Culture effects of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) on cryopreserved human adipose-derived stromal/stem cell proliferation and adipogenesis

Serially Transplanted Nonpericytic CD146(-) Adipose Stromal/Stem Cells in Silk Bioscaffolds Regenerate Adipose Tissue In Vivo

Progenitors derived from the stromal vascular fraction (SVF) of white adipose tissue (WAT) possess the ability to form clonal populations and differentiate along multiple lineage pathways. However, the literature continues to vacillate between defining adipocyte progenitors as "stromal" or "stem" cells. Recent studies have demonstrated that a nonpericytic subpopulation of adipose stromal cells, which possess the phenotype, CD45(-) /CD31(-) /CD146(-) /CD34(+) , are mesenchymal, and suggest this may be an endogenous progenitor subpopulation within adipose tissue. We hypothesized that an adipose progenitor could be sorted based on the expression of CD146, CD34, and/or CD29 and when implanted in vivo these cells can persist, proliferate, and regenerate a functional fat pad over serial transplants. SVF cells and culture expanded adipose stromal/stem cells (ASC) ubiquitously expressing the green fluorescent protein transgene (GFP-Tg) were fractionated by flow cytometry. Both freshly isolated SVF and culture expanded ASC were seeded in three-dimensional silk scaffolds, implanted subcutaneously in wild-type hosts, and serially transplanted. Six-week WAT constructs were removed and evaluated for the presence of GFP-Tg adipocytes and stem cells. Flow cytometry, quantitative polymerase chain reaction, and confocal microscopy demonstrated GFP-Tg cell persistence, proliferation, and expansion, respectively. Glycerol secretion and glucose uptake assays revealed GFP-Tg adipose was metabolically functional. Constructs seeded with GFP-Tg SVF cells or GFP-Tg ASC exhibited higher SVF yields from digested tissue, and higher construct weights, compared to nonseeded controls. Constructs derived from CD146(-) CD34(+) -enriched GFP-Tg ASC populations exhibited higher hemoglobin saturation, and higher frequency of GFP-Tg cells than unsorted or CD29(+) GFP-Tg ASC counterparts. These data demonstrated successful serial transplantation of nonpericytic adipose-derived progenitors that can reconstitute adipose tissue as a solid organ. These findings have the potential to provide new insights regarding the stem cell identity of adipose progenitor cells.

Vasopressin-induced Ca(2+) signals in human adipose-derived stem cells

Intracellular Ca(2+) signals are essential for stem cell differentiation due to their ability to control signaling pathways involved in this process. Arginine vasopression (AVP) is a neurohypophyseal hormone that increases intracellular Ca(2+) concentration during adipogenesis via V1a receptors, Gq-proteins and the PLC-IP3 pathway in human adipose-derived stromal/stem cells (hASCs). These Ca(2+) signals originate through calcium release from pools within the endoplasmic reticulum and the extracellular space. AVP supplementation to the adipogenic media inhibits adipogenesis and key adipocyte marker genes. This review focuses on the intersection between AVP, Ca(2+) signals and ASC differentiation.

RIA fractions contain mesenchymal stroma cells with high osteogenic potency

INTRODUCTION

The gold standard for treatment of non-union is the transplantation of autologous bone from iliac crest. As an alternative, material can be harvested by femoral reaming with the Reamer-Irrigator-Aspirator(®) (RIA)-System. This material might be a source for human mesenchymal stroma cells (MSCs) with osteogenic potency. The aim of this study was the characterisation of cells harvested with the RIA system and the comparison of their properties with cells isolated from bone marrow ("BM") and fat tissue ("adipose"). The RIA material was separated into the liquid aspiration fraction ("liquid") and the solid RIA fraction. From the solid RIA fraction the cells were cultured either directly ("native") or after collagenase digestion and filtration ("filtrate"). Stem cell characteristics were analysed and the osteogenic potential was investigated in vitro and in vivo.

MATERIALS & METHODS

Fat tissue and bone marrow were harvested from nine patients (three women, six males, with a mean of 48.1 years) with atrophic non-union RIA material. The cells were isolated and characterised by flow cytometry, three lineage differentiation capacities and colony-forming unit fibroblast assay. Gene expression profiles were performed and osteogenic differentiation in vivo was analysed.

RESULTS

All three RIA fractions contained mesenchymal stromal cells (MSCs) as demonstrated by CFU-F assay, three linage differentiation and surface marker analysis. The RIA-MSCs exhibited a significantly higher osteogenic potential in vitro compared to adipose-MSCs, whereas no difference was seen compared to BM-MSCs. Quantitative RT-PCR analysis revealed an expression of osteogenic markers in all isolated cells. The implantation of MSCs with β-TCP scaffolds into the mice muscle showed significantly higher bone formation for the filtrate RIA-MSC, native RIA-MSC and BM-MSC groups compared to the adipose-MSC group. The filtrate RIA-MSCs formed twice as much new bone in vivo compared to BM-MSCs.

CONCLUSION

The present study showed high potency of cells isolated by reaming. Even in the irrigation fluid, which is normally discarded, cells with the characteristics of stromal stem cells were isolated. In comparison to adipose-MSCs and BM-MSCs, the RIA-MSCs showed a similar or even better osteogenic potential in vitro and in vivo and this supports their usability in orthopaedic surgery.

