No abstract

Spina bifida (SB) patients afflicted with myelomeningocele typically possess a neurogenic urinary bladder and exhibit varying degrees of bladder dysfunction. Although surgical intervention in the form of enterocystoplasty is the current standard of care in which to remedy the neurogenic bladder, it is still a stop-gap measure and is associated with many complications due to the use of bowel as a source of replacement tissue. Contemporary bladder tissue engineering strategies lack the ability to reform bladder smooth muscle, vasculature, and promote peripheral nerve tissue growth when using autologous populations of cells. Within the context of this study, we demonstrate the role of two specific populations of bone marrow (BM) stem/progenitor cells used in combination with a synthetic elastomeric scaffold that provides a unique and alternative means to current bladder regeneration approaches. In vitro differentiation, gene expression, and proliferation are similar among donor mesenchymal stem cells (MSCs), whereas poly(1,8-octanediol-cocitrate) scaffolds seeded with SB BM MSCs perform analogously to control counterparts with regard to bladder smooth muscle wall formation in vivo. SB CD34 + hematopoietic stem/progenitor cells cotransplanted with donor-matched MSCs cause a dramatic increase in tissue vascularization as well as an induction of peripheral nerve growth in grafted areas compared with samples not seeded with hematopoietic stem/progenitor cells. Finally, MSC/CD34 + grafts provided the impetus for rapid urothelium regeneration. Data suggest that autologous BM stem/progenitor cells may be used as alternate, nonpathogenic cell sources for SB patient-specific bladder tissue regeneration in lieu of current enterocystoplasty procedures and have implications for other bladder regenerative therapies.

Animal models that have been used to examine the regenerative capacity of cell-seeded scaffolds in a urinary bladder augmentation model have ultimately translated poorly in the clinical setting. This may be due to a number of factors including cell types used for regeneration and anatomical/ physiological differences between lower primate species and their human counterparts. We postulated that mesenchymal stem cells (MSCs) could provide a cell source for partial bladder regeneration in a newly described nonhuman primate bladder (baboon) augmentation model. Cell-sorted2 baboon MSCs transduced with green fluorescent protein (GFP) were seeded onto small intestinal submucosa (SIS) scaffolds. Baboons underwent an approximate 40%-50% cystectomy followed by augmentation cystoplasty with the aforementioned scaffolds or controls and finally enveloped with omentum. Bladders from sham, unseeded SIS, and MSC/SIS scaffolds were subjected to trichrome, H&E, and immunofluorescent staining 10 weeks postaugmentation. Immunofluorescence staining for muscle markers combined with an anti-GFP antibody revealed that >90% of the cells were GFP Disclosure of potential conflicts of interest is found at the end of this article.

Current attempts at tissue regeneration utilizing synthetic and decellularized biologic-based materials have typically been met in part by innate immune responses in the form of a robust inflammatory reaction at the site of implantation or grafting. This can ultimately lead to tissue fibrosis with direct negative impact on tissue growth, development, and function. In order to temper the innate inflammatory response, anti-inflammatory signals were incorporated through display on self-assembling peptide nanofibers to promote tissue healing and subsequent graft compliance throughout the regenerative process. Utilizing an established urinary bladder augmentation model, the highly pro-inflammatory biologic scaffold (decellularized small intestinal submucosa) was treated with anti-inflammatory peptide amphiphiles (AIF-PAs) or control peptide amphiphiles and used for augmentation. Significant regenerative advantages of the AIF-PAs were observed including potent angiogenic responses, limited tissue collagen accumulation, and the modulation of macrophage and neutrophil responses in regenerated bladder tissue. Upon further characterization, a reduction in the levels of M2 macrophages was observed, but not in M1 macrophages in control groups, while treatment groups exhibited decreased levels of M1 macrophages and stabilized levels of M2 macrophages. Pro-inflammatory cytokine production was decreased while anti-inflammatory cytokines were up-regulated in treatment groups. This resulted in far fewer incidences of tissue granuloma and bladder stone formation. Finally, functional urinary bladder testing revealed greater bladder compliance and similar capacities in groups treated with AIF-PAs. Data demonstrate that AIF-PAs can alleviate galvanic innate immune responses and provide a highly conducive regenerative milieu that may be applicable in a variety of clinical settings.

Data demonstrate that mesenchymal stem cells and smooth muscle cells express the same contractile proteins and can function similarly in vitro. Endothelial progenitor cells also have the ability to form vasculature in an in vivo chorioallantoic membrane model. These findings provide evidence that mesenchymal stem cells and endothelial progenitor cells have characteristics that may be applicable for bladder tissue regeneration.