Adipose Tissue Stromal Fraction Research Articles

Parallels in Immunometabolic Adipose Tissue Dysfunction with Ageing and Obesity.

Ageing, like obesity, is often associated with alterations in metabolic and inflammatory processes resulting in morbidity from diseases characterised by poor metabolic control, insulin insensitivity, and inflammation. Ageing populations also exhibit a decline in immune competence referred to as immunosenescence, which contributes to, or might be driven by chronic, low-grade inflammation termed “inflammageing”. In recent years, animal and human studies have started to uncover a role for immune cells within the stromal fraction of adipose tissue in driving the health complications that come with obesity, but relatively little work has been conducted in the context of immunometabolic adipose function in ageing. It is now clear that aberrant immune function within adipose tissue in obesity—including an accumulation of pro-inflammatory immune cell populations—plays a major role in the development of systemic chronic, low-grade inflammation, and limiting the function of adipocytes leading to an impaired fat handling capacity. As a consequence, these changes increase the chance of multiorgan dysfunction and disease onset. Considering the important role of the immune system in obesity-associated metabolic and inflammatory diseases, it is critically important to further understand the interplay between immunological processes and adipose tissue function, establishing whether this interaction contributes to age-associated immunometabolic dysfunction and inflammation. Therefore, the aim of this article is to summarise how the interaction between adipose tissue and the immune system changes with ageing, likely contributing to the age-associated increase in inflammatory activity and loss of metabolic control. To understand the potential mechanisms involved, parallels will be drawn to the current knowledge derived from investigations in obesity. We also highlight gaps in research and propose potential future directions based on the current evidence.

Mesenchymal stem cells: new players in retinopathy therapy.

Retinopathies in human and animal models have shown to occur through loss of pericytes resulting in edema formation, excessive immature retinal angiogenesis, and neuronal apoptosis eventually leading to blindness. In recent years, the concept of regenerating terminally differentiated organs with a cell-based therapy has evolved. The cells used in these approaches are diverse and include tissue-specific endogenous stem cells, endothelial progenitor (EPC), embryonic stem cells, induced pluripotent stem cells (iPSC) and mesenchymal stem cells (MSC). Recently, MSC derived from the stromal fraction of adipose tissue have been shown to possess pluripotent differentiation potential in vitro. These adipose stromal cells (ASC) have been differentiated in a number of laboratories to osteogenic, myogenic, vascular, and adipocytic cell phenotypes. In vivo, ASC have been shown to have functional and phenotypic overlap with pericytes lining microvessels in adipose tissues. Furthermore, these cells either in paracrine mode or physical proximity with endothelial cells, promoted angiogenesis, improved ischemia–reperfusion, protected from myocardial infarction, and were neuroprotective. Owing to the easy isolation procedure and abundant supply, fat-derived ASC are a more preferred source of autologous mesenchymal cells compared to bone marrow MSC. In this review, we present evidence that these readily available ASC from minimally invasive liposuction will facilitate translation of ASC research into patients with retinal diseases in the near future.

Regenerative Therapeutic Potential of Adipose Stromal Cells in Early Stage Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of blindness in working-age adults. Early stage DR involves inflammation, vascular leakage, apoptosis of vascular cells and neurodegeneration. In this study, we hypothesized that cells derived from the stromal fraction of adipose tissue (ASC) could therapeutically rescue early stage DR features. Streptozotocin (STZ) induced diabetic athymic nude rats received single intravitreal injection of human ASC into one eye and saline into the other eye. Two months post onset of diabetes, administration of ASC significantly improved “b” wave amplitude (as measured by electroretinogram) within 1–3 weeks of injection compared to saline treated diabetic eyes. Subsequently, retinal histopathological evaluation revealed a significant decrease in vascular leakage and apoptotic cells around the retinal vessels in the diabetic eyes that received ASC compared to the eyes that received saline injection. In addition, molecular analyses have shown down-regulation in inflammatory gene expression in diabetic retina that received ASC compared to eyes that received saline. Interestingly, ASC were found to be localized near retinal vessels at higher densities than seen in age matched non-diabetic retina that received ASC. In vitro, ASC displayed sustained proliferation and decreased apoptosis under hyperglycemic stress. In addition, ASC in co-culture with retinal endothelial cells enhance endothelial survival and collaborate to form vascular networks. Taken together, our findings suggest that ASC are able to rescue the neural retina from hyperglycemia-induced degeneration, resulting in importantly improved visual function. Our pre-clinical studies support the translational development of adipose stem cell-based therapy for DR to address both retinal capillary and neurodegeneration.

