Expression of MUC7 in kidneys with bacterial infection

Background. Mucins are glycoproteins secreted by epithelial cells of various organ systems exerting multiple functions. MG2 as the protein transcript of the MUC7 gene has first been described as secreted by serous salivary glands in the oral cavity. We sought to explore changes of MUC7 expression in the kidney stimulated by bacterial infection of the upper urinary tract. Methods. We investigated the gene expression of MUC7 by reverse transcriptase-polymerase chain reaction in voided urine specimens from 15 patients with acute pyelonephritis compared to 15 healthy volunteers. Furthermore, the gene and protein expression of MUC7 was studied in 15 renal tissue samples with chronic bacterial pyelonephritis versus 10 normal human kidney samples taken from tumor-bearing organs. Results. MUC7 gene expression was detected in 5 of 15 voided urine samples of patients with pyelonephritis and in 2 samples from 15 healthy volunteers (Fisher's exact test P=0.39). MUC7 gene expression was detected in 7 of 15 tissue samples of kidneys with chronic pyelonephritis and in none of 10 normal renal tissue samples from tumor bearing organs (p=0.02). Immunohistochemical staining with the monoclonal antibody PANH3 revealed protein expression in 6 of the 15 tissue samples with chronic pyelonephritis, but not in normal tissue samples. Conclusion. Upregulated MUC7 expression in the urinary tract particularly in renal tubular epithelium can occur under inflammatory conditions. This indicates a putative role of MUC7 as an antimicrobial host defense molecule within the urogenital tract.