This discovery came after that of bone marrow-derived stem cells in the 1960’s and thus immediately posed as an alternative source of stem cells for use in regenerative therapies. It is not surprising, that since this discovery, adipose stem cells have been the focus of numerous studies and clinical trials.
Creating a great level of confusion with fat-derived stem cells has been the lack of universal consensus on what to call them. Some of the common names that have been used are: adipose-derived stromal cells (ADSCs), adipose-derived adult stem cells (ASCs), adipose mesenchymal stem cells (AMSCs) and adipose-derived stem cells (ADSCs) [2].
Despite all this, by far the most important thing to be aware of is the distinction between 1) fat-derived cells that are obtained from fat tissue and include a mixture of different cell types and 2) fat-derived cells that are culture expanded within the lab and include fewer cell types [2] [3]. The International Federation for Adipose Therapeutics and Science (IFATS) and the International Society for Cellular Therapy (ISCT), stepped in to provide some clarity on the matter and have stated that the former should not be referred to as stem cells but rather stromal vascular fraction (SVF) and the latter to adipose tissue-derived stromal/stem cells (ASCs) (where stromal refers to connective tissue) [4]. ASCs are essentially a type of mesenchymal stem cell [4].
Stromal Vascular Fraction or ‘SVF’ is simply the term used to describe the isolated mixture of cell types found in adult fat. These are the cells that remain after the removal of blood and extracellular fat tissue. To name a few, SVF is comprised of adipose-derived stem/stromal cells, endothelial precursor cells (inner lining of blood vessel), endothelial cells, fibroblasts (cells found in connective tissue), preadipocytes (fat forming cells), macrophages and haematopoietic stem cells (blood forming) [4] [5].
The wonderful thing about SVF is that it may be obtained for autologous use. A patient in need of the regenerative possibilities that SVF has to offer can choose to harvest this cell source from their own fat tissue, allow for it to be processed and then administered to their injured site. SVF has become of such significant interest in developing cell therapies to date due to the characteristic ability to modulate the immune system and stimulate regeneration [6]. SVF contains a number of different cell types, as well as a type of mesenchymal stem cell, that together have shown to secrete signalling molecules and growth factors that stimulate rejuvenation within the microenvironment of damaged tissue [6].
Clinical application of SVF was first demonstrated in 2008 where it was used to enhance breast augmentations [7]. As of March 2018, 84 clinical trials on ‘stromal vascular fraction’ are presented on www.clinicaltrials.gov. SVF if being investigated for a vast number of treatments, from pulmonary diseases [8], immune disorders (graft versus host disease and Crohn’s disease) [9] to cartilage regeneration in osteoarthritis [10] and neuronal diseases (multiple sclerosis) [11].
This rapid rise of the use of SVF and cultured ASCs, due to their immense therapeutic potential in any number of treatments, needs to come with a high level of responsibility. Current controversies linked with fat-derived cell therapies, are due to the lack of an international consensus being reached on the best methods of obtaining and characterising SVF and ASCs [3]. Most countries are still in the process of developing proper regulatory guidelines for stem cell therapies [3]. In this regard, administering facilities need to ensure that patients are always aware of the benefits versus the risks and an informed consent must always be obtained. Patients have an equal responsibility to ensure that they understand the procedure, that they are aware of the risks versus the benefits and that the procedure is being conducted by a well-recognised and accredited facility.
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