A familiar stranger: CD34 expression and putative functions in SVF cells of adipose tissue

Starvation and Inflammation Modulate Adipose Mesenchymal Stromal Cells' Molecular Signature

Mesenchymal stromal cells (MSCs) and their released factors (secretome) are intriguing options for regenerative medicine approaches based on the management of inflammation and tissue restoration, as in joint disorders like osteoarthritis (OA). Production strategy may modulate cells and secretome fingerprints, and for the latter, the effect of serum removal by starvation used in clinical-grade protocols has been underestimated. In this work, the effect of starvation on the molecular profile of interleukin 1 beta (IL1β)-primed adipose-derived MSCs (ASCs) was tested by assessing the expression level of 84 genes related to secreted factors and 84 genes involved in defining stemness potential. After validation at the protein level, the effect of starvation modulation in the secretomes was tested in a model of OA chondrocytes. IL1β priming in vitro led to an increase in inflammatory mediators' release and reduced anti-inflammatory potential on chondrocytes, features reversed by subsequent starvation. Therefore, when applying serum removal-based clinical-grade protocols for ASCs' secretome production, the effects of starvation must be carefully considered and investigated.

Insights into the role of adipose-derived stem cells and secretome: potential biology and clinical applications in hypertrophic scarring

Scar tissue is the inevitable result of repairing human skin after it has been subjected to external destructive stimuli. It leads to localized damage to the appearance of the skin, accompanied by symptoms such as itching and pain, which reduces the quality of life of the patient and causes serious medical burdens. With the continuous development of economy and society, there is an increasing demand for beauty. People are looking forward to a safer and more effective method to eliminate pathological scarring. In recent years, adipose-derived stem cells (ADSCs) have received increasing attention from researchers. It can effectively improve pathological scarring by mediating inflammation, regulating fibroblast proliferation and activation, and vascular reconstruction. This review focuses on the pathophysiological mechanisms of hypertrophic scarring, summarizing the therapeutic effects of in vitro, in vivo, and clinical studies on the therapeutic effects of ADSCs in the field of hypertrophic scarring prevention and treatment, the latest application techniques, such as cell-free therapies utilizing ADSCs, and discussing the advantages and limitations of ADSCs. Through this review, we hope to further understand the characterization of ADSC and clarify the effectiveness of its application in hypertrophic scarring treatment, so as to provide clinical guidance.

Inflammation and Starvation Affect Housekeeping Gene Stability in Adipose Mesenchymal Stromal Cells

Due to the scientific success of in vitro and in vivo model studies, the interest in using mesenchymal stromal cells (MSCs) for the treatment of orthopaedic conditions is growing. In the context of osteoarthritis (OA), MSCs, and, in particular, those derived from adipose tissues (ASCs), have found broader access to clinical use as active components of minimally manipulated orthobiologics, as well as clinically expanded cell preparations, or to collect their released factors (secretome) for cell-free approaches. In this regard, while both inflammatory priming and starvation are common strategies used to empower cell potency or collect the secretome, respectively, little is known about the possible influence of these approaches on the stability of housekeeping genes (HKGs) for molecular studies able to fingerprint cell phenotype or potency. In this report, the reliability of five commonly used HKGs (ACTB, B2M, GAPDH, HPRT1 and RPLP0) was tested in ASCs cultured under standard protocol after inflammatory priming or starvation. Gene expression data were computed with four different applets able to rank genes depending on their stability in either single or combined conditions. The obtained final ranking suggests that for each treatment, a specific HKG is needed, and that starvation is the condition with the stronger effect on HKGs' stability and, therefore, reliability. The normalization effect of proper HKGs' use was then validated on three genes involved in OA and whose product is released by ASCs. Overall, data presented herein confirm that the choice of the best HKG has to be carefully considered and that each specific condition has to be tested to identify the most reliable candidate.

Injectable polyisocyanide hydrogel as healing supplement for connective tissue regeneration in an abdominal wound model

In pelvic organ prolapse (POP) patients, the uterus, bladder and/or rectum descends into vagina due to weakened support tissues. High recurrence rates after POP surgery suggest an urgent need for improved surgical outcomes. Our aim is to promote connective tissue healing that results in stimulated tissue support functions by surgically applying a hydrogel functionalized with biological cues. We used known vaginal wound healing promoting factors (basic fibroblast growth factor, β-estradiol, adipose-derived stem cells) in the biomimetic and injectable polyisocyanide (PIC) hydrogel, which in itself induces regenerative vaginal fibroblast behavior. The regenerative capacity of injected PIC hydrogel, and the additional pro-regenerative effects of these bioactive factors was evaluated in abdominal wounds in rabbits. Assessment of connective tissue healing (tensile testing, histology, immunohistochemistry) revealed that injection with all PIC formulations resulted in a statistically significant stiffness and collagen increase over time, in contrast to sham. Histological evaluation indicated new tissue growth with moderate to mild immune activity at the hydrogel - tissue interface. The results suggest that PIC injection in an abdominal wound improves healing towards regaining load-bearing capacity, which encourages us to investigate application of the hydrogel in a more translational vaginal model for POP surgery in sheep.

CD34-Structure, Functions and Relationship with Cancer Stem Cells

The CD34 protein was identified almost four decades ago as a biomarker for hematopoietic stem cell progenitors. CD34 expression of these stem cells has been exploited for therapeutic purposes in various hematological disorders. In the last few decades, studies have revealed the presence of CD34 expression on other types of cells with non-hematopoietic origins, such as interstitial cells, endothelial cells, fibrocytes, and muscle satellite cells. Furthermore, CD34 expression may also be found on a variety of cancer stem cells. Nowadays, the molecular functions of this protein have been involved in a variety of cellular functions, such as enhancing proliferation and blocking cell differentiation, enhanced lymphocyte adhesion, and cell morphogenesis. Although a complete understanding of this transmembrane protein, including its developmental origins, its stem cell connections, and other functions, is yet to be achieved. In this paper, we aimed to carry out a systematic analysis of the structure, functions, and relationship with cancer stem cells of CD34 based on the literature overview.

Stromal Vascular Fraction Obtained From Subcutaneous Adipose Tissue: Ex-Obese and Older Population as Main Clinical Targets

INTRODUCTION

Human adipose tissue contains a heterogeneous and synergistic mixture of cells called stromal vascular fraction (SVF) with highly proliferative and angiogenic properties, conferring promising applicability in the field of regenerative medicine. This study aims to investigate if age, body mass index (BMI), history of obesity and massive weight loss, and harvest site are related to SVF cell marker expression.

METHODS

A total of 26 samples of subcutaneous adipose tissue were harvested from patients admitted to the Plastic and Reconstructive department in University Hospital Center of São João, Porto, Portugal, for body contouring surgery. The percentage of cells expressing CD31, CD34, CD45, CD73, CD90, and CD105 was assessed and compared with patient's age, BMI, history of obesity and massive weight loss (ex-obese group), and harvest site.

RESULTS

In the ex-obese group, a significantly higher number of cells expressing CD90 (P = 0.002) was found. BMI, harvest site, and age appear to have no association with SVF subpopulations.

CONCLUSIONS

This study suggests that ex-obese patients have a higher percentage of SVF cells expressing CD90, which correlates with higher proliferative and angiogenic rates. The effect of former obesity and massive weight loss on the expression of CD90 is a new and relevant finding because it makes this population a suitable candidate for reconstructive and aesthetic surgery and other fields of regenerative medicine. The use of SVF appears also promising in older patients because no negative correlation between increasing age and different cell markers expression was found.

Evolution of developmental and comparative immunology in poultry: The regulators and the regulated

Avian has a unique immune system that evolved in response to environmental pressures in all aspects of innate and adaptive immune responses, including localized and circulating lymphocytes, diversity of immunoglobulin repertoire, and various cytokines and chemokines. All of these attributes make birds an indispensable vertebrate model for studying the fundamental immunological concepts and comparative immunology. However, research on the immune system in birds lags far behind that of humans, mice, and other agricultural animal species, and limited immune tools have hindered the adequate application of birds as disease models for mammalian systems. An in-depth understanding of the avian immune system relies on the detailed studies of various regulated and regulatory mediators, such as cell surface antigens, cytokines, and chemokines. Here, we review current knowledge centered on the roles of avian cell surface antigens, cytokines, chemokines, and beyond. Moreover, we provide an update on recent progress in this rapidly developing field of study with respect to the availability of immune reagents that will facilitate the study of regulatory and regulated components of poultry immunity. The new information on avian immunity and available immune tools will benefit avian researchers and evolutionary biologists in conducting fundamental and applied research.

