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Smooth muscle is a major component of human tissues and is essential for the normal function of a multitude of organs including the intestine, urinary tract and the vascular system. The use of stem cells for cell-based tissue engineering and regeneration strategies represents a promising alternative for smooth muscle repair. For such strategies to succeed, a reliable source of smooth muscle precursor cells must be identified. Adipose tissue provides an abundant source of multipotent cells. In this study, the capacity of processed lipoaspirate (PLA) and adipose-derived stem cells to differentiate into phenotypic and functional smooth muscle cells was evaluated. To induce differentiation, PLA cells were cultured in smooth muscle differentiation medium. Smooth muscle differentiation of PLA cells induced genetic expression of all smooth muscle markers and further confirmed by increased protein expression of smooth muscle cell-specific α actin (ASMA), calponin, caldesmon, SM22, myosin heavy chain (MHC), and smoothelin. Clonal studies of adipose derived multipotent cells demonstrated differentiation of these cells into smooth muscle cells in addition to trilineage differentiation capacity. Importantly, smooth muscle-differentiated cells, but not their precursors, exhibit the functional ability to contract and relax in direct response to pharmacologic agents. In conclusion, adipose-derived cells have the potential to differentiate into functional smooth muscle cells and, thus, adipose tissue can be a useful source of cells for treatment of injured tissues where smooth muscle plays an important role.

Adipose tissue can be harvested in large amounts with minimal morbidity. It contains numerous cells types, including adipocytes, preadipocytes, vascular endothelial cells and vascular smooth muscle cells; it also contains cells that have the ability to differentiate into several lineages, such as fat, bone, cartilage, skeletal, smooth, and cardiac muscle, endothelium, hematopoietic cells, hepatocytes and neuronal cells. Cloning studies have shown that some adipose-derived stem cells (ADSCs) have multilineage differentiation potential. ADSCs are also capable of expressing multiple growth factors, including vascular endothelial growth factor and hepatocyte growth factor. Early, uncontrolled, non-randomized clinical research, applying fresh adipose-derived cells into a cranial defect or undifferentiated ADSCs into fistulas in Crohn's disease, has shown healing and an absence of side effects. The combination of these properties, and the large quantity of cells that can be obtained from fat, suggests that this tissue will be a useful tool in biotechnology.

Background—In diabetes or atherosclerosis, ectopic bone, fat, cartilage, and marrow often develop in arteries. However the mechanism is unknown. We have previously identified a subpopulation of vascular cells (calcifying vascular cells, CVC), derived by dilutional cloning of bovine aortic medial cells, and showed that they undergo osteoblastic differentiation and mineralization. We now show that CVC have the potential to differentiate along other mesenchymal lineages.Methods and Results—To determine the multilineage potential of CVC, molecular and functional markers of multiple mesenchymal lineages were assessed. Chondrogenic potential of CVC was evidenced by expression of types II and IX collagen and cytochemical staining for Alcian blue. Leiomyogenic potential of CVC was evidenced by the expression of smooth muscle-α actin, calponin, caldesmon, and myosin heavy chain. Stromogenic potential of CVC was evidenced by the ability to support growth of colony-forming units of hematopoietic progenitor cells from human CD34+umbilical cord blood cells for a period of 5 weeks. Adipogenic potential was not observed. CVC were immunopositive to antigens to CD29 and CD44 but not to CD14 or CD45, consistent with other mesenchymal stem cells. CVC retained multipotentiality despite passaging and expansion through more than 20 to 25 population triplings, indicating a capacity for self-renewal.Conclusions—These results suggest that the artery wall contains cells that have the potential for multiple lineages similar to mesenchymal stem cells but with a unique differentiation repertoire.

Much of the work conducted on adult stem cells has focused on mesenchymal stem cells (MSCs) found within the bone marrow stroma. Adipose tissue, like bone marrow, is derived from the embryonic mesenchyme and contains a stroma that is easily isolated. Preliminary studies have recently identified a putative stem cell population within the adipose stromal compartment. This cell population, termed processed lipoaspirate (PLA) cells, can be isolated from human lipoaspirates and, like MSCs, differentiate toward the osteogenic, adipogenic, myogenic, and chondrogenic lineages. To confirm whether adipose tissue contains stem cells, the PLA population and multiple clonal isolates were analyzed using several molecular and biochemical approaches. PLA cells expressed multiple CD marker antigens similar to those observed on MSCs. Mesodermal lineage induction of PLA cells and clones resulted in the expression of multiple lineage-specific genes and proteins. Furthermore, biochemical analysis also confirmed lineage-specific activity. In addition to mesodermal capacity, PLA cells and clones differentiated into putative neurogenic cells, exhibiting a neuronal-like morphology and expressing several proteins consistent with the neuronal phenotype. Finally, PLA cells exhibited unique characteristics distinct from those seen in MSCs, including differences in CD marker profile and gene expression.

