In vitro evaluation of endothelial progenitor cells from adipose tissue as potential angiogenic cell sources for bladder angiogenesis

Adipose-Derived Stem Cells: Angiogenetic Potential and Utility in Tissue Engineering

Adipose tissue (AT) is a large and important energy storage organ as well as an endocrine organ with a critical role in many processes. Additionally, AT is an enormous and easily accessible source of multipotent cell types used in our day for all types of tissue regeneration. The ability of adipose-derived stem cells (ADSCs) to differentiate into other types of cells, such as endothelial cells (ECs), vascular smooth muscle cells, or cardiomyocytes, is used in tissue engineering in order to promote/stimulate the process of angiogenesis. Being a key for future successful clinical applications, functional vascular networks in engineered tissue are targeted by numerous in vivo and ex vivo studies. The article reviews the angiogenic potential of ADSCs and explores their capacity in the field of tissue engineering (TE).

Autologous Endothelial Progenitor Cells and Bioactive Factors Improve Bladder Regeneration

Insufficient vascularization is still a challenge that impedes bladder tissue engineering and results in unsatisfied smooth muscle regeneration. Since bladder regeneration is a complex articulated process, the aim of this study is to investigate whether combining multiple pathways by exploiting a combination of biomaterials, cells, and bioactive factors, contributes to the improvements of smooth muscle regeneration and vascularization in tissue-engineered bladder. Autologous endothelial progenitor cells (EPCs) and bladder smooth muscle cells (BSMCs) are cultured and incorporated into our previously prepared porcine bladder acellular matrix (BAM) for bladder augmentation in rabbits. Simultaneously, exogenous vascular endothelial growth factor (VEGF) and platelet-derived growth factor BB (PDGF-BB) mixed with Matrigel were injected around the implanted cells-BAM complex. In the results, compared with control rabbits received bladder augmentation with porcine BAM seeded with BSMCs, the experimental animals showed significantly improved smooth muscle regeneration and vascularization, along with more excellent functional recovery of tissue-engineered bladder, due to the additional combination of autologous EPCs and bioactive factors, including VEGF and PDGF-BB. Furthermore, cell tracking suggested that the seeded EPCs could be directly involved in neovascularization. Therefore, it may be an effective method to combine multiple pathways for tissue-engineering urinary bladder.

Cell Cultures as a Versatile Tool in the Research and Treatment of Autoimmune Connective Tissue Diseases

Cell cultures are an important part of the research and treatment of autoimmune connective tissue diseases. By culturing the various cell types involved in ACTDs, researchers are able to broaden the knowledge about these diseases that, in the near future, may lead to finding cures. Fibroblast cultures and chondrocyte cultures allow scientists to study the behavior, physiology and intracellular interactions of these cells. This helps in understanding the underlying mechanisms of ACTDs, including inflammation, immune dysregulation and tissue damage. Through the analysis of gene expression patterns, surface proteins and cytokine profiles in peripheral blood mononuclear cell cultures and endothelial cell cultures researchers can identify potential biomarkers that can help in diagnosing, monitoring disease activity and predicting patient's response to treatment. Moreover, cell culturing of mesenchymal stem cells and skin modelling in ACTD research and treatment help to evaluate the effects of potential drugs or therapeutics on specific cell types relevant to the disease. Culturing cells in 3D allows us to assess safety, efficacy and the mechanisms of action, thereby aiding in the screening of potential drug candidates and the development of novel therapies. Nowadays, personalized medicine is increasingly mentioned as a future way of dealing with complex diseases such as ACTD. By culturing cells from individual patients and studying patient-specific cells, researchers can gain insights into the unique characteristics of the patient's disease, identify personalized treatment targets, and develop tailored therapeutic strategies for better outcomes. Cell culturing can help in the evaluation of the effects of these therapies on patient-specific cell populations, as well as in predicting overall treatment response. By analyzing changes in response or behavior of patient-derived cells to a treatment, researchers can assess the response effectiveness to specific therapies, thus enabling more informed treatment decisions. This literature review was created as a form of guidance for researchers and clinicians, and it was written with the use of the NCBI database.

Stromal vascular fraction in the treatment of myositis

Muscle regeneration is a physiological process that converts satellite cells into mature myotubes under the influence of an inflammatory environment progressively replaced by an anti-inflammatory environment, with precise crosstalk between immune and muscular cells. If the succession of these phases is disturbed, the immune system can sometimes become auto-reactive, leading to chronic muscular inflammatory diseases, such as myositis. The triggers of these autoimmune myopathies remain mostly unknown, but the main mechanisms of pathogenesis are partially understood. They involve chronic inflammation, which could be associated with an auto-reactive immune response, and gradually with a decrease in the regenerative capacities of the muscle, leading to its degeneration, fibrosis and vascular architecture deterioration. Immunosuppressive treatments can block the first part of the process, but sometimes muscle remains weakened, or even still deteriorates, due to the exhaustion of its capacities. For patients refractory to immunosuppressive therapies, mesenchymal stem cells have shown interesting effects but their use is limited by their availability. Stromal vascular fraction, which can easily be extracted from adipose tissue, has shown good tolerance and possible therapeutic benefits in several degenerative and autoimmune diseases. However, despite the increasing use of stromal vascular fraction, the therapeutically active components within this heterogeneous cellular product are ill-defined and the mechanisms by which this therapy might be active remain insufficiently understood. We review herein the current knowledge on the mechanisms of action of stromal vascular fraction and hypothesise on how it could potentially respond to some of the unmet treatment needs of refractory myositis.

