Role of c-Jun N-terminal kinase in the PDGF-induced proliferation and migration of human adipose tissue-derived mesenchymal stem cells

Angiopoietin-like growth factor-derived peptides as biological activators of adipose-derived mesenchymal stromal cells

Adipose-derived mesenchymal stromal cells (AD-MSCs) are an essential issue in modern medicine. Extensive preclinical and clinical studies have shown that mesenchymal stromal/stem cells, including AD-MSCs, have specific properties (ability to differentiate into other cells, recruitment to the site of injury) of particular importance in the regenerative process. Ongoing research aims to elucidate factors supporting AD-MSC culture and differentiation in vitro. Angiopoietin-like proteins (ANGPTLs), known for their pleiotropic effects in lipid and glucose metabolism, may play a significant role in this context. Regeneration is a complex and dynamic process controlled by many factors. ANGPTL6 (Angiopoietin-related growth factor, AGF), among many activities modulated the biological activity of stem cells. This study examined the influence of synthesized AGF-derived peptides, designated as AGF9 and AGF27, on AD-MSCs. AGF9 and AGF27 enhanced the viability and migration of AD-MSCs and acted as a chemotactic factor for these cells. AGF9 stimulated chondrogenesis and lipid synthesis during AD-MSCs differentiation, influenced AD-MSCs cytokine secretion and modulated transcriptome for such basic cell activities as migration, transport of molecules, and apoptosis. The ability of AGF9 to modulate the biological activity of AD-MSCs warrants the consideration of this peptide a noteworthy therapeutic agent that deserves further investigation for applications in regenerative medicine.

Predominant control of PDGF/PDGF receptor signaling in the migration and proliferation of human adipose‑derived stem cells under culture conditions with a combination of growth factors

Human adipose-derived stem cells (hASCs) play important roles in regenerative medicine and tissue engineering. However, their clinical applications are limited because of their instability during cell culture. Platelet lysates (PLTs) contain large amounts of growth factors