Abstract
Tissue engineering research has shown rapid progress; however, techniques for effectively inducing blood capillary formation within fabricated grafts have not been well-established. Therefore, the development of such technologies remains a primary target in this field. Several methods have previously been examined and can be generally classified into those that promote host angiogenesis or those that are related to the development of grafts with angiogenic potential.
Methods that involve the promotion of host angiogenesis include gene transfection or treatment with angiogenesis-promoting factors. Interestingly, modified transplantation techniques have successfully created over 1 mm thick grafts in vivo. Thus, concepts involving in vivo tissue fabrication techniques to create thicker tissue constructs possessing intact microvascular networks have recently been established.
To promote graft angiogenic potential, several approaches including fabrication of microcapillaries in vitro, and the inclusion of either endothelial progenitor cells or bone marrow derived cells within the grafts have also been examined.
Moreover, recently we have reported that engineered myocardial tissue grafts containing active endothelial cells in a network-like formation maintain the ability for neovascularization during culture and transplantation due to the use of cell sheet technology. Additionally, the amount of vessels in grafts in vivo is affected by the ratio of endothelial cells in vitro.
Considering clinical applications, techniques that can create tissue grafts with functional vessels are likely required for many patients. Therefore, new technologies for the establishment of vascular networks withing bioengineered tissues in vitro are required for the further development of regenerative medicine.