Immunomagnetic Delivery of Adipose-Derived Endothelial Progenitor Cells for the Repair of Renal Ischemia-Reperfusion Injury in a Rat Model

Renal ischemia-reperfusion injury (IRI) is a significant cause of acute kidney injury (AKI) and usually brings severe public health consequences. Adipose-derived endothelial progenitor cell (AdEPCs) transplantation is beneficial for AKI but suffers from low delivery efficiency. This study was conducted to explore the protective effects of magnetically delivered AdEPCs on the repair of renal IRI. Two types of magnetic delivery methods, namely the endocytosis magnetization (EM) method and the immunomagnetic (IM) method were fabricated using PEG@Fe₃O₄ and CD133@Fe₃O₄, and their cytotoxicities in AdEPCs were assessed. In the renal IRI rat model, magnetic AdEPCs were injected via the tail vein and a magnet was placed beside the injured kidney for magnetic guidance. The distribution of transplanted AdEPCs, renal function, and tubular damage were evaluated. Our results suggested that CD133@Fe₃O₄ had the minimum negative effects on the proliferation, apoptosis, angiogenesis, and migration of AdEPCs compared with PEG@Fe₃O₄. Renal magnetic guidance could significantly enhance the transplantation efficiency and the therapeutic outcomes of AdEPCs-PEG@Fe₃O₄ and AdEPCs-CD133@Fe₃O₄ in the injured kidneys. However, under renal magnetic guidance, AdEPCs-CD133@Fe₃O₄ had stronger therapeutic effects than PEG@Fe₃O₄ after renal IRI. The immunomagnetic delivery of AdEPCs with CD133@Fe₃O₄ could be a promising therapeutic strategy for renal IRI.

Stem cell therapy in the treatment of organic and dysfunctional endometrial pathology

BACKGROUND

Intrauterine adhesions caused by postpartum curettage, spontaneous abortions, interrupted pregnancies, endometrial ablations, infections and inflammations, can lead to a loss of endometrial function, with consequent hypomenorrhea and infertility in women of reproductive age. In a non-negligible percentage of cases, the available surgical methods and hormone therapy, with sequential administration of estrogen and progesterone, are ineffective. In fact, severe damage to the basal layer of the endometrium causes the loss of endometrial cell precursors and leads to the failure of regeneration of the functional layer to which the endometrium is cyclically exposed. Today, many researchers are evaluating the use of stem cells of different origins as a potential therapy to restore endometrial function.

METHODS

Our interest has been focused on adipose-derived stromal/stem cells (ADSCs) obtained by collecting subcutaneous adipose tissue and subsequently treating it with the MilliGraft^® method. This procedure produces a cell suspension, the stromal vascular fraction (SVF), which includes ADSCs and soluble factors such as proteins and extracellular vesicles (exosomes). The SVF thus obtained was characterized in its cellular composition and its functional factors. Our clinical protocol for the future use of adipose tissue in endometrial regeneration in its different phases is presented.

RESULTS

The data obtained, even though they still require further support and implementation, show the regenerative properties of SVF obtained from adipose tissue using a mechanical method.

CONCLUSIONS

These findings can contribute to the development of cell therapies using stem cells of different derivations which are increasingly being utilized in the treatment of endometrial lesions from adherent or dysfunctional pathologies.

Anti-Aging Effect of the Stromal Vascular Fraction/Adipose-Derived Stem Cells in a Mouse Model of Skin Aging Induced by UVB Irradiation

Adipose-derived stem cells(ADSCs) have been used for anti-photo-aging. But the purification of ADSCs requires in vitro amplification and culture, there is considerable risk of direct treatment for patients. Stromal vascular fraction(SVF) is a biologically and clinically interesting heterogeneous cell population contains ADSCs. There are few reports on anti-aging effects of SVF in photo-aging skin. The present study investigated the anti-aging effect of stromal vascular fraction (SVF) and adipose-derived stem cells (ADSCs) injection in photo-aging skin. The relationship between the dosage of injection and effect was also discussed. Thirty healthy, 6-week-old, nude rats were randomly divided into the control and experimental groups. The experimental group needing ultraviolet B (UVB) irradiation five days per week, and a duration of 8 weeks. According to different dose regimens of SVF and ADSCs, experiment rats were randomly grouped as the model control group, low-dose (LD) treatment group, middle-dose (MD) treatment group and high-dose (HD) treatment group. At 7 and 28 days post-treatment, specimens were harvested for histological and immunohistochemical analysis. We found that certain concentrations of cells (MD and HD groups) could improve the texture of photoaged skin. Changes in the epidermal cell layer were clearly observed after 7 days of treatment. The epidermal layer becomes thinner and more tender. After 28 days of treatment, the dermal tissue was thickened and the collagen content and proportion were improved. All these indicators showed no significant difference between the same dosages in the two treatment groups. Our results demonstrate that SVF may have anti-aging potential in photo-aging skin and the ADSCs play an important role in SVF. SVF maybe a potential agent for photo-anging skin and the most effective dose of SVF was 106 cells /100 µl/injection point. The proper injection interval may be 1.5 cm.

