Immunohistochemical Expression of Ki-67 And Cd34 In the Kidney in Experimentally Induced Ulcerative Colitis: Proliferative Activity and Microvascular Remodeling in Rats

Abstract

Background. Ulcerative colitis (UC) is a chronic relapsing inflammatory bowel disease (IBD) with frequent extraintestinal, including renal, involvement. The behaviour of the proliferation marker Ki-67 and the endothelial/microvascular marker CD34 in the kidney under experimental UC is insufficiently characterised.

Methods. Sixty 9-month-old white outbred rats were studied: a control group (n = 20) and a UC group (n = 40; 5 deaths). UC was induced by a single intrarectal instillation of 1 mL of 8 % acetic acid followed by 20 days of observation. Paraffin kidney sections (4–5 µm) were immunostained for Ki-67 and CD34 using heat-induced epitope retrieval in citrate buffer (pH 6.0), an avidin–biotin peroxidase system and 3,3′-diaminobenzidine (DAB), with haematoxylin counterstain. CD34 microvessel density (MVD) was assessed by the Weidner hotspot method (≥ 5 fields, ×200) and the relative CD34-positive area by digital analysis (QuPath 0.5.0). Data were summarised as mean ± SD and analysed in IBM SPSS Statistics 23.

Results. In controls, renal Ki-67 nuclear staining was rare and sporadic, in keeping with the very low baseline proliferation of the normal kidney. In the UC group the Ki-67 index rose markedly (mean 35.4 %; range 22.7–59.7 %), predominantly in the tubular epithelium of injury zones, in interstitial inflammatory cells (lymphocytes, histiocytes, fibroblasts) and in glomerular mesangial cells, whereas capillary endothelium and podocytes remained negative. CD34 MVD fell from 45.2 ± 2.1 to 32.8 vessels/mm² (−27.4 %), with peritubular capillary rarefaction in fibrotic areas, reduced glomerular CD34 accompanying mesangial expansion, and only focal neoangiogenesis; the mean CD34-positive area was 59.3 %.

Conclusion. Experimental UC produces a dissociation between enhanced cellular proliferation and microvascular rarefaction in the kidney, a combination that favours progression of interstitial fibrosis. Ki-67 and CD34 are promising quantitative markers for early detection and monitoring of UC-associated renal injury.

Keywords:

Ulcerative colitis, kidney, Ki-67, CD34

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