Silicon micromachining to tissue engineer branched vascular channels for liver fabrication

To date, many approaches to engineering new tissue have emerged and they ha ve all relied on vascularization from the host to provide permanent engraft ment and mass transfer of oxygen and nutrients. Although this approach has been useful in many tissues, it has not been as successful in thick, comple x tissues, particularly those comprising the large vital organs such as the liver, kidney, and heart. In this study, we report preliminary results usi ng micromachining technologies on silicon and Pyrex surfaces to generate co mplete vascular systems that may be integrated with engineered tissue befor e implantation. Using standard photolithography techniques, trench patterns reminiscent of branched architecture of vascular and capillary networks we re etched onto silicon and Pyrex surfaces to serve as templates. Hepatocyte s and endothelial cells were cultured and subsequently lifted as single-cel l monolayers from these two-dimensional molds. Both cell types were viable and proliferative on these surfaces. In addition, hepatocytes maintained al bumin production. The lifted monolayers were then folded into compact three -dimensional tissues. Thus, with the use microfabrication technology in tis sue engineering, it now seems feasible to consider lifting endothelial cell s as branched vascular networks from two-dimensional templates that mag ult imately be combined with layers of parenchymal tissue, such as hepatocytes, to form three-dimensional conformations of living vascularized tissue for implantation.