Comprehensive insight into endothelial progenitor cell-derived extracellular vesicles as a promising candidate for disease treatment

Endothelial progenitor cells (EPCs), which are a type of stem cell, have been found to have strong angiogenic and tissue repair capabilities. Extracellular vesicles (EVs) contain many effective components, such as cellular proteins, microRNAs, messenger RNAs, and long noncoding RNAs, and can be secreted by different cell types. The functions of EVs depend mainly on their parent cells. Many researchers have conducted functional studies of EPC-derived EVs (EPC-EVs) and showed that they exhibit therapeutic effects on many diseases, such as cardiovascular disease, acute kidney injury, acute lung injury, and sepsis. In this review article, we comprehensively summarized the biogenesis and functions of EPCs and EVs and the potent role of EPC-EVs in the treatment of various diseases. Furthermore, the current problems and future prospects have been discussed, and further studies are needed to compare the therapeutic effects of EVs derived from various stem cells, which will contribute to the accelerated translation of these applications in a clinical setting.

State of the field: cellular and exosomal therapeutic approaches in vascular regeneration

Pathologies of the vasculature including the microvasculature are often complex in nature, leading to loss of physiological homeostatic regulation of patency and adequate perfusion to match tissue metabolic demands. Microvascular dysfunction is a key underlying element in the majority of pathologies of failing organs and tissues. Contributing pathological factors to this dysfunction include oxidative stress, mitochondrial dysfunction, endoplasmic reticular (ER) stress, endothelial dysfunction, loss of angiogenic potential and vascular density, and greater senescence and apoptosis. In many clinical settings, current pharmacologic strategies use a single or narrow targeted approach to address symptoms of pathology rather than a comprehensive and multifaceted approach to address their root cause. To address this, efforts have been heavily focused on cellular therapies and cell-free therapies (e.g., exosomes) that can tackle the multifaceted etiology of vascular and microvascular dysfunction. In this review, we discuss 1) the state of the field in terms of common therapeutic cell population isolation techniques, their unique characteristics, and their advantages and disadvantages, 2) common molecular mechanisms of cell therapies to restore vascularization and/or vascular function, 3) arguments for and against allogeneic versus autologous applications of cell therapies, 4) emerging strategies to optimize and enhance cell therapies through priming and preconditioning, and, finally, 5) emerging strategies to bolster therapeutic effect. Relevant and recent clinical and animal studies using cellular therapies to restore vascular function or pathologic tissue health by way of improved vascularization are highlighted throughout these sections.

Effect of uncultured adipose-derived stromal vascular fraction on preventing urethral stricture formation in rats

Urethral stricture (US) remains a challenging disease without effective treatment options due to the high recurrence rate. This study aims to evaluate the preventive effect of uncultured adipose derived stromal vascular fraction (SVF) on urethral fibrosis in a rat model of US. Results demonstrated that US rats displayed hyperechogenic urethral wall with a narrowed lumen compared with sham rats, while SVF rats exhibited less extensive urethral changes. By histology, US rats showed obvious submucosal fibrosis in the urethral specimens, while SVF rats exhibited mild submucosal fibrosis with less extensive tissue changes. Furthermore, US rats showed increased gene and protein expression of collagen I (2.0 ± 0.2, 2.2 ± 0.2, all were normalized against GAPDH, including the following), collagen III (2.5 ± 0.3, 1.2 ± 0.1), and TGFβ1R (2.8 ± 0.3, 1.9 ± 0.2), while SVF cells administration contributed to decreased gene and protein expression of collagen I (1.6 ± 0.2, 1.6 ± 0.2), collagen III (1.8 ± 0.4, 0.9 ± 0.1), and TGFβ1R (1.8 ± 0.3, 1.3 ± 0.2), in parallel with the improvement of vascularization and increased expression of VEGF (1.7 ± 0.1) and bFGF (3.1 ± 0.3). Additionally, SVF served anti-inflammatory effect through regulation of inflammatory cytokines and cells, accompanied with conversion of the macrophage phenotype. Our findings suggested that uncultured SVF presented an inhibitory effect on stricture formation at an early stage of urethral fibrosis.