ASCs and their role in obesity and metabolic diseases

We describe adipose stromal/stem cells (ASCs) in the structural/functional context of the adipose tissue (AT) stem niche (adiponiche), including cell-cell interactions and the microenvironment, and emphasize findings obtained in humans and in lineage-tracing models. ASCs have distinctive markers, 'colors', and anatomical 'locations' which influence their functions. Each adiponiche component can become impaired, thereby contributing to the pathological AT alterations seen in obesity and metabolic diseases. We discuss adiposopathy with a focus on adiponiche dysfunction, and underline the mechanisms that control AT expansion and energy balance. Better understanding of adiponiche regulation and ASC features could help to identify therapeutic targets that favor weight loss and counteract weight regain, and also contribute to innovative strategies for regenerative medicine.

Adipose-derived stromal cells for nonhealing wounds: Emerging opportunities and challenges

Wound healing complications affect thousands of people each year, thus constituting a profound economic and medical burden. Chronic wounds are a highly complex problem that usually affects elderly patients as well as patients with comorbidities such as diabetes, cancer (surgery, radiotherapy/chemotherapy) or autoimmune diseases. Currently available methods of their treatment are not fully effective, so new solutions are constantly being sought. Cell-based therapies seem to have great potential for use in stimulating wound healing. In recent years, much effort has been focused on characterizing of adipose-derived mesenchymal stromal cells (AD-MSCs) and evaluating their clinical use in regenerative medicine and other medical fields. These cells are easily obtained in large amounts from adipose tissue and show a high proregenerative potential, mainly through paracrine activities. In this review, the process of healing acute and nonhealing (chronic) wounds is detailed, with a special attention paid to the wounds of patients with diabetes and cancer. In addition, the methods and technical aspects of AD-MSCs isolation, culture and transplantation in chronic wounds are described, and the characteristics, genetic stability and role of AD-MSCs in wound healing are also summarized. The biological properties of AD-MSCs isolated from subcutaneous and visceral adipose tissue are compared. Additionally, methods to increase their therapeutic potential as well as factors that may affect their biological functions are summarized. Finally, their therapeutic potential in the treatment of diabetic and oncological wounds is also discussed.

Novel cell sources for bone regeneration

A plethora of both acute and chronic conditions, including traumatic, degenerative, malignant, or congenital disorders, commonly induce bone disorders often associated with severe persisting pain and limited mobility. Over 1 million surgical procedures involving bone excision, bone grafting, and fracture repair are performed each year in the U.S. alone, resulting in immense levels of public health challenges and corresponding financial burdens. Unfortunately, the innate self-healing capacity of bone is often inadequate for larger defects over a critical size. Moreover, as direct transplantation of committed osteoblasts is hindered by deficient cell availability, limited cell spreading, and poor survivability, an urgent need for novel cell sources for bone regeneration is concurrent. Thanks to the development in stem cell biology and cell reprogramming technology, many multipotent and pluripotent cells that manifest promising osteogenic potential are considered the regenerative remedy for bone defects. Considering these cells' investigation is still in its relative infancy, each of them offers their own particular challenges that must be conquered before the large-scale clinical application.

A further look at quantitative trait loci for growth and fatness traits in a White Duroc × Erhualian F3 intercross population

Genetic analysis of porcine growth and fatness traits is beneficial to the swine industry and provides a reference to understand human obesity. Here, we obtained 29 growth and fatness traits for 473 individuals from a White Duroc × Erhualian F₃ intercross population. Basic statistical analyses showed that: (1) Positive correlations between different-stage body weights were detected, the shorter the time interval the stronger the correlation. (2) Strong correlations existed in the paired fatness traits. (3) With the growth of age, the correlation between fatness and body weight was increasing. All pigs were genotyped by Illumina 50 K SNP chips and their whole-genome genotypes were imputed referred to 109 re-sequencing data. We performed common and imputation-based GWASs for these traits. Two genome-wide significant loci on swine chromosome (SSC) 4 and 7 were repeatedly detected. The strongest association (P = 3.24 × 10^-19) was detected at 31.96 Mb on SSC7 for leaf fat weight. On this locus, seven major haplotypes were identified, of which two were novel and had an increasing-fatness effect. In the imputation-based GWAS, three new loci were identified. Our findings provide further insights into and enhance our understanding of genetic mechanism of porcine growth and fat deposition.

Differentiated PDGFRα-Positive Cells: A Novel In-Vitro Model for Functional Studies of Neuronal Nitric Oxide Synthase

It is evident that depletion of interstitial cells and dysfunction of nitric oxide (NO) pathways are key players in development of several gastrointestinal (GI) motility disorders such as diabetic gastroparesis (DGP). One of the main limitations of DGP research is the lack of isolation methods that are specific to interstitial cells, and therefore conducting functional studies is not feasible. The present study aims (i) to differentiate telomerase transformed mesenchymal stromal cells (iMSCs) into platelet-derived growth factor receptor-α-positive cells (PDGFRα-positive cells) using connective tissue growth factor (CTGF) and L-ascorbic acids; (ii) to investigate the effects of NO donor and inhibitor on the survival rate of differentiated PDGFRα-positive cells; and (iii) to evaluate the impact of increased glucose concentrations, mimicking diabetic hyperglycemia, on the gene expression of neuronal nitric oxide synthase (nNOS). A fibroblastic differentiation-induction medium supplemented with connective tissue growth factor was used to differentiate iMSCs into PDGFRα-positive cells. The medium was changed every day for 21 days to maintain the biological activity of the growth factors. Gene and protein expression, scanning electron and confocal microscopy, and flow cytometry analysis of several markers were conducted to confirm the differentiation process. Methyl tetrazolium cell viability, nitrite measurement assays, and immunostaining were used to investigate the effects of NO on PDGFRα-positive cells. The present study, for the first time, demonstrated the differentiation of iMSCs into PDGFRα-positive cells. The outcomes of the functional studies showed that SNAP (NO donor) increased the survival rate of differentiated PDGFRα-positive cells whereas LNNA (NO inhibitor) attenuated these effects. Further experimentations revealed that hyperglycemia produced a significant increase in expression of nNOS in PDGFRα-positive cells. Differentiation of iMSCs into PDGFRα-positive cells is a novel model to conduct functional studies and to investigate the involvement of NO pathways. This will help in identifying new therapeutic targets for treatment of DGP.

Chemically Defined Xeno- and Serum-Free Cell Culture Medium to Grow Human Adipose Stem Cells

Adipose tissue is an abundant source of stem cells. However, liposuction cannot yield cell quantities sufficient for direct applications in regenerative medicine. Therefore, the development of GMP-compliant ex vivo expansion protocols is required to ensure the production of a "cell drug" that is safe, reproducible, and cost-effective. Thus, we developed our own basal defined xeno- and serum-free cell culture medium (UrSuppe), specifically formulated to grow human adipose stem cells (hASCs). With this medium, we can directly culture the stromal vascular fraction (SVF) cells in defined cell culture conditions to obtain hASCs. Cells proliferate while remaining undifferentiated, as shown by Flow Cytometry (FACS), Quantitative Reverse Transcription PCR (RT-qPCR) assays, and their secretion products. Using the UrSuppe cell culture medium, maximum cell densities between 0.51 and 0.80 × 10⁵ cells/cm² (=2.55-4.00 × 10⁵ cells/mL) were obtained. As the expansion of hASCs represents only the first step in a cell therapeutic protocol or further basic research studies, we formulated two chemically defined media to differentiate the expanded hASCs in white or beige/brown adipocytes. These new media could help translate research projects into the clinical application of hASCs and study ex vivo the biology in healthy and dysfunctional states of adipocytes and their precursors. Following the cell culture system developers' practice and obvious reasons related to the formulas' patentability, the defined media's composition will not be disclosed in this study.

