Objectives. the study of the nature and severity of the reorganization of the structural elements of the bladder wall on experimental models of IC / BPS at the optical and ultrastructural levels.
Materials and methods. The experimental model of IC / SBMP was created on 22 white New Zealand female rabbits weighing 1500–2000 g. The animals were divided into 2 groups: group 1 – 15 rabbits, which were introduced into the bladder wall urine taken from the animal’s bladder; Group 2 (control) – 7 animals that were injected into the bladder wall with a 0.9% NaCl solution. The biomaterial was examined by electron microscopy. The structural elements of the lamina propria of the bladder mucosa were evaluated.
Results. In the bladder mucosa of the experimental model, perivascular infiltration by inflammatory cells, pronounced edema of the lamina propria of the bladder mucosa, and the presence of numerous plasma cells having close contacts with macrophages, fibroblasts, and lymphocytes were revealed. In the nucleus of lymphocytes of a peripherally located supercondensed heterochromatin showed their apoptotic state. Edematous fluid was determined, penetrating mainly through the fenestra, located in the peripheral parts of the endothelial cells of capillaries and postcapillary venules.
Conclusion The study of the structural elements of the lamina propria of the bladder mucosa in the experiment by the method of electron microscopy made it possible to identify changes caused by the inflammatory process, both of an acute and productive nature. The results obtained showed that toxic damage to the lamina propria of the bladder mucosa causes apoptosis of fibroblasts of the lamina propria, leads to loosening of collagen fibers and, ultimately, to a decrease in the protective factors of the mucous membrane.

Keywords: bladder mucosa, interstitial cystitis/painful bladder syndrome, electron microscopy, morphometry, experimental model