Stem cells have made quite a lot of progress in regenerative medicine. With the evolving treatment, new sources of stem cells are explored for better availability and an easy extraction process. Adipose-derived stem cells(ADSCs) have been the recent development in this area. They have garnered interest from the scientific community for applications in diverse diseases.
Adipose Tissue
Around 2001, adipose tissue was introduced as a novel source of mesenchymal stem cells (MSCs). Adipose tissue is present throughout the body in subcutaneous regions (beneath the skin), intra-articular regions (within joints), intramuscular regions (around muscle), intrahepatic regions (in the liver), visceral regions (around internal organs), etc. It comprises three distinct cell types.
-
Brown adipose tissue cells, or adipocytes, are responsible for thermogenesis. They have multi-locular morphology with small lipid droplets. They are found in the heart, pancreas, kidney, trachea and bones.
-
White adipocytes have subcutaneous localization and are unilocular with large lipid droplets. Its key function is storing fats, and its hyperplasia causes obesity.
-
Beige adipocytes reside with the white adipocytes and serve both the functions- thermogenesis and fat storage. They are unilocular, containing small lipid droplets, thus showing characteristics from both cell types. They differentiate into brown adipocytes.
Adipose-Derived Stem Cells (ADSCs)
The most common source of ADSCs is the subcutaneous tissue from the abdomen, thigh, hips, or buttocks. Adipose stromal cells, Adipose Stem Cells, and adipose-derived MSCs are a few other names for ADSCs. Typically discarded during plastic surgical procedures like liposuction, this tissue can be utilized for ADSCs extraction. The process requires mincing of the adipose tissue and its enzymatic degradation of the tissue pieces by incubation in collagenase solution. The centrifugation results in the stromal vascular fraction in the pellet. It contains diverse cellular composition- ADSCs, fibroblasts, endothelial cells, pericytes, smooth muscle cells, leukocytes, erythrocytes, etc.
Adherence of ADSCs to the culture dish separates them from the rest of the cell types. With a spindle morphology, they show a typical doubling time of 2-5 days. Human adipose-derived stem cells are positive for MSC markers such as CD13, CD29, CD44, CD63, CD73, CD90, and CD105, while lacking hematopoietic markers CD14, CD31, CD45, and CD144.
Effects of ADSCs in Regenerative Medicine
Adipose Stem Cells in Regenerative Medicine are popular for the secretion of soluble growth factors such as basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), insulin-like growth factor 1 (IGF1), transforming growth factor-β1 (TGFβ1) and hepatocyte growth factor (HGF). In response to growth factors, these cells can proliferate and differentiate into adipogenic, chondrogenic, and osteogenic lineages. They also mediate tissue regeneration via paracrine signalling. Although ASCs are mesodermal in origin, they have shown ectodermal and endodermal differentiation. In a defined medium, they have demonstrated markers of neural cells, such as Schwann cells and glial cells. They can also transform into hepatocytes and β-islet cells under the influence of certain growth factors.
Therapeutic Applications of Human ADSCs
Ischemia: Normal cells cannot survive ischemic and hypoxic environments. However, ADSCs secrete factors bFGF and VEGF during hypoxia. They promote angiogenesis, aiding cell survival in harsh environments and subsequent healing in ischemic tissues.
Bone Tissue Regeneration: The osteogenic potential of ADSCs can treat bone injury. Their implantation along with a scaffold promotes bone regeneration. These scaffolds provide the surface for attachment and growth of ADSCs. They can include natural and synthetic polymer materials with osteoinductive and osteogenic properties.
Cartilage Tissue Engineering: ADSCs can contribute to the treatment of osteoarthritis by owing to its chondrogenic differentiation. Scaffolds composed of fibrin, alginate, and chondroitin sulfate can drive the ADSCs differentiation into chondrogenic lineage.
Neuroregeneration: Studies have shown that ADSCs can form a neural conduit in the in vitro and in vivo settings, demonstrating their therapeutic potential for neurological disorders.
Wound healing: A phase III study reported that the ADSCs treatment can result in higher rate of healing, which is attributable to its immunosuppressive activity and stimulation of matrix protein formation. It has been effective for severe symptoms such as fibrosis, atrophy, ulcers, etc.
Graft vs Host Disease (GVHD): Transplants are often associated with the risks of GVHD which can utilize the immunomodulatory property of ASCs. A report demonstrated improvements in refractory GVHD after ADSCs administration. Adipose-Derived Stem Cells (ADSCs) treatment also resulted in positive outcomes in haematological and immunological disorders.
Cardiovascular Disorders: ADSCs also have anti-apoptotic property which is beneficial for cardiovascular diseases. Their administration has resulted in improvements in myocardial infarction. They can also recruit other stem cells thus contributing to innate healing with implications in cardiac remodeling and fibrosis.
Conclusion
ADSCs can treat various chronic disorders. Their effortless isolation and higher cellular yield have prompted their application. ASCs are now participating in the race for stem cell therapy along with bone marrow MSCs and Umbilical Cord MSCs. Many phase III clinical trials have proven their efficacy and safety. However, their low numbers call for more research and trials on ADSCs for their effective clinical translation.
Caption
You must be logged in to post a comment.