A novel cryopreservation solution for adipose tissue based on metformin

Autologous fat grafting (AFG) often needs multiple sessions due to low volume retention. Young adipose tissue demonstrates a more pronounced therapeutic effect; thus, the cryopreservation of adipose tissue of young origin is particularly crucial. This study investigated the protective effect of a new cryopreservation solution combining trehalose, glycerol, and metformin on adipose tissue.

This study initially examined the effect of various concentrations of metformin (0, 1, 2, 4, and 8 mM) on oxidative damage in adipose tissue to identify the optimal concentration. Subsequently, 1.5 mL of fresh human adipose tissue was subjected to freezing using trehalose + glycerol (TG group), trehalose + glycerol + metformin (TGM group), and the common cryoprotectant dimethyl sulfoxide (DMSO) + fetal bovine serum (FBS) (DF group). Samples were cryopreserved in liquid nitrogen for 2 weeks. After thawing, 1 mL of adipose tissue from each group was transplanted subcutaneously into the backs of nude mice. The cryoprotective effects on adipose tissue viability were evaluated during transplantation one month after transplantation.

The 2 mM concentration of metformin exhibited the lowest reactive oxygen species (ROS) level (29.20 ± 1.73) compared to other concentrations (P < 0.05). Cell proliferation and migration assays also supported the superior performance of the 2 mM concentration. Apoptotic analyses of stromal vascular fraction (SVF) cells showed the lowest levels in the 2 mM group. Compared to other cryopreservation groups, the adipose tissue in the TGM group closely resembled fresh adipose tissue in terms of gross structure and histological characteristics, with the lowest apoptosis rate of SVF cells. In vivo analysis revealed the highest tissue retention rate in the TGM group, with histological examination indicating robust structural integrity.

The TGM cryopreservation solution, containing metformin, greatly preserves adipose tissue, reduces apoptosis, and improves tissue retention rates. This solution was non-toxic and safe, making it well-suited for tissue cryopreservation in clinical settings.