L-carnitine in a certain concentration increases expression of cell surface marker CD34 and apoptosis in the rat bone marrow CD34+ hematopoietic stem cells

BACKGROUND

Stem cell based therapy has been encouraged as an attractive method in regenerative medicine. Poor survival and maintenance of the cells transferred into the damaged tissue are broadly accepted as serious barriers to enhancing the efficacy of regenerative medicine. For this reason, some antioxidants such as L-carnitine (LC) are used as a favorite strategy to improve cell survival and retention properties.

AIMS

This study aims to evaluate the effect of LC on the expression of CD34 marker and its effect on apoptosis and SUZ12 gene expression.

METHODS

Rat bone marrow mono-nuclear cells (rBMNCs) were isolated. Then, CD34+ hematopoietic stem cells (HSCs) were enriched using the magnetic activated cell sorting (MACS) method. The cells were treated with 0.2 and 0.4 mM LC. Gene and protein expression levels of the CD34 were then measured by real-time PCR and flow cytometry, respectively. The percentage of apoptosis and SUZ12 gene expression were measured using the Annexin V/PI method and real-time PCR, respectively.

RESULTS

The results showed that in the experimental group, of the CD34+ HSCs treated with 0.2 mM LC, gene and protein expressions of CD34 increased by 1.7 fold and 0.49%, respectively. At the concentration of 0.4 mM, the early cell apoptosis increased by 25.9% (P<0.05). Also, in the concentration of 0.2 and 0.4 mM LC, the SUZ12 gene expression increased by 1.10 and 1.75 folds compared to the control group (P<0.05 and P<0.01), respectively.

CONCLUSION

The results of this study could be used to improve chronic myeloid leukemia (CML) as a multidirectional therapeutic strategy.

Extracellular Vesicles from Adipose Tissue Stem Cells in Diabetes and Associated Cardiovascular Disease; Pathobiological Impact and Therapeutic Potential

Adipose tissue-derived stem cells (ADSCs) are pluripotent mesenchymal stem cells found in relatively high percentages in the adipose tissue and able to self-renew and differentiate into many different types of cells. “Extracellular vesicles (EVs), small membrane vesicular structures released during cell activation, senescence, or apoptosis, act as mediators for long distance communication between cells, transferring their specific bioactive molecules into host target cells”. There is a general consensus on how to define and isolate ADSCs, however, multiple separation and characterization protocols are being used in the present which complicate the results’ integration in a single theory on ADSCs’ and their derived factors’ way of action. Metabolic syndrome and type 2 diabetes mellitus (T2DM) are mainly caused by abnormal adipose tissue size, distribution and metabolism and so ADSCs and their secretory factors such as EVs are currently investigated as therapeutics in these diseases. Moreover, due to their relatively easy isolation and propagation in culture and their differentiation ability, ADSCs are being employed in preclinical studies of implantable devices or prosthetics. This review aims to provide a comprehensive summary of the current knowledge on EVs secreted from ADSCs both as diagnostic biomarkers and therapeutics in diabetes and associated cardiovascular disease, the molecular mechanisms involved, as well as on the use of ADSC differentiation potential in cardiovascular tissue repair and prostheses.

An Approach towards a GMP Compliant In-Vitro Expansion of Human Adipose Stem Cells for Autologous Therapies

Human Adipose Tissue Stem Cells (hASCs) are a valuable source of cells for clinical applications (e.g., treatment of acute myocardial infarction and inflammatory diseases), especially in the field of regenerative medicine. However, for autologous (patient-specific) and allogeneic (off-the-shelf) hASC-based therapies, in-vitro expansion is necessary prior to the clinical application in order to achieve the required cell numbers. Safe, reproducible and economic in-vitro expansion of hASCs for autologous therapies is more problematic because the cell material changes for each treatment. Moreover, cell material is normally isolated from non-healthy or older patients, which further complicates successful in-vitro expansion. Hence, the goal of this study was to perform cell expansion studies with hASCs isolated from two different patients/donors (i.e., different ages and health statuses) under xeno- and serum-free conditions in static, planar (2D) and dynamically mixed (3D) cultivation systems. Our primary aim was I) to compare donor variability under in-vitro conditions and II) to develop and establish an unstructured, segregated growth model as a proof-of-concept study. Maximum cell densities of between 0.49 and 0.65 × 10⁵ hASCs/cm² were achieved for both donors in 2D and 3D cultivation systems. Cell growth under static and dynamically mixed conditions was comparable, which demonstrated that hydrodynamic stresses (P/V = 0.63 W/m³, τ_nt = 4.96 × 10⁻³ Pa) acting at N_s1u (49 rpm for 10 g/L) did not negatively affect cell growth, even under serum-free conditions. However, donor-dependent differences in the cell size were found, which resulted in significantly different maximum cell densities for each of the two donors. In both cases, stemness was well maintained under static 2D and dynamic 3D conditions, as long as the cells were not hyperconfluent. The optimal point for cell harvesting was identified as between cell densities of 0.41 and 0.56 × 10⁵ hASCs/cm² (end of exponential growth phase). The growth model delivered reliable predictions for cell growth, substrate consumption and metabolite production in both types of cultivation systems. Therefore, the model can be used as a basis for future investigations in order to develop a robust MC-based hASC production process for autologous therapies.

CD34+CD146+ adipose-derived stromal cells enhance engraftment of transplanted fat

Fat grafting is a surgical technique able to reconstruct and regenerate soft tissue. The adipose‐derived stromal cells (ASCs) within the stromal vascular fraction are believed to drive these beneficial effects. ASCs are increasingly recognized to be a heterogeneous group, comprised of multiple stem and progenitor subpopulations with distinct functions. We hypothesized the existence of an ASC subpopulation with enhanced angiogenic potential. Human ASCs that were CD34+CD146+, CD34+CD146−, or CD34+ unfractionated (UF) were isolated by flow cytometry for comparison of expression of proangiogenic factors and endothelial tube‐forming potential. Next, lipoaspirate was enriched with either CD34+CD146+, CD34+CD146−, CD34+ UF ASCs, or was not enriched, and grafted beneath the scalp skin of immunodeficient CD‐1 Nude mice (10 000 cells/200 μL/graft). Fat retention was monitored radiographically more than 8 weeks and fat grafts were harvested for histological assessment of quality and vascularization. The CD34+CD146+ subpopulation comprised ~30% of ASCs, and exhibited increased expression of vascular endothelial growth factor and angiopoietin‐1 compared to CD34+CD146− and CD34+ UF ASCs, and increased expression of fibroblast growth factor‐2 compared to CD34+CD146− ASCs. The CD34+CD146+ subpopulation exhibited enhanced induction of tube‐formation compared to CD34+CD146− ASCs. Upon transplantation, fat enriched CD34+CD146+ ASCs underwent less resorption and had improved histologic quality and vascularization. We have identified a subpopulation of CD34+ ASCs with enhanced angiogenic effects in vitro and in vivo, likely mediated by increased expression of potent proangiogenic factors. These findings suggest that enriching lipoaspirate with CD34+CD146+ ASCs may enhance fat graft vascularization and retention in the clinical setting.

The Effect of Blood-Derived Products on the Chondrogenic and Osteogenic Differentiation Potential of Adipose-Derived Mesenchymal Stem Cells Originated from Three Different Locations

Background

Adipose-derived mesenchymal stem cells (AD-MSCs) from fat tissue considered “surgical waste” during joint surgery may provide a potent source for regenerative medicine. Intra-articular, homologous fat tissue (Hoffa's fat pad, pouch fat) might possess a superior chondrogenic and osteogenic differentiation potential in comparison to extra-articular, nonhomologous fat. Blood products might further enhance this potential.

Methods

AD-MSCs were isolated from fat tissue of 3 donors from 3 locations each, during total knee replacement. Isolated cells were analyzed via flow cytometry. Cells were supplemented with blood products: two types of platelet-rich plasma (EPRP—PRP prepared in the presence of EDTA; CPRP—PRP prepared in the presence of citrate), hyperacute serum (hypACT), and standard fetal calf serum (FCS) as a positive control. The viability of the cells was determined by XTT assay, and the progress of differentiation was tested via histological staining and monitoring of specific gene expression.