Mitigating the non-specific uptake of immunomagnetic microparticles enables the extraction of endothelium from human fat

Endothelial cells are among the fundamental building blocks for vascular tissue engineering. However, a clinically viable source of endothelium has continued to elude the field. Here, we demonstrate the feasibility of sourcing autologous endothelium from human fat – an abundant and uniquely dispensable tissue that can be readily harvested with minimally invasive procedures. We investigate the challenges underlying the overgrowth of human adipose tissue-derived microvascular endothelial cells by stromal cells to facilitate the development of a reliable method for their acquisition. Magnet-assisted cell sorting strategies are established to mitigate the non-specific uptake of immunomagnetic microparticles, enabling the enrichment of endothelial cells to purities that prevent their overgrowth by stromal cells. This work delineates a reliable method for acquiring human adipose tissue-derived microvascular endothelial cells in large quantities with high purities that can be readily applied in future vascular tissue engineering applications.

Antonyshyn et al. establish a methodology for acquiring human adipose tissue-derived microvascular endothelial cells that can be readily applied in future vascular tissue engineering applications. The authors developed strategies to mitigate the non-specific uptake of immunomagnetic microparticles to facilitate the immunoselection of endothelial cells by magnet-assisted cell sorting.

Endothelial Cells as Tools to Model Tissue Microenvironment in Hypoxia-Dependent Pathologies

Endothelial cells (ECs) lining the blood vessels are important players in many biological phenomena but are crucial in hypoxia-dependent diseases where their deregulation contributes to pathology. On the other hand, processes mediated by ECs, such as angiogenesis, vessel permeability, interactions with cells and factors circulating in the blood, maintain homeostasis of the organism. Understanding the diversity and heterogeneity of ECs in different tissues and during various biological processes is crucial in biomedical research to properly develop our knowledge on many diseases, including cancer. Here, we review the most important aspects related to ECs’ heterogeneity and list the available in vitro tools to study different angiogenesis-related pathologies. We focus on the relationship between functions of ECs and their organo-specificity but also point to how the microenvironment, mainly hypoxia, shapes their activity. We believe that taking into account the specific features of ECs that are relevant to the object of the study (organ or disease state), especially in a simplified in vitro setting, is important to truly depict the biology of endothelium and its consequences. This is possible in many instances with the use of proper in vitro tools as alternative methods to animal testing.

Cellular Based Strategies for Microvascular Engineering

Vascularization is a major hurdle in complex tissue and organ engineering. Tissues greater than 200 μm in diameter cannot rely on simple diffusion to obtain nutrients and remove waste. Therefore, an integrated vascular network is required for clinical translation of engineered tissues. Microvessels have been described as <150 μm in diameter, but clinically they are defined as <1 mm. With new advances in super microsurgery, vessels less than 1 mm can be anastomosed to the recipient circulation. However, this technical advancement still relies on the creation of a stable engineered microcirculation that is amenable to surgical manipulation and is readily perfusable. Microvascular engineering lays on the crossroads of microfabrication, microfluidics, and tissue engineering strategies that utilize various cellular constituents. Early research focused on vascularization by co-culture and cellular interactions, with the addition of angiogenic growth factors to promote vascular growth. Since then, multiple strategies have been utilized taking advantage of innovations in additive manufacturing, biomaterials, and cell biology. However, the anatomy and dynamics of native blood vessels has not been consistently replicated. Inconsistent results can be partially attributed to cell sourcing which remains an enigma for microvascular engineering. Variations of endothelial cells, endothelial progenitor cells, and stem cells have all been used for microvascular network fabrication along with various mural cells. As each source offers advantages and disadvantages, there continues to be a lack of consensus. Furthermore, discord may be attributed to incomplete understanding about cell isolation and characterization without considering the microvascular architecture of the desired tissue/organ.

Human adipose-derived mesenchymal stem cells accelerate decellularized neobladder regeneration

Decellularized natural bladder matrices (neobladders) represent an exciting means to regenerate the bladder following bladder cancer-associated cystectomy. In this study, we compare the evolution of decellularized matrices with recellularized matrices by seeding it with human adipose-derived mesenchymal stem cells (ADSC) after implantation following partial cystectomy in rats. We discovered significant anatomical differences since 10 days after neobladder implantation with the ADSC-containing matrices promoting a significant recovery of mature p63- and cytokeratin 7-positive urothelium. We also discovered significantly induced expression of the vimentin mesoderm marker in the submucosal layer in ADSC-seeded matrices. Interestingly, we found a higher expression of smooth muscle actin in transversal and longitudinal smooth muscle layers with ADSC-seeded matrices. Furthermore, ADSC also showed increased vascularization and nerve innervation of the neobladder as determined by the distribution of CD31 and S100β reactivity, respectively. We believe that ADSC and their paracrine-acting pro-regenerative secretome within decellularized matrices represent an efficient bladder substitution strategy; however, we require a fuller understanding of the mechanisms involved before clinical studies can begin.

Bioprinting of Vascularized Tissue Scaffolds: Influence of Biopolymer, Cells, Growth Factors, and Gene Delivery

Over the past decades, tissue regeneration with scaffolds has achieved significant progress that would eventually be able to solve the worldwide crisis of tissue and organ regeneration. While the recent advancement in additive manufacturing technique has facilitated the biofabrication of scaffolds mimicking the host tissue, thick tissue regeneration remains challenging to date due to the growing complexity of interconnected, stable, and functional vascular network within the scaffold. Since the biological performance of scaffolds affects the blood vessel regeneration process, perfect selection and manipulation of biological factors (i.e., biopolymers, cells, growth factors, and gene delivery) are required to grow capillary and macro blood vessels. Therefore, in this study, a brief review has been presented regarding the recent progress in vasculature formation using single, dual, or multiple biological factors. Besides, a number of ways have been presented to incorporate these factors into scaffolds. The merits and shortcomings associated with the application of each factor have been highlighted, and future research direction has been suggested.

