A study of adipogenic development in the skin dermis

Abstract

With the rise of obesity, the process of fat development, adipogenesis, is increasingly important to understand. In particular, several studies have indicated differences in the developmental origins and properties of different adipose depots. This thesis is concerned with adipogenesis in the recently identified adipose tissue depot in the lower dermis of the skin, divided from the underlying subcutaneous fat by the panniculus carnosus muscle layer in rodents. The study was aimed at developing new experimental tools, and providing new insights into the timing of adipose tissue development in this depot in mice. Experiments also explored the process of mitotic clonal expansion, and miRNAs in adipogenesis.

Essential to the study of adipogenesis in developing skin is the establishment of model systems that reflect events in vivo and that are capable of being manipulated experimentally. Two models: a substrate organ culture system and a 3D cell aggregate spherical model were developed and refined. These were then used for investigation into the timing of adipogenesis in the lower dermis. Staining of C/EBPα transcription factor and lipids in spherical cell culture revealed that cells between the ages of E14.5 and E18.5 were committed to undergo adipogenesis. This early timing of events was further suggested by collagen IV staining of mouse back skin showing distinct differences in expression between the upper and lower dermis at E14.5.

The first stage of adipogenesis in vitro, mitotic clonal expansion, was also explored. Experiments showed important differences between the uniform sequence of events of adipogenesis in vitro and the range of scenarios in 3D systems suggesting clonal expansion might not be necessary. Finally, a preliminary study on the role of miRNAs in skin adipogenesis was conducted using qPCR. This yielded some interesting initial trends which can be further investigated in future studies.