Adipogenic potential of adipose stem cell subpopulations. Plast Reconstr Surg. 2011;128:663-672. [PMID: 21572381 DOI: 10.1097/prs.0b013e318221db33]

The effect of adipose-derived stem cells (ADSC) treatment on kidney histopathological appearance on the Wistar rat models with grade five kidney trauma

Objectives

Kidney trauma is the most common urological trauma. Technological advances have made conservative management possible for almost all kidney trauma. However, grade five kidney trauma needs to be carefully examined due to its various complications, especially late complications that often delayed in recognition thus forming irreversible morbidity, with the most common late complication is kidney damage due to ischemic and fibrotic process. This study aims to confirm the effect of Adipose-Derived Stem Cells (ADSC) on the prevention of fibrosis in grade five kidney trauma using Wistar rat models, where the fibrosis process will be measured with histopathological examination which had features of glomerular sclerosis, tubular atrophy, and interstitial fibrosis in kidney tissue, then followed by histopathological scoring and total renal score.

Methods

A total of 22 adult rats were divided into five groups: one healthy control group, two trauma groups without ADSC, and two others trauma groups with ADSC. Two different treatment times were set: two weeks and four weeks after treatment. The data were tested for normality (Shapiro-Wilk test), while differences between groups were assessed using one-way ANOVA or Kruskal-Wallis test if the distribution was not normal.

Results

For the result of total renal score, statistical analysis reveal a significant difference in the total renal score in the kidney trauma with ADSC group compared with kidney trauma without ADSC group in fourth week of observation (p=0.001).

Conclusions

These findings highlighted ADSC capability to prevent fibrosis caused by grade five kidney trauma on the Wistar rat models, as proven by significantly reduced histopathological grading on fibrosis.

Navigating the Adipocyte Precursor Niche: Cell-Cell Interactions, Regulatory Mechanisms and Implications for Adipose Tissue Homeostasis

Support for stem cell self-renewal and differentiation hinges upon the intricate microenvironment termed the stem cell 'niche'. Within the adipose tissue stem cell niche, diverse cell types, such as endothelial cells, immune cells, mural cells, and adipocytes, intricately regulate the function of adipocyte precursors. These interactions, whether direct or indirect, play a pivotal role in governing the balance between self-renewal and differentiation of adipocyte precursors into adipocytes. The mechanisms orchestrating the maintenance and coordination of this niche are still in the early stages of comprehension, despite their crucial role in regulating adipose tissue homeostasis. The complexity of understanding adipocyte precursor renewal and differentiation is amplified due to the challenges posed by the absence of suitable surface receptors for identification, limitations in creating optimal ex vivo culture conditions for expansion and constraints in conducting in vivo studies. This review delves into the current landscape of knowledge surrounding adipocyte precursors within the adipose stem cell niche. We will review the identification of adipocyte precursors, the cell-cell interactions they engage in, the factors influencing their renewal and commitment toward adipocytes and the transformations they undergo during instances of obesity.

Convergent alteration of the mesenchymal stem cell heterogeneity in adipose tissue during aging

Adipose-derived stem cells (ASCs) from distinct age groups possess different characteristics; however, the age-associated changes in ASCs heterogenicity remain largely unknown. In this study, several publicly available single-cell RNA sequencing (RNA-seq) data cohorts of inguinal adipose tissues, including young (2 weeks), adult (8 weeks), and old (18 months) C57BL/6 mice, were analyzed. Transcriptomic clustering of integrated single-cell RNA-seq data from different age groups revealed the existence of five ASCs subtypes. Interestingly, ASCs showed a loss of heterogeneity with aging, and ASCs subtype 4 (ASC-4) was the dominant subpopulation accounting for more than 98% of aged ASCs converging to the terminal differentiation state. The multidirectional differentiation potentials of different ASCs subtypes were largely distinct while the adipogenic ability of ASC-4 increased with age persistently. Regulon analysis of ASC subtypes further identified Cebpb as the ASC-4-specific transcription factor, which was known as one of the major adipogenic regulators. Analysis of ligand-receptor pairs between ASCs and other cell types in adipose tissue identified age-associated upregulation of inflammatory responses-associated factors including CCL2 and CCL7. Treatment with 100 ng/mL CCL2 in vitro could significantly promote the adipogenesis of ASCs through enhanced phosphorylation of AKT and decreased expression of β-catenin. In addition, supplementation of 100 ng/mL CCL7 could significantly increase the expression of inflammatory genes and ASC-4-specific transcriptional factors in 2-week-old ASCs, potentially acting as a driver of ASCs convergence. Our findings help to delineate the complex biological processes of ASCs aging and shed light on better regenerative and therapeutic applications of ASCs.

Reciprocal Effect of Environmental Stimuli to Regulate the Adipogenesis and Osteogenesis Fate Decision in Bone Marrow-Derived Mesenchymal Stem Cells (BM-MSCs)

Mesenchymal stem cells derived from bone marrow (BM-MSCs) can differentiate into adipocytes and osteoblasts. Various external stimuli, including environmental contaminants, heavy metals, dietary, and physical factors, are shown to influence the fate decision of BM-MSCs toward adipogenesis or osteogenesis. The balance of osteogenesis and adipogenesis is critical for the maintenance of bone homeostasis, and the interruption of BM-MSCs lineage commitment is associated with human health issues, such as fracture, osteoporosis, osteopenia, and osteonecrosis. This review focuses on how external stimuli shift the fate of BM-MSCs towards adipogenesis or osteogenesis. Future studies are needed to understand the impact of these external stimuli on bone health and elucidate the underlying mechanisms of BM-MSCs differentiation. This knowledge will inform efforts to prevent bone-related diseases and develop therapeutic approaches to treat bone disorders associated with various pathological conditions.

Comparative characterization of frozen-thawed CD146+ and CD146- subsets of CD73+CD90+CD105+CD34+ human ASCs

Background

Mesenchymal stem cells are currently used to treat several diseases. Populations of putative stem cells found in the adipose tissue (ASCs) have been shown to possess particularly enhanced functionalities. Nonetheless, there is lack of evidence that evaluates the effects of cryopreservation techniques on well-defined functional ASC populations characterized by immunophenotypical repertoire.

Objective

We therefore embarked a study to compare the frozen-thawed ASC subsets: CD73+CD90+CD105+CD34+CD146-(CD34+CD146), CD73+CD90+CD105+CD34+CD146+(CD34+CD146+), and CD73+CD90+CD105+CD34+(CD34+). We assessed their characterization in different functional assays.

Method

The ASC immunophenotypical subsets-purified by a flow cytometry sorting technique-were frozen in liquid nitrogen. After a period, they were thawed to examine their differentiation ability, colony-forming units, viability, and growth rate.

Results

We confirmed that inside the primary cell culture system, the proportion of CD34+, CD34+CD146-, and CD34+CD146+ took up 80%, 62%, and 19% on average, respectively. All populations could be frozen and stored in liquid nitrogen with retention of more than 85% of cell viability and displayed comparable stemness characteristics. Most importantly, the CD34+CD146+ subpopulation displayed a higher proliferation rate than other groups.