Induced Pluripotent Stem Cell-Derived Mesenchymal Stromal Cells Are Functionally and Genetically Different From Bone Marrow-Derived Mesenchymal Stromal Cells

There has been considerable interest in the generation of functional mesenchymal stromal cell (MSC) preparations from induced pluripotent stem cells (iPSCs) and this is now regarded as a potential source of unlimited, standardized, high‐quality cells for therapeutic applications in regenerative medicine. Although iMSCs meet minimal criteria for defining MSCs in terms of marker expression, there are substantial differences in terms of trilineage potential, specifically a marked reduction in chondrogenic and adipogenic propensity in iMSCs compared with bone marrow‐derived (BM) MSCs. To reveal the cellular basis underlying these differences, we conducted phenotypic, functional, and genetic comparisons between iMSCs and BM‐MSCs. We found that iMSCs express very high levels of both KDR and MSX2 compared with BM‐MSCs. In addition, BM‐MSCs had significantly higher levels of PDGFRα. These distinct gene expression profiles were maintained during culture expansion, suggesting that prepared iMSCs are more closely related to vascular progenitor cells (VPCs). Although VPCs can differentiate along the chondrogenic, osteogenic, and adipogenic pathways, they require different inductive conditions compared with BM‐MSCs. These observations suggest to us that iMSCs, based on current widely used preparation protocols, do not represent a true alternative to primary MSCs isolated from BM. Furthermore, this study highlights the fact that high levels of expression of typical MSC markers such as CD73, CD90, and CD105 are insufficient to distinguish MSCs from other mesodermal progenitors in differentiated induced pluripotent stem cell cultures. stem cells2019;37:754–765

Protective Effects of Uncultured Adipose-Derived Stromal Vascular Fraction on Testicular Injury Induced by Torsion-Detorsion in Rats

Torsion‐detorsion (T/D)‐induced testicular injury may lead to male subfertility and even infertility. Stem cell therapy provides an alternative to attenuate testicular injury and promote spermatogenesis. Adipose‐derived stromal vascular fraction (SVF) can be acquired conveniently without in vitro expansion, which may avoid the potential risks of microbial contamination, xenogenic nutritional sources, etc., during cell culture. In this study, we investigate the protective effects of autologous uncultured SVF on testicular injury and spermatogenesis in a rat model of T/D. Animals were randomly divided into sham, T/D+ phosphate‐buffered saline, and T/D + SVF groups (18 rats in each group). SVF was isolated, labeled with lipophilic fluorochrome chloromethylbenzamido dialkylcarbocyanine, and transplanted into T/D testis by local injection. At 3, 7, 14, and 28 days F surgery, testicular tissue and serum samples were harvested for histopathological, immunohistochemical, Western blot, and enzyme‐linked immunosorbent assays. Histopathological findings demonstrated severe injury in the testis with decreased Johnsen's score led by T/D, while uncultured SVF reduced testicular injury and elevated the decreased score. Injected SVF cells were mainly integrated into interstitial region and seminiferous tubules, enhanced the secretion of basic fibroblast growth factor and stem cell factor in the testis, contributed to the declining level of malondialdehyde and restoration of hormonal homeostasis, and then reduced the injury of Leydig cells and germ cells, as well as promoting spermatogenesis. Our findings demonstrated that autologous uncultured SVF could protect the testis from testicular ischemia‐reperfusion injury and promote spermatogenesis, which provide significant clinical implications for the prevention of infertility induced by testicular T/D. stem cells translational medicine2019;8:383–391

Plasticity of Adipose Tissue-Derived Stem Cells and Regulation of Angiogenesis

Adipose tissue is recognized as an important organ with metabolic, regulatory, and plastic roles. Adipose tissue-derived stem cells (ASCs) with self-renewal properties localize in the stromal vascular fraction (SVF) being present in a vascular niche, thereby, contributing to local regulation of angiogenesis and vessel remodeling. In the past decades, ASCs have attracted much attention from biologists and bioengineers, particularly, because of their multilineage differentiation potential, strong proliferation, and migration abilities in vitro and high resistance to oxidative stress and senescence. Current data suggest that the SVF serves as an important source of endothelial progenitors, endothelial cells, and pericytes, thereby, contributing to vessel remodeling and growth. In addition, ASCs demonstrate intriguing metabolic and interlineage plasticity, which makes them good candidates for creating regenerative therapeutic protocols, in vitro tissue models and microphysiological systems, and tissue-on-chip devices for diagnostic and regeneration-supporting purposes. This review covers recent achievements in understanding the metabolic activity within the SVF niches (lactate and NAD+ metabolism), which is critical for maintaining the pool of ASCs, and discloses their pro-angiogenic potential, particularly, in the complex therapy of cardiovascular and cerebrovascular diseases.

