Alginate-Gelatin Microspheres Protect Human Mesenchymal Stem Cells During Deep Cryopreservation

 The need for on-demand biological products has been raised during the last decades. To prepare ready-to-use organ-related products, it necessitates a bulk cell reservoir. In this regard, stem cells, especially mesenchymal stem cells, have numerous therapeutic properties in tissue repair. Therefore, the advent of novel cell banking systems is inevitable to maintain cells ready-to-use.

 In the current study, the cryoprotective effects of alginate-gelatin were investigated on human mesenchymal stem cells after seven days.

 Mesenchymal stem cells were classified into two groups; the Control and Encapsulated cells. Cells were encapsulated by using the mixture of alginate (1% v/v) and 2% gelatin and 1% CaCl2, a cross-linker, and vitrified in liquid nitrogen in freezing medium containing 10% dimethyl sulfoxide. After seven days, mesenchymal stem cells were thawed and decapsulated by 0.01 M sodium citrate solution. The cell survival rate was monitored by using MTT assay. Flow cytometry analysis of annexin-V/PI was used to determine the number of apoptotic cells.

 These data showed that encapsulation had a superior effect on maintaining cell viability after the freeze-thaw procedure compared to the control group (P < 0.05). We found a significant decrease in the number of early- and late-stage apoptotic cells in mesenchymal stem cells inside the alginate-gelatin microspheres seven days after deep freezing (P < 0.05). As expected, cell cycle analysis specified the lack of dynamic activity in cells from both groups. Cells at phases S and G2/M reached zero.

 These findings showed that encapsulation of human mesenchymal stem cells with alginate-gelatin microspheres could reduce deep freeze/thaw insult and decrease the detrimental effect of cryoprotectant compared to non-capsulated cells.