Conclusion

Our data demonstrated that the frozen-thawed CD34+CD146+ cells might represent a promising source for autologous cellular-based therapy. These findings set the basis for ASC subpopulations-based application in future potential clinical settings.

Adipose Tissue Development Relies on Coordinated Extracellular Matrix Remodeling, Angiogenesis, and Adipogenesis

Despite developing prenatally, the adipose tissue is unique in its ability to undergo drastic growth even after reaching its mature size. This development and subsequent maintenance rely on the proper coordination between the vascular niche and the adipose compartment. In this review, the process of adipose tissue development is broken down to explain (1) the ultrastructural matrix remodeling that is undertaken during simultaneous adipogenesis and angiogenesis, (2) the paracrine crosstalk involved during adipose development, (3) the mechanical regulators involved in adipose growth, and (4) the proteolytic and paracrine oversight for matrix remodeling during adipose development. It is crucial to gain a better understanding of the complex relationships that exist between adipose tissue and the vasculature during tissue development to provide insights into the pathological tissue expansion of obesity and to develop improved soft-tissue reconstruction techniques.

Adipose tissue in bone regeneration - stem cell source and beyond

Adipose tissue (AT) is recognized as a complex organ involved in major home-ostatic body functions, such as food intake, energy balance, immunomodulation, development and growth, and functioning of the reproductive organs. The role of AT in tissue and organ homeostasis, repair and regeneration is increasingly recognized. Different AT compartments (white AT, brown AT and bone marrow AT) and their interrelation with bone metabolism will be presented. AT-derived stem cell populations - adipose-derived mesenchymal stem cells and pluripotent-like stem cells. Multilineage differentiating stress-enduring and dedifferentiated fat cells can be obtained in relatively high quantities compared to other sources. Their role in different strategies of bone and fracture healing tissue engineering and cell therapy will be described. The current use of AT- or AT-derived stem cell populations for fracture healing and bone regenerative strategies will be presented, as well as major challenges in furthering bone regenerative strategies to clinical settings.

Expression of the Adipocyte Progenitor Markers MSCA1 and CD36 is Associated With Adipose Tissue Function in Children

CONTEXT

MSCA1 (mesenchymal stem cell antigen 1) and CD36 (cluster of differentiation 36) have been described as novel adipocyte progenitor markers in adults with a potential relevance for obesity and adipocyte progenitor function.

OBJECTIVE

With the early manifestation of obesity in children and formation of adipose tissue (AT) dysfunction, children provide the opportunity to characterize the function of MSCA1 and CD36 during physiological AT accumulation and with obesity and related disease.

METHODS

We investigated MSCA1 and CD36 expression in adipocytes and stroma vascular fraction (SVF) cells from 133 children of the Leipzig AT Childhood cohort with regard to AT accumulation and biology. In a subsample we analyzed how MSCA1 and CD36 expression is related to adipose progenitor capacities in vitro (ie, proliferation, differentiation and mitochondrial function).

RESULTS

Both MSCA1 and CD36 are differentially expressed in adipocytes and SVF cells of children. MSCA1 expression is positively correlated to obesity-associated AT dysfunction (ie, adipocyte hypertrophy and serum high-sensitivity C-reactive protein), and high SVF MSCA1 expression is associated with increased mitochondrial respiration in vitro. CD36 expression is not associated with AT dysfunction but SVF CD36 expression is downregulated in children with overweight and obesity and shows a positive association with the differentiation capacity of SVF cells ex vivo and in vitro.

CONCLUSION

Both MSCA1 and CD36 are associated with obesity-related alterations in AT of children. In particular, CD36 expression predicts adipogenic potential of SVF cells, indicating a potential role in the regulation of adipocyte hyperplasia and hypertrophy with obesity development in children.

Comparison of the Characteristics of Breast Milk-derived Stem Cells with the Stem Cells Derived from the Other Sources: A Comparative Review

Breast milk (BrM) not only supplies nutrition, but it also contains a diverse population of cells. It has been estimated that up to 6% of the cells in human milk possess the characteristics of mesenchymal stem cells (MSC). Available data also indicate that these cells are multipotent and capable of self-renewal and differentiation with other cells. In this review, we have compared different characteristics, such as CD markers, differentiation capacity, and morphology of stem cells, derived from human breast milk (hBr-MSC) with human bone marrow (hBMSC), Wharton's jelly (WJMSC), and human adipose tissue (hADMSC). Through the literature review, it was revealed that human breast milk-derived stem cells specifically express a group of cell surface markers, including CD14, CD31, CD45, and CD86. Importantly, a group of markers, CD13, CD29, CD44, CD105, CD106, CD146, and CD166, were identified, which were common in the four sources of stem cells. WJMSC, hBMSC, hADMSC, and hBr-MSC are potently able to differentiate into the mesoderm, ectoderm, and endoderm cell lineages. The ability of hBr-MSCs todifferentiate into the neural stem cells, neurons, adipocyte, hepatocyte, chondrocyte, osteocyte, and cardiomyocytes has made these cells a promising source of stem cells in regenerative medicine, while isolation of stem cells from the commonly used sources, such as bone marrow, requires invasive procedures. Although autologous breast milk-derived stem cells are an accessible source for women who are in the lactation period, breast milk can be considered as a source of stem cells with high differentiation potential without any ethical concern.

Changing the Paradigm of Craniofacial Reconstruction: A Prospective Clinical Trial of Autologous Fat Transfer for Craniofacial Deformities

OBJECTIVE

This study aimed to prospectively assess outcomes for surgical autologous fat transfer (AFT) applied for traumatic and postsurgical craniofacial deformities. The minimally invasive nature of AFT has potential for reduced risk and superior outcomes compared with current reconstructive options.

BACKGROUND

Craniofacial deformities have functional and psychosocial sequelae and can profoundly affect quality of life. Traditional reconstructive options are invasive, invasive, complex, and often lack precision in outcomes. Although AFT is safe, effective, and minimally invasive, only anecdotal evidence exists for reconstruction of craniofacial deformities.

METHODS

In this Institutional Review Board-approved prospective cohort study, 20 subjects underwent AFT (average volume: 23.9 ± 13.2 mL). Volume retention over time was determined using high-resolution computed tomography. Flow cytometry was used to assess cellular subpopulations and viability in the stromal vascular fraction. Quality of life assessments were performed. After the completion of 9-month follow-up, 5 subjects were enrolled for a second treatment.

RESULTS

No serious adverse events occurred. Volume retention averaged 63 ± 17% at 9 months. Three-month retention strongly predicted 9-month retention (r=0.996, P < 0.0001). There was no correlation between the total volume injected and retention. Patients undergoing a second procedure had similar volume retention as the first (P = 0.05). Age, sex, body mass index, and stromal vascular fraction cellular composition did not impact retention. Surprisingly, former smokers had greater volume retention at 9 months compared with nonsmokers (74.4% vs 56.2%, P = 0.009). Satisfaction with physical appearance (P = 0.002), social relationships (P = 0.02), and social functioning quality of life (P = 0.05) improved from baseline to 9 months.