Isolation, Expansion, and Adipogenic Induction of CD34+CD31+ Endothelial Cells from Human Omental and Subcutaneous Adipose Tissue

Obesity is accompanied by an extensive remodeling of adipose tissue primarily via adipocyte hypertrophy. Extreme adipocyte growth results in a poor response to insulin, local hypoxia, and inflammation. By stimulating the differentiation of functional white adipocytes from progenitors, radical hypertrophy of the adipocyte population can be prevented and, consequently, the metabolic health of adipose tissue can be improved along with a reduction of inflammation. Also, by stimulating a differentiation of beige/brown adipocytes, the total body energy expenditure can be increased, resulting in weight loss. This approach could prevent the development of obesity co-morbidities such as type 2 diabetes and cardiovascular disease. This paper describes the isolation, expansion, and differentiation of white and beige adipocytes from a subset of human adipose tissue endothelial cells that co-express the CD31 and CD34 markers. The method is relatively cheap and is not labor-intensive. It requires access to human adipose tissue and the subcutaneous depot is suitable for sampling. For this protocol, fresh adipose tissue samples from morbidly obese subjects [body mass index (BMI) >35] are collected during bariatric surgery procedures. Using a sequential immunoseparation from the stromal vascular fraction, enough cells are produced from as little as 2-3 g of fat. These cells can be expanded in culture over 10-14 days, can be cryopreserved, and retain their adipogenic properties with passaging up to passage 5-6. The cells are treated for 14 days with an adipogenic cocktail using a combination of human insulin and the PPARγ agonist-rosiglitazone. This methodology can be used for obtaining proof of concept experiments on molecular mechanisms that drive adipogenic responses in adipose endothelial cells, or for screening new drugs that can enhance the adipogenic response directed either towards white or beige/brown adipocyte differentiation. Using small subcutaneous biopsies, this methodology can be used to screen out non-responder subjects for clinical trials aimed to stimulate beige/brown and white adipocytes for the treatment of obesity and co-morbidities.

Stromal Vascular Fraction Loaded Silk Fibroin Mats Effectively Support the Survival of Diabetic Mice after Pancreatic Islet Transplantation

The aim of this study is to assess whether stromal vascular fraction (SVF)-soaked silk fibroin nonwoven mats (silk-SVF) can preserve the functionality of encapsulated pancreatic endocrine cells (alginate-PECs) after transplantation in the subcutaneous tissue of diabetic mice. Silk scaffolds are selected to create an effective 3D microenvironment for SVF delivery in the subcutaneous tissue before diabetes induction: silk-SVF is subcutaneously implanted in the dorsal area of five healthy animals; after 15 d, mice are treated with streptozotocin to induce diabetes and then alginate-PECs are implanted on the silk-SVF. All animals appear in good health, increasing weight during time, and among them, one presents euglycemia until the end of experiments. On the contrary, when PECs are simultaneously implanted with SVF after diabetes induction, mice are euthanized due to suffering. This work clearly demonstrates that silk-SVF creates a functional niche in subcutaneous tissue and preserves endocrine cell survival and engraftment.

Tissue engineering for urinary tract reconstruction and repair: Progress and prospect in China

Several urinary tract pathologic conditions, such as strictures, cancer, and obliterations, require reconstructive plastic surgery. Reconstruction of the urinary tract is an intractable task for urologists due to insufficient autologous tissue. Limitations of autologous tissue application prompted urologists to investigate ideal substitutes. Tissue engineering is a new direction in these cases. Advances in tissue engineering over the last 2 decades may offer alternative approaches for the urinary tract reconstruction. The main components of tissue engineering include biomaterials and cells. Biomaterials can be used with or without cultured cells. This paper focuses on cell sources, biomaterials, and existing methods of tissue engineering for urinary tract reconstruction in China. The paper also details challenges and perspectives involved in urinary tract reconstruction.

Crosstalk between Stem and Progenitor Cellular Mediators with Special Emphasis on Vasculogenesis

The cellular components and molecular processes of signaling during vasculogenesis have been investigated for decades. Considerable efforts have been made to unravel regulatory mechanisms of vasculogenesis through crosstalk between vasculogenic playmakers located in the vascular niche, namely hematopoietic stem cells, endothelial progenitor cells, and mesenchymal stem and progenitor cells. Recent studies have increased the knowledge about signaling events within vascular microenvironment that leads to vasculogenesis. Findings from these recent studies indicate the impact of cellular crosstalk through signaling pathways such as vascular endothelial growth factor signaling, wingless and Notch signaling in vasculogenesis and vascular development. In this review, we highlight the signaling signature between stem and progenitor cellular mediators during vasculogenesis. We further focus on hematopoietic stem cell-endothelial progenitor cell crosstalk during vasculogenesis and discuss their potential implications and benefits for therapeutic interventions and regenerative therapy.

