Development of orbital adipose-derived stem cells as a model for studying the formation of baggy lower eyelids.

In old population, there is often a protrusion of the orbital fat pad underlying the skin in the lower eyelids, giving an aspect of palpable pouches. It is generally thought that orbital fat hyperplasia is the main contributing factor to the formation of baggy lower eyelids, and resection of excessive orbital fat pad is routinely performed during the eyelid cosmetic surgery. In our clinical study, however, it was revealed that the adipocytes in orbital fat tissue from older people became smaller compared to those from the young individuals. Based on this finding, we hypothesize that the orbital fat size may not increase, but decrease with age, and the declined fat depot volume is related to the reduced fat cell size and impaired differentiation of preadipocytes into fat cells. Adipose-derived stem cells (ASCs) are a population of postnatal stem cells residing in the fat tissue, capable of differentiating into preadipocytes and subsequently into mature fat cells throughout the lifespan. As preadipocytes are a substantial component of fat tissue and can greatly influence the fat composition and function, we speculate that orbital adipose-derived stem cells can be used as an excellent model to determine effects of aging on orbital fat. By evaluating the age-related changes in preadipocyte number, replication, and differentiation, we can reveal alterations in orbital fat cellularity and function with age, and investigate the relationship between orbital fat volume and the of baggy lower eyelid formation.