CONCLUSIONS

For craniofacial defects, AFT is less invasive and safer than traditional reconstructive options. It is effective, predictable, and reaches volume stability at 3 months. Patient-reported outcomes demonstrate a positive life-changing impact.

Adipose tissue-derived stem cells: a comparative review on isolation, culture, and differentiation methods

Adipose tissue-derived stem cells (ADSCs) are an available source of mesenchymal stem cells with the appropriate capacity to in vitro survive, propagate, and differentiate into cells from three lineages of ectoderm, mesoderm, and endoderm. The biological features of ADSCs depend on the donor physiology and health status, isolation procedure, culture conditions, and differentiation protocols used. Adipose tissue samples are provided by surgery and lipoaspiration-based methods and subjected to various mechanical and chemical digestion techniques to finally generate a heterogeneous mixture named stromal vascular fraction (SVF). ADSCs are purified through varied cell populations that exist within SVF and cultured under standard conditions to give rise to a highly rich resource of stem cells directly applied in the clinic or differentiated into a wide range of cells. The development and optimization of conventional isolation, expansion, and differentiation methods seem noteworthy to preserve the desirable biological functions of ADSCs in pre-clinical and clinical investigations.

Adipose-Derived Stem Cells for Regenerative Wound Healing Applications: Understanding the Clinical and Regulatory Environment

There is growing interest in the regenerative potential of adipose-derived stem cells (ADSCs) for wound healing applications. ADSCs have been shown to promote revascularization, activate local stem cell niches, reduce oxidative stress, and modulate immune responses. Combined with the fact that they can be harvested in large numbers with minimal donor site morbidity, ADSC products represent promising regenerative cell therapies. This article provides a detailed description of the defining characteristics and therapeutic potential of ADSCs, with a focus on understanding how ADSCs promote tissue regeneration and repair. It summarizes the current regulatory environment governing the use of ADSC products across Europe and the United States and examines how various adipose-derived products conform to the current UK legislative framework. Advice is given to clinicians and researchers on how novel ADSC therapeutics may be developed in accordance with regulatory guidelines.

Evolution of ASC Immunophenotypical Subsets During Expansion In Vitro

Adipose-derived stromal/stem cells (ASCs) are currently being considered for clinical use for a number of indications. In order to develop standardized clinical protocols, it is paramount to have a full characterization of the stem cell preparations. The surface marker expression of ASCs has previously been characterized in multiple studies. However, most of these studies have provided a cross-sectional description of ASCs in either earlier or later passages. In this study, we evaluate the dynamic changes of 15 different surface molecules during culture. Using multichromatic flow cytometry, ASCs from three different donors each in passages 1, 2, 4, 6, and 8 were analyzed for their co-expression of markers associated with mesenchymal stem cells, wound healing, immune regulation, ASC markers, and differentiation capacity, respectively. We confirmed that at an early stage, ASC displayed a high heterogeneity with a plethora of subpopulations, which by culturing became more homogeneous. After a few passages, virtually all ASCs expressed CD29, CD166 and CD201, in addition to canonical markers CD73, CD90, and CD105. However, even at passage 8, there were several predominant lineages that differed with respect to the expression of CD34, CD200 and CD271. Although the significance of remaining subpopulations still needs to be elucidated, our results underscore the necessity to fully characterize ASCs prior to clinical use.

Increase in Leptin and PPAR-γ Gene Expression in Lipedema Adipocytes Differentiated in vitro from Adipose-Derived Stem Cells

Lipedema is a painful loose connective tissue disorder characterized by a bilaterally symmetrical fat deposition in the lower extremities. The goal of this study was to characterize the adipose-derived stem cells (ASCs) of healthy and lipedema patients by the expression of stemness markers and the adipogenic and osteogenic differentiation potential. Forty patients, 20 healthy and 20 with lipedema, participated in this study. The stromal vascular fraction (SVF) was obtained from subcutaneous thigh (SVF-T) and abdomen (SVF-A) fat and plated for ASCs characterization. The data show a similar expression of mesenchymal markers, a significant increase in colonies (p < 0.05) and no change in the proliferation rate in ASCs isolated from the SVF-T or SVF-A of lipedema patients compared with healthy patients. The leptin gene expression was significantly increased in lipedema adipocytes differentiated from ASCs-T (p = 0.04) and the PPAR-γ expression was significantly increased in lipedema adipocytes differentiated from ASCs-A (p = 0.03) compared to the corresponding cells from healthy patients. No significant changes in the expression of genes associated with inflammation were detected in lipedema ASCs or differentiated adipocytes. These results suggest that lipedema ASCs isolated from SVF-T and SVF-A have a higher adipogenic differentiation potential compared to healthy ASCs.

Photoaging Skin Therapy with PRP and ADSC: A Comparative Study

BACKGROUND

Stem cells from adipose tissue (ADSCs) and platelet-rich plasma (PRP) are innovative modalities that arise due to their regenerative potential.

OBJECTIVE

The aim of this study was to characterize possible histological changes induced by PRP and ADSC therapies in photoaged skin.

METHODS

A prospective randomized study involving 20 healthy individuals, showing skin aging. They underwent two therapeutic protocols (protocol 1: PRP; protocol 2: ADSCs). Biopsies were obtained before and after treatment (4 months).

RESULTS

PRP protocol showed unwanted changes in the reticular dermis, mainly due to the deposition of a horizontal layer of collagen (fibrosis) and elastic fibers tightly linked. Structural analyses revealed infiltration of mononuclear cells and depot of fibrotic material in the reticular dermis. The ADSC protocol leads to neoelastogenesis with increase of tropoelastin and fibrillin. There was an improvement of solar elastosis inducing an increment of macrophage polarization and matrix proteinases. These last effects are probably related to the increase of elastinolysis and the remodeling of the dermis.

CONCLUSIONS

The PRP promoted an inflammatory process with an increase of reticular dermis thickness with a fibrotic aspect. On the other hand, ADSC therapy is a promising modality with an important antiaging effect on photoaged human skin.

Lipedema: A Call to Action!

Lipedema is a chronic progressive disease characterized by abnormal fat distribution resulting in disproportionate, painful limbs. It almost exclusively affects women, leading to considerable disability, daily functioning impairment, and psychosocial distress. Literature shows both scarce and conflicting data regarding its prevalence. Lipedema has been considered a rare entity by several authors, though it may be a far more frequent condition than thought. Despite the clinical impact on women's health, lipedema is in fact mostly unknown, underdiagnosed, and too often misdiagnosed with other similarly presenting diseases. Polygenic susceptibility combined with hormonal, microvascular, and lymphatic disorders may be partly responsible for its development. Furthermore, consistent information on lipedema pathophysiology is still lacking, and an etiological treatment is not yet available. Weight loss measures exhibit minimal effect on the abnormal body fat distribution, resulting in eating disorders, increased obesity risk, depression, and other psychological complaints. Surgical techniques, such as liposuction and excisional lipectomy, represent therapeutic options in selected cases. This review aims to outline current evidence regarding lipedema epidemiology, pathophysiology, clinical presentation, differential diagnosis, and management. Increased awareness and a better understanding of its clinical presentation and pathophysiology are warranted to enable clinicians to diagnose and treat affected patients at an earlier stage.

