Adipose tissue stem cells meet preadipocyte commitment: going back to the future.
Adipocytes, the most abundant cells in adipose tissue, contain a single large free fatty acids and glycerol to meet the energy requirements of the body. . Adipose-derived stem cells are able to differentiate to other types of cells of the same. Adipose tissue stem cells meet preadipocyte commitment: going back to the future. Adipose-derived stem cells differentiate to keratocytes in vitro. Mol. Vis. Dec 2, Adipose tissue stem cells meet preadipocyte commitment: going back to preadipocyte differentiation collided with developments in stem cell.
Indeed, the presence of cardiovascular risk factors, such as hypertension, coronary disease, diabetes mellitus, and obesity, alter and reduce the functionality of adipose-derived stem cells, putting in doubt the efficacy of their autologous implantation. In the present article, white adipose tissue is described, the stem cells found in this tissue are characterized, and the use of these cells is discussed according to the preclinical and clinical trials performed so far.
This specialized tissue is of mesenchymal origin, consisting of a combination of white adipose tissue WAT and brown adipose tissue, with each tissue type showing distinct functions, morphologies, and distributions.
In both tissues, the predominant cell is the adipocyte, comprising between one- and two-thirds of the total, and the remaining tissue is composed of different types of cells constituting the stromal vascular fraction SVF.
White Adipose Tissue Although WAT is distributed throughout the body, its principal deposits are subcutaneous, where it acts as an energy storage system, and in the visceral or intra-abdominal region, where it protects against possible trauma.
The 2 tissues show different adipokine expression profiles, 1 metabolic functions, 2 vascular density, and innervation. Visceral adipose tissue shows a higher angiogenic potential and more acute inflammatory profile than subcutaneous tissue. Individuals with peripheral obesity subcutaneous distribution do not show the characteristic medical complications of obesity.
In contrast, increased visceral adipose tissue central obesity is associated with a state of hyperglycemia, hyperinsulinemia, hypertriglyceridemia, hypercholesterolemia, reduced circulating levels of high-density lipoproteins, decreased glucose tolerance, increased apolipoprotein B-rich lipoproteins, and hepatic steatosis.
All of these conditions are characteristics of insulin resistance syndrome, which increases the risk of the development of type 2 diabetes mellitus. In times of caloric excess, adipose tissue stores fat in the form of triglycerides.
These lipids are then released into the blood in times of energy demand to be used as an energy source in other tissues, such as the liver, kidneys, skeletal muscle, and myocardium. Adipocytes, the most abundant cells in adipose tissue, contain a single large cytoplasmic vacuole that mainly stores triglycerides and cholesterol esters. Adipocytes contain the machinery necessary for lipid metabolism Figure 1.
Indeed, fatty acids not only show an energy function, but also act as regulatory signals of the gene expression of proteins involved in lipid metabolism, 10 favor a prothrombotic state, and are associated with inflammatory processes.
When calorie consumption exceeds energy expenditure, a metabolic state develops that promotes adipocyte hypertrophy increased size and hyperplasia increased number. New or small adipocytes are more sensitive to insulin and show a marked capacity for the uptake of free fatty acids and triglycerides in the postprandial period. These distended adipocytes become hyperlipolytic and resistant to insulin and its antilipolytic signals.
Another important function performed by adipocytes is that of endocrines cells, as discussed below. Diagram illustrating the lipogenesis and lipolysis processes occurring in mature adipocytes. After eating and an increase in blood insulin, lipogenesis is activated in adipocytes. In this process, adipocytes, via lipoprotein lipase, degrade the triglycerides of chylomicrons and of very-low-density lipoprotein to fatty acids.
These molecules enter the adipocyte to be esterified with glycerol-3 phosphate and synthesize the triglycerides that are stored in the lipid vacuole. Mesenchymal stem cells MSCs from the adult human are multipotent cells and are able to differentiate into osteocytes, chondrocytes, adipocytes and cell lines when stimulated under appropriate conditions Jaiswal et al.
Thus, theoretically, these cells could be multiplied in the laboratory and induced to form specific cell types Pereira The MSCs were first studied in and it was observed that some cells were well adhered to culture plates.
The morphology of these cells was very similar to that of fibroblasts in vitro and that cells were clustered and formed some colonies Johnstone These cells were derived from mesodermal progenitors, but recently it was discovered that they also originated from the neuro-epithelium of the embryo, as observed by the fact the they expressed the marker Sox-1 Takashima et al.
The first place where these stem cells were found was in the vascular bone marrow stroma, located in all the tissues. However, MSCs have also been observed inside the wall of blood vessels Crisan et al. Besides the bone marrow, there are MSCs that are in peripheral blood and are also in the umbilical cord, but when compared to the amount of cells found in these sites with those found in bone marrow, bone marrow becomes more interesting by having a larger amount of MSCs, although the growing conditions for these cells are not well-established Wexler et al.