Coadministration of adipose-derived stem cells and control-released basic fibroblast growth factor facilitates angiogenesis in a murine ischemic hind limb model

OBJECTIVE

Adipose-derived stem cells (ASCs) have angiogenic potential owing to their differentiation into endothelial cells and their release of angiogenic growth factors to elicit paracrine effects. In addition, control-released basic fibroblast growth factor (bFGF) sustained with a gelatin hydrogel also supports effective angiogenesis. We sought to determine if coadministration of ASCs and control-released bFGF into murine ischemic limbs facilitates angiogenesis.

METHODS

Levels of growth factors in the conditioned media of ASCs cultured with or without control-released bFGF were measured by enzyme-linked immunosorbent assays. A murine ischemic hind limb model was generated and intramuscularly injected with the following: gelatin hydrogel (group 1), a high number of ASCs (group 2), control-released bFGF (group 3), a small number of ASCs and control-released bFGF (group 4), and a high number of ASCs and control-released bFGF (group 5). Macroscopic and microscopic vascular changes were evaluated until day 7 by laser Doppler perfusion imaging and histologic analyses, respectively.

RESULTS

Secretion of hepatocyte growth factor, vascular endothelial growth factor, and transforming growth factor-β1 was enhanced by control-released bFGF. Vascular improvement was achieved in groups 4 and 5 according to laser Doppler perfusion imaging. Hematoxylin and eosin staining and CD31 immunohistochemical staining demonstrated an increase in the vascular density, vessel diameter, and thickness of vessel walls in groups 4 and 5. Cells positively stained for CD146, α-smooth muscle actin, and transforming growth factor-β1 were observed around vessel walls in groups 4 and 5.

CONCLUSIONS

These findings suggest that coadministration of ASCs and control-released bFGF facilitates angiogenesis in terms of vessel maturation in a murine ischemic hind limb model.

Maternal stress predicts altered biogenesis and the profile of mitochondrial proteins in the frontal cortex and hippocampus of adult offspring rats

Currently, much attention is focused on the influence of mitochondrial disturbances at the onset of depression. The goal of this study was to investigate the impact of prenatal stress (an animal model of depression) on the mitochondrial biogenesis proteins and mitoproteome profile in the frontal cortex and hippocampus of adult 3-month-old male rats following a prenatal stress procedure. Our results show that rats that were exposed to prenatal stress stimuli displayed depression-like behaviors based on the sucrose preference and elevated plus maze tests. It has been found that the level of the PGC-1α protein was reduced in the frontal cortex and hippocampus of the adult offspring after the prenatal stress procedure. Moreover, in the frontal cortex, the level of the pro-apoptotic protein Bax was up-regulated. Two-dimensional electrophoresis coupled with mass spectrometry showed the statistically significant down-regulation of the mitochondrial ribosomal protein L12 (Mrpl12) and mitochondrial NADH dehydrogenase [ubiquinone] flavoprotein 2 (NDUFV2) as well as the up-regulation of the Tubulin Polymerization Promoting Proteins (Tppp/p25) in the frontal cortex. In contrast, in the hippocampus, the mitochondrial pyruvate dehydrogenase E1 component subunit beta, the voltage-dependent anion-selective channel protein 2 (VDAC2), and the GTP-binding nuclear protein RAN (RAN) were down-regulated and the expression of phosphatidylethanolamine-binding protein 1 (PEBP-1) was enhanced. These findings provide new evidence that stress during pregnancy may lead not only to behavioral deficits, but also to disturbances in the brain mitoproteome profile in adult rat offspring.

Overexpression of Hif-1α in Mesenchymal Stem Cells Affects Cell-Autonomous Angiogenic and Osteogenic Parameters

Reconstruction of large bone defects still represents a major medical challenge. In recent years tissue engineering has developed techniques based on adult mesenchymal stem cells (MSCs) that could represent an attractive therapeutical option to treat large bone defects in the future. It has been demonstrated in various animal models that ex vivo expanded MSCs are capable of promoting the regeneration of skeletal defects after implantation. However, for the efficient regeneration of bone in tissue engineering applications, a rapid vascularization of implanted grafts is essential to ensure the survival of cells in the early post-implantational phase. A promising strategy to enhance vascularization of MSC-containing implants could consist of overexpression of the angiogenic master transcription factor Hypoxia-inducible factor 1 (Hif-1) in the MSCs in order to induce angiogenesis and support osteogenesis. In the present study, we overexpressed Hif-1α in MSCs by using recombinant adenoviruses and investigated cell-autonomous effects. Overexpression of Hif-1α enhanced proliferation, migration, cell survival and expression of pro-angiogenic genes. Other parameters such as expression of the osteogenic markers BMP-2 and RunX2 were decreased. Hif-1α overexpression had no effect on invasion, senescence and osteogenic differentiation of MSCs. Our experiments revealed multifarious effects of Hif-1α overexpression on cell-autonomous parameters. Therefore, Hif-1α overexpression may represent a therapeutic option to improve cellular functions of MSCs to treat critical sized bone defects.