Adipose tissue sciences have rapidly expanded since the identification of regenerative cells contained within the stromal vascular fraction (SVF) of fat. Isolation of the SVF, containing adipose-derived stem cells (ADSC), can be accomplished efficiently in the operating room or in the laboratory through enzymatic digestion of the adipose tissue and concentration of SVF. Cells can be directly re-injected as a mesotherapeutic agent, recombined with a tissue scaffold (e.g., cell-enriched fat grafts) or expanded in culture for tissue-engineered cell therapeutics. The potential for cell therapy is under current investigation by researchers around the world. This chapter reviews laboratory methods for isolating ADSCs and the ongoing clinical trials evaluating cell therapeutic efficacy across many specialties, including cardiology, neurology, immunology, tissue engineering, sports medicine, and plastic and reconstructive surgery.

Human adipose tissue has been shown to contain a population of cells that possesses extensive proliferative capacity and the ability to differentiate into multiple cell lineages. These cells are referred to as adipose tissue-derived stem cells (ADSCs) and are generally similar, though not identical, to mesenchymal stem cells (also referred to as marrow stromal cells). ADSCs for research are most conveniently extracted from tissue removed during an elective cosmetic liposuction procedure but may also be obtained from resected adipose tissue. This chapter describes surgical procedures associated with improved ADSC recovery and the processes by which aspirated adipose tissue is washed and digested with collagenase to yield a heterogeneous population from which ADSCs can be expanded. The large volume of tissue obtained from a liposuction procedure (average approximately 2 L), combined with the relatively high frequency of ADSC within the digestate, yields substantially more stem cells than can be realized from marrow without extensive expansion in culture.

Background Human adipose tissue has been shown to contain multipotent cells with properties similar to mesenchymal stromal cells. While there have been many studies of the biology of these cells, no study has yet evaluated issues associated with tissue harvest. Methods Adipose tissue was obtained from the subcutaneous space of the abdomen and hips of 10 donors using both syringe and pump-assisted liposuction. Tissue was digested with collagenase and then assayed for the presence of different stem and progenitor cell types using clonogenic culture assays, including fibroblast colony-forming unit (CFU-F) and alkaline phosphatase-positive colony-forming unit (CFU-AP). Paired analysis of samples obtained from the same individual was used to compare harvest method and site. Results Syringe suction provided significantly greater recovery of adipocytes and a non-significant trend towards improved recovery of cells in the adipocyte-depleted fraction. There was considerable donor-to-donor variation in stem cell recovery. However, paired analysis of tissue obtained from different subcutaneous sites in the same donor showed that tissue harvested from the hip yielded 2.3-fold more CFU-F/unit volume and a 7-fold higher frequency of CFU-AP than that obtained from the abdomen. These differences were statistically significant. Discussion Harvest site influences the stem and progenitor cell content of subcutaneous adipose tissue.

Tissue engineering offers considerable promise in the repair or replacement of diseased and/or damaged tissues. The cellular component of this regenerative approach will play a key role in bringing these tissue engineered constructs from the laboratory bench to the clinical bedside. However, the ideal source of cells still remains unclear and may differ depending upon the application. Current research for many applications is focused on the use of adult stem cells. The properties of adult stem cells that make them well-suited for regenerative medicine are (1) ease of harvest for autologous transplantation, (2) high proliferation rates for ex vivo expansion and (3) multilineage differentiation capacity. This review will highlight the use of adipose tissue as a reservoir of adult stem cells and draw conclusions based upon comparisons with bone marrow stromal cells. (Keio JM ed 54 (3): 132-141, September 2005)

Recent preclinical and clinical studies have suggested that adult stem cells have the ability to promote the retention or restoration of cardiac function in acute and chronic ischemia. Published clinical studies have used autologous donor cells, including skeletal muscle myoblasts, cultured peripheral blood cells, or bone marrow cells. However, our research and that of others indicates that human adipose tissue is an alternative source of cells with potential for cardiac cell therapy. These findings include the presence of cells within adipose tissue that can differentiate into cells expressing a cardiomyocytic or endothelial phenotype, as well as angiogenic and antiapoptotic growth factors. This potential is supported by preclinical studies in large animals.