Increased mast cell number in human hypertensive nephropathy

1 Institute of Anatomy, Charité Universitätsmedizin Berlin, Free University and Humboldt University, Berlin; 2 Department of Nephrology and Center for Cardiovascular Research, Charité Universitätsmedizin Berlin, Charité Campus Mitte, Humboldt University, Berlin; 3 Otto Heubner Center, Charité Universitätsmedizin Berlin, Free University and Humboldt University, Berlin; and 4 Department of Pathology, University of Erlangen, Germany Submitted 8 August 2007 ; accepted in final form 1 August 2008 Mast cells have recently been related to nonallergic chronic organ damage and fibrosis. In the present study, we analyzed mast cell number, localization, and maturation in the kidney of a relatively unique group of middle-aged accident victims with primary essential hypertension and in normotensive controls ( n = 8 per group, Caucasians, predominantly male). Hypertensive kidneys showed a significantly higher degree of arteriolosclerosis. However, glomerular and tubulointerstitial matrix accumulation did not differ significantly to normotensive controls indicating a relatively early stage of hypertensive nephropathy. Using toluidine blue staining, renal mast cell number was found to be fivefold higher in hypertensive subjects compared with normotensive controls. Mast cells were primarily located in the peritubular interstitial spaces, some perivascular, but not in glomeruli. In a series of immunohistological staining studies, mast cell maturation grading showed that expression of early hematopoietic precursor cell marker CD34 did not differ between both groups. In contrast, mast cells were mostly positive for IgE receptor, tryptase, and chymase indicating a mature, differentiated cell phenotype in hypertensive nephropathy. Renal expression of stem cell factor was markedly upregulated in primary hypertension. Kidney macrophage and lymphocyte numbers were similar in both groups. In conclusion, human hypertensive kidney disease shows an early and conspicuous upregulation of stem cell factor along with an increased number of mature mast cells. The results suggest that renal mast cell accumulation may play a role in the pathogenesis of human hypertensive nephropathy. CD34; chymase; tryptase; stem cell factor Address for reprint requests and other correspondence: H. Peters, Dept. of Nephrology, Charité Universitätsmedizin Berlin, Charité, Campus Mitte, Humboldt Univ., Charitéplatz 1, D-10117 Berlin, Germany (e-mail: Harm.Peters{at}charite.de )