Results

Blood products enhance ex vivo cell metabolism. Chondrogenesis is enhanced by EDTA-PRP and osteogenesis by citrate PRP, whereas hyperacute serum enhances both differentiations comparably. This finding was consistent in histological analysis as well as in gene expression. Lower blood product concentrations and shorter differentiation periods lead to superior histological results for chondrogenesis. Both PRP types had a different biological effect depending upon concentration, whereas hyperacute serum seemed to have a more consistent effect, independent of the used concentration.

Conclusion

(i) Blood product preparation method, (ii) type of anticoagulant, (iii) differentiation time, and (iv) blood product concentration have a significant influence on stem cell viability and the differentiation potential, favouring no use of anticoagulation, shorter differentiation time, and lower blood product concentrations. Cell-free blood products like hyperacute serum may be considered as an alternative supplementation in regenerative medicine, especially for stem cell therapies.

CD34 cells in somatic, regenerative and cancer stem cells: Developmental biology, cell therapy, and omics big data perspective

The transmembrane phosphoglycoprotein protein CD34 has conventionally been regarded as a marker for hematopoietic progenitors. Its expression on these cells has been leveraged for cell therapy applications in various hematological disorders. More recently, the expression of CD34 has also been reported on cells of nonhematopoietic origin. The list includes somatic cells such as endothelial cells, fibrocytes and interstitial cells and regenerative stem cells such as corneal keratocytes, muscle satellite cells, and muscle-derived stem cells. Furthermore, its expression on some cancer stem cells (CSCs) has also been reported. Till date, the functional roles of this molecule have been implicated in a multitude of cellular processes including cell adhesion, signal transduction, and maintenance of progenitor phenotype. However, the complete understanding about this molecule including its developmental origins, its embryonic connection, and associated functions is far from complete. Here, we review our present understanding of the structure and putative functions of the CD34 molecule based upon our literature survey. We also probed various biological databases to retrieve data related to the expression and associated molecular functions of CD34. Such information, upon synthesis, is hence likely to provide the suitability of such cells for cell therapy. Moreover, we have also covered the existing cell therapy and speculated cell therapy applications of CD34⁺ cells isolated from various lineages. We have also attempted here to speculate the role(s) of CD34 on CSCs. Finally, we discuss number of large-scale proteomics and transcriptomics studies that have been performed using CD34⁺ cells.

Influence of glucose and insulin in human adipogenic differentiation models with adipose-derived stem cells

Autologous fat grafting represents an attractive source for tissue engineering applications in the field of reconstructive medicine. However, in adipogenic differentiation protocols for human adipose-derived stem cells, the concentration of glucose and insulin varies considerably. With the intent to gain maximum tissue augmentation, we focused on the late phase of adipogenesis. In this study, we modified the differentiation protocol for adipose-derived stem cells by prolongation of the induction period and the application highly concentrated glucose and insulin. Human adipose-derived stem cells were isolated from subcutaneous depots and differentiated in a standard induction medium for the first two weeks, followed by two weeks with varying glucose and insulin concentrations. Morphological changes assessed using Oil-Red-O staining were examined for corresponding alterations in the expression of the adipogenic markers peroxisome proliferator-activated receptor gamma (PPARγ) and lipoprotein lipase (LPL). Furthermore, glucose and lactate levels in conditioned media were monitored over the period of differentiation. We found high-glucose media increasing the level of lipid accumulation and the size of single droplets whereas insulin significantly showed a dose-dependent negative effect on fat storage. However, whereas high glucose stimulated PPARγ transcription, expression levels in insulin-treated cells remained constant. Results permit assumptions that a high-glucose medium intensifies the degree of differentiation in mature adipocytes providing conditions to promote graft volume while we have identified highly concentrated insulin treatment as an inhibitor of lipid storage in the late adipogenic differentiation.

Human intracerebroventricular (ICV) injection of autologous, non-engineered, adipose-derived stromal vascular fraction (ADSVF) for neurodegenerative disorders: results of a 3-year phase 1 study of 113 injections in 31 patients

We have chosen to test the safety of human intracerebroventricular (ICV) brain injections of autologous non-genetically-modified adipose-derived stromal vascular fraction (ADSVF). In this IRB-approved trial, 24 patients received ICV ADSVF via an implanted reservoir between 5/22/14 and 5/22/17. Seven others were injected via their ventriculo-peritoneal shunts. Ten patients had Alzheimer's disease (AD), 6 had amyotrophic lateral sclerosis (ALS), 6 had progressive multiple sclerosis (MS-P), 6 had Parkinson's "Plus" (PD+), 1 had spinal cord injury, 1 had traumatic brain injury, and 1 had stroke. Median age was 74 (range 41-83). Injections were planned every 2-3 months. Thirty-one patients had 113 injections. Patients received SVF injection volumes of 3.5-20 cc (median:4 cc) containing 4.05 × 10⁵ to 6.2 × 10⁷ cells/cc, which contained an average of 8% hematopoietic and 7.5% adipose stem cells. Follow-up ranged from 0 to 36 months (median: 9.2 months). MRIs post injection(s) were unchanged, except for one AD patient whose hippocampal volume increased from < 5th percentile to 48th percentile (NeuroQuant^® volumetric MRI). Of the 10 AD patients, 8 were stable or improved in tests of cognition. Two showed improvement in P-tau and ß-amyloid levels. Of the 6 MS-P patients all are stable or improved. Four of 6 ALS patients died of disease progression. Twelve of 111 injections (11%) led to 1-4 days of transient meningismus, and mild temperature elevation, which resolved with acetaminophen and/or dexamethasone. Two (1.8% of injections) required hospitalization for these symptoms. One patient (0.9% of injections) had his reservoir removed and later replaced for presumed infection. In this Phase 1 safety trial, ADSVF was safely injected into the human brain ventricular system in patients with no other treatment options. Secondary endpoints of clinical improvement or stability were particularly promising in the AD and MS-P groups. These results will be submitted for a Phase 2 FDA-approved trial.

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.

Human adipocytes and CD34+ cells from the stromal vascular fraction of the same adipose tissue differ in their energy metabolic enzyme configuration

Adipose tissue plays a role in energy storage and metabolic balance and is composed of different cell types. The metabolic activity of the tissue itself has been a matter of research for a long time, but comparative data about the energy metabolism of different cell types of human subcutaneous adipose tissue are sparse. Therefore, we compared the activity of major energy metabolic pathways of adipocytes and CD34⁺ cells from the stromal vascular fraction (SVF) separated from the same tissue. This CD34⁺ cell fraction is enriched with adipose tissue-derived mesenchymal progenitors, as they account for the largest proportion of CD34⁺ cells of the SVF. Adipocytes displayed significantly higher mitochondrial enzyme capacities compared to CD34⁺ SVF-cells, as shown by the higher activities of isocitrate dehydrogenase and ß-hydroxyacyl-CoA dehydrogenase. Inversely, the CD34⁺ SVF-cells showed higher capacities for cytosolic carbohydrate metabolism, represented by the activity of glycolysis and the pentose phosphate pathway. Thus, the CD34⁺ SVF-cells may ensure the provision of pentose phosphates and reduction equivalents for the replication of DNA during proliferation. The data indicate that these two cell fractions of the human adipose tissue vary in their metabolic configuration adapted to their physiological demands regarding proliferation and differentiation in vivo.