An Animal Model of Local Breast Cancer Recurrence in the Setting of Autologous Fat Grafting for Breast Reconstruction

Autologous fat grafting after breast cancer surgery is commonly performed, but concerns about oncologic risk remain. To model the interaction between fat grafting and breast cancer cells, two approaches were employed. In the first approach, graded numbers of viable MDA‐MB‐231 or BT‐474 cells were admixed directly into human fat grafts and injected subcutaneously into immune‐deficient mice to determine if the healing graft is a supportive environment for the tumor. In the second approach, graded doses of MDA‐MB‐231 cells were suspended in Matrigel and injected into the mammary fat pads of mice. Two weeks after the tumor cells engrafted, 100 μL of human adipose tissue was grafted into the same site. Histologically, MDA‐MB‐231 cells seeded within fat grafts were observed and stained positive for human‐specific pan‐cytokeratin and Ki67. The BT‐474 cells failed to survive when seeded within fat grafts at any dose. In the second approach, MDA‐MB‐231 cells had a strong trend toward lower Ki67 staining at all doses. Regression analysis on all groups with fat grafts and MDA‐MB‐231 revealed fat tissue was associated with lower cancer cell Ki67 staining. Healing fat grafts do not support the epithelial BT‐474 cell growth, and support the mesenchymal MDA‐MB‐231 cell growth only at doses ten times greater than in Matrigel controls. Moreover, fat grafts in association with MDA‐MB‐231 cancer cells already present in the wound resulted in decreased tumor proliferation and increased fibrosis. These findings suggest that clinical fat grafting does not induce breast cancer cell growth, and may even have a suppressive effect. stemcellstranslationalmedicine2018;7:125–134

Injectable Tissue Replacement and Regeneration: Anatomic Fat Grafting to Restore Decayed Facial Tissues

Aging is a dynamic process that can be modeled and understood tissue by tissue and cell by cell. Numerous authors have helped us understand the anatomy of facial fat compartments and the effects of aging on our facial tissues such as skin, fat, bone and fibrous ligaments. Injectable tissue replacement and regeneration (ITR2) is a method to replace decayed tissues of the face using “like tissues” in an effort to delay or slow the rate of tissue decay seen in facial aging. Facial topography and proportion analysis are performed to diagnose individual-specific losses of facial fat. The degree of sun damage and skin thinning is noted as is the degree of loss in the superficial fat compartment. Deep compartment fat loss is evaluated as is pyriform aperture, orbital, mandibular ramus, mandibular body, and chin resorption. From this analysis, a detailed treatment plan is formulated. Using a mechanical device, 3 different fat grafts are created: 2 mm (millifat), 1 mm (microfat), and 500 microns (cell optimized, matrix rich nanofat); anatomic replacement of all areas of tissue loss is carried out. Millifat is used for deep compartment and bone losses, microfat for superficial fat losses above the facial musculature and nanofat is used intradermally and as a biological cream for topical application. The rationale behind this standardized approach is explained and the scientific foundations for the idea are presented. Reduction in tissue decay appears to be a valid observation, but awaits others confirmation.

Cryopreservation of Stromal Vascular Fraction Cells Reduces Their Counts but Not Their Stem Cell Potency

Adipose-derived stem cells are derived from the nonfat component of adipose tissue termed the stromal vascular fraction (SVF). The use of freshly isolated autologous SVF cells as an alternative to adult stem cells is becoming more common. Repeated SVF administration for improved clinical outcomes is complicated by the need for repeated liposuction. This can be overcome by cryopreservation of SVF cells. The current study aimed to assess whether SVF cells retain their stem cell potency during cryopreservation.

Methods

SVF cells isolated from lipoaspirates (donor age: 46.1 ± 11.7 y; body mass index: 29.3 ± 4.8 kg/m²) were analyzed either immediately after isolation or following cryopreservation at -196°C. Analyses included assessment of nucleated cell counts by methylene blue staining, colony-forming unit fibroblast counts, surface marker expression using a flow cytometric panel (CD45, CD34, CD31, CD73, CD29, and CD105), expansion in culture, and differentiation to fat and bone.

Results

While cryopreservation reduced the number of viable SVF cells, stem cell potency was preserved, as demonstrated by no significant difference in the proliferation, surface marker expression in culture, bone and fat differentiation capacity, and the number of colony-forming unit fibroblasts in culture, in cryopreserved versus fresh SVF cells. Importantly, reduced cell counts of cryopreserved cells were due, mainly, to a reduction in hematopoietic CD45+ cells, which was accompanied by increased proportions of CD45-CD34+CD31- stem cell progenitor cells compared to fresh SVF cells.

Conclusions

Cryopreservation of SVF cells did not affect their in vitro stem cell potency and may therefore enable repeated SVF cell administrations, without the need for repeated liposuction.

Membrane metallo-endopeptidase (Neprilysin) regulates inflammatory response and insulin signaling in white preadipocytes

OBJECTIVE

Accumulation of visceral white adipose tissue (WAT) associates with insulin resistance, adipose tissue inflammation, and metabolic syndrome, whereas accumulation of subcutaneous WAT may be protective. We aimed to identify molecular mechanisms that might provide mechanistic insights underlying the phenotypic differences in these tissues. Membrane Metallo-Endopeptidase (MME/Neprislyin) is an extracellular, membrane-bound protease enriched in subcutaneous WAT that can target degradation of a variety of peptides, including insulin, IL6, and β-amyloids. We hypothesized that MME contributes to adipose depot-specific metabolic properties.

METHODS

We performed RNA sequencing on human subcutaneous and visceral preadipocytes and array gene expression profiling in murine subcutaneous and visceral preadipocytes. We conducted several insulin signaling and inflammatory response experiments on different cellular states of MME expression.

RESULTS

MME in white preadipocytes is expressed at a higher level in subcutaneous compared to visceral WAT and favors insulin signaling and a low inflammatory response. Thus, knockdown of MME in subcutaneous preadipocytes increased the inflammatory response to substance P and amyloid β aggregates. This associated with increased basal insulin signaling and decreased insulin-stimulated signaling. Moreover, MME differentially regulates the internalization and turnover of the α/β subunits of the insulin receptor.

CONCLUSION

MME is a novel regulator of the insulin receptor in adipose tissue. Given the clinical significance of both chronic inflammation and insulin sensitivity in metabolic disease, these results show a potentially new target to increase insulin sensitivity and decrease inflammatory susceptibility.

