Angiogenesis Enhancement in a Liver Extracellular Matrix-Derived Hydrogel through Co-culture of Human Umbilical Vein Endothelial Cells and Adipose Tissue Mesenchymal Stem Cells

Background and purpose: The development of a bioengineered liver construct with integrated blood vessels, utilizing tissue engineering technology, is urgently needed in the healthcare system to address the growing demand for liver transplantation. For the successful development of this construct, the matrix must support liver cell viability, functionality, and the formation of microvasculature. Furthermore, one of the essential factors for the formation of blood vessels in engineered constructs is the presence of endothelial cells and pericytes, which play a crucial role in stabilizing the vascular network. Materials and methods: Endothelial cells were cultured within a hydrogel derived from liver extracellular matrix (LEM) as the control group. In the co-culture group, endothelial cells and mesenchymal stem cells (MSCs) were cultured together within the hydrogel. Blood vessel formation, vascular density, and the differentiation of MSCs into pericytes were evaluated 10 days after cell culture in the hydrogel. These assessments aimed to determine the efficacy of the LEM-derived hydrogel in supporting angiogenesis and facilitating cell interactions for the development of a stable vascular structure. Results: Immature blood vessels were formed within the LEM-derived hydrogel in both the control and co-culture groups. However, the vascular density was significantly higher in the co-culture group compared to the control group. Furthermore, the expression of the α-sma gene, a key regulator of angiogenesis, was significantly elevated in the co-culture group. The presence of the α-sma protein was also observed in the co-culture group. Conclusion: The LEM-derived hydrogel supports the establishment of polarity in endothelial cells, facilitating blood vessel formation within the engineered liver construct. The required cell density for effective blood vessel formation is 100,000 cells per 30 microliters. Moreover, the co-culture of endothelial cells and MSCs significantly enhances angiogenesis. MSCs contribute to this process through paracrine mechanisms and their differentiation into pericytes.