Understanding the effects of mature adipocytes and endothelial cells on fatty acid metabolism and vascular tone in physiological fatty tissue for vascularized adipose tissue engineering

Engineering of large vascularized adipose tissue constructs is still a challenge for the treatment of extensive high-graded burns or the replacement of tissue after tumor removal. Communication between mature adipocytes and endothelial cells is important for homeostasis and the maintenance of adipose tissue mass but, to date, is mainly neglected in tissue engineering strategies. Thus, new co-culture strategies are needed to integrate adipocytes and endothelial cells successfully into a functional construct. This review focuses on the cross-talk of mature adipocytes and endothelial cells and considers their influence on fatty acid metabolism and vascular tone. In addition, the properties and challenges with regard to these two cell types for vascularized tissue engineering are highlighted.

High density lipoprotein promotes proliferation of adipose-derived stem cells via S1P1 receptor and Akt, ERK1/2 signal pathways

INTRODUCTION

Adipose-derived stem cells (ADSC) are non-hematopoietic mesenchymal stem cells that have shown great promise in their ability to differentiate into multiple cell lineages. Their ubiquitous nature and the ease of harvesting have attracted the attention of many researchers, and they pose as an ideal candidate for applications in regenerative medicine. Several reports have demonstrated that transplanting ADSC can promote repair of injured tissue and angiogenesis in animal models. Survival of these cells after transplant remains a key limiting factor for the success of ADSC transplantation. Circulating factors like High Density Lipoprotein (HDL) has been known to promote survival of other stems cells like bone marrow derived stem cells and endothelial progenitor cells, both by proliferation and by inhibiting cell apoptosis. The effect of HDL on transplanted adipose-derived stem cells in vivo is largely unknown.

METHODS

This study focused on exploring the effects of plasma HDL on ADSC and delineating the mechanisms involved in their proliferation after entering the bloodstream. Using the MTT and BrdU assays, we tested the effects of HDL on ADSC proliferation. We probed the downstream intracellular Akt and ERK1/2 signaling pathways and expression of cyclin proteins in ADSC using western blot.

RESULTS

Our study found that HDL promotes proliferation of ADSC, by binding to sphingosine-1- phosphate receptor-1(S1P1) on the cell membrane. This interaction led to activation of intracellular Akt and ERK1/2 signaling pathways, resulting in increased expression of cyclin D1 and cyclin E, and simultaneous reduction in expression of cyclin-dependent kinase inhibitors p21 and p27, therefore promoting cell cycle progression and cell proliferation.

CONCLUSIONS

These studies raise the possibility that HDL may be a physiologic regulator of stem cells and increasing HDL concentrations may be valuable strategy to promote ADSC transplantation.

Autologous Stem Cell Therapy: How Aging and Chronic Diseases Affect Stem and Progenitor Cells

During recent years different types of adult stem/progenitor cells have been successfully applied for the treatment of many pathologies, including cardiovascular diseases. The regenerative potential of these cells is considered to be due to their high proliferation and differentiation capacities, paracrine activity, and immunologic privilege. However, therapeutic efficacy of the autologous stem/progenitor cells for most clinical applications remains modest, possibly because of the attenuation of their regenerative potential in aged patients with chronic diseases such as cardiovascular diseases and metabolic disorders. In this review we will discuss the risk factors affecting the therapeutic potential of adult stem/progenitor cells as well as the main approaches to mitigating them using the methods of regenerative medicine.

Adipose-derived mesenchymal stromal/stem cells: An update on their phenotype in vivo and in vitro

Adipose tissue is a rich, ubiquitous and easily accessible source for multipotent stromal/stem cells and has, therefore, several advantages compared to other sources of mesenchymal stromal/stem cells. Several studies have tried to identify the origin of the stromal/stem cell population within adipose tissue in situ. This is a complicated attempt because no marker has currently been described which unambiguously identifies native adipose-derived stromal/stem cells (ASCs). Isolated and cultured ASCs are a non-uniform preparation consisting of several subsets of stem and precursor cells. Cultured ASCs are characterized by their expression of a panel of markers (and the absence of others), whereas their in vitro phenotype is dynamic. Some markers were expressed de novo during culture, the expression of some markers is lost. For a long time, CD34 expression was solely used to characterize haematopoietic stem and progenitor cells, but now it has become evident that it is also a potential marker to identify an ASC subpopulation in situ and after a short culture time. Nevertheless, long-term cultured ASCs do not express CD34, perhaps due to the artificial environment. This review gives an update of the recently published data on the origin and phenotype of ASCs both in vivo and in vitro. In addition, the composition of ASCs (or their subpopulations) seems to vary between different laboratories and preparations. This heterogeneity of ASC preparations may result from different reasons. One of the main problems in comparing results from different laboratories is the lack of a standardized isolation and culture protocol for ASCs. Since many aspects of ASCs, such as the differential potential or the current use in clinical trials, are fully described in other recent reviews, this review further updates the more basic research issues concerning ASCs’ subpopulations, heterogeneity and culture standardization.

Changes in mitochondrial function are pivotal in neurodegenerative and psychiatric disorders: how important is BDNF?

