Bone marrow derived cells facilitate urinary bladder regeneration by attenuating tissue inflammatory responses

INTRODUCTION: Inflammatory responses following tissue injury are essential for proper tissue regeneration. However, dysfunctional or repetitive inflammatory tissue assaults can lead to poor tissue regeneration and ultimate tissue failure via fibrosis. Previous attempts at urinary bladder tissue regeneration utilizing polymeric and biologic scaffolding materials tended to elicit these responses leading to poor tissue regeneration. Recent advances in bladder regeneration utilizing bone marrow derived mesenchymal stem cells (MSCs) and CD34(+) hematopoietic stem/progenitor cells (HSPCs) with biocompatible citric acid based scaffolds have provided an environment that not only promotes the growth of architecturally germane and physiologically functional tissue, but also modulates aspects of the innate immune response. MATERIAL AND METHODS: Within this study MSCs, CD34(+) HSPCs, or MSC/CD34(+) HSPC seeded POC [poly (1,8-octanediol-co-citrate)] scaffolds were utilized in an established rodent bladder augmentation model to evaluate inflammation as it pertains to bladder tissue regeneration. RESULTS: Quantified data from post-augmentation regenerated tissue samples at the 4 week time-point demonstrated that POC/MSC and POC/MSC + CD34(+) HSPC grafts markedly reduced the presence of pro-inflammatory CD68(+) macrophages and MPO(+) neutrophils compared to unseeded POC or POC/CD34(+) HSPC-only seeded grafts. Pro-inflammatory cytokines TNFα and IL-1b were also significantly down-regulated with a concomitant increase in the anti-inflammatory cytokines IL-10 and IL-13 in the aforementioned POC/MSC and POC/MSC + CD34(+) HSPC composites. Furthermore, this led to fewer instances of bladder tissue granuloma formation combined with greater muscle content and tissue angiogenic events as previous data has demonstrated. CONCLUSIONS: Data indicates that POC/MSC and POC/MSC + CD34(+) HSPC grafts attenuate the innate inflammatory response and promote bladder tissue regeneration.