Yung Te Hou

Growth factor/heparin-immobilized collagen gel system enhances viability of transplanted hepatocytes and induces angiogenesis

Hepatocyte transplantation is being explored as a treatment strategy for end-stage liver disease; however, the main limitation is the insufficient vascularization of transplanted hepatocytes. To overcome this problem, a suitable 3D microenvironment and the types of transplanted cells must be considered for hepatocyte transplantation. In this study, a growth factor (GF)/heparin-immobilized collagen gel-filled polyurethane foam (PUF) scaffold was developed for angiogenesis induction and hepatocyte transplantation. First, a vascular endothelial growth factor (VEGF)/heparin-immobilized, collagen-gel-filled PUF scaffold was developed to establish a prevascularized cavity in the subcutaneous space in rats. Second, accompanied by 70% partial hepatectomy (PH), hepatocytes were embedded inside heparin-immobilized, collagen-gel-filled PUF scaffolds, and were transplanted into the VEGF-induced prevascularized cavity. The benefits of using this system were confirmed by using three types of hepatocytes, namely single hepatocyte, hepatocyte spheroids, and fetal hepatocytes. The normalized hemoglobin content and live nucleus numbers were determined separately to evaluate the angiogenesis and viability of transplanted hepatocytes. In summary, after PH pretreatment, transplantation of fetal hepatocyte-embedded, heparin-immobilized, collagen-gel-filled PUF scaffold into a VEGF-induced prevascularized cavity appears to be a promising strategy for future liver tissue engineering.

Effect of a hepatocyte growth factor/heparin-immobilized collagen system on albumin synthesis and spheroid formation by hepatocytes

A hepatocyte growth factor (HGF)/heparin-immobilized collagen system was used as a synthetic extracellular matrix for hepatocyte culture. The albumin synthesis, nucleus numbers and morphology of the hepatocytes were determined separately to evaluate the hepatocyte number and hepatocyte-specific function under this system. The benefits of the HGF/heparin-immobilized collagen system for hepatocyte culture were confirmed by three types of culture methods in vitro, namely 2D film cultures, 2D gel cultures and 3D gel cultures. In 2D collagen film cultures, hepatocytes exhibited the highest albumin synthesis (1.42 microg/well/day) in HGF/heparin-immobilized collagen films at 7 days of culture. Heparin inhibited hepatocyte adhesion while HGF promoted hepatocyte migration, and spheroid formation was easily detected in HGF/heparin-immobilized collagen films. In 2D collagen gel cultures, albumin synthesis of around 15 microg/well/day was detected and maintained for more than 18 days on HGF/heparin-immobilized collagen gels. Similar findings were obtained in 3D HGF/heparin-immobilized collagen gel cultures, which exhibited albumin synthesis of up to 30 microg/well/day. The albumin synthesis by hepatocytes was two-fold higher in 3D gel cultures compared with 2D gel cultures, and was maintained for over 2 weeks compared with 2D film cultures using the HGF/heparin-immobilized collagen system. Taken together, the HGF/heparin-immobilized collagen system was effective for albumin synthesis by hepatocytes in both 2D film cultures and 3D gel cultures, and therefore shows good potential for tissue engineering use.