The brain is at the very limit of its energy supply and has evolved specific means of adapting function to energy supply, of which mitochondria form a crucial link. Neurotrophic and inflammatory processes may not only have opposite effects on neuroplasticity, but also involve opposite effects on mitochondrial oxidative phosphorylation and glycolytic processes, respectively, modulated by stress and glucocorticoids, which also have marked effects on mood. Neurodegenerative processes show marked disorders in oxidative metabolism in key brain areas, sometimes decades before symptoms appear (Parkinson's and Alzheimer's diseases). We argue that brain-derived neurotrophic factor couples activity to changes in respiratory efficiency and these effects may be opposed by inflammatory cytokines, a key factor in neurodegenerative processes.

Understanding the role of growth factors in modulating stem cell tenogenesis

Current treatments for tendon injuries often fail to fully restore joint biomechanics leading to the recurrence of symptoms, and thus resulting in a significant health problem with a relevant social impact worldwide. Cell-based approaches involving the use of stem cells might enable tailoring a successful tendon regeneration outcome. As growth factors (GFs) powerfully regulate the cell biological response, their exogenous addition can further stimulate stem cells into the tenogenic lineage, which might eventually depend on stem cells source. In the present study we investigate the tenogenic differentiation potential of human- amniotic fluid stem cells (hAFSCs) and adipose-derived stem cells (hASCs) with several GFs associated to tendon development and healing; namely, EGF, bFGF, PDGF-BB and TGF-β1. Stem cells response to biochemical stimuli was studied by screening of tendon-related genes (collagen type I, III, decorin, tenascin C and scleraxis) and proteins found in tendon extracellular matrix (ECM) (Collagen I, III, and Tenascin C). Despite the fact that GFs did not seem to influence the synthesis of tendon ECM proteins, EGF and bFGF influenced the expression of tendon-related genes in hAFSCs, while EGF and PDGF-BB stimulated the genetic expression in hASCs. Overall results on cellular alignment morphology, immunolocalization and PCR analysis indicated that both stem cell source can be biochemically induced towards tenogenic commitment, validating the potential of hASCs and hAFSCs for tendon regeneration strategies.

Cellular and molecular implications of mature adipocyte dedifferentiation

There is a voluminous amount of scientific literature dealing with the involvement of adipocytes in molecular regulation of carcass composition, obesity, metabolic syndrome, or diabetes. To form adipocytes (process termed adipogenesis) nearly all scientific papers refer to the use of preadipocytes, adipofibroblasts, stromal vascular cells or adipogenic cell lines, and their differentiation to form lipid-assimilating cells containing storage triacylglyceride. However, mature adipocytes, themselves, possess ability to undergo dedifferentiation, form proliferative-competent progeny cells (the exact plasticity is unknown) and reinitiate formation of cells capable of lipid metabolism and storage. The progeny cells would make a viable (and alternative) cell system for the evaluation of cell ability to reestablish lipid assimilation, ability to differentially express genes (as compared to other adipogenic cells), and to form other types of cells (multi-lineage potential). Understanding the dedifferentiation process itself and/or dedifferentiated fat cells could contribute to our knowledge of normal growth processes, or to disease function. Indeed, the ability of progeny cells to form other cell types could turn-out to be important for processes of tissue reconstruction/engineering and may have implications in clinical, biochemical or molecular processes.

Effects of epidermal growth factor and basic fibroblast growth factor on the proliferation and osteogenic and neural differentiation of adipose-derived stem cells

Stem cells used for clinical tissue regeneration therapy should have the capacity of self-renewal, high proliferation, and differentiation and be able to be transplanted in large numbers. Although high concentrations of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) may induce the differentiation of stem cells, these factors have been widely used to enhance the propagation of stem cells, including adipose-derived mesenchymal stem cells (ASCs). However, the effects of low concentrations of EGF and bFGF on stem cells need to be evaluated carefully. This study illustrates that low concentrations of EGF (5 ng/mL) and bFGF (10 ng/mL) increase the proliferative ability of ASCs and induce the typical spindle-shaped cell morphology. EGF and bFGF added to medium promoted neural lineage differentiation and impaired the mesodermal differentiation ability of ASCs. This study demonstrates that even low concentrations of EGF and bFGF may limit the differentiation ability of stem cells during stem cell expansion in vitro. EGF and bFGF supplementation should be carefully considered in stem cells for clinical applications.

Voltage-gated K+ channels in adipogenic differentiation of bone marrow-derived human mesenchymal stem cells

AIM

To determine the presence of voltage-gated K(+) (Kv) channels in bone marrow-derived human mesenchymal stem cells (hMSCs) and their impact on differentiation of hMSCs into adipocytes.

METHODS

For adipogenic differentiation, hMSCs were cultured in adipogenic medium for 22 d. The degrees of adipogenic differentiation were examined using Western blot, Oil Red O staining and Alamar assay. The expression levels of Kv channel subunits Kv1.1, Kv1.2, Kv1.3, Kv1.4, Kv2.1, Kv3.1, Kv3.3, Kv4.2, Kv4.3, and Kv9.3 in the cells were detected using RT-PCR and Western blot analysis.

