Abstract
Clinical use of adipose-derived stem cells (ASCs) for a variety of indications is rapidly expanding in medicine. Most commonly, ASCs are isolated at the point of care from lipoaspirate tissue as the stromal vascular fraction (SVF). The cells are immediately administered to the patient as an injection or used to enrich fat grafts. Isolation of ASCs from adipose tissue is a relatively simple process performed routinely in cell biology laboratories, but isolation at the point of care for immediate clinical administration requires special methodology to prevent contamination, ensure integrity of clinical research and comply with regulatory requirements. A lack of practical laboratory experience, regulatory uncertainty and a relative paucity of objective published data can make selection of the optimum separation method for specific indications a difficult task for the clinician and can discourage clinical adoption. In this paper, we discuss the processes which can be used to separate SVF cells from fat tissue. We compare the various mechanical and enzymatic methods. We discuss the practical considerations involved in selecting an appropriate method from a clinical perspective. Studies consistently show that breakdown of the extracellular matrix achieved with proteolytic enzymes affords significantly greater efficiency to the separation process. SVF isolated through mechanical methods is equally safe, less costly and less time consuming but the product contains a higher frequency of blood mononuclear cells and fewer progenitor cells. Mechanical methods can provide a low cost, rapid and simple alternative to enzymatic isolation methods, and are attractive when smaller quantities of ASCs are sufficient.
Highlights
The clinical use of autologous adipose-derived stem cells (ASCs) is rapidly expanding because of promising results across a wide range of conditions
Enzymatic methods are more efficient in isolating stromal vascular fraction (SVF) cells because disruption of the collagen-based extracellular matrix (ECM) which binds together adipocytes and other cells of adipose tissue
Shah et al cultured samples from each method to determine ASC content. They reported that once samples reached 80–90 % confluence that an average of 25,000 adiposederived stem cells per cc of lipoaspirate processed were found in the sample acquired using this mechanical method, but 480,000 adipose-derived stem cells per cc of lipoaspirate we found in the sample acquired using the enzymatic method
Summary
The clinical use of autologous adipose-derived stem cells (ASCs) is rapidly expanding because of promising results across a wide range of conditions. The surge in clinical applications for ASCs increases the need for clear and reliable information about the efficiency, cost and safety of automated equipment and manual techniques which facilitate separation of the stromal vascular fraction (SVF) from adipose tissue. Adipose-derived stem cells are often not administered as a pure isolate but rather as one constituent of stromal vascular fraction, a heterogeneous mixture of cells resulting from the mechanical or enzymatic processing of aspirated adipose tissue. Enzymatic methods are more efficient in isolating SVF cells because disruption of the collagen-based extracellular matrix (ECM) which binds together adipocytes and other cells of adipose tissue. Published yields of viable, nucleated SVF cells achieved using manual, collagenase-based digestions range from 100,000 nucleated cells/cc to 1,300,000 nucleated cells/ cc of lipoaspirate processed (Table 1). Mechanical methods seek alternative non-enzymatic means of removing SVF cells
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