Design and evaluation of a novel subatmospheric pressure bioreactor for the preconditioning of tissue-engineered vascular constructs.

PURPOSE: The pre-conditioning of tissue-engineered vascular scaffolds with mechanical stimuli is being recognised as an essential step in producing a functional vascular construct. In this study we design and evaluate a novel bioreactor, which exerts a mechanical strain on developing vascular scaffolds via subatmospheric pressure. METHODS: We design and construct a bioreactor, which exerts subatmospheric pressure via a vacuum assisted closure unit. Vascular scaffolds seeded with human umbilical endothelial cells were evaluated for structural integrity, microbial contamination, cellular viability, von Willebrand factor (VWF) production, cell proliferation and morphology under a range of subatmospheric pressures (75-200mmHg). RESULTS: The bioreactor produced sustained subatmospheric pressures, which exerted a mechanical strain on the vascular scaffold. No microbial contamination was found during the study. The structural integrity of the vascular construct was maintained. There was no difference in cellular viability between control or subatmospheric pressure groups (p = 0.817). Cells continued to produce VWF under a range of subatmospheric pressures. Cells subjected to subatmospheric pressures of 125mmHg and 200mmHg exhibited higher levels of growth than cells in atmospheric pressure at 24 (p≤0.016) and 48 hour (p≤0.001). Negative pressure affected cellular morphology, which were more organised, elongated and expanded when exposed to subatmospheric pressure. CONCLUSIONS: We have constructed and validated a novel subatmospheric bioreactor. The bioreactor maintained a continuous subatmospheric pressure to the vascular scaffolds in a stable, sterile and constant environment. The bioreactor exerted a strain on the vascular sheets, which was shown to alter cellular morphology and enhance cellular proliferation.

Evaluation of xenogenic extracellular matrices as adjuvant scaffolds for the treatment of stress urinary incontinence.

INTRODUCTION AND HYPOTHESIS: Tissue-engineered biomaterials have shown recent promise as adjuvant scaffolds for treating stress urinary incontinence (SUI). The objective of the present study was to compare their mechanical and regenerative properties with synthetic biomaterials in this urogynaecological setting. METHODS: The biomechanical properties of polypropylene (Serasis®; n = 12), four-ply urinary bladder matrix (UBM; n = 12) and four-ply small intestinal submucosa (SIS; n = 12) were determined with uni-axial tensile testing protocols and compared with stress-strain curves. Subsequently, human dermal fibroblasts (2.5 × 10(4)cells/cm(2)) were cultured onto each biomaterial under conventional laboratory growth conditions for 12 consecutive days. Attachment, viability, and proliferative activity of fibroblasts were evaluated and compared using quantitative viability indicators and scanning electron microscopy. RESULTS: There were no significant differences in the biomechanical properties of each biomaterial assessed. Incremental stiffness at 0-10 % strain measured 5.73 ± 0.36 MPa for polypropylene compared with 8.23 ± 0.92 MPa and 6.81 ± 0.83 MPa for SIS and UBM respectively (p > 0.05). Viability and proliferative activity of fibroblasts differed significantly on all three biomaterials with the luminal and abluminal surfaces of the UBM demonstrating significantly greater rates of fibroblast proliferation compared with polypropylene and SIS (p < 0.01). CONCLUSION: This is the first comparative study on porcine UBM, porcine SIS, and synthetic polypropylene as adjuvant scaffolds for the treatment of SUI. Our results demonstrate that porcine UBM may provide an attractive alternative owing to its superior remodelling potential.