Regenerative Capacity of Adipose Derived Stem Cells (ADSCs), Comparison with Mesenchymal Stem Cells (MSCs)

Adipose tissue is now on the top one of stem cell sources regarding its accessibility, abundance, and less painful collection procedure when compared to other sources. The adipose derived stem cells (ADSCs) that it contains can be maintained and expanded in culture for long periods of time without losing their differentiation capacity, leading to large cell quantities being increasingly used in cell therapy purposes. Many reports showed that ADSCs-based cell therapy products demonstrated optimal efficacy and efficiency in some clinical indications for both autologous and allogeneic purposes, hence becoming considered as potential tools for replacing, repairing, and regenerating dead or damaged cells. In this review, we analyzed the therapeutic advancement of ADSCs in comparison to bone marrow (BM) and umbilical cord (UC)-mesenchymal stem cells (MSCs) and designed the specific requirements to their best clinical practices and safety. Our analysis was focused on the ADSCs, rather than the whole stromal vascular fraction (SVF) cell populations, to facilitate characterization that is related to their source of origins. Clinical outcomes improvement suggested that these cells hold great promise in stem cell-based therapies in neurodegenerative, cardiovascular, and auto-immunes diseases.

Regenerative Capacity of Adipose Derived Stem Cells (ADSCs), Comparison with Mesenchymal Stem Cells (MSCs)

Adipose tissue is now on the top one of stem cell sources regarding its accessibility, abundance, and less painful collection procedure when compared to other sources. The adipose derived stem cells (ADSCs) that it contains can be maintained and expanded in culture for long periods of time without losing their differentiation capacity, leading to large cell quantities being increasingly used in cell therapy purposes. Many reports showed that ADSCs-based cell therapy products demonstrated optimal efficacy and efficiency in some clinical indications for both autologous and allogeneic purposes, hence becoming considered as potential tools for replacing, repairing, and regenerating dead or damaged cells. In this review, we analyzed the therapeutic advancement of ADSCs in comparison to bone marrow (BM) and umbilical cord (UC)-mesenchymal stem cells (MSCs) and designed the specific requirements to their best clinical practices and safety. Our analysis was focused on the ADSCs, rather than the whole stromal vascular fraction (SVF) cell populations, to facilitate characterization that is related to their source of origins. Clinical outcomes improvement suggested that these cells hold great promise in stem cell-based therapies in neurodegenerative, cardiovascular, and auto-immunes diseases.

A short-term plastic adherence incubation of the stromal vascular fraction leads to a predictable GMP-compliant cell-product

Introduction:Mesenchymal stromal/stem cells (MSCs) derived from fat tissue are an encouraging tool for regenerative medicine. They share properties similar to the bone marrow-derived MSCs, but the amount of MSCs per gram of fat tissue is 500x higher. The fat tissue can easily be digested by collagenase, releasing a heterogeneous cell fraction called stromal vascular fraction (SVF) which contains a variable amount of stromal/stem cells. In Europe, cell products like the SVF derived from fat tissue are considered advanced therapy medicinal product (ATMPs). As a consequence, the manufacturing process has to be approved via GMP-compliant process validation. The problem of the process validation for SVF is the heterogeneity of this fraction.

Methods: Here, we modified existing purification strategies by adding an additional plastic adherence incubation of maximal 20 hours after SVF isolation. The resulting cell fraction was characterized and compared to SVF as well as cultivated adipose-derived stromal/stem cells (ASCs) with respect to viability and cell yield, the expression of surface markers, differentiation potential and cytokine expression.

Results: Short-term incubation significantly reduced the heterogeneity of the resulting cell fraction compared to SVF. The cells were able to differentiate into adipocytes, chondrocytes, and osteoblasts. More importantly, they expressed trophic proteins which have been previously associated with the beneficial effects of MSCs. Furthermore, GMP compliance of the production process described herein was acknowledged by the national regulatory agencies (DE_BB_01_GMP_2017_1018).

Conclusion: Addition of a short purification-step after the SVF isolation is a cheap and fast strategy to isolate a homogeneous uncultivated GMP-compliant cell fraction of ASCs.

Temporospatial localization of telocytes during esophageal morphogenesis in rabbit

Telocytes (TCs) are CD34 and Vimentin positive (+) immunoreactive stromal cells with a small-sized body and several extremely long telopodes. TCs have been described to provide a mechanical support throughout the tissue by making cellular connections (homo- or hetero) to form a 3D network. Such network can transmit the intercellular signaling. Recently, TCs have been described in the esophageal wall. However, information concerning the role of these cells in esophageal organization and development is rare. Thus, we aimed to record the temporo-spatial localization pattern of TCs during esophageal morphogenesis in rabbit. Embryos and fetuses of New Zealand White rabbits (10th-30th gestational days) were collected. Using CD34 immunostaining, TCs have not been demonstrated in the wall of the developing esophagus till the end of the second third of pregnancy. On 24th gestational day, CD34+ TCs were organized in the adventitia of the esophageal wall specifically in close association with the endothelial cells lining the micro vessels. Later on 26th gestational day, CD34+TCs were additionally expressed in the sub-mucosa and in lamina propria (sub-epithelial). On 28th gestational day, additional CD34⁺TCs were detected among the smooth muscle bundles of the muscular layer. Reaching the last gestational day, CD34⁺TCs formed several sheaths in the esophageal wall namely sub epithelial sheath, sub-mucosal, muscular (circular and longitudinal) and inter-muscular sheaths and an outer adventitial one. On the other hand, vimentin immunohistochemistry revealed wider spread TCs positivity in all developmental ages. Presumptively, arrangement of CD34 and vimentin positive TCs in all layers of the developing esophageal wall hypothesizes that TC may play a potential role as a progenitor cell initially in differentiation of the epithelial and muscular precursors and finally in shaping of the various layers of the rabbit esophageal wall during its morphogenesis. TCs are also proposed to be involved in the angiogenesis of the esophageal blood capillaries.

Adipocyte biology: It is time to upgrade to a new model

Globally, the obesity pandemic is profoundly affecting quality of life and economic productivity, but efforts to address this, especially on a pharmacological level, have generally proven unsuccessful to date, serving as a stark demonstration that our understanding of adipocyte biology and pathophysiology is incomplete. To deliver better insight into adipocyte function and obesity, we need improved adipocyte models with a high degree of fidelity in representing the in vivo state and with a diverse range of experimental applications. Adipocyte cell lines, especially 3T3-L1 cells, have been used extensively over many years, but these are limited in terms of relevance and versatility. In this review, I propose that primary adipose-derived stromal/stem cells (ASCs) present a superior model with which to study adipocyte biology ex vivo. In particular, ASCs afford us the opportunity to study adipocytes from different, functionally distinct, adipose depots and to investigate, by means of in vivo/ex vivo studies, the effects of many different physiological and pathophysiological factors, such as age, body weight, hormonal status, diet and nutraceuticals, as well as disease and pharmacological treatments, on the biology of adipocytes and their precursors. This study will give an overview of the characteristics of ASCs and published studies utilizing ASCs, to highlight the areas where our knowledge is lacking. More comprehensive studies in primary ASCs will contribute to an improved understanding of adipose tissue, in healthy and dysfunctional states, which will enhance our efforts to more successfully manage and treat obesity.

Wet milling of large quantities of human excision adipose tissue for the isolation of stromal vascular fraction cells

The isolation of stromal vascular fraction (SVF) cells from excised human adipose tissue, for clinical or research purposes, implies the tedious and time consuming process of manual mincing prior to enzymatic digestion. Since no efficient alternative technique to this current standard procedure has been proposed so far, the aim of this study was to test a milling procedure, using two simple, inexpensive and commercially available manual meat grinders, to process large amounts of adipose tissue. The procedure was assessed on adipose tissue resections from seven human donors and compared to manual mincing with scalpels. The processed adipose tissues were digested and the resulting SVF cells compared in terms of number, clonogenicity and differentiation capacity. After 10 min of processing, either device tested yielded on average sixfold more processed material for subsequent cell isolation than manual mincing. The isolation yield of SVF cells (isolated cells per ml of adipose tissue), their viability, phenotype, clonogenicity and osteogenic/adipogenic differentiation capacity, tested by production of mineralized matrix and lipid vacuoles, respectively, were comparable. This new method is practical and inexpensive and represents an efficient alternative to the current standard for large scale adipose tissue resection processing. A device based on the milling principle could be embedded within a streamlined system for isolation and clinical use of SVF cells from adipose tissue excision.

