A system for the direct co-culture of endothelium on smooth muscle cells

A modular tissue engineering construct containing smooth muscle cells and endothelial cells

Human umbilical vein endothelial cells (HUVEC) were seeded on sub-mm sized collagen cylinders containing embedded umbilical vein smooth muscle cells (UVSMC). These cylindrical "modules" are intended to be used as a vascularized construct, in which HUVEC lined channels are created by the random packing of the modules in situ or within a larger container. Embedding UVSMC cultured in medium containing 10% FBS had an adverse effect on subsequently seeded HUVEC junction morphology; HUVEC/UVSMC co-culturing was done in HUVEC medium (2% FBS with the addition of 0.03 mg/mL endothelial cell growth supplement) as compared to HUVEC seeded on collagen-only modules. In contrast, embedding UVSMC cultured in serum-free medium prior to embedding improved EC junction morphology. Such serum-free culturing, also prevented the UVSMC induced contraction of the collagen modules. On the other hand, embedding serum-free cultured UVSMC promoted HUVEC proliferation and NO secretion compared to those modules embedded with 10% serum cultured UVSMC. These results suggest, not surprisingly, that embedded UVSMC phenotype plays an important role in the seeded HUVEC phenotype, and that the response can be modulated by the UVSMC culture medium serum concentration. These studies were undertaken with a view to using the UVSMC to modulate the thrombogenicity of the HUVEC. Exploration of this outcome awaits further studies directed to understanding the mechanism of the cellular interactions.

Quick layer-by-layer assembly of aligned multilayers of vascular smooth muscle cells in deep microchannels

One of the main challenges in vascular tissue engineering has been mimicking the complex native three-dimensional (3D) architecture of smooth muscle cells (SMCs). In the current study, we performed layer-by-layer (LBL) seeding of SMCs in a microchanneled scaffold, with or without interleaving a thin layer of collagen type I hydrogel, toward fabricating the 3D microarchitecture. This LBL process avoids the "steric hindrance" effect observed in direct 3D culture of SMCs in collagen hydrogel. More importantly, the LBL process enables the building up of multilayers of aligned and confluent SMCs. Within each layer, the SMCs as well as the SMC F-actin and alpha-actin filaments align along the direction of the scaffold microchannels, which would potentially improve the tensile and contractile strength of the tissue engineered construct, desirable properties for an engineered vasculature. In addition, rapid two-dimensional (2D) patterning of SMCs is possible with high seeding density, which makes the LBL method feasible for fabrication of multilayered structures in a short time, rendering it useful in clinical therapeutic applications.

Adhesion and function of human endothelial cells co-cultured on smooth muscle cells

To evaluate interactions between human endothelial cells (ECs) and smooth muscle cells (SMCs) for the development of tissue-engineered vessels, we examined the adhesion and key cell properties of human ECs grown on quiescent human aortic SMCs. ECs attached to SMCs spread more slowly than ECs attached to fibronectin surfaces, and ECs aligned along the direction of the SMCs. ECs attached firmly and less than 5% of the cells were removed by shear stresses as high as 300 dyn cm(-2). Unlike porcine SMCs and co-cultures, human SMCs or co-cultures do not contract under flow, and the human ECs and SMCs in co-culture align toward the direction of flow. A confluent endothelium could be maintained in co-culture for over 30 days, and some of the ECs reoriented perpendicular to the SMCs after 9 days in static culture. Surface tissue factor levels in ECs and SMCs were less in co-culture than in monoculture. Co-culture induced an increase in calponin expression in SMCs. These findings show that human co-cultures can be maintained for long culture periods, where the endothelium remains confluent and responds to long-term exposure to flow, and EC-SMC interactions lead to an increase in SMC differentiation and an EC surface that is less thrombotic.

Development of the wing-attached rod for acceleration of “Biotube” vascular grafts fabricationin vivo

To accelerate the fabrication of in vivo tissue-engineered autologous vascular prosthetic tissues, the "Biotube," a novel wing-attached rod mold was designed for a tissue rolling technique based on a two-step in body tissue incubation (IBTI) process. The new mold consisted of a silicone rod (3-mm diameter, 23-mm length) partly connected to a poly(ethylene terephthalate) film (a wing, 23 x 19 x 0.1 mm). While the molds were embedded into the dorsal subcutaneous pouches of rabbits for 2 weeks (primary IBTI), they were encapsulated fully with thin connective tissues. After removal of the wing materials, the remaining saccular membranous tissues were rolled up on the core tubular tissues that had formed around the silicone rods. Following another 2-week embedding of the assembled tissues (secondary IBTI), the layered tissues fused to each other to form compliant and stiff tubular tissues, "Rolled Biotubes." The wall thickness of the Rolled Biotubes was about 800 microm and the burst strength was about 4000 mmHg, both of which were significantly higher than those of Biotubes prepared by one-step, 4-week IBTI or two-step, 2-week IBTI (p < 0.05). A Rolled Biotube could be applied as middle or large caliber arterial prostheses.

Control of spatial cell attachment on carbon nanofiber patterns on polycarbonate urethane

A highly aligned pattern of carbon nanofibers (CNF) on polycarbonate urethane (PCU) for tissue engineering applications was created by placing a CNF-ethanol solution in 30 microm width copper grid grooves on top of PCU. In vitro results provided the first evidence that fibroblasts and vascular smooth muscle cells selectively adhered to the PCU regions. However, endothelial cells did not display a preference for adhesion to the CNF compared with PCU regions. Previous studies have shown selective adhesion of osteoblasts (bone-forming cells) on CNF compared with PCU regions. Thus, the present results suggest that CNF aligned on PCU may be useful substrates for the control of spatial cell attachment, criteria useful for the design of a wide range of tissue engineering materials, from orthopedic to vascular.