RESULTS

The expression levels of Kv2.1 and Kv3.3 subunits were markedly increased on d 16 and 22. In contrast, the expression levels of other Kv channel subunits, including Kv1.1, Kv1.2, Kv1.3, Kv1.4, Kv4.2, Kv4.3, and Kv9.3, were decreased as undifferentiated hMSCs differentiated into adipocytes. Addition of the Kv channel blocker tetraethylammonium (TEA, 10 mmol/L) into the adipogenic medium for 6 or 12 d caused a significant decrease, although not complete, in lipid droplet formation and adipocyte fatty acid-binding protein 2 (aP(2)) expressions. Addition of the selective Kv2.1 channel blocker guangxitoxin (GxTX-1, 40 nmol/L) into the adipogenic medium for 21 d also suppressed adipogenic differentiation of the cells.

CONCLUSION

The results demonstrate that subsets of Kv channels including Kv2.1 and Kv3.3 may play an important role in the differentiation of hMSCs into adipocytes.

Mimicking the functional niche of adipose-derived stem cells for regenerative medicine

INTRODUCTION

A stem cell (SC) niche is defined as the microenvironment in which the adult SC resides and includes surrounding cells, low oxygen content and growth factor gradients. Crosstalk between SCs and their niche provides signals that keep SCs quiescent, or modulates their activation.

AREAS COVERED

This review discusses the characterization of niche conditions in the adipose-derived stem cell (ASC) in vivo environment, and introduces key signalling pathways and autocrine/paracrine regulators of ASCs.

EXPERT OPINION

Control of in vivo niche factors (such as low oxygen content, generation of reactive oxygen species and activation of platelet-derived growth factor receptor signalling) should increase ASC yields synergistically and reduce production costs. Additionally, the preconditioning of ASCs with these niche factors prior to transplantation might enhance their regenerative potential. ASC niche is complex, and there are components of the niche that we may not yet understand. Therefore, future research needs to focus on identifying the key regulatory factors of the ASC niche in vivo, and developing a novel method to mimic these niche factors for in vitro manipulation.

Concise review: Adipose-derived stem cells as a novel tool for future regenerative medicine

The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs offers a paradigm shift that may provide alternative therapeutic solutions for a number of diseases. The use of either embryonic stem cells (ESCs) or induced pluripotent stem cells in clinical situations is limited due to cell regulations and to technical and ethical considerations involved in the genetic manipulation of human ESCs, even though these cells are, theoretically, highly beneficial. Mesenchymal stem cells seem to be an ideal population of stem cells for practical regenerative medicine, because they are not subjected to the same restrictions. In particular, large number of adipose-derived stem cells (ASCs) can be easily harvested from adipose tissue. Furthermore, recent basic research and preclinical studies have revealed that the use of ASCs in regenerative medicine is not limited to mesodermal tissue but extends to both ectodermal and endodermal tissues and organs, although ASCs originate from mesodermal lineages. Based on this background knowledge, the primary purpose of this concise review is to summarize and describe the underlying biology of ASCs and their proliferation and differentiation capacities, together with current preclinical and clinical data from a variety of medical fields regarding the use of ASCs in regenerative medicine. In addition, future directions for ASCs in terms of cell-based therapies and regenerative medicine are discussed.

Recombinant fibroblast growth protein enhances healing ability of experimentally induced tendon injury in vivo

This study was designed to investigate the effects of recombinant human basic fibroblast growth factor (bFGF) on a complete superficial digital flexor tendon (SDFT) rupture after surgical repair in rabbits. Eighty mature New Zealand White rabbits of both sexes were randomly divided into two equal groups: Treated and Control. Each group was subdivided into two 28- and 84-day post-injury subgroups. After tenotomy and surgical repair, the animals were immobilized for 14 days. In the treated group, bFGF was directly applied subcutaneously over the lesion on days 3, 7 and 10 after injury. The control animals received normal saline injection of the same viscosity and volume and at the same intervals. Ultrasonographical observations were conducted at weekly intervals. The animals were euthanized at 28 and 84 days after injury. The tendons were evaluated at macroscopic, histopathologic and ultrastructural levels and were assessed for biomechanical and percentage dry weight parameters. Compared to injured control animals, treated animals showed a decrease in the diameter of the injured tendon and peritendinous adhesion as well as increased tenoblast proliferation, collagen production and ultimate strength of the injured tendons (p < 0.005). At 84 days after injury, treatment resulted in enhanced maturation of the cellular and collagen elements and improved tissue alignment and density. These improvements resulted in increased biomechanical performance of the injured tendons compared to controls (p = 0.001). bFGF showed promising curative effects on restoration of the biomechanical and morphological properties of the ruptured SDFT in rabbits and may be applicable in clinical studies.