Loss of Vascular CD34 Results in Increased Sensitivity to Lung Injury

Survival during lung injury requires a coordinated program of damage limitation and rapid repair. CD34 is a cell surface sialomucin expressed by epithelial, vascular, and stromal cells that promotes cell adhesion, coordinates inflammatory cell recruitment, and drives angiogenesis. To test whether CD34 also orchestrates pulmonary damage and repair, we induced acute lung injury in wild-type (WT) and Cd34^-/- mice by bleomycin administration. We found that Cd34^-/- mice displayed severe weight loss and early mortality compared with WT controls. Despite equivalent early airway inflammation to WT mice, CD34-deficient animals developed interstitial edema and endothelial delamination, suggesting impaired endothelial function. Chimeric Cd34^-/- mice reconstituted with WT hematopoietic cells exhibited early mortality compared with WT mice reconstituted with Cd34^-/- cells, supporting an endothelial defect. CD34-deficient mice were also more sensitive to lung damage caused by influenza infection, showing greater weight loss and more extensive pulmonary remodeling. Together, our data suggest that CD34 plays an essential role in maintaining vascular integrity in the lung in response to chemical- and infection-induced tissue damage.

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.

Use of Freshly Isolated Human Adipose Stromal Cells for Clinical Applications

The clinical use of adipose-derived cells is being explored very actively around the world for various human diseases. Adipose tissue is an abundant tissue source that can be easily harvested using liposuction. Human lipoaspirates contain a significant amount of mesenchymal stromal cells, as well as other progenitors and terminally differentiated cell types. This review covers the isolation of adipose stromal vascular fraction (SVF), the quality control and safety analysis of freshly isolated cell suspensions. The comparison between freshly isolated stromal cells and culture expanded cells from adipose tissue samples is also highlighted. This article provides a brief but comprehensive review about SVF isolation in the clinical setting, cell characterization, and biological potency of freshly obtained adipose stromal cells.

Adipose tissue-derived stromal vascular fraction in regenerative medicine: a brief review on biology and translation

Adipose/fat tissue provides an abundant source of stromal vascular fraction (SVF) cells for immediate administration and can also give rise to a substantial number of cultured, multipotent adipose-derived stromal cells (ADSCs). Recently, both SVF and ADSCs have gained wide-ranging translational significance in regenerative medicine. Initially used for cosmetic breast enhancement, this mode of treatment has found use in many diseases involving immune disorders, tissue degeneration, and ischaemic conditions. In this review, we try to address several important aspects of this field, outlining the biology, technology, translation, and challenges related to SVF- and ADSC-based therapies. Starting from the basics of SVF and ADSC isolation, we touch upon recently developed technologies, addressing elements of novel methods and devices under development for point-of-care isolation of SVF. Characterisation of SVF cells and ADSCs is also an evolving area and we look into unusual expression of CD34 antigen as an interesting marker for such purposes. Based on reports involving different cells of the SVF, we draw a potential mode of action, focussing on angiogenesis since it involves multiple cells, unlike immunomodulation which is governed predominantly by ADSCs. We have looked into the latest research, experimental therapies, and clinical trials which are utilising SVF/ADSCs in conditions such as multiple sclerosis, Crohn’s disease, peripheral neuropathy, osteoarthritis, diabetic foot ulcer, and so forth. However, problems have arisen with regards to the lack of proper regulatory guidelines for such therapies and, since the introduction of US Food and Drug Administration draft guidelines and the Reliable and Effective Growth for Regenerative Health Options that Improve Wellness (REGROW) Act, the debate became more public with regards to safe and efficacious use of these cells.

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.

Semi-automated extraction and characterization of Stromal Vascular Fraction using a new medical device

INTRODUCTION

The stem cell rich Stromal Vascular Fraction (SVF) can be harvested by processing lipo-aspirate or fat tissue with an enzymatic digestion followed by centrifugation. To date neither a standardised extraction method for SVF nor a generally admitted protocol for cell application in patients exists. A novel commercially available semi-automated device for the extraction of SVF promises sterility, consistent results and usability in the clinical routine. The aim of this work was to compare the quantity and quality of the SVF between the new system and an established manual laboratory method.

MATERIAL AND METHODS

SVF was extracted from lipo-aspirate both by a prototype of the semi-automated UNiStation™ (NeoGenesis, Seoul, Korea) and by hand preparation with common laboratory equipment. Cell composition of the SVF was characterized by multi-parametric flow-cytometry (FACSCanto-II, BD Biosciences). The total cell number (quantity) of the SVF was determined as well the percentage of cells expressing the stem cell marker CD34, the leucocyte marker CD45 and the marker CD271 for highly proliferative stem cells (quality).

RESULTS

Lipo-aspirate obtained from six patients was processed with both the novel device (d) and the hand preparation (h) which always resulted in a macroscopically visible SVF. However, there was a tendency of a fewer cell yield per gram of used lipo-aspirate with the device (d: 1.1×105±1.1×105 vs. h: 2.0×105±1.7×105; p = 0.06). Noteworthy, the percentage of CD34+ cells was significantly lower when using the device (d: 57.3% ±23.8% vs. h: 74.1% ±13.4%; p = 0.02) and CD45+ leukocyte counts tend to be higher when compared to the hand preparation (d: 20.7% ±15.8% vs. h: 9.8% ±7.1%; p = 0.07). The percentage of highly proliferative CD271+ cells was similar for both methods (d:12.9% ±9.6% vs. h: 13.4% ±11.6%; p = 0.74) and no differences were found for double positive cells of CD34+/CD45+ (d: 5.9% ±1.7% vs. h: 1.7% ±1.1%; p = 0.13), CD34+/CD271+ (d: 24.1% ±12.0% vs. h: 14.2% ±8.5%; p = 0.07).

DISCUSSION

The semi-automated closed system provides a considerable amount of sterile SVF with high reproducibility. Furthermore, the SVF extracted by both methods showed a similar cell composition which is in accordance with the data from literature. This semi-automated device offers an opportunity to take research and application of the SVF one step further to the clinic.

Skin Tissue Engineering: Application of Adipose-Derived Stem Cells

Perception of the adipose tissue has changed dramatically over the last few decades. Identification of adipose-derived stem cells (ASCs) ultimately transformed paradigm of this tissue from a passive energy depot into a promising stem cell source with properties of self-renewal and multipotential differentiation. As compared to bone marrow-derived stem cells (BMSCs), ASCs are more easily accessible and their isolation yields higher amount of stem cells. Therefore, the ASCs are of high interest for stem cell-based therapies and skin tissue engineering. Currently, freshly isolated stromal vascular fraction (SVF), which may be used directly without any expansion, was also assessed to be highly effective in treating skin radiation injuries, burns, or nonhealing wounds such as diabetic ulcers. In this paper, we review the characteristics of SVF and ASCs and the efficacy of their treatment for skin injuries and disorders.

C-Kit, CD34 & α-SMA Immunohistochemical Features in Classic Kaposi Sarcoma and Kaposiform Hemangioendothelioma

Purpose & Methods:

The aim of this work was to study the clinicopathological features of Kaposi sarcoma (KS) & kaposiform hemangioendothelioma (KHE) and analyze their immunohistochemical expression of c-Kit, CD34, α-SMA. The study was performed on cutaneous 10 classic KS & 8 KHE.

Results:

KHE shows several dilated lymphatic channels, focal capillary formation, lack of nuclear atypia and mitosis within tumor cells. These features help to exclude Kaposi sarcoma in spite of the kaposiform pattern of tumor cells. C-Kit was expressed by tumor cells in all KHE cases and in 60% only of KS. All elements within both tumor groups expressed CD34 antibody. α-SMA was expressed by tumor cells in 70% of KS cases and none of KHE.

Conclusion:

C-Kit and CD34 seem to be reliable at labeling KS and KHE as they can help in diagnosis of these tumors in routinely processed tissue but they don’t differentiate between them. If α-SMA also labeled the tumor, then KHE diagnosis can be ruled out. KS & KHE exemplify stem cell tumors that could give smooth muscle cell–like phenotype in KS. Anti C-kit therapy should be tested in KS & KHE to prevent recurrence.