Adipose-derived stem cells: Sources, potency, and implications for regenerative therapies

Adipose-derived stem cells (ASCs) are a subset of mesenchymal stem cells (MSCs) that can be obtained easily from adipose tissues and possess many of the same regenerative properties as other MSCs. ASCs easily adhere to plastic culture flasks, expand in vitro, and have the capacity to differentiate into multiple cell lineages, offering the potential to repair, maintain, or enhance various tissues. Since human adipose tissue is ubiquitous and easily obtained in large quantities using a minimally invasive procedure, the use of autologous ASCs is promising for both regenerative medicine and organs damaged by injury and disease, leading to a rapidly increasing field of research. ASCs are effective for the treatment of severe symptoms such as atrophy, fibrosis, retraction, and ulcers induced by radiation therapy. Moreover, ASCs have been shown to be effective for pathological wound healing such as aberrant scar formation. Additionally, ASCs have been shown to be effective in treating severe refractory acute graft-versus-host disease and hematological and immunological disorders such as idiopathic thrombocytopenic purpura and refractory pure red cell aplasia, indicating that ASCs may have immunomodulatory function. Although many experimental procedures have been proposed, standardized harvesting protocols and processing techniques do not yet exist. Therefore, in this review we focus on the current landscape of ASC isolation, identification, location, and differentiation ability, and summarize the recent progress in ASC applications, the latest preclinical and clinical research, and future approaches for the use of ASCs.

Effects of enzyme and cryoprotectant concentrations on yield of equine adipose-derived multipotent stromal cells

OBJECTIVE To evaluate effects of various concentrations of collagenase and dimethyl sulfoxide (DMSO) on yield of equine adipose-derived multipotent stromal cells (ASCs) before and after cryopreservation. SAMPLE Supragluteal subcutaneous adipose tissue from 7 Thoroughbreds. PROCEDURES Tissues were incubated with digests containing 0.1%, 0.05%, or 0.025% type I collagenase. Part of each resulting stromal vascular fraction was cryopreserved in 80% fetal bovine serum (FBS), 10% DMSO, and 10% Dulbecco modified Eagle medium F-12 and in 95% FBS and 5% DMSO. Half of each fresh and cryopreserved heterogeneous cell population was not immunophenotyped (unsorted) or was immunophenotyped for CD44⁺, CD105⁺, and major histocompatability complex class II (MHCII; CD44⁺-CD105⁺-MHCII⁺ cells and CD44⁺-CD105⁺-MHCII^- cells). Cell proliferation (cell viability assay), plasticity (CFU frequency), and lineage-specific target gene and oncogene expression (reverse transcriptase PCR assays) were determined in passage 1 cells before and after culture in induction media. RESULTS Digestion with 0.1% collagenase yielded the highest number of nucleated cells. Cell surface marker expression and proliferation rate were not affected by collagenase concentration. Cryopreservation reduced cell expansion rate and CD44⁺-CD105⁺-MHCII^- CFUs; it also reduced osteogenic plasticity of unsorted cells. However, effects appeared to be unrelated to DMSO concentrations. There were also variable effects on primordial gene expression among cell isolates. CONCLUSIONS AND CLINICAL RELEVANCE Results supported the use of 0.1% collagenase in an adipose tissue digest and 5% DMSO in cryopreservation medium for isolation and cryopreservation, respectively, of equine ASCs. These results may be used as guidelines for standardization of isolation and cryopreservation procedures for equine ASCs.

An updated review of adipose derived-mesenchymal stem cells and their applications in musculoskeletal disorders

INTRODUCTION

Adipose-derived mesenchymal stem cells (ASCs) represent a new therapeutic strategy in biomedicine with many potential applications, especially in musculoskeletal disorders. Preclinical and clinical studies based on the administration of ASCs support their efficacy in bone regeneration, joint repair, tendon injury and skeletal muscle alterations. Many of these novel treatments may improve patients' quality of life and prognosis. However, several concerns about the use of stem cells remain unsolved, particularly regarding their safety and side effects. The present work aims to review the nature, clinical trials and patents involving the use of ASCs in musculoskeletal disorders.

AREAS COVERED

In this article, we describe ASCs' isolation, culture and differentiation in vivo and in vitro, advances on ASCs' applications in bone, cartilage, muscle and tendon repair, and patents involving the use of ASCs.

EXPERT OPINION

The use of ASCs in musculoskeletal disorders presents significant therapeutic advantages, including limited autoimmune response, potential cell expansion ex vivo, high plasticity to differentiate into several mesodermal cell lineages, and additional effects of therapeutic interest such as secretion of neurotrophic factors and anti-inflammatory properties. For these reasons, ASCs are promising therapeutic agents for clinical applications in musculoskeletal disorders.

Obesity-Activated Adipose-Derived Stromal Cells Promote Breast Cancer Growth and Invasion

Obese women diagnosed with breast cancer have an increased risk for metastasis, and the underlying mechanisms are not well established. Within the mammary gland, adipose-derived stromal cells (ASCs) are heterogeneous cells with the capacity to differentiate into multiple mesenchymal lineages. To study the effects of obesity on ASCs, mice were fed a control diet (CD) or high-fat diet (HFD) to induce obesity, and ASCs were isolated from the mammary glands of lean and obese mice. We observed that obesity increased ASCs proliferation, decreased differentiation potential, and upregulated expression of α-smooth muscle actin, a marker of activated fibroblasts, compared to ASCs from lean mice. To determine how ASCs from obese mice impacted tumor growth, we mixed ASCs isolated from CD- or HFD-fed mice with mammary tumor cells and injected them into the mammary glands of lean mice. Tumor cells mixed with ASCs from obese mice grew significantly larger tumors and had increased invasion into surrounding adipose tissue than tumor cells mixed with control ASCs. ASCs from obese mice demonstrated enhanced tumor cell invasion in culture, a phenotype associated with increased expression of insulin-like growth factor-1 (IGF-1) and abrogated by IGF-1 neutralizing antibodies. Weight loss induced in obese mice significantly decreased expression of IGF-1 from ASCs and reduced the ability of the ASCs to induce an invasive phenotype. Together, these results suggest that obesity enhances local invasion of breast cancer cells through increased expression of IGF-1 by mammary ASCs, and weight loss may reverse this tumor-promoting phenotype.

Decellularized and matured esophageal scaffold for circumferential esophagus replacement: Proof of concept in a pig model

Surgical resection of the esophagus requires sacrificing a long portion of it. Its replacement by the demanding gastric pull-up or colonic interposition techniques may be avoided by using short biologic scaffolds composed of decellularized matrix (DM). The aim of this study was to prepare, characterize, and assess the in vivo remodeling of DM and its clinical impact in a preclinical model. A dynamic chemical and enzymatic decellularization protocol of porcine esophagus was set up and optimized. The resulting DM was mechanically and biologically characterized by DNA quantification, histology, and histomorphometry techniques. Then, in vitro and in vivo tests were performed, such as DM recellularization with human or porcine adipose-derived stem cells, or porcine stromal vascular fraction, and maturation in rat omentum. Finally, the DM, matured or not, was implanted as a 5-cm-long esophagus substitute in an esophagectomized pig model. The developed protocol for esophageal DM fulfilled previously established criteria of decellularization and resulted in a scaffold that maintained important biologic components and an ultrastructure consistent with a basement membrane complex. In vivo implantation was compatible with life without major clinical complications. The DM's scaffold in vitro characteristics and in vivo implantation showed a pattern of constructive remodeling mimicking major native esophageal characteristics.

