Construction of Pedicled Smooth Muscle Tissues by Combining the Capsule Tissue and Cell Sheet Engineering

Abstract

The survival of engineered tissue requires the formation of its own capillary network, which can anastomose with the host vasculature after transplantation. Currently, while many strategies, such as modifying the scaffold material, adding endothelial cells, or angiogenic factors, have been researched, engineered tissue implanted in vivo cannot timely access to sufficient blood supply, leading to ischemic apoptosis or shrinkage. Constructing vascularized engineered tissue with its own axial vessels and subsequent pedicled transfer is promising to solve the problem of vascularization in tissue engineering. In this study, we used the tissue expander capsule as a novel platform for vascularizing autologous smooth muscle cell (SMC) sheets and fabricating vascularized engineered tissue with its own vascular pedicle. First, we verified which time point was the most effective for constructing an axial capsule vascular bed. Second, we compared the outcome of SMC sheet transplantation onto the expander capsule and classical dorsal subcutaneous tissue, which was widely used in other studies for vascularization. Finally, we transplanted multilayered SMC sheets onto the capsule bed twice to verify the feasibility of fabricating thick pedicled engineered smooth muscle tissues. The results indicated that the axial capsule tissue could be successfully induced, and the capsule tissue 1 week after full expansion was the most vascularized. Quantitative comparisons of thickness, vessel density, and apoptosis of cell sheet grafts onto two vascular beds proved that the axial capsule vascular bed was more favorable to the growth and vascularization of transplants than classical subcutaneous tissue. Furthermore, thick vascularized smooth muscle tissues with the vascular pedicle could be constructed by multi-transplanting cell sheets onto the capsule bed. The combination of axial capsule vascular bed and cell sheet engineering may provide an efficient strategy to overcome the problem of slow or insufficient vascularization in tissue engineering.

Bladder reconstruction using autologous smooth muscle cell sheets grafted on a pre-vascularized capsule

“…Autologous SMC sheet grafting has the potential for reliable bladder reconstruction. The retention, survival, and engraftment of transplanted cells in cell sheet therapy are largely influenced by the degree of vascularization in the transplanted area, and lack of sufficient vasculature limits the viable tissue thickness to 3 layers 8 , 18 . In the sheet-only group, 6 layered pre-vascularized SMC sheets were directly transplanted onto the bladder muscular wall defects one at a time.…”

“…SMCs and EPCs were cultured as previously described 18 - 20 . Briefly, a pure detrusor strip approximately 10 × 5 mm was cut down from the bladder wall.…”

“…Tissue expander capsules were induced according to our previously described methods 16 - 18 . Briefly, skin incisions were cut in the bilateral inguinal region and bilateral superficial circumflex iliac (SCI) artery and vein, branches of the femoral artery and vein, were exposed.…”

“…Cell sheet transplantation was performed according to previously described methods 18 , 19 . Briefly, triple-layer cell sheet constructs were placed on top of a transparent polypropylene support sheet (3 cm × 2 cm) and transplanted onto the capsule vascular bed by sliding from the nonadhesive polypropylene sheet (Figure 1 C).…”

“…In our previous studies, we have prefabricated a vascularized capsule pouch and proved that it may serve as an in vivo bioreactor for thick vascularized smooth muscle tissue flap prefabrication and could also be used as an induced vascular bed for buccal mucosa-lined flap prefabrication for tubularized urethral reconstruction 16 - 18 . We recently developed a simple, cost-effective, and minimally invasive strategy for harvesting pre-vascularized smooth muscle cell (SMC) sheets using a coculture system, in which SMCs were cocultured with endothelial progenitor cells (EPCs) on common polystyrene dishes 19 .…”