Mesenchymal stem cells (MSCs) are considered to be one of the most promising types of adult stem cells for therapeutic applications. It is their ability to differentiate into several different cell types, ease of ex vivo expansion in cell culture, and non-immunogenicity that has made them an attractive target to exploit for clinical means. Mesenchymal stem cells can be isolated from a variety of tissue sources such as bone marrow, umbilical cord blood, peripheral blood, and adipose tissue (Wagner et al,. 2005). Their presence within several different tissue sources suggest MSCs may play an important role in organ homeostasis by maintaining and repairing tissue damage (Porada, et al., 2010). The most predominant source of MSCs is derived from bone marrow, which is a relatively non-invasive method. However, many researchers have begun to focus on MSCs derived from adipose tissues, which are commonly referred to as adipose stem cells (ASCs).
Adipose stem cells have garnered much attention within the stem cell community and are considered by many as the next breakthrough stem cell type. ASCs have the capacity to differentiate into adipogenic, osteogenic, chondrogenic and other mesenchymal lineages (Zuk et al., 2002). In addition, there is supporting evidence to suggest that ASCs have the ability to differentiate into cells of non-mesodermal origin, such as hepatocytes, endothelial cells, neurons, endocrine pancreatic cells, and cardiomyocytes (Schaffler and Buchler, 2007; Zuk et al., 2002). Numerous cosmetic surgery procedures produce an abundance of lipoaspirate, which is a disposable byproduct from liposuction, and provide an important source to derive ASCs (Wilson et al., 2011). As such, ASCs are more readily accessible, and believed to be richly abundant in adipose tissue that enables isolation in higher numbers as compared to bone marrow derived MSCs (Fraser et al., 2006).
Despite these advantages, it is still questionable as to whether ASCs can be deemed as an alternative stem cell source for clinical applications. Isolation of ASCs from adipose tissue involves enzymatic digestion of the tissue with collagenase, which can lead to variability in the number and quality of stem cells. Articlesization of the techniques utilized to isolate and purify ASCs need to be implemented to ensure practicality and effectiveness within in a commercial bioprocessing and clinical setting. In addition, there is evidence to suggest isolation of ASCs results in a heterogeneous stem cell population with distinct ASCs subpopulations that exhibit different lineage differentiation potential (Rada et al., 2011). This illustrates some of the many challenges associated with ASCs and other adult stem cell types; the issue with identifying and isolating the intended stem cell population and driving these cells towards a targeted endpoint for a specific clinical use.
In short, the success of ASCs as a potential therapeutic application will heavily depend on elucidating the molecular characterization of ASCs, manipulating the intended stem cell population towards a specific endpoint, and translating these findings into an effective, practical clinical therapy.