Effects of Long-Term Cryopreservation on Fat Grafts: An Experimental Study

Lee, Hee Jong; Kim, Eun Key

Abstract

BACKGROUND
Although microfat grafting is now used to augment soft tissue, resorption of some amount of fat is inevitable. There are no consistent guidelines for the duration of fat storage. This study evaluated absolute fat mass and pathological changes according to storage duration.
METHODS
Nude mice were injected with fresh fat or fat that had been stored for 3 weeks, 5 months, 9 months, 15 months, or 22 months. After 15 weeks, fat graft weight and pathology (viable cells, structural integrity, microvessel formation, cystic degeneration, fibrosis, and cellular infiltration) were assessed.
RESULTS
After 15 weeks, the average weight of the remaining fat was 486 mg in the control group and 298, 160, 180, 106, 88, and 80 mg in the 3-week and 5-, 9-, 15-, 22-, and 36-month storage groups, respectively. The average weight of fat tissue significantly decreased to less than 20% in the 5-month group. Also, there was a significant decrease in structural integrity and an increase in cystic degeneration in the 5-month group. Tissue vascularization tended to decrease according to the duration of cryopreservation.
CONCLUSIONS
The mean weight of the fat grafts preserved in a general freezer was reduced by 61.3% compared with that of the fresh fat group, which was not statistically significant. The mean fat graft weight was, however, significantly reduced following storage in a general freezer for longer than 5 months. In addition, there were decreases in viable adipocytes and increases in fibrocystic degeneration and inflammatory changes when long-term preserved fat was grafted.