Hyperplasia as a mechanism for rapid resealing urothelial injuries and maintaining high transepithelial resistance

Abstract

When the urothelial barrier, i.e., the blood-urine barrier, is injured, rapid resealing of the injury is crucial for the normal functioning of the organism. In order to investigate the mechanisms required for rapid resealing of the barrier, we established in vitro models of hyperplastic and normoplastic urothelia. We found that hyperplastic urothelia achieve significantly higher transepithelial resistance (TER) than normoplastic urothelia. However, the expression of cell junctional (claudin-8, occludin, E-cadherin) and differentiation-related proteins (cytokeratin 20 and uroplakins) is weaker in hyperplastic urothelia. Further investigation of cell differentiation status at the ultrastructural level confirmed that superficial urothelial cells (UCs) in hyperplastic urothelial models achieve a lower differentiation stage than superficial UCs in normoplastic urothelial models. With the establishment of such in vitro models and the aid of TER measurements, flow cytometry, molecular and ultrastructural analysis, we here provide unequivocal evidence that the specific cell-cycle distribution and, consequently, the number of cell layers have a significant influence on the barrier function of urothelia. We demonstrate the importance of hyperplasia for the rapid restoration of the urothelial barrier and the maintenance of high TER until the UCs reach a highly differentiated stage and restoration of the urothelial barrier after injury is complete. The information that this approach provides is unique and we expect that further exploitation of hyperplastic and normoplastic urothelial models in future studies may advance our understanding of blood-urine barrier development and functionality.

A Novel Strain of Porcine Adenovirus Detected in Urinary Bladder Urothelial Cell Culture

“…Cells were sub-cultured until the XIII passage. The NPU cell cultures were cultured in UroM medium, which does not allow the growth of fibroblasts [11] and is adapted for the growth of porcine urothelial cells, at 37 °C in a 95% humidified atmosphere of 5% CO 2 in air as in [12,13]. The medium was changed on alternate days.…”

Properties of the Urothelium that Establish the Blood–Urine Barrier and Their Implications for Drug Delivery

“…Interdigitation is found at the superficial UC borders, and this membrane zipper might contribute to the barrier function. The membrane overlap does not include TJs and is thought to fasten two cells better together by providing more apical membrane surface contact, additionally increasing the electrical resistance of the junction and possibly stabilizing the TJs (Kreplak et al 2007;Višnjar et al 2012;Višnjar and Kreft 2013). TER is a measure of ion permeability (Lewis 2000), and the main route of passive ion permeation does not traverse the cells, but the cell junctions.…”

In vitro assessment of potential bladder papillary neoplasm treatment with functionalized polyethyleneimine coated magnetic nanoparticles

“…Cultures of primary normal porcine urothelial cells (NPU) were established from porcine urinary bladder as described previously. 35 For the establishment of the highly differentiated normal porcine urothelial (NPU) cell model, which represents a biomimetic model of a normal differentiated urothelium in vivo, cells were grown in UroM medium without FBS and with physiological 2.5 mM calcium concentration for 3 weeks before experiments.…”