Abstract
Complications associated with urinary bladder augmentation provide the motivation to delineate alternative bladder tissue regenerative engineering strategies. We describe the results of varying the proportion of bone marrow (BM) mesenchymal stem cells (MSCs) to CD34 + hematopoietic stem/progenitor cells (HSPCs) co-seeded onto synthetic POC [poly(1,8 octamethylene citrate)] or small intestinal submucosa (SIS) scaffolds and their contribution to bladder tissue regeneration. Human BM MSCs and CD34 + HSPCs were co-seeded onto POC or SIS scaffolds at cell ratios of 50 K CD34 + HSPCs/15 K MSCs (CD34-50/MSC15); 50 K CD34 + HSPCs/30 K MSCs (CD34-50/MSC30); 100 K CD34 + HSPCs/15 K MSCs (CD34-100/MSC15); and 100 K CD34 + HSPCs/30 K MSCs (CD34-100/MSC30), in male (M/POC; M/SIS; n = 6/cell seeded scaffold) and female (F/POC; F/SIS; n = 6/cell seeded scaffold) nude rats (n = 96 total animals). Explanted scaffold/composite augmented bladder tissue underwent quantitative morphometrics following histological staining taking into account the presence (S+) or absence (S−) of bladder stones. Urodynamic studies were also performed. Regarding regenerated tissue vascularization, an upward shift was detected for some higher seeded density groups including the CD34-100/MSC30 groups [F/POC S− CD34-100/MSC30 230.5 ± 12.4; F/POC S+ CD34-100/MSC30 245.6 ± 23.4; F/SIS S+ CD34-100/MSC30 278.1; F/SIS S− CD34-100/MSC30 187.4 ± 8.1; (vessels/mm2)]. Similarly, a potential trend toward increased levels of percent muscle (≥ 45% muscle) with higher seeding densities was observed for F/POC S− [CD34-50/MSC30 48.8 ± 2.2; CD34-100/MSC15 53.9 ± 2.8; CD34-100/MSC30 50.7 ± 1.7] and for F/SIS S− [CD34-100/MSC15 47.1 ± 1.6; CD34-100/MSC30 51.2 ± 2.3]. As a potential trend, higher MSC/CD34 + HSPCs cell seeding densities generally tended to increase levels of tissue vascularization and aided with bladder muscle growth. Data suggest that increasing cell seeding density has the potential to enhance bladder tissue regeneration in our model.
Highlights
Complications associated with urinary bladder augmentation provide the motivation to delineate alternative bladder tissue regenerative engineering strategies
Upward shifts were not detected in M/small intestinal submucosa (SIS) S−, and this construct differed from the others with a reduced range of vessels at the 5001–10,000 size (Fig. 1B)
In constructs with similar S+ and S− subset trends (F/POC, F/SIS), the increase in total vessels/mm[2] (F/POC) or vessels/mm[2] of a particular size (F/POC, F/SIS) observed with higher seeding densities was statistically significant [assessed without S+/S− subsets; F/POC (S+ and S− animals) total vessels/ mm[2] CD34-50/MSC15 179.2 ± 17.0 vs CD34-100/MSC30 235.5 ± 10.4 (p < 0.01) and vessels/mm2, 5001–10,000 size, CD34-50/MSC15 41.7 ± 9.9 vs CD34-100/MSC30 84.6 ± 14.0 (p < 0.05); F/SIS (S+ and S− animals) vessels/ mm2, ≤ 5000 size, CD34-50/MSC15 76.3 ± 7.4 vs CD34-100/MSC15 130.9 ± 12.2 (p < 0.01) and CD34-100/MSC30 129.7 ± 11.7 (p < 0.01)]. Aside from these comparisons, differences between CD34-50/MSC15 and greater cell seeding density groups were not determined to be statistically significant for any construct
Summary
Complications associated with urinary bladder augmentation provide the motivation to delineate alternative bladder tissue regenerative engineering strategies. The use of synthetic polymerics combined with autologous bladder SMCs and urothelial cells (UC) has not been able to reliably and convincingly demonstrate the regeneration of physiologically relevant bladder tissue in the clinical setting This is especially pertinent with regards to whole bladder tissue vascularization and functional bladder smooth muscle regeneration. In a proof-of-principle study, elastic POC [poly(1,8 octamethylene citrate)] scaffolds co-seeded with human spina bifida derived BM mesenchymal stem cells (MSCs) and donor matched CD34 + hematopoietic stem/progenitor cells (HSPCs) have been shown to act synergistically promoting by various facets of bladder tissue regeneration in a nude rat bladder augmentation model. Data from that study demonstrated significant whole-graft tissue vascularization, peripheral nerve regeneration, and robust smooth muscle and urothelium regeneration[28] In these studies, the proportion of MSCs to CD34 + HSPCs was held static at the time of scaffold seeding. Within the context of this study, we wished to determine whether bladder tissue regeneration could be positively influenced by varying the ratios of MSCs to CD34 + HSPCs on POC scaffolds within a nude rat bladder augmentation model by making intra-scaffold anatomic and bladder physiological comparisons
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