Comparative study on metabolite level in tissue-specific human mesenchymal stem cells by an ultra-performance liquid chromatography quadrupole time of flight mass spectrometry

Mesenchymal stem cells (MSCs) are a promising therapeutic option for cell-based therapy due to their immunomodulatory and regenerative properties. They can be isolated from various adult tissues, including bone marrow, fat, dental tissue, and glandular tissue. Although they share common characteristics, little is known about the biological differences between MSC populations derived from different tissues. In this study, we used MS to compare the endogenous metabolite level in the human MSCs originating from the bone marrow, adipose tissue, periodontal ligaments, and salivary glands. Using an optimized metabolomics technique, we verified that human MSCs exhibit differences in the endogenous metabolite level depending on their source material, while the multivariate analysis showed that 5 lysophosphatidylcholines and 3 lysophosphatidylethanolamines can serve as markers for the discrimination between MSC sources and may be related to differences in their differentiation capacity. These results may significantly contribute to further mechanistic studies on the MSCs and provide novel insights into the properties and optimal usage of MSCs from different tissues.

Current perspectives on biological approaches for osteoarthritis

Musculoskeletal injuries that disrupt the structure and function of diarthrodial joints can cause permanent biomechanical alterations and lead to a more severe, chronic condition. Despite advancements that have been made to restore tissue function and delay the need for joint replacement, there are currently no disease-modifying therapies for osteoarthritis (OA). To reduce the risk of OA, innovative preventive medicine approaches have been developed over the last decade to treat the underlying pathology. Several biological approaches are promising treatment modalities for various stages of OA owing to their minimally invasive nature and actively dynamic physiological mechanisms that attenuate tissue degradation and inflammatory responses. Individualized growth factor and cytokine therapies, tissue-engineered biomaterials, and cell-based therapies have revolutionary potential for orthopedic applications; however, the paucity of standardization and categorization of biological components and their counterparts has made it difficult to determine their clinical and biological efficacy. Cell-based therapies and tissue-engineered biologics have become lucrative in sports medicine and orthopedics; nonetheless, there is a continued effort to produce a biological treatment modality tailored to target intra-articular structures that recapitulates tissue function. Advanced development of these biological treatment modalities will potentially optimize tissue healing, regeneration, and joint preservation strategies. Therefore, the purpose of this paper is to review current concepts on several biological treatment approaches for OA.

Function of microRNAs in the Osteogenic Differentiation and Therapeutic Application of Adipose-Derived Stem Cells (ASCs)

Traumatic wounds with segmental bone defects represent substantial reconstructive challenges. Autologous bone grafting is considered the gold standard for surgical treatment in many cases, but donor site morbidity and associated post-operative complications remain a concern. Advances in regenerative techniques utilizing mesenchymal stem cell populations from bone and adipose tissue have opened the door to improving bone repair in the limbs, spine, and craniofacial skeleton. The widespread availability, ease of extraction, and lack of immunogenicity have made adipose-derived stem cells (ASCs) particularly attractive as a stem cell source for regenerative strategies. Recently it has been shown that small, non-coding miRNAs are involved in the osteogenic differentiation of ASCs. Specifically, microRNAs such as miR-17, miR-23a, and miR-31 are expressed during the osteogenic differentiation of ASCs, and appear to play a role in inhibiting various steps in bone morphogenetic protein-2 (BMP2) mediated osteogenesis. Importantly, a number of microRNAs including miR-17 and miR-31 that act to attenuate the osteogenic differentiation of ASCs are themselves stimulated by transforming growth factor β-1 (TGFβ-1). In addition, transforming growth factor β-1 is also known to suppress the expression of microRNAs involved in myogenic differentiation. These data suggest that preconditioning strategies to reduce TGFβ-1 activity in ASCs may improve the therapeutic potential of ASCs for musculoskeletal application. Moreover, these findings support the isolation of ASCs from subcutaneous fat depots that tend to have low endogenous levels of TGFβ-1 expression.

Esophageal adenocarcinoma microenvironment: Peritumoral adipose tissue effects associated with chemoresistance

Peritumoral microenvironment affects cancer development and chemoresistance, and visceral adipose tissue may play a critical role. We aimed to identify depot‐specific adipose characteristics associated with carcinogenesis and resistance to neoadjuvant therapy in esophageal adenocarcinoma (EAC). We analyzed: (i) the peritumoral adipose tissue of rats following the induction of esophageal carcinogenesis; (ii) the peritumoral and distal (omental) adipose tissue of patients affected by EAC; (iii) adipose‐derived stem cells (ADSC) isolated from healthy patients and treated with conditioned medium (CM), collected from tumoral and adipose tissue of patients with EAC. In peritumoral adipose tissue of rats, CD34, CD31 and vascular endothelial growth factor (VEGF) expression increased progressively during EAC development. In patients with EAC, expression of CD34, CD45, CD90 and nucleostemin (NSTM) was higher in peritumoral than in distal adipose tissue and decreased in the presence of neoadjuvant therapy. Moreover, expression of NSTM, octamer‐binding transcription factor 4 (OCT‐4) and VEGF was higher in peritumoral (but not in distal) adipose tissue of chemoresistant patients. In ADSC, treatment with peritumoral adipose tissue CM increased the adipogenic potential and the expression of CD34, CD90, NSTM and OCT‐4. These effects were similar to those induced by cancer‐derived CM, but were not observed in ADSC treated with distal adipose tissue CM and were partially reduced by a leptin antagonist. Last, ADSC treated with peritumoral CM of chemoresistant patients displayed increased expression of NSTM, OCT‐4, leptin, leptin receptor, alpha‐smooth muscle actin (α‐SMA), CD34 and VEGF. These results suggest that peritumoral adipose tissue may promote, by paracrine signaling, the expression of depot‐specific factors associated with therapeutic resistance.

Autologous fat tissue grafting improves pulmonary healing after laser metastasectomy

BACKGROUND

Extensive clinical experience has demonstrated the potential usefulness of autologous fat tissue (AFT) graft in tissue reconstruction, repair or regeneration. In the present study, we evaluated the feasibility and safety of AFT in the repair of surgically injured lung surface.

METHODS

Eighty consecutive procedures of pulmonary metastasectomy by laser precision resection, were performed in 66 patients between March 2010 and December 2012. In the first 20 procedures, AFT graft was applied on the wounded pulmonary surface without closure of parenchymal surface. The following 40 procedures were carried on without AFT (20 leaving the resection margins open and 20 closing the resection margins with a running suture). In the remaining 20 procedures, AFT was applied and the resection margins closed. The efficacy of this technique was evaluated by comparing the AFT group with the non-AFT group, with respect to prolonged alveolar air leakage (PAAL), time to drain removal, length of hospital stay, and patient survival at four years.