With these characteristics, they could be called mesenchymal stem cells Ugarti et al. With all these features, they arouse great interest in research aimed on regenerative medicine Jiang et al. The MSCs have been collected from different adult tissues and studies have shown that when these cells were studied separately, there were significant differences between them, according to their origin Puissant et al.
Mesenchymal stem cells MSCs are found in the perivascular adipose tissue, called mesenchymal stem cells derived from adipose tissue. These cells have the same genes and the same differentiation potential of mesenchymal cells from other locals Lin et al. The great advantage of these mesenchymal cells is their abundance, availability and accessibility, when compared to other sources of MSCs Zuk et al.
Behaving like stem cells, adipocytes have the multipotent capacity to undergo chondrogenic, osteogenic, cardiogenic, neurogenic and angiogenic differentiation Poulos et al. The MSCs can differentiate into osteoblasts, adipocytes, chondrocytes Ringe et al.
Its plasticity, however, is not restricted to mesenchymal derivatives. Reports suggest that MSCs can also differentiate into neurons Moorman et al. The expansion of MSCs from different sources bone marrow cells, peripheral blood, embryonic annexes, among others has been widely studied due to their ability to differentiate into several lineages, and represent a promising population for cell-based therapies in veterinary medicine.
There is still little information about the origins of MSCs, but there is a theory that it may be from neuroectodermal origin, from neuroepithelial cells Takashinma et al. These MSCs can be isolated from various organs of the body such as bone marrow, adipose tissue, synovial membrane, muscle, dermis, deciduous teeth, umbilical cord, placenta, liver, spleen and thymus Caplan ; Meirelles et al.
Mesenchymal stem cells: emphasis in adipose tissue
The population of stem cells derived from adipose tissue digested with collagenase, also called stromal vascular fraction, is able to differentiate into several cell lineages, including adipose tissue, cartilage, bone, skeletal muscle, neuronal cells, endothelial cells, cardiomyocytes and smooth muscle cells Ferrari et al. Adipose tissue represents the ideal source of autologous stem cells, since its acquisition is easy, with minimal discomfort for the patient and often with greater proliferative capacity than the cells derived from bone marrow.
This characteristic may be intrinsic to the cells, or a result of increased density of stem cells in the initial population. Thus, there is less invasiveness and complexity in the collection, which results in less suffering for the patient, associated with the ability to recover significant numbers of mesenchymal cells, sufficient to prevent extensive expansion in the culture to generate effective clinical potential of cells derived from adipose tissue in relation to other methodologies Yokomizo et al.
MSCs show promising results in preclinical studies and clinical trials in heart disease, lung, spinal cord and central nervous system injuries, and bone defects in cartilage Nardi and Meirelles. The bioengineered of tissue in combination with biomaterials has shown satisfactory results with the use of MSCs Zhang et al. When the cells are isolated from the donor tissue, they can be kept in various forms. A small piece of tissue that adheres to a surface of growth, either spontaneously, or by mechanical aid, like blood clots, or an extracellular matrix constituent of the collagen, generally gives support for the cell's growth.
This kind of culture is known as a primary explant and the cells that migrate from the tissue are growing cells. These are selected in the first instance due to their ability to migrate from the explant and subsequently, if sub-cultured, the ability of proliferation. When a sample of tissue is disaggregated, either mechanically, or enzymatically, a suspension of cells and small aggregates capable of binding to a solid substrate is formed, forming then a monolayer.
The cells monolayer with the capacity to proliferate is selected from the first subculture, and like the primary explant, it can possibly originate a stem cell line. The disaggregated tissue is capable of producing large crops faster than explant culture, but the latter may be preferred when small fragments are obtained, or when tissue frailty prevents the cell's survival after disaggregated Freshney The cultivation of MSCs is performed by selecting the cells with adhesiveness to plastic, whereas cells that remain in suspension are easily removed.
The other "contaminants" cell type such as macrophages, are removed after a certain number of passages in culture Javazon et al. They can be expanded by more than 40 generations keeping multipotent capacity while reducing the rates of mitosis, and there is a high probability of accumulation of mutations, making it inadvisable to its clinical use in these circumstances Deans and Moseley Another characteristic of MSCs is that when grown in low-density, the adhesion and colony formation is fast.
It is assumed that these colonies are derived from a single precursor cell Deans and Moseley However, even after years of studies on the composition of cell cultures, the selection of these cells still remains empirical. Some cell cultures are commercially available and are listed in Table 2. Adipose tissue is derived from the embryonic mesenchyme and contains a stroma that is easily isolated. Some studies have shown that there is a potential stem cell compartment in adipose stroma.
