Receptor protein tyrosine kinase Ron is highly expressed in colorectal mucosa of ulcerative colitis patients.

Background/Aims: Ulcerative colitis (UC) is an inflammatory bowel disease with an unknown pathophysiological background. To identify possible regeneration or proliferation factors in colorectal mucosa of UC patients, we screened receptor-type protein tyrosine kinases in human colorectal mucosa. Methodology: Total RNA was isolated from biopsy specimens of normal and UC patients. After reverse transcription, polymerase chain reaction (PCR) amplification was carried out with cDNA using degenerative primers designed to correspond to stretches of amino acids preserved in the kinase domain. This was followed by subcloning into a plasmid vector. A total of 297 clones were determined by automated sequencing and database homology searches. Results: The analyses revealed that Ron (Recepteur d'Origine Nantals) is highly expressed in the mucosa of UC patients compared with normal mucosa. Subsequently, to investigate in vivo expression of Ron, immunohistological detection was performed with the normal and UC colorectal specimens. Ron was expressed in crypt cells, especially in the bottom of the crypta in normal colonic mucosa, though expression in active UC was distributed widely and strongly in the whole crypta. Conclusions: The specific high expression of Ron in the colorectal mucosa of UC patients suggests that this receptor might play roles in the pathophysiological background of this disease.