Hypothesis / aims of study
There are several molecular diagnostic markers of OAB, however clinical diagnosis of OAB is still symptom-based. The urothelium directly contacts with urine, secreted proteins from the urothelium could be released into urine. In previously study, we demonstrated that urothelial protein expression is dynamically altered by OAB. These altered proteins in OAB urothelium could be used as potential diagnostic markers.In this study we tried to compare the profile of proteins secreted by OAB urothelium with those secreted by normal bladder urothelium to identify molecular diagnostic markers for OAB.
Study design, materials and methods
The study was conducted using male Sprague-Dawley rats, subdivided into sham control (n=40) and partial BOO groups (n=60). Partial BOO was induced for 2 weeks and DO was confirmed with measuring cystometry. The urothelium was carefully removed from the smooth muscle layer under a dissecting microscope and its protein expression was analyzed by LTQ-Velos mass spectrometer. The identified proteins were analyzed to discover upstream molecules, and potential biomarkers that are associated with OAB by using Ingenuity Pathway Analysis (IPA) tool. The analysis was done against the Ingenuity Knowledge Base.
The results of this analysis identified 17 putative upstream regulators. Complement component 3b/4b receptor 1-like, huntingtin, and inhibin α act as upstream regulators of Cryab, Aldoa, Tpm2, Myl9, Cnn1, Myh1, and C3, and may cause activation of muscle contraction. Six of the upstream regulators, huntingtin, inhibin α, integrin α2, complement component 3b/4b receptor 1-like, HNF1 homeobox B, and platelet derived growth factor family, may also affect positively the cell movement of leukocytes and neutrophils as well as cellular infiltration by leukocytes through the regulation of many other proteins identified in the urothelium. These regulators are involved primarily in inflammation and cytoskeletal organization.
We identified 37 extracellular proteins that were exclusively expressed in normal sham control or OAB rat urothelium (Table 1). Of these, 11 proteins were expressed only in the OAB urothelium and are involved mainly in inflammation. The other 24 proteins were expressed only in sham control urothelium and were related primarily to cellular and tissue structure formation.
Interpretation of results
Extracellular proteins expressed by urothelium that are released into the urine could also be used as noninvasive OAB diagnostic markers. These potential markers are closely related to the pathophysiological changes that occur in OAB. In addition, expression of the up-regulated proteins was verified by real-time PCR experiment. Detecting these proteins or their peptide fragments in urine may be a useful tool for the diagnosis. Verification of these proteins in the urine of OAB patients may be useful noninvasive diagnostic markers for OAB.