Treatment of Chronic Headache of Cervical Origin With Lipostructure: An Observational Study

To test feasibility, safety, and efficacy of local transplant of stromal fraction of adipose tissue in the treatment of chronic headaches of cervical origin. Chronic headaches of cervical origin (chronic cervicogenic headache and occipital neuralgia) are characterized by persistent pain due to the involvement of the great occipital nerve, with concurrent myofascial spasm and the consequent nerve entrapment within the trapezoid tunnel. Tolerability and effectiveness of treatment of chronic cervicogenic headaches refractory to conventional therapies were evaluated in 24 patients. The visual analog scale of pain and the medication use diary were used in the 3 months preceding treatment; moreover, in order to verify the quality of life, patients are required to fill before surgery the neck pain disability index, the headache disability index, migraine disability assessment scale questionnaire, and the short-form 12 standard v1 questionnaire. Follow-up examination was performed at 3 and 6 months. In 19 cases (79.2%), a good clinical response was recorded. At 6-month follow-up analysis, recurrence of occipital pain was recorded in 7 cases (29.2%); there is a significant reduction in disability and pain scores, and also a significant reduction of need for pharmacologic treatment and a fast return to previous work capacities. The key point of our therapeutic strategy might be the regenerative role of stromal fraction of adipose tissue transplanted in the area of the occipital nerve entrapment; the results of the present study are encouraging both in terms of reduction of pain scores and in terms of quality of life improvement. The technique is minimally invasive, and no complications were recorded; indeed, the procedure seems to be safe and effective, and thus, a randomized study with larger follow-up and in a large series will be started.

Adipose tissue houses different subtypes of stem cells

Adipose tissue stromal fraction (ASF) contains multipotent cells capable of differentiation towards several lineages and may be used for the treatment of various degenerative diseases. However, the multipotent cells within ASF have not been fully characterized. In this study we have attempted to characterize stem cells in the ASF obtained through serial dilution. Five single-cell clones were studied. It was found that the single-cell clones exhibited slight but significant differences in proliferative capacity and differentiation potential. We conclude that ASF houses different subtypes of stem cells.

209 EPIGENETIC MODIFICATION WITH ZEBULARINE AND VALPROIC ACID AND EXPRESSION OF PLURIPOTENCY GENES IN BOVINE ADIPOSE STEM CELLS

Bovine adipose-derived stem cells (ASC), a form of adult stem cells, are somatic cells that have similar characteristics of embryonic stem (ES) cells. ASC are multipotent and have been found to express genes associated with pluripotency, Oct4, Sox2 and Nanog. The unique properties of ASC make them a desirable source for reprogramming experiments. When somatic cells are reprogrammed, there are certain epigenetic changes or modifications that must occur. Epigenetic modifications will change the chromatin configuration without changing the DNA sequence. Somatic cells can be exposed to small molecules that induce some of these changes. Two epigenetic modifying factors are a DNA methyltranferase inhibitor, zebularine (Zeb) and a histone deacetylase inhibitor, valproic acid (VPA). By altering gene expression with these epigenetic modifiers, the cells may be stimulated to reprogram more efficiently than untreated cells. Three lines of bovine ASC were isolated from the stromal fraction of adipose tissue and expanded through 3 passages in DMEM (high glucose) supplemented with 10% fetal bovine serum. Cells were cultured by addition of 5 mM VPA or 100 μM Zeb to the culture medium and cultured for 5, 7, 10 or 14 days before mRNA was isolated and converted to cDNA. Control groups, consisting of untreated bovine ASC from the same cell lines, were cultured for the same time periods as the treatment groups. Quantitative RT-PCR was performed to determine transcript levels for Oct4, Sox2, Nanog and poly adenylate polymerase (PAP) as a reference gene. Transcript levels were quantified by relative quantification using the ΔΔCT method and expressed as ratios of the target genes (Oct4, Sox2 and Nanog) to the reference gene (PAP) and normalized against a calibrator consisting of untreated bovine ADS cells. Normalized ratios were log-transformed before analysis by ANOVA to correct for lack of normality. A one-way ANOVA was completed to test the statistical significance among the control and treatment groups. Pairwise comparison was conducted to test expression levels between individual treatments. When cells were treated for 5 days, Oct4 and Nanog expression levels were increased (P ≤ 0.05) between the control and both treatment groups. Expression of Sox2 was not different (P = 0.06) across treatment groups. Based on pair wise comparisons gene expression in VPA and Zeb treated groups were not different. Treatment for 7, 10, or 14 days did not result in any difference in transcript levels between the treatment groups and control for any of the genes analysed. VPA and Zeb treatment for 5 days may have produced a partial reprogramming. This partial reprogramming could aid in the bovine ASC reaching complete pluripotency when combined with other reprogramming techniques. This work was financed in part by a grant from the LSU System for the ACRES/LSU Collaborative Research Program.

