Wholly vascularized millimeter-sized engineered tissues by cell-sized microscaffolds.

Area of Science:

• Tissue Engineering
• Biomaterials Science
• Regenerative Medicine

Background:

• Fabricating vascularized millimeter-sized engineered tissues in vitro remains a significant challenge.
• Previous 'sedimentary culture' methods using collagen microfibers (CMFs) yielded tissues with non-uniform cell distribution due to size-dependent sedimentation.
• A need exists for improved methods to achieve homogeneous cell distribution and vascularization in engineered tissues.

Purpose of the Study:

• To develop cell-sized CMFs for uniform engineered tissue fabrication.
• To enhance vascularization within millimeter-sized engineered tissues.
• To improve cell distribution in engineered tissues using a refined sedimentary culture method.

Main Methods:

• Thermal crosslinking of type I collagen at 200°C for 24 hours to create stable CMFs.
• Fabrication of 20-μm CMFs (CMF-20) through homogenization and sonication of crosslinked collagen.
• Adsorption of fibronectin (FN) onto CMF-20 (FN-CMF-20) to promote endothelial cell migration and vascular network formation.

Main Results:

• Cell-sized CMF-20 exhibited similar sedimentation velocity to cells, enabling uniform cell distribution in engineered tissues via sedimentary culture.
• Engineered tissues fabricated with FN-CMF-20 showed significantly improved blood capillary network distribution within 1.6-mm constructs.
• The refined sedimentary culture method successfully produced millimeter-sized tissues with homogeneous cell distribution and enhanced vascularization.

Conclusions:

• Cell-sized CMFs, particularly FN-CMF-20, are effective for fabricating homogeneous, vascularized millimeter-sized engineered tissues.
• The improved sedimentary culture technique offers a promising approach for advancing in vitro tissue engineering.
• This methodology opens new avenues for creating complex, functional engineered tissues for various applications.