Seeking the stemmiest stem cell; how to get more from your fat

Abstract

Human adipose derived stem cells (ASC) are of interest to the field of regenerative medicine. They are multipotent (can differentiate into fat, bone, muscle, cartilage) and they can be accessed relatively easily from lipoaspirate, the by-product of liposuction. Lipoaspirate is processed to yield a heterogenous cell pellet known as the stromal vascular fraction (SVF). Typically SVF is cultured for up to 4 weeks using standard tissue culture conditions to yield a purified population of ASC. We have been using multicolour flow cytometry to analyse and sort stem cell and progenitor populations in complex tissues such as adipose tissue. We have observed significantly higher differentiation potential in ASC isolated from the SVF using flow cytometry when compared to ASC purified using the standard tissue culture method. This data indicates that the freshly sorted ASC are more potent and could therefore perform better in a clinical setting. However due to the technical complexities that are associated with flow cytometry this isolation procedure is unlikely to translate easily to a clinical setting. Therefore we are currently assessing the utility of a magnetic-activated cell sorting (MACS) approach for ASC isolation. Here we use “negative selection” to label all non-ASC within the SVF with a novel cocktail of commercially available antibodies attached to magnetic microbeads. Our preliminary data indicates that this approach results in cells with high purity, high yields and high levels of differentiation potential. Therefore the MACS approach could offer a simple method to rapidly isolate potent ASC that can be easily translated to the clinic. By understanding the molecular basis of differentiation potential we could use molecular tools to enhance the potency and clinical utility of ASC. To this end we have used microarray technology to analyse the differential expression of mRNAs and microRNAs between ASC with high (FACS sorted cells) versus low (purified by plastic adherence) differentiation potential. Data will be shown indicating that specific microRNAs are associated with high potency ASC. We observe that when these microRNAs are over-expressed in cells differentiation potential is significantly improved. This suggests that manipulation of the expression of specific microRNAs could be used to enhance the ‘steminess’ of ASC.