Upregulation of CC Chemokine Receptor 7 (CCR7) Enables Migration of Xenogeneic Human Adipose-Derived Mesenchymal Stem Cells to Rat Secondary Lymphoid Organs

Background

CC chemokine receptor 7 (CCR7) expression is vital for cell migration to secondary lymphoid organs (SLOs). Our previous work showed that inducing CCR7 expression enabled syngeneic mesenchymal stem cells (MSCs) to migrate into SLOs, resulting in enhanced immunosuppressive performance in mice. Given that human adipose-derived stem cells (hASCs) are widely used in clinical therapy, we further investigated whether upregulation of CCR7 enables xenogeneic hASCs to migrate to rat SLOs.

Material/Methods

hASCs rarely express CCR7; therefore, hASCs were transfected with lentivirus encoding rat CCR7 (rCCR7) plus green fluorescence protein (GFP) or GFP alone. CCR7 mRNA and cell surface expression of rCCR7-hASCs and GFP-hASCs were examined by reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry (FCM), respectively. The phenotype, differentiation, and proliferation capacity of each cell type was also determined. To examine migration, rCCR7-hASCs and GFP-hASCs were injected intravenously into Lewis rats, and the proportion of GFP-positive cells in the spleen and lymph nodes was determined with FCM.

Results

mRNA and cell surface protein expression of CCR7 was essentially undetectable in hASCs and GFP-ASCs; however, CCR7 was highly expressed in rCCR7-ASCs. rCCR7-hASCs, GFP-hASCs, and hASCs shared a similar immunophenotype, and maintained the ability of multilineage differentiation and proliferation. In addition, the average proportion of GFP-positive cells was significantly higher following transplantation of rCCR7-hASCs compared with GFP-hASCs (p<0.01).

Conclusions

These results suggest that upregulation of rat CCR7 expression does not change the phenotype, differentiation, or proliferation capacity of hASCs, but does enable efficient migration of hASCs to rat SLOs.

Transplantation of Immortalized CD34+ and CD34- Adipose-Derived Stem Cells Improve Cardiac Function and Mitigate Systemic Pro-Inflammatory Responses

Adipose-derived stem cells (ADSCs) have the potential to differentiate into various cell lineages and they are easily obtainable from patients, which makes them a promising candidate for cell therapy. However, a drawback is their limited life span during in vitro culture. Therefore, hTERT-immortalized CD34+ and CD34- mouse ADSC lines (mADSCs^hTERT) tagged with GFP were established. We evaluated the proliferation capacity, multi-differentiation potential, and secretory profiles of CD34+ and CD34- mADSCs^hTERTin vitro, as well as their effects on cardiac function and systemic inflammation following transplantation into a rat model of acute myocardial infarction (AMI) to assess whether these cells could be used as a novel cell source for regeneration therapy in the cardiovascular field. CD34+ and CD34- mADSCs^hTERT demonstrated phenotypic characteristics and multi-differentiation potentials similar to those of primary mADSCs. CD34+ mADSCs^hTERT exhibited a higher proliferation ability compared to CD34- mADSCs^hTERT, whereas CD34- mADSCs^hTERT showed a higher osteogenic differentiation potential compared to CD34+ mADSCs^hTERT. Primary mADSCs, CD34+, and CD34- mADSCs^hTERT primarily secreted EGF, TGF-β1, IGF-1, IGF-2, MCP-1, and HGFR. CD34+ mADSCs^hTERT had higher secretion of VEGF and SDF-1 compared to CD34- mADSCs^hTERT. IL-6 secretion was severely reduced in both CD34+ and CD34- mADSCs^hTERT compared to primary mADSCs. Transplantation of CD34+ and CD34- mADSCs^hTERT significantly improved the left ventricular ejection fraction and reduced infarct size compared to AMI-induced rats after 28 days. At 28 days after transplantation, engraftment of CD34+ and CD34- mADSCs^hTERT was confirmed by positive Y chromosome staining, and differentiation of CD34+ and CD34- mADSCs^hTERT into endothelial cells was found in the infarcted myocardium. Significant decreases were observed in circulating IL-6 levels in CD34+ and CD34- mADSCs^hTERT groups compared to the AMI-induced control group. Transplantation of CD34- mADSCs^hTERT significantly reduced circulating MCP-1 levels compared to the AMI control and CD34+ mADSCs^hTERT groups. GFP-tagged CD34+ and CD34- mADSCs^hTERT are valuable resources for cell differentiation studies in vitro as well as for regeneration therapy in vivo.

Adipose tissue-derived mesenchymal stem cells and platelet-rich plasma: stem cell transplantation methods that enhance stemness

Because of their ease of isolation and relative abundance, adipose-derived mesenchymal stem cells (ASCs) are a particularly attractive autologous cell source for various therapeutic purposes. ASCs retain a high proliferation capacity in vitro and have the ability to undergo extensive differentiation into multiple cell lineages. Moreover, ASCs secrete a wide range of growth factors that can stimulate tissue regeneration. Therefore, the clinical use of ASCs is feasible. However, the potential of ASCs differs depending on the donor's medical condition, including diseases such as diabetes. Recent studies demonstrated that ASCs from diabetic donors exhibit reduced proliferative potential and a smaller proportion of stem cell marker-positive cells. Therefore, to ensure the success of regenerative medicine, tissue engineering methods must be improved by the incorporation of factors that increase the proliferation and differentiation of stem/progenitor cells when autologous cells are used. Platelet-rich plasma (PRP), which contains high levels of diverse growth factors that can stimulate stem cell proliferation and cell differentiation in the context of tissue regeneration, has recently been identified as a biological material that could be applied to tissue regeneration. Thus, co-transplantation of ASCs and PRP represents a promising novel approach for cell therapy in regenerative medicine. In this review, we describe the potential benefits of adding PRP to ASCs and preclinical and clinical studies of this approach in various medical fields. We also discuss the mechanisms of PRP action and future cell-based therapies using co-transplantation of ASCs and PRP.

Peripheral Nerve Repair: Multimodal Comparison of the Long-Term Regenerative Potential of Adipose Tissue-Derived Cells in a Biodegradable Conduit

Tissue engineering is a popular topic in peripheral nerve repair. Combining a nerve conduit with supporting adipose-derived cells could offer an opportunity to prevent time-consuming Schwann cell culture or the use of an autograft with its donor site morbidity and eventually improve clinical outcome. The aim of this study was to provide a broad overview over promising transplantable cells under equal experimental conditions over a long-term period. A 10-mm gap in the sciatic nerve of female Sprague-Dawley rats (7 groups of 7 animals, 8 weeks old) was bridged through a biodegradable fibrin conduit filled with rat adipose-derived stem cells (rASCs), differentiated rASCs (drASCs), human (h)ASCs from the superficial and deep abdominal layer, human stromal vascular fraction (SVF), or rat Schwann cells, respectively. As a control, we resutured a nerve segment as an autograft. Long-term evaluation was carried out after 12 weeks comprising walking track, morphometric, and MRI analyses. The sciatic functional index was calculated. Cross sections of the nerve, proximal, distal, and in between the two sutures, were analyzed for re-/myelination and axon count. Gastrocnemius muscle weights were compared. MRI proved biodegradation of the conduit. Differentiated rat ASCs performed significantly better than undifferentiated rASCs with less muscle atrophy and superior functional results. Superficial hASCs supported regeneration better than deep hASCs, in line with published in vitro data. The best regeneration potential was achieved by the drASC group when compared with other adipose tissue-derived cells. Considering the ease of procedure from harvesting to transplanting, we conclude that comparison of promising cells for nerve regeneration revealed that particularly differentiated ASCs could be a clinically translatable route toward new methods to enhance peripheral nerve repair.

Human dental pulp stem cells (hDPSCs): isolation, enrichment and comparative differentiation of two sub-populations

Background

Human dental pulp represents a suitable alternative source of stem cells for the purpose of cell-based therapies in regenerative medicine, because it is relatively easy to obtain it, using low invasive procedures. This study characterized and compared two subpopulations of adult stem cells derived from human dental pulp (hDPSCs). Human DPSCs, formerly immune-selected for STRO-1 and c-Kit, were separated for negativity and positivity to CD34 expression respectively, and evaluated for cell proliferation, stemness maintenance, cell senescence and multipotency.