Adipose-derived mesenchymal stromal/stem cells: tissue localization, characterization, and heterogeneity

Adipose tissue as a stem cell source is ubiquitously available and has several advantages compared to other sources. It is easily accessible in large quantities with minimal invasive harvesting procedure, and isolation of adipose-derived mesenchymal stromal/stem cells (ASCs) yields a high amount of stem cells, which is essential for stem-cell-based therapies and tissue engineering. Several studies have provided evidence that ASCs in situ reside in a perivascular niche, whereas the exact localization of ASCs in native adipose tissue is still under debate. ASCs are isolated by their capacity to adhere to plastic. Nevertheless, recent isolation and culture techniques lack standardization. Cultured cells are characterized by their expression of characteristic markers and their capacity to differentiate into cells from meso-, ecto-, and entodermal lineages. ASCs possess a high plasticity and differentiate into various cell types, including adipocytes, osteoblasts, chondrocytes, myocytes, hepatocytes, neural cells, and endothelial and epithelial cells. Nevertheless, recent studies suggest that ASCs are a heterogeneous mixture of cells containing subpopulations of stem and more committed progenitor cells. This paper summarizes and discusses the current knowledge of the tissue localization of ASCs in situ, their characterization and heterogeneity in vitro, and the lack of standardization in isolation and culture methods.

Platelet-rich plasma greatly potentiates insulin-induced adipogenic differentiation of human adipose-derived stem cells through a serine/threonine kinase Akt-dependent mechanism and promotes clinical fat graft maintenance

The potential plasticity and therapeutic utility in tissue regeneration of human adipose-derived stem cells (ASCs) isolated from adult adipose tissue have recently been highlighted. The use of autologous platelet-rich plasma (PRP) represents an alternative strategy in regenerative medicine for the local release of multiple endogenous growth factors. Here we investigated the signaling pathways and effects of PRP and human recombinant insulin on proliferation and adipogenic differentiation of ASCs in vitro. PRP stimulated proliferation (EC(50) = 15.3 ± 1.3% vol/vol), whereas insulin's effect was the opposite (IC(50) = 3.0 ± 0.5 μM). Although PRP alone did not increase adipogenesis, in association with insulin it prevented ASC proliferative arrest, greatly enhanced intracytoplasmic lipid accumulation, strongly increased serine/threonine kinase Akt phosphorylation and mouse monoclonal anti-sterol regulatory element binding protein-1 accumulation, and downregulated Erk-1 activity; adipogenic effects were markedly prevented by the Akt inhibitor wortmannin. PRP with insulin synergistically upregulated fibroblast growth factor receptor (FGFR) and downregulated epidermal growth factor receptor (ErbB) expression; moreover, PRP in association prevented insulin-induced insulin-like growth factor-1 receptor and insulin receptor downregulation. The inhibition of FGFR-1, epidermal growth factor receptor (EGFR), and epidermal growth factor receptor-2 (ErbB2) activity reduced ASC proliferation, but only that of FGFR-1 reduced adipogenesis and Akt phosphorylation, whereas the ErbB2 inhibition effects were the opposite. However, EGFR activity was needed for ErbB2-mediated inhibition of ASC adipogenesis. Clinically, the injection of insulin further ameliorated patients' 1-year PRP-induced fat graft volume maintenance and contour restoring. Our results ascertain that PRP in association with insulin greatly potentiates adipogenesis in human ASCs through a FGFR-1 and ErbB2-regulated Akt mechanism. The ameliorated clinical fat graft maintenance suggests additional useful translational applications of combined PRP-insulin treatment in regenerative medicine.

EGF receptor (ERBB1) abundance in adipose tissue is reduced in insulin-resistant and type 2 diabetic women

CONTEXT

Indications of adipose tissue dysfunction correlate with systemic insulin resistance and type 2 diabetes. It has been suggested that a defect in adipose tissue turnover may be involved in the development of these disorders. Whether this dysfunction causes or exacerbates systemic insulin resistance is not fully understood. OBJECTIVES, PARTICIPANTS, AND MEASURES: We tested whether the expression of members of the mitogenic ErbB family was reduced in adipose tissue of insulin-resistant individuals and whether ErbB1 and ErbB2 were involved in adipogenesis. Thirty-two women covering a wide range of body mass index values and insulin sensitivity participated in the cross-sectional portion of this study. We also studied preadipocytes isolated from 12 insulin-sensitive individuals to evaluate the impact of ErbB1 or ErbB2 inhibition on adipogenesis in vitro. For this purpose, we measured phospho-ErbB1 and phospho-ErbB2 levels using ELISA and the expression of peroxisome proliferator-activated receptor γ (PPARγ) and PPARγ-regulated genes by real-time PCR.

RESULTS

Among the ErbB family members, only ErbB1 expression was correlated with insulin sensitivity. Additionally, ErbB1 levels correlated positively with PPARγ and several PPARγ-regulated genes including acyl-coenzyme A synthetase long-chain family member 1 (ACSL1), adiponectin, adipose tissue triacylglycerol lipase (ATGL), diacylglycerol acyl transferase 1 (DGAT1), glycerol-3-phosphate dehydrogenase 1 (GPD1), and lipoprotein lipase (LPL), but negatively with CD36 and fatty acid-binding protein 4 (FABP4). In preadipocyte culture, ErbB1, but not ErbB2, inhibition was associated with a reduction in the expression of all the above-mentioned genes.

CONCLUSIONS

These findings demonstrate a key role for ErbB1 in adipogenesis and suggest that lower ErbB1 protein abundance may lead to adipose tissue dysfunction.