Concise Review: Fat and Furious: Harnessing the Full Potential of Adipose-Derived Stromal Vascular Fraction

Due to their capacity to self-renew, proliferate and generate multi-lineage cells, adult-derived stem cells offer great potential for use in regenerative therapies to stop and/or reverse degenerative diseases such as diabetes, heart failure, Alzheimer's disease and others. However, these subsets of cells can be isolated from different niches, each with differing potential for therapeutic applications. The stromal vascular fraction (SVF), a stem cell enriched and adipose-derived cell population, has garnered interest as a therapeutic in regenerative medicine due to its ability to secrete paracrine factors that accelerate endogenous repair, ease of accessibility and lack of identified major adverse effects. Thus, one can easily understand the rush to employ adipose-derived SVF to treat human disease. Perhaps faster than any other cell preparation, SVF is making its way to clinics worldwide, while critical preclinical research needed to establish SVF safety, efficacy and optimal, standardized clinical procedures are underway. Here, we will provide an overview of the current knowledge driving this phenomenon, its regulatory issues and existing studies, and propose potential unmapped applications. Stem Cells Translational Medicine 2017;6:1096-1108.

Comparison of human adipose stromal vascular fraction and adipose-derived mesenchymal stem cells for the attenuation of acute renal ischemia/reperfusion injury

Stem cells therapy has been suggested as a promising option for the treatment of acute kidney injury (AKI). This study was performed to compare the abilities of xenogenic transplantation of human adipose stromal vascular fraction (SVF) and adipose-derived mesenchymal stem cells (AdMSCs) to facilitate the recovery of renal function and structure in a rat model of ischemia/reperfusion (IR) induced AKI. SVF or AdMSCs were transplanted to the injured kidney through intra-parenchymal injection. Significantly improved renal function and reduced tubular injury were observed in SVF and AdMSCs groups. Administration of SVF or AdMSCs contributed to significantly improved cell proliferation and markedly reduced cell apoptosis in parallel with reduced microvascular rarefaction in injured kidney. IR injury resulted in higher levels of inflammatory cytokines, whereas xenogenic transplantation of SVF or AdMSCs reduced but not induced inflammatory cytokines expression. Additionally, in vitro study showed that administration of SVF or AdMSCs could also significantly promote the proliferation and survival of renal tubular epithelial cells underwent hypoxia/reoxygenation injury through secreting various growth factors. However, cell proliferation was significantly promoted in SVF group than in AdMSCs group. In conclusion, our study demonstrated that administration of SVF or AdMSCs was equally effective in attenuating acute renal IR injury.

Progenitor Cells for Arterial Repair: Incremental Advancements towards Therapeutic Reality

Coronary revascularization remains the standard treatment for obstructive coronary artery disease and can be accomplished by either percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery. Considerable advances have rendered PCI the most common form of revascularization and improved clinical outcomes. However, numerous challenges to modern PCI remain, namely, in-stent restenosis and stent thrombosis, underscoring the importance of understanding the vessel wall response to injury to identify targets for intervention. Among recent promising discoveries, endothelial progenitor cells (EPCs) have garnered considerable interest given an increasing appreciation of their role in vascular homeostasis and their ability to promote vascular repair after stent placement. Circulating EPC numbers have been inversely correlated with cardiovascular risk, while administration of EPCs in humans has demonstrated improved clinical outcomes. Despite these encouraging results, however, advancing EPCs as a therapeutic modality has been hampered by a fundamental roadblock: what constitutes an EPC? We review current definitions and sources of EPCs as well as the proposed mechanisms of EPC-mediated vascular repair. Additionally, we discuss the current state of EPCs as therapeutic agents, focusing on endogenous augmentation and transplantation.

The Current Use of Stem Cells in Bladder Tissue Regeneration and Bioengineering

Many pathological processes including neurogenic bladder and malignancy necessitate bladder reconstruction, which is currently performed using intestinal tissue. The use of intestinal tissue, however, subjects patients to metabolic abnormalities, bladder stones, and other long-term sequelae, raising the need for a source of safe and reliable bladder tissue. Advancements in stem cell biology have catapulted stem cells to the center of many current tissue regeneration and bioengineering strategies. This review presents the recent advancements in the use of stem cells in bladder tissue bioengineering.

Endothelial progenitor cells from human fetal aorta cure diabetic foot in a rat model

OBJECTIVE

Recent evidence has suggested that circulating endothelial progenitor cells (EPCs) can repair the arterial endothelium during vascular injury. However, a reliable source of human EPCs is needed for therapeutic applications. In this study, we isolated human fetal aorta (HFA)-derived EPCs and analyzed the capacity of EPCs to differentiate into endothelial cells. In addition, because microvascular dysfunction is considered to be the major cause of diabetic foot (DF), we investigated whether transplantation of HFA-derived EPCs could treat DF in a rat model.

