Optimal Preparation Protocol of Cell-Encapsulating Alginate Capsules for Long-Term Cell-Based Therapy

Cell-based therapy is an excellent therapeutic modality that involves cell transplantation into patients; however, given that most transplanted cells die immediately post-transplantation, the application of this strategy remains limited. Cell encapsulation is a promising technique for prolonging the survival of transplanted cells, although a definitive encapsulation protocol is yet to be established. Herein, we selected sodium alginate as a polymer for cell encapsulation and optimized the structure and function of cell-encapsulating alginate capsules. First, alginate capsules were prepared using various concentrations of sodium alginate and calcium chloride solution. The NanoLuc luciferase (Nluc)-expressing murine mesenchymal stem cell line C3H10T1/2 was used to prepare the alginate capsules, and cell survival was evaluated after transplantation into mice. The structural properties of the alginate capsules were dependent on the preparation conditions. Capsules with adequate hardness were obtained using 1% sodium alginate and 10% calcium chloride solutions. Alginate capsules encapsulating 5 x 10(3) C3H10T1/2/Nluc cells/10 mu L maintained a constant cell number over time under in vitro culture conditions. After transplantation into mice, C3H10T1/2/Nluc cells encapsulated in alginate capsules exhibited a significantly longer survival (>= 40 days) than suspended cells. Based on these findings, cell-encapsulating alginate capsules with optimal properties can be used for long-term cell-based therapies.