Remodeling lipid metabolism and improving insulin responsiveness in human primary myotubes

Objective

Disturbances in lipid metabolism are strongly associated with insulin resistance and type 2 diabetes (T2D). We hypothesized that activation of cAMP/PKA and calcium signaling pathways in cultured human myotubes would provide further insight into regulation of lipid storage, lipolysis, lipid oxidation and insulin responsiveness.

Methods

Human myoblasts were isolated from vastus lateralis, purified, cultured and differentiated into myotubes. All cells were incubated with palmitate during differentiation. Treatment cells were pulsed 1 hour each day with forskolin and ionomycin (PFI) during the final 3 days of differentiation to activate the cAMP/PKA and calcium signaling pathways. Control cells were not pulsed (control). Mitochondrial content, ¹⁴C lipid oxidation and storage were measured, as well as lipolysis and insulin-stimulated glycogen storage. Myotubes were stained for lipids and gene expression measured.

Results

PFI increased oxidation of oleate and palmitate to CO₂ (p<0.001), isoproterenol-stimulated lipolysis (p = 0.01), triacylglycerol (TAG) storage (p<0.05) and mitochondrial DNA copy number (p = 0.01) and related enzyme activities. Candidate gene and microarray analysis revealed increased expression of genes involved in lipolysis, TAG synthesis and mitochondrial biogenesis. PFI increased the organization of lipid droplets along the myofibrillar apparatus. These changes in lipid metabolism were associated with an increase in insulin-mediated glycogen storage (p<0.001).

Conclusions

Activation of cAMP/PKA and calcium signaling pathways in myotubes induces a remodeling of lipid droplets and functional changes in lipid metabolism. These results provide a novel pharmacological approach to promote lipid metabolism and improve insulin responsiveness in myotubes, which may be of therapeutic importance for obesity and type 2 diabetes.

Injectable hydrogel scaffold from decellularized human lipoaspirate

Soft tissue fillers are rapidly gaining popularity for aesthetic improvements or repair of adipose tissue deficits. Several injectable biopolymers have been investigated for this purpose, but often show rapid resorption or limited adipogenesis and do not mimic the native adipose extracellular matrix (ECM). We have generated an injectable adipose matrix scaffold by efficiently removing both the cellular and lipid contents of human lipoaspirate. The decellularized material retained the complex composition of peptides and glycosaminoglycans found in native adipose ECM. This matrix can be further processed by solubilizing the extracted ECM to generate a thermally responsive hydrogel that self-assembles upon subcutaneous injection. This hydrogel also supports the growth and survival of patient matched adipose-derived stem cells in vitro. The development of an injectable hydrogel from human lipoaspirate represents a minimally invasive option for adipose tissue engineering in terms of both the collection of source material and delivery of the scaffold.

Adipogenic differentiation of adult equine mesenchymal stromal cells

Equine adipose tissue-derived mesenchymal stem cells (ASCs) have only recently been investigated for their adipogenic, chondrogenic, and osteogenic differentiation potential. This chapter will briefly outline the molecular mechanisms leading to adipogenesis and the methods of equine adipose tissue harvest, ASC isolation, and adipogenic differentiation. The reader is also directed to other reported methods of adipogenesis for ASCs and mesenchymal stem cells (MSCs) from other tissues.

Adipogenic differentiation of adipose-derived stem cells

The primary physiological function of adipose-derived stem cells (ASCs) is to differentiate into adipose tissue. It is now possible to isolate, expand, and cryopreserve ASC from adipose depots of many animal species. These ASC can be induced to undergo adipogenic differentiation in vitro by exposure to a cocktail of chemical agents or inductive growth factors. The current chapter describes methods to induce adipogenesis and to quantify this differentiation process in vitro.

Comparative epigenomic analysis of murine and human adipogenesis

We report the generation and comparative analysis of genome-wide chromatin state maps, PPARγ and CTCF localization maps, and gene expression profiles from murine and human models of adipogenesis. The data provide high-resolution views of chromatin remodeling during cellular differentiation and allow identification of thousands of putative preadipocyte- and adipocyte-specific cis-regulatory elements based on dynamic chromatin signatures. We find that the specific locations of most such elements differ between the two models, including at orthologous loci with similar expression patterns. Based on sequence analysis and reporter assays, we show that these differences are determined, in part, by evolutionary turnover of transcription factor motifs in the genome sequences and that this turnover may be facilitated by the presence of multiple distal regulatory elements at adipogenesis-dependent loci. We also utilize the close relationship between open chromatin marks and transcription factor motifs to identify and validate PLZF and SRF as regulators of adipogenesis.

Mitochondria and neuroplasticity

The production of neurons from neural progenitor cells, the growth of axons and dendrites and the formation and reorganization of synapses are examples of neuroplasticity. These processes are regulated by cell-autonomous and intercellular (paracrine and endocrine) programs that mediate responses of neural cells to environmental input. Mitochondria are highly mobile and move within and between subcellular compartments involved in neuroplasticity (synaptic terminals, dendrites, cell body and the axon). By generating energy (ATP and NAD(+)), and regulating subcellular Ca(2+) and redox homoeostasis, mitochondria may play important roles in controlling fundamental processes in neuroplasticity, including neural differentiation, neurite outgrowth, neurotransmitter release and dendritic remodelling. Particularly intriguing is emerging data suggesting that mitochondria emit molecular signals (e.g. reactive oxygen species, proteins and lipid mediators) that can act locally or travel to distant targets including the nucleus. Disturbances in mitochondrial functions and signalling may play roles in impaired neuroplasticity and neuronal degeneration in Alzheimer's disease, Parkinson's disease, psychiatric disorders and stroke.