RESULTS

The occurrence of PAAL was lower in the AFT group as compared to non-AFT group (17.5% versus 42.5%, p = 0.027), and median time to drain removal shorter (4 versus 6 days respectively, p = 0.016). Overall 4-year survival was 70% for AFT group, and 59% for non-AFT group (p = 0.34).

CONCLUSIONS

This prospective cohort observational study demonstrated the feasibility and safety of AFT pulmonary grafting after laser metastasectomy. AFT graft improved pulmonary healing, by reducing the incidence and severity of PAAL. Moreover, there was no evidence of tumor promotion in the metastatic setting, with a similar overall survival at 4 years.

The adipose tissue-derived stromal vascular fraction cells from lipedema patients: Are they different?

BACKGROUND AIMS

Lipedema is a hormone-related disease of women characterized by enlargement of the extremities caused by subcutaneous deposition of adipose tissue. In healthy patients application of autologous adipose tissue-derived cells has shown great potential in several clinical studies for engrafting of soft tissue reconstruction in recent decades. The majority of these studies have used the stromal vascular fraction (SVF), a heterogeneous cell population containing adipose-derived stromal/stem cells (ASC), among others. Because cell identity and regenerative properties might be affected by the health condition of patients, we characterized the SVF cells of 30 lipedema patients in comparison to 22 healthy patients.

METHODS

SVF cells were analyzed regarding cell yield, viability, adenosine triphosphate content, colony forming units and proliferative capacity, as well as surface marker profile and differentiation potential in vitro.

RESULTS

Our results demonstrated a significantly enhanced SVF cell yield isolated from lipedema compared with healthy patients. In contrast, the adipogenic differentiation potential of SVF cells isolated from lipedema patients was significantly reduced compared with healthy patients. Interestingly, expression of the mesenchymal marker CD90 and the endothelial/pericytic marker CD146 was significantly enhanced when isolated from lipedema patients.

DISCUSSION

The enhanced number of CD90⁺ and CD146⁺ cells could explain the increased cell yield because the other tested surface marker were not reduced in lipedema patients. Because the cellular mechanism and composition in lipedema is largely unknown, our findings might contribute to a better understanding of its etiology.

Cancer Risk after Fat Transfer: A Multicenter Case-Cohort Study

BACKGROUND

Fat transfer is an increasingly popular method for refining postmastectomy breast reconstructions. However, concern persists that fat transfer may promote disease recurrence. Adipocytes are derived from adipose-derived stem cells and express adipocytokines that can facilitate active breast cancer cells in laboratory models. The authors sought to evaluate the association between fat transfer to the reconstructed breast and cancer recurrence in patients diagnosed with local or regional invasive breast cancers.

METHODS

A multicenter, case-cohort study was performed. Eligible patients from four centers (Memorial Sloan Kettering, M. D. Anderson Cancer Center, Alvin J. Siteman Cancer Center, and the University of Chicago) were identified by each site's institutional tumor registry or cancer data warehouse. Eligibility criteria were as follows: mastectomy with immediate breast reconstruction between 2006 and 2011, age older than 21 years, female sex, and incident diagnosis of invasive ductal carcinoma (stage I, II, or III). Cases consisted of all recurrences during the study period, and controls consisted of a 30 percent random sample of the study population. Cox proportional hazards regression was used to evaluate for association between fat transfer and time to recurrence in bivariate and multivariate models.

RESULTS

The time to disease recurrence unadjusted hazard ratio for fat transfer was 0.99 (95 percent CI, 0.56 to 1.7). After adjustment for age, body mass index, stage, HER2/Neu receptor status, and estrogen receptor status, the hazard ratio was 0.97 (95 percent CI, 0.54 to 1.8).

CONCLUSION

In this population of breast cancer patients who had mastectomy with immediate reconstruction, fat transfer was not associated with a higher risk of cancer recurrence.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Comparative analysis of three human adipocyte size measurement methods and their relevance for cardiometabolic risk

OBJECTIVE

To determine whether adipocyte diameters from three measurement methods are similarly associated with adiposity measurements and cardiometabolic variables.

METHODS

Surgical samples of omental and abdominal subcutaneous adipose tissue were obtained in a sample of 60 women (age 35-59 years; body mass index 20.3-41.1 kg/m² ). Median adipocyte diameter of the main cell population was determined by collagenase digestion, osmium tetroxide fixation, and histological analysis. Adiposity and cardiometabolic risk factors were assessed.

RESULTS

Adipocyte diameter was consistently smaller with formalin fixation than with collagenase digestion, whereas osmium-fixed cells were larger (P < 0.0001, for all). Median adipocyte diameters derived from all methods were intercorrelated (r = 0.46-0.83, P < 0.001 for all). Positive associations were found between adipocyte diameters from all techniques and regional or total adiposity measurements (P < 0.01 for all). Omental adipocyte diameter was positively associated with fasting glucose, insulin, and homeostatic model assessment of insulin resistance (r = 0.30-0.52, P < 0.05 for all), with osmium-fixed cell size as a stronger correlate. Osmium-fixed cell diameter was also a better correlate of plasma adiponectin and leptin.

CONCLUSIONS

Although measurement techniques generated systematic differences in adipocyte size, associations with adiposity were only slightly affected by the technique. Osmium fixation generated stronger associations with cardiometabolic risk factors than collagenase digestion and histological analysis.

Method for selective quantification of adipose-derived stromal/stem cells in tissue

Fat grafts are valuable for soft-tissue regeneration and augmentation. However, fat graft systems require further improvement for the prediction of graft retention. The concentration of adipose-derived stromal/stem cells (ASCs) is one of the most important factors that affect graft retention; however, current cell quantification techniques have not been applied to adipose tissue. Here we developed a method for the selective quantification of ASCs in tissue (SQAT). We identified a characteristic methylated site in the CD31 promoter after searching for specific markers of ASCs. This DNA methylation was not detected in any cell type other than ASCs in adipose tissue. Therefore, analyzing this methylation may be a suitable approach for quantifying ASCs in tissues because DNA is readily extracted from tissues. SQAT is based on quantifying this methylation by quantitative polymerase chain reaction using methylation-sensitive HapII-treated DNA as the template. SQAT was validated based on the numbers of ASCs determined by CD31⁻/CD34⁺-based flow cytometry. The results obtained by both methods were perfectly correlated, thereby demonstrating that SQAT is a useful tool for quantifying ASCs. SQAT analysis using ASCs isolated from suctioned fat according to the standard protocol (i.e., collagenase treatment) showed that the yield of ASCs was 59% ± 21%, which suggests that the ASC isolation technique requires further improvement. Furthermore, SQAT is an excellent method for quantifying ASCs in arbitrary samples (particularly tissue), which could dramatically improve ASC isolation technologies and fat graft systems, thereby facilitating the prediction of graft retention.

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.

