechanisms,andimportanceofMD cellsandCCN1inglomerularendothelialmaintenanceandrepair.
The specificaims areto(i)Examine the role and mechanism of MD cells in the maintenance of normal glomerular capillary structure and function,(ii)StudytheregulationoftheMDcellangiogenesispromotingprogram,and(iii)Testforrenal andcardiovasculardiseasemodifyingrolesandmechanismsofMDcells.
Kidney diseases are associated with significant comorbidities and mortalities and affect close to a third of the US population, yet their pathophysiology remains incompletely understood. Glomerular endothelial cells play pivotal roles in the maintenance of the normal structure and function of the healthy glomerulus and also in the development of glomerular injury in kidney diseases, yet their primarypathogenicrolehasbeenlargelyoverlooked.Weproposetostudytheroleofmaculadensa cells and their primary angiogenic factor CCN1 in the normal and diseased kidney, and to develop newtherapeuticanddiagnosticapproachesforglomerularkidneydiseases.