This cell population, called processed lipoaspirate PLAcan differentiate into osteogenic, adipogenic, myogenic and chondrogenic progenitor cells. However, the most appropriate process for obtaining the aspirate and the number of viable cells in tissues are not well established Pereira et al. They are expected to become seed cells for improving tendon healing such as tissue engineering, cell therapy and gene therapy.
Adipose-derived Mesenchymal Stem Cells and Their Reparative Potential in Ischemic Heart Disease
ADSCs have been obtained from humans, mice, rats, and bovines, but few studies have used goats. Goat ADSC had normal diploid cells after subculture. Proliferation of goat ADSCs was faster than rat cells in the same conditions.
Adipogenic induction resulting in lipid droplets and peroxisome proliferator-activated receptor PPARc2 expression were observed. Adipogenic differentiation was confirmed by Nile Red staining of lipid droplets. After feeding ADSCs with adipogenic-inducing medium for 21 days, oil droplets were present in the cytoplasm Fig.
The oil droplets appeared to be larger in goat cells than in rat cells and the droplets had a rounder shape measure. The expression of peroxisome proliferator-activated receptor PPARc2 was seen in both goat and rat adipogenic-induced cells Fig.
CHICKEN According to Khuong and Jeonginchicken epithelial oviduct cells COCs are part of important supportive tissues in chicken reproductive organs responsible for secretion of the majority of chicken egg protein. In chickens, the biological process of adipocyte differentiation has been extensively studied in vitro using a number of cell types, including a preadipocyte precursor cell line, a number of other undifferentiated cell lines, and chicken embryonic fibroblasts.
However, adipogenic differentiation in epithelial cells has not yet been achieved. Also, chicken serum strongly induced 3T3-L1 preadipocyte cell differentiation into adipocyte. In addition, mRNA expressed levels of peroxisome proliferator-activated receptor gamma, adipocyte fatty acid-binding protein aP2and CCAAT enhancer-binding protein alpha were significantly increased 48 h after induction.
These results suggested that COCs could be induced to differentiate into adipocyte-like cells. Moreover, through this study, they confirmed that chicken serum was an effective adipocyte differentiation-inducing agent. RABBIT Stem cells obtained from the adipose tissue of rabbits are seeded in culture dishes of 25 ml volume at a rate of 2. From the first 48 h, the medium is changed every two days, the first two exchanges being mediated by a PBS washing to remove any residue of erythrocytes, or adipose tissue that could have left over in the plaque.
However, common expansion using fetal bovine serum FBS cannot be used for clinical applications and xenogenic proteins must be avoided. Adipose tissue from equine, canine and porcine donors was digested with collagenase to isolate the ASCs. From all three animal species, the adipogenic and osteogenic differentiation potential of ASCs cultured with different media was analyzed in vitro. The cell proliferation analysis showed a population doubling time of h for canine cells, h for porcine cells and h for equine cells, expanded in different media.
Yet, all the cells maintained their potential to differentiate into adipocytes and osteoblasts. UltraCulture medium containing UltroserG can for all examined species be recommended if FBS needs to be avoided in the expansion of donor-derived stem cells.
Additionally, a third medium was tested: After 72 h, the medium was exchanged and thereby non-adherent cells were washed away. Cells were counted using a hemocytometer and re-seeded in new culture dishes. Differentiation was achieved by culturing in the medium induction for five days, followed by medium conservation for two days.
This sequence was repeated twice. Equine samples were induced to differentiate with autologous serum instead of FBS. Subsequently, lipid droplet formation was assessed with Oil Red-O staining Fig. The deficiency of orexin is implicated in narcolepsy, a disease associated with the obesity, paradoxically facing the reduced food intake.
They showed that obesity in orexin-null mice was associated with the impaired brown adipose tissue BAT thermogenesis. Failure of thermogenesis in OX-null mice was due to inability of brown preadipocytes to differentiate.
Their study suggested that obesity associated with OX depletion was linked to brown-fat hypoactivity, which led to dampening of energy expenditure. Thus, orexin plays an integral role in adaptive thermogenesis and body weight regulation via effects on BAT differentiation and function.
Cellular populations derived from the adult human bone marrow and adult interstitial white adipose tissue contained multipotential cells that could be induced to differentiate down the adipocyte lineage.
According to Sarkanenthe induction of adequate vascularization, a major challenge in tissue engineering, has been tried with numerous methods but with unsatisfactory results. Adipose tissue, an active endocrine organ with dense vasculature, secretes a wide number of angiogenic and adipogenic factors and seems an attractive source for these bioactive factors. They produced a novel cell-free extract from mature human adipose tissue adipose tissue extract, ATE and analyzed the ability of this extract to induce angiogenesis and adipogenesis in vitro and studied the cytokine and growth factor composition of ATE with ELISA and cytokine array.