No abstract

Cell aggregates hold significant therapeutic promise for in vitro cell analysis, ex vivo tissue models, and in vivo cell therapy and tissue engineering. Traditional methods of making cell aggregates require long incubation times and can only produce three-dimensional-spheroid-shaped aggregates. We propose a novel method of making cell aggregates of diverse sizes and shapes using lipid-conjugated heparin. Shaking the cell suspension containing a small amount of lipid-conjugated heparin for approximately 30 min produced cell aggregates. This approach can be applied to any cell type, including stem cells, fibroblast cells, and T lymphocytes. The shape of biocompatible templates could modulate the shape of cell aggregates. In addition to layered, multicompartmental cell aggregates on template, template-free, tube-shaped cell aggregates could also be made. The cell aggregates formed were alive and maintained biological activities.

Direct reprogramming which changes the fate of matured cell is a very useful technique with a great interest recently. This approach can eliminate the drawbacks of direct usage of stem cells and allow the patient specific treatment in regenerative medicine. Overexpression of diverse factors such as general reprogramming factors or lineage specific transcription factors can change the fate of already differentiated cells. On the other hand, biomaterials can provide physical and topographical cues or biochemical cues on cells, which can dictate or significantly affect the differentiation of stem cells. The role of biomaterials on direct reprogramming has not been elucidated much, but will be potentially significant to improve the efficiency or specificity of direct reprogramming. In this review, the strategies for general direct reprogramming and biomaterials-guided stem cell differentiation are summarized with the addition of the up-to-date progress on biomaterials for direct reprogramming.