Tubular Compressed Collagen Scaffolds for Ureteral Tissue Engineering in a Flow Bioreactor System

Abstract

Ureteral replacement by tissue engineering might become necessary following tissue loss after excessive ureteral trauma, after retroperitoneal cancer, or even after failed reconstructive surgery. This need has driven innovation in the design of novel scaffolds and specific cell culture techniques for urinary tract reconstruction. In this study, compressed tubular collagen scaffolds were evaluated, addressing the physical and biological characterization of acellular and cellular collagen tubes in a new flow bioreactor system, imitating the physiological pressure, peristalsis, and flow conditions of the human ureter. Collagen tubes, containing primary human smooth muscle and urothelial cells, were evaluated regarding their change in gene and protein expression under dynamic culture conditions. A maximum intraluminal pressure of 22.43 ± 0.2 cm H2O was observed in acellular tubes, resulting in a mean wall shear stress of 4 dynes/cm(2) in the tubular constructs. Dynamic conditions directed the differentiation of both cell types into their mature forms. This was confirmed by their gene expression of smooth muscle alpha-actin, smoothelin, collagen type I and III, elastin, laminin type 1 and 5, cytokeratin 8, and uroplakin 2. In addition, smooth muscle cell alignment predominantly perpendicular to the flow direction was observed, comparable to the cell orientation in native ureteral tissue. These results revealed that coculturing human smooth muscle and urothelial cells in compressed collagen tubes under human ureteral flow-mimicking conditions could lead to cell-engineered biomaterials that might ultimately be translated into clinical applications.

Overview of Urethral Reconstruction by Tissue Engineering: Current Strategies, Clinical Status and Future Direction

“…It was also shown by Vardar et al [67], that mechanical stimulation can up-regulate expression of collagen type 1 and elastin as of major components of urinary tract extra cellular matrix [67].…”

Biomanufacturing Seamless Tubular and Hollow Collagen Scaffolds with Unique Design Features and Biomechanical Properties

“…Previously reported techniques for creating collagen‐based tubular structures include rolling collagen sheets into tubes by suturing or gluing the ends together and pouring a collagen solution into a tubular mold followed by drying. Although a method to condense collagen has been previously reported, the development of a biomanufacturing process that can create seamless and consistent collagen scaffolds in the form of complex 3D structures matching an organ of interest with appropriate mechanical properties is highly desirable.…”

“…A critical criterion for the molded tube to be applied successfully as a neo‐urinary conduit is its ability to withstand a fluid pressure (“strength”) that is encountered in a physiological ureter during urinary transport and its ability to allow lumen expansion with minimal change in the fluid pressure (“compliance”) as a neo‐urinary conduit. These properties are even more critical when constructing a urinary bladder . Since tube burst pressure is related to its material composition, diameter, and wall thickness, we first created seamless collagen tubes with varying dry wall thicknesses, which corresponded to the initial volume loads of utilized collagen solutions (Figure C).…”

“…However, they are mechanically dynamic and biologically complex. In the case of the genitourinary tract, it is lined by the urothelium, which represents one of the most impenetrable barriers in the human body that is required to transport and store toxic urinary metabolites . Their structural design incorporates a multifolded lumen and a multilayer muscle cell arrangement that allows for muscle contraction and relaxation, required for large volume changes needed for urine to flow without rupturing the lumen surface at a higher fluid shear stress ( Figure A,B).…”

Mechanical induction of bi-directional orientation of primary porcine bladder smooth muscle cells in tubular fibrin-poly(vinylidene fluoride) scaffolds for ureteral and urethral repair using cyclic and focal balloon catheter stimulation

“…15–19 For bladder TE, the cell-seeded scaffold is extended by the cyclic application hydrostatic pressure, ranging from 0 to 100 Pa. 20–22 For ureteral TE, Vardar et al. 14 developed a physiologically relevant peristaltic fluid flow bioreactor which was used to apply mechanical stimuli to cell-loaded tubular, type-1 collagen gels. Jeong et al.…”