Vascular and Endothelial Regeneration

Adipose tissue is the final tissue to develop and is strongly involved in energy homeostasis. It can represent up to 50% of body weight in obesity. Beside its metabolic role, endocrine functions appeared to play a key role in interconnecting adipose tissue with other tissues of the organism and in numerous physiological functions. The presence of adipocyte progenitors has long been demonstrated throughout life in the stromal fraction of adipose tissue. Now, it appears that these cells are multipotent and share numerous features with mesenchymal stem cells (MSC) derived from bone marrow. They also display some specificities and a strong pro-angiogenic potential. Altogether, these data emphasize the need to reconsider the potential of adipose tissue. Moreover, since fat pads are easy to sample, numerous and promising perspectives are now opening up in regenerative medicine, particularly in ischemic situations.

IFATS Collection: Using Human Adipose-Derived Stem/Stromal Cells for the Production of New Skin Substitutes

The ability to harvest and culture stem cell populations from various human postnatal tissues is central to regenerative medicine applications, including tissue engineering. The discovery of multipotent mesenchymal stem cells within the stromal fraction of adipose tissue prompted their use for the healing and reconstruction of many tissues. Here, we examined the influence of adipose-derived stem/stromal cells (ASCs) on skin's regenerative processes, from a tissue engineering perspective. Using a self-assembly approach, human skin substitutes were produced. They featured a stromal compartment containing human extracellular matrix endogenously produced from either dermal fibroblasts or adipose-derived stem/stromal cells differentiated or not toward the adipogenic lineage. Human keratinocytes were seeded on each stroma and cultured at the air-liquid interface to reconstruct a bilayered skin substitute. These new skin substitutes, containing an epidermis and a distinctive stroma devoid of synthetic biomaterial, displayed characteristics similar to human skin. The influence of the type of stromal compartment on epidermal morphogenesis was assessed by the evaluation of tissue histology, the expression of key protein markers of the epidermal differentiation program (keratin [K] 14, K10, transglutaminase), the expression of dermo-epidermal junction components (laminins, collagen VII), and the presence of basement membrane and hemidesmosomes. Our findings suggest that adipose-derived stem/stromal cells could usefully substitute dermal fibroblasts for skin reconstruction using the self-assembly method. Finally, by exploiting the adipogenic potential of ASCs, we also produced a more complete trilayered skin substitute consisting of the epidermis, the dermis, and the adipocyte-containing hypodermis, the skin's deepest layer. Disclosure of potential conflicts of interest is found at the end of this article.

Complete differentiation of adipocyte precursors. A culture system for studying the cellular nature of adipose tissue.

Evidence for the complete morphological maturation of precursor cells into adipocytes in vitro is presented. Cells were isolated from the stromal fraction of adipose tissue from adult humans and from rats and were grown in culture. Abdominal skin fibroblasts were used as controls. All cell strains were initially fusiform and replicated. On reaching monolayer confluency, they were transferred to an enriched growth medium in which the human and rat adipocyte precursors differentiated into a homogeneous population of cells, morphologically indistinguishable from mature adipocytes. In contrast, skin fibroblasts from the same person or animal, and grown under identical culture conditions, did not accumulate lipid and retained their fusiform contour. The same results were obtained in the first six subcultures that were studied. Thus, there is firm evidence that fat tissue of adult humans and rats contains adipocyte precursors that differentiate into mature fat cells. The culture system that has been described will facilitate the elucidation of the factors involved in replication and differentiation of adipocyte precursors.

Isolation of fat cell precursors from adult rat adipose tissue

The possible existence of adipocyte precursors in adult rat adipose tissue was investigated. Cells were isolated from the stromal fraction of adipose tissue and were grown in culture. Skin fibroblasts were used as controls. The stromal fraction cells were initially fusiform and proliferated; in culture, they accumulated lipid inclusions, became rounder and acquired an eccentric nucleus. In contrast, the skin fibroblasts from the same rat grown under identical culture conditions, did not exhibit any appreciable lipid accumulation. The doubling time for both the stromal fraction cells and skin fibroblasts was 40-60 h. At confluency, the stromal fraction cells contained 5-7 times more glyceride-glycerol than skin fibroblasts. Thus, adipose tissue of adult rats contains cells with the potential to proliferate and acquire morphological characteristics similar to those of adipocytes.