Biocompatibility and tissue integration of autologous fat grafts and synthetic implants following submucosal implantation into the urinary bladder

Background: In urological practice, the search continues for volume-forming materials with optimal biocompatibility, a prolonged therapeutic effect, and a minimal risk of complications. This issue is particularly critical in reconstructive and functional urology, where longterm stability of the outcome is required without inducing damage to the surrounding tissues. Existing synthetic and biological fillers present several limitations, including a tendency toward resorption, fibrosis, shape instability, and the risk of immune reactions. Although the efficacy of certain materials has been demonstrated, issues related to their long-term biocompatibility and morpho-functional stability remain unresolved.
Methods: Ninety-six sexually mature male Belgian rabbits were used in the experiment. Under intravenous anesthesia, a submucosal injection of the volume-forming material (0.3 mL) was administered into the wall of the urinary bladder. Four types of materials were employed in the study: autologous fat graft, autologous fat graft combined with platelet-rich plasma (PRP), poly-L-lactic acid (aesPLLa), and macroparticles of a polyacrylate-polyvinyl alcohol copolymer. Animals were divided into four experimental groups according to the type of material administered. To assess tissue responses and graft characteristics, subgroups of eight animals from each experimental group were euthanized on days 14, 30, and 90 post-intervention for comprehensive morphological evaluation, including histological, histochemical, histomorphometric, and morphometric analyses. The primary evaluation parameters included the intensity of the inflammatory response, the degree of vascularization, the nature of cellular infiltration, the extent of fibrotic changes, and the preservation of the implanted material.
Results: The study demonstrated that the combination of an autologous fat graft with platelet-rich plasma (PRP) promoted more intensive microvascular network formation, reduced inflammatory infiltration, and ensured a more uniform distribution of the transplanted tissue compared with the other experimental groups. The obtained data indicate the high biocompatibility of this combination and its potential effectiveness as an alternative to synthetic volume-forming materials, particularly in clinical settings requiring a prolonged volumetric effect with minimal risk of complications.
Conclusions: The combination of platelet-rich plasma (PRP) with an autologous fat graft, as well as the use of the synthetic material polyacrylate and polyvinyl alcohol copolymer, appear to be the most promising approaches for achieving a stable and biocompatible volume-forming effect in the correction of lower urinary tract pathologies. At the same time, despite the confirmed high biocompatibility of the investigated substrates in the short term, questions regarding their long-term safety remain unresolved, including the risk of fibrotic changes and potential functional impairments of the urinary bladder. These aspects warrant further investigation and clinical validation.