Results

The STRO-1⁺/c-Kit⁺/CD34⁺ hDPSCs showed a slower proliferation, gradual loss of stemness, early cell senescence and apoptosis, compared to STRO-1⁺/c-Kit⁺/CD34⁻ hDPSCs. Both the subpopulations demonstrated similar abilities to differentiate towards mesoderm lineages, whereas a significant difference was observed after the neurogenic induction, with a greater commitment of STRO-1⁺/c-Kit⁺/CD34⁺ hDPSCs. Moreover, undifferentiated STRO-1⁺/c-Kit⁺/CD34⁻ hDPSCs did not show any expression of CD271 and nestin, typical neural markers, while STRO-1⁺/c-Kit⁺/CD34⁺ hDPSCs expressed both.

Conclusions

These results suggest that STRO-1⁺/c-Kit⁺/CD34⁻ hDPSCs and STRO-1⁺/c-Kit⁺/CD34⁺ hDPSCs might represent two distinct stem cell populations, with different properties. These results trigger further analyses to deeply investigate the hypothesis that more than a single stem cell population resides within the dental pulp, to better define the flexibility of application of hDPSCs in regenerative medicine.

Obesity and weight loss could alter the properties of adipose stem cells?

The discovery that adipose tissue represents an interesting source of multipotent stem cells has led to many studies exploring the clinical potential of these cells in cell-based therapies. Recent advances in understanding the secretory capacity of adipose tissue and the role of adipokines in the development of obesity and associated disorders have added a new dimension to the study of adipose tissue biology in normal and diseased states. Subcutaneous adipose tissue forms the interface between the clinical application of regenerative medicine and the establishment of the pathological condition of obesity. These two facets of adipose tissue should be understood as potentially related phenomena. Because of the functional characteristics of adipose stem cells, these cells represent a fundamental tool for understanding how these two facets are interconnected and could be important for therapeutic applications. In fact, adipose tissue stem cells have multiple functions in obesity related to adipogenic, angiogenic and secretory capacities. In addition, we have also previously described a predominance of larger blood vessels and an adipogenic memory in the subcutaneous adipose tissue after massive weight loss subsequent to bariatric surgery (ex-obese patients). Understanding the reversibility of the behavior of adipose stem cells in obeses and in weight loss is relevant to both physiological studies and the potential use of these cells in regenerative medicine.

Concise review: evidence for CD34 as a common marker for diverse progenitors

CD34 is a transmembrane phosphoglycoprotein, first identified on hematopoietic stem and progenitor cells. Clinically, it is associated with the selection and enrichment of hematopoietic stem cells for bone marrow transplants. Due to these historical and clinical associations, CD34 expression is almost ubiquitously related to hematopoietic cells, and it is a common misconception that CD34-positive (CD34⁺) cells in nonhematopoietic samples represent hematopoietic contamination. The prevailing school of thought states that multipotent mesenchymal stromal cells (MSC) do not express CD34. However, strong evidence demonstrates CD34 is expressed not only by MSC but by a multitude of other nonhematopoietic cell types including muscle satellite cells, corneal keratocytes, interstitial cells, epithelial progenitors, and vascular endothelial progenitors. In many cases, the CD34⁺ cells represent a small proportion of the total cell population and also indicate a distinct subset of cells with enhanced progenitor activity. Herein, we explore common traits between cells that express CD34, including associated markers, morphology and differentiation potential. We endeavor to highlight key similarities between CD34⁺ cells, with a focus on progenitor activity. A common function of CD34 has yet to be elucidated, but by analyzing and understanding links between CD34⁺ cells, we hope to be able to offer an insight into the overlapping properties of cells that express CD34. Stem Cells2014;32:1380–1389

Mesenchymal stem cells: potential for therapy and treatment of chronic non-healing skin wounds

Wound healing is a complex physiological process including overlapping phases (hemostatic/inflammatory, proliferating and remodeling phases). Every alteration in this mechanism might lead to pathological conditions of different medical relevance. Treatments for chronic non-healing wounds are expensive because reiterative treatments are needed. Regenerative medicine and in particular mesenchymal stem cells approach is emerging as new potential clinical application in wound healing. In the past decades, advance in the understanding of molecular mechanisms underlying wound healing process has led to extensive topical administration of growth factors as part of wound care. Currently, no definitive treatment is available and the research on optimal wound care depends upon the efficacy and cost-benefit of emerging therapies. Here we provide an overview on the novel approaches through stem cell therapy to improve cutaneous wound healing, with a focus on diabetic wounds and Systemic Sclerosis-associated ulcers, which are particularly challenging. Current and future treatment approaches are discussed with an emphasis on recent advances.

Behavior of in situ human native adipose tissue CD34+ stromal/progenitor cells during different stages of repair. Tissue-resident CD34+ stromal cells as a source of myofibroblasts

CD34+ adipose stromal cells are scattered in the adipose tissue and found in the CD34+ population of the stromal vascular fraction (SVF). This fraction includes adipose-derived stromal/stem/progenitor cells (ASCs), which have attracted considerable attention and show great promise for the future of regenerative medicine. Studies in this field have been undertaken mainly in vitro. In this work, however, we assessed the characteristics of human adipose tissue-resident CD34+ stromal cells in normal conditions and when activated in vivo during inflammatory/repair processes at different stages of evolution. In normal adipose tissue, these cells showed a characteristic location (peri/paravascular and between adipocytes), a fusiform or stellate morphology, long and moniliform processes, and scarce organelles. During inflammatory/repair stages, native CD34+ stromal cells increased in size, proliferated, developed numerous organelles of synthesis, lost CD34 expression, and differentiated into myofibroblasts (αSMA expression and typical ultrastructure). In double-stained sections, cells expressing both CD34 and αSMA were observed. CD34 expression correlated positively with a high proliferative capacity (Ki-67 expression). Conversely, CD34 expression was lost with successive mitoses and with increased numbers of macrophages in the granulation tissue. CD34+ stromal cell behavior varied depending on proximity to (with myofibroblast differentiation) or remoteness from (with activated plump cells conserving CD34 expression) injury. In conclusion, our observations point to human adipose tissue-resident CD34+ stromal cells as an important source of myofibroblasts during inflammatory/repair processes. Moreover, stromal cell activation may occur with or without αSMA expression (with or without myofibroblast transformation) and with loss or persistence of CD34 expression, respectively.

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

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

Three specific antigens to isolate endothelial progenitor cells from human liposuction material

BACKGROUND AIMS

Human endothelial progenitor cells (EPC) play an important role in regenerative medicine and contribute to neovascularization on vessel injury. They are usually enriched from peripheral blood, cord blood and bone marrow. In human fat tissue, EPC are rare and their isolation remains a challenge.

METHODS

Fat tissue was prepared by collagenase digestion, and the expression of specific marker proteins was evaluated by flow cytometry in the stromal vascular fraction (SVF). For enrichment, magnetic cell sorting was performed with the use of CD133 microbeads and EPC were cultured until colonies appeared. A second purification was performed with CD34; additional isolation steps were performed with the use of a combination of CD34 and CD31 microbeads. Enriched cells were investigated by flow cytometry for the expression of endothelial specific markers, by Matrigel assay and by the uptake of acetylated low-density lipoprotein.

RESULTS

The expression pattern confirmed the heterogeneous nature of the SVF, with rare numbers of CD133+ detectable. EPC gained from the SVF by magnetic enrichment showed cobblestone morphology of outgrowth endothelial cells and expressed the specific markers CD31, CD144, vascular endothelial growth factor (VEGF)R2, CD146, CD73 and CD105. Functional integrity was confirmed by uptake of acetylated low-density lipoprotein and the formation of tube-like structures on Matrigel.

CONCLUSIONS

Rare EPC can be enriched from human fat tissue by magnetic cell sorting with the use of a combination of microbeads directed against CD133, an early EPC marker, CD34, a stem cell marker, and CD31, a typical marker for endothelial cells. In culture, they differentiate into EC and hence could have the potential to contribute to neovascularization in regenerative medicine.