A novel composition for the culture of human adipose stem cells which includes complement C3

Adipose tissue is an easily accessible and abundant source of stem cells. Adipose stem cells (ASCs) are currently being researched as treatment options for repair and regeneration of damaged tissues. The standard culture conditions used for expansion of ASCs contain fetal bovine serum (FBS) which is undefined, could transmit known and unknown adventitious agents, and may cause adverse immune reactions. We have described a novel culture condition which excludes the use of FBS and characterised the resulting culture. Human ASCs were cultured in the novel culture medium, which included complement protein C3. These cultures, called C-ASCs, were compared with ASCs cultured in medium supplemented with FBS. Analysis of ASCs for surface marker profile, proliferation characteristics and differentiation potential indicated that the C-ASCs were similar to ASCs cultured in medium containing FBS. Using a specific inhibitor, we show that C3 is required for the survival of C-ASCs. This novel composition lends itself to being developed into a defined condition for the routine culture of ASCs for basic and clinical applications.

Hybrid adipogenic implants from adipose stem cells for soft tissue reconstruction in vivo

A critical barrier in tissue regeneration is scale-up. Bioengineered adipose tissue implants have been limited to ∼10  mm in diameter. Here, we devised a 40-mm hybrid implant with a cellular layer encapsulating an acellular core. Human adipose-derived stem cells (ASCs) were seeded in alginate. Poly(ethylene)glycol-diacrylate (PEGDA) was photopolymerized into 40-mm-diameter dome-shaped gel. Alginate-ASC suspension was painted onto PEGDA surface. Cultivation of hybrid constructs ex vivo in adipogenic medium for 28 days showed no delamination. Upon 4-week in vivo implantation in athymic rats, hybrid implants well integrated with host subcutaneous tissue and could only be surgically separated. Vascularized adipose tissue regenerated in the thin, painted alginate layer only if ASC-derived adipogenic cells were delivered. Contrastingly, abundant fibrous tissue filled ASC-free alginate layer encapsulating the acellular PEGDA core in control implants. Human-specific peroxisome proliferator-activated receptor-γ (PPAR-γ) was detected in human ASC-seeded implants. Interestingly, rat-specific PPAR-γ was absent in either human ASC-seeded or ASC-free implants. Glycerol content in ASC-delivered implants was significantly greater than that in ASC-free implants. Remarkably, rat-specific platelet/endothelial cell adhesion molecule (PECAM) was detected in both ASC-seeded and ASC-free implants, suggesting anastomosis of vasculature in bioengineered tissue with host blood vessels. Human nuclear staining revealed that a substantial number of adipocytes were of human origin, whereas endothelial cells of vascular wall were of chemaric human and nonhuman (rat host) origins. Together, hybrid implant appears to be a viable scale-up approach with volumetric retention attributable primarily to the acellular biomaterial core, and yet has a biologically viable cellular interface with the host. The present 40-mm soft tissue implant may serve as a biomaterial tissue expander for reconstruction of lumpectomy defects.

Polyvinylpyrrolidone (PVP) mitigates the damaging effects of intracellular ice formation in adult stem cells

The objective of this work was to assess the effect of 10% (w/v) polyvinylpyrrolidone (PVP) on the pattern of intracellular ice formation (IIF) in human adipose tissue derived adult stem cells (ASCs) in the absence of serum and other cryoprotective agents (CPAs). The freezing experiments were carried out using a fluorescence microscope equipped with a Linkam cooling stage using two cooling protocols. Both the cooling protocols had a common cooling ramp: cells were cooled from 20 degrees C to -8 degrees C at 20 degrees C/min and then further cooled to -13 degrees C at 1 degrees C/min. At this point we employed either cooling protocol 1: the cells were cooled from -13 degrees C to -40 degrees C at a pre-determined cooling rate of 1, 5, 10, 20, or 40 degrees C/min and then thawed back to 20 degrees C at 20 degrees C/min; or cooling protocol 2: the cells were re-warmed from -13 degrees C to -5 degrees C at 20 degrees C/min and then re-cooled at a pre-determined rate of 1, 5, 10, 20, or 40 degrees C/min to -40 degrees C. Almost all (>95%) of the ASCs frozen in 1x PBS and protocol 1 exhibited IIF. However, almost none (<5%) of the ASCs frozen in 1x PBS and protocol 2 exhibited IIF. Similarly, almost all (>95%) of the ASCs frozen in 10% PVP in PBS and protocol 1 exhibited IIF. However, ~0, ~40, ~47, ~67, and ~100% of the ASCs exhibited IIF when frozen in 10% PVP in PBS and utilizing protocol 2 at a cooling rate of 1, 5, 10, 20, or 40 degrees C/min, respectively.