Background and purpose: Ureteropelvic junction obstruction (UPJO) is defined as an impediment to urinary flow from the renal pelvis into the ureter. The exact cause remains an enigma despite investigations along embryologic, anatomic, and histologic lines. Our goal was to investigate in vivo the expression profile of cytokines in hyperplastic urothelial cells as a means of determining the source of UPJO.
Materials and methods: Cellular proteomes of matched normal and hyperplastic urothelial cells were analyzed by laser capture microdissection (LCM) and tissue microdissection and human cytokine proteomic chips. All specimens (N = 9) were surgically obtained from patients undergoing laparoscopic dismembered pyeloplasty and were immediately embedded in O.C.T. solution and flash-frozen in liquid nitrogen. Tissue sections (6 microm) were mounted on uncoated glass slides using a cryostat, fixed in 70% ethanol, stained with hematoxylin and eosin, and sequentially dehydrated in ethanol and xylene. Typically, paired samples of normal and hyperplastic urothelial cells were procured on separate caps from serial sections of each specimen by the Arcturus PixCell II LCM system using 3000 laser pulses and a spot diameter of 30 microm. Total proteins were harvested and quantitated. Differential expression profile analysis of 43 cytokines in normal and hyperplastic cells were performed using human protein chips. Briefly, the membranes were initially probed with protein (150 ng) from normal or hyperplastic cells and sequentially reacted with a cocktail of biotinylated cytokine antibodies and horseradish peroxidase-conjugated streptavidin. The membranes were developed using enhanced chemiluminescence and analyzed by densitometry.
Results: Comparative densitometric analysis revealed twofold to fourfold upregulation of growth-related oncogene alpha (GRO-alpha), interleukin (IL)-1alpha, interferon (INF)-gamma, IL-8, tumor necrosis factor (TNF)-alpha, RANTES, and macrophage inflammatory protein-1beta (MIP-1beta) and twofold to fourfold downregulation of transforming growth factor (TGF)-beta and IL-10 in hyperplastic urothelial cells compared with paired control cells.
Conclusions: We here report the efficient application of LCM and proteomic array chips for expression profile analysis of cytokines in vivo. Because the etiology and pathogenesis of UPJO are still fragmentary, the marked heterogeneity of the observed cytokine alterations reported here may be of significance. Further studies are required to elucidate the functional significance of the differentially expressed cytokines in the pathogenesis of the disease.