METHODS

EPCs were isolated from clinically aborted fetal aorta. RT-PCR, fluorescence-activated cell sorting, immunofluorescence, and an enzyme-linked immunosorbent assay were used to examine the expressions of CD133, CD34, CD31, Vascular Endothelial Growth Factor Receptor 2 (VEGFR2), von Willebrand Factor (vWF), and Endothelial Leukocyte Adhesion Molecule-1 (ELAM-1). Morphology and Dil-uptake were used to assess function of the EPCs. We then established a DF model by injecting microcarriers into the hind-limb arteries of Goto-Kakizaki rats and then transplanting the cultured EPCs into the ischemic hind limbs. Thermal infrared imaging, oxygen saturation apparatus, and laser Doppler perfusion imaging were used to monitor the progression of the disease. Immunohistochemistry was performed to examine the microvascular tissue formed by HFA-derived EPCs.

RESULTS

We found that CD133, CD34, and VEGFR2 were expressed by HFA-derived EPCs. After VEGF induction, CD133 expression was significantly decreased, but expression levels of vWF and ELAM-1 were markedly increased. Furthermore, tube formation and Dil-uptake were improved after VEGF induction. These observations suggest that EPCs could differentiate into endothelial cells. In the DF model, temperature, blood flow, and oxygen saturation were reduced but recovered to a nearly normal level following injection of the EPCs in the hind limb. Ischemic symptoms also improved. Injected EPCs were preferentially and durably engrafted into the blood vessels. In addition, anti-human CD31+-AMA+-vWF+ microvasculars were detected after transplantation of EPCs.

CONCLUSION

Early fetal aorta-derived EPCs possess strong self-renewal ability and can differentiate into endothelial cells. We demonstrated for the first time that transplanting HFA-derived EPCs could ameliorate DF prognosis in a rat model. These findings suggest that the transplantation of HFA-derived EPCs could serve as an innovative therapeutic strategy for managing DF.

Production of endothelial progenitor cells from skin fibroblasts by direct reprogramming for clinical usages

Endothelial progenitor cells (EPCs) play an important role in angiogenesis. However, they exist in limited numbers in the human body. This study was aimed to produce EPCs, for autologous transplantation, using direct reprogramming of skin fibroblasts under GMP-compliant conditions. Fibroblasts were collected and cultured from the skin in DMEM/F12 medium supplemented with 5% activated platelet-rich plasma and 1% antibiotic-antimycotic solution. They were then transfected with mRNA ETV2 and incubated in culture medium under hypoxia (5% oxygen) for 14 d. Phenotype analysis of transfected cells confirmed that single-factor ETV2 transfection successfully reprogrammed dermal fibroblasts into functional EPCs. Our results showed that ETV2 mRNA combined with hypoxia can give rise to functional EPCs. The cells exhibited functional phenotypes similar to endothelial cells derived from umbilical cord vein; they expressed CD31 and VEGFR2, and formed capillary-like structures in vitro. Moreover, these EPCs could significantly improve hindlimb ischemia in mouse models. Although the direct conversion efficacy was low (3.12 ± 0.98%), altogether our study demonstrates that functional EPCs can be produced from fibroblasts and can be used in clinical applications.

Preischemic Administration of Nonexpanded Adipose Stromal Vascular Fraction Attenuates Acute Renal Ischemia/Reperfusion Injury and Fibrosis

: Ischemia/reperfusion (IR)-induced acute kidney injury (AKI) is a common clinical syndrome. Stem/progenitor cell therapy is a promising option to foster the intrinsic capacity for kidney regeneration. However, there are still several challenges to be resolved, including the potential risks during cell culture, low retention rate after transplantation, and unclear effect on the progression of chronic kidney disease (CKD). Recently, nonexpanded adipose stromal vascular fraction (SVF) has been regarded as an attractive cell source for cell-based therapy. Preconditioning with ischemia has been suggested as a useful method to promote the retention and survival of transplanted cells in vivo. In this study, freshly isolated autologous SVF was transplanted to the kidney of rats before ischemia, and then an IR-induced AKI model was established. Postischemic administration of SVF to the kidney was performed after renal IR injury was induced. A higher cell retention rate was detected in the preischemic group. Preischemic administration of SVF showed stronger functional and morphologic protection from renal IR injury than postischemic administration, through enhancing tubular cell proliferation and reducing apoptosis. Progression of kidney fibrosis was also significantly delayed by preischemic administration of SVF, which exhibited stronger inhibition of transforming growth factor-β1-induced epithelia-mesenchymal transition and microvascular rarefaction. In addition, in vitro study showed that prehypoxic administration of SVF could significantly promote the proliferation, migration, and survival of hypoxic renal tubular epithelial cells. In conclusion, our study demonstrated that preischemic administration of nonexpanded adipose SVF protected the kidney from both acute IR injury and long-term risk of developing CKD.

SIGNIFICANCE

Renal ischemia/reperfusion (IR) injury is a common clinical syndrome. Cell-based therapy provides a promising option to promote renal repair after IR injury. However, several challenges still remain because of the potential risks during cell culture, low retention rate after transplantation, and unclear effect on the progression of chronic kidney disease. Stromal vascular fraction (SVF) is considered as an attractive cell source. This study demonstrated that preischemic administration of uncultured SVF could increase cell retention and then improve renal function and structure at both early and long-term stage after IR, which may provide a novel therapeutic approach for IR injury.