Characterization of human adipose tissue-derived stem cells with enhanced angiogenic and adipogenic properties

Autologous fat grafting is a popular method for soft tissue reconstructions but graft survival remains highly unpredictable. Supplementation of the graft with the stromal vascular fraction (SVF) or cultured adipose tissue-derived stem cells (ASCs) can enhance graft viability. In this study we have examined the phenotypic properties of a selected population of cells isolated from ASCs, with a view to determining their suitability for transplantation into grafts. ASCs were isolated from the SVF of human abdominal fat (n = 8 female patients) and CD146⁺ cells were selected using immunomagnetic beads. The angiogenic and adipogenic properties of the positively selected cells were compared with the negative fraction. CD146⁺ cells expressed the immunophenotypic characteristics of pericytes. With prolonged in vitro expansion, CD146^- cells exhibited increased population doubling times and morphological signs of senescence, whereas CD146⁺ cells did not. CD146⁺ cells expressed higher levels of the angiogenic molecules VEGF-A, angiopoietin-1 and FGF-1. Conditioned medium taken from CD146⁺ cells significantly increased formation of in vitro endothelial cell tube networks, whereas CD146^- cells did not. CD146⁺ cells could be differentiated into adipocytes in greater numbers than CD146^- cells. Consistent with this, differentiated CD146⁺ cells expressed higher levels of the adipocyte markers adiponectin and leptin. These results suggest that CD146⁺ cells selected from a heterogeneous mix of ASCs have more favourable angiogenic and adipogenic properties, which might provide significant benefits for reconstructive and tissue-engineering applications. Copyright © 2016 John Wiley & Sons, Ltd.

Enrichment of Adipose-Derived Stromal Cells for BMPR1A Facilitates Enhanced Adipogenesis

BACKGROUND

Reconstruction of soft tissue defects has traditionally relied on the use of grafts and flaps, which may be associated with variable resorption and/or significant donor site morbidity. Cell-based strategies employing adipose-derived stromal cells (ASCs), found within the stromal vascular fraction (SVF) of adipose tissue, may offer an alternative strategy for soft tissue reconstruction. In this study, we investigated the potential of a bone morphogenetic protein receptor type 1A (BMPR1A)(+) subpopulation of ASCs to enhance de novo adipogenesis.

METHODS

Human lipoaspirate was enzymatically digested to isolate SVF and magnetic-activated cell separation was utilized to obtain BMPR1A(+) and BMPR1A(-) cells. These cells, along with unenriched cells, were expanded in culture and evaluated for adipogenic gene expression and in vitro adipocyte formation. Cells from each group were also labeled with a green fluorescent protein (GFP) lentivirus and transplanted into the inguinal fat pads, an adipogenic niche, of immunocompromised mice to determine their potential for de novo adipogenesis. Confocal microscopy along with staining of lipid droplets and vasculature was performed to evaluate the formation of mature adipocytes by transplanted cells.

RESULTS

In comparison to BMPR1A(-) and unenriched ASCs, BMPR1A(+) cells demonstrated significantly enhanced adipogenesis when cultured in an adipogenic differentiation medium, as evidenced by increased staining with Oil Red O and increased expression of peroxisome proliferator-activating receptor gamma (PPAR-γ) and fatty acid-binding protein 4 (FABP4). BMPR1A(+) cells also formed significantly more adipocytes in vivo, as demonstrated by quantification of GFP+ adipocytes. Minimal formation of mature adipocytes was appreciated by BMPR1A(-) cells.

CONCLUSIONS

BMPR1A(+) ASCs show an enhanced ability for adipogenesis in vitro, as shown by gene expression and histological staining. Furthermore, within an adipogenic niche, BMPR1A(+) cells possessed an increased capacity to generate de novo fat compared to BMPR1A(-) and unenriched cells. This suggests utility for the BMPR1A(+) subpopulation in cell-based strategies for soft tissue reconstruction.

Behaviour of telocytes during physiopathological activation

We consider CD34+ stromal cells/telocytes (CD34+ SC/TCs) in normal and pathological conditions. These cells are involved in organisation and control of the extracellular matrix, structural support, creation of microenvironments, intercellular communication, neurotransmission, immunomodulation and immunosurveillance, inhibition of apoptosis, and control, regulation and source of other cell types. CD34+ SC/TCs are widely reported in the origin of interstitial cells of Cajal and in regeneration in the heart, skeletal muscle, skin, respiratory tree, liver, urinary system and the eye. In addition, we contribute CD34+ SC/TC hyperplasia associated with several processes, including neurogenous hyperplasia (neuroma of the appendix), hyperplasia of Leydig cells in undescended testes (Cryptorchidism), peripheral areas of inflammatory/repair processes (pericicatricial tissue and transitional zones between diseased segments in Crohn's disease and normal bowel), benign tumours (neurofibromas, Antoni-B zones of neurilemmomas, granular cell tumours, and melanocytic nevi) and in some lesions with myxoid, oedematous and degenerative changes (Reinke's oedema, myxomatous mitral valve degeneration, thyroid-associated ophthalmopathy and basophilic degenerative changes of the collagen in the dermis). We pay particular attention to the role of CD34+ SC/TCs during repair through granulation tissue, including morphologic changes, loss of CD34 expression and gain of αSMA expression with myofibroblast transformation, and interactions with pericytes, endothelial and inflammatory cells. Finally, we consider CD34 or αSMA expression in stromal cells of malignant epithelial tumours, and the role of CD34+ SC/TCs in the origin of carcinoma-associated fibroblasts (CAFs) and myofibroblasts. In conclusion, CD34+ SC/TCs play an important role in the maintenance and modulation of tissue homeostasis and in morphogenesis/renewal/repair.

Telocyte Behaviour During Inflammation, Repair and Tumour Stroma Formation

In this chapter, we outline the role of human CD34+ stromal cells/telocytes (CD34+ SC/TCs) as progenitor cells during repair. The in vivo activation phenomena of CD34+ SC/TCs in this process include increased size; separation from the neighbouring structures (mainly of the vascular walls); association with inflammatory cells, predominantly macrophages; development of the organelles of synthesis (rough endoplasmic reticulum and Golgi apparatus); cell proliferation with presence of mitosis and high proliferative index (transit-amplifying cells); and fibroblastic and myofibroblastic differentiation. A procedure to study these tissue-resident cells, comparison of their behaviour in vivo and in vitro and different behaviour depending on location, time, type of injury (including tumour stroma) and greater or lesser proximity to the injury are also considered.

Isolation, Expansion, and Immortalization of Human Adipose-Derived Mesenchymal Stromal Cells from Biopsies and Liposuction Specimens

Human adipose tissue has proven to be an abundant, accessible, and rich source of adult mesenchymal stromal cells, suitable for tissue engineering and regenerative medicine. However, a major complication in fully investigating these cells may derive from their limited life span.Although methods to isolate, expand, and immortalize these cells have been widely reported in the literature, exhaustive explanations on the problems that can be encountered during these processes and how these can be solved have never been described. It is of fundamental importance to follow a common protocol to achieve reliable and reproducible results. Here, we describe a protocol to isolate and expand human adipose stromal cells from specimens obtained from tissue biopsies and liposuction surgical interventions. Finally, we broadly describe the cell immortalization technique, and particular attention is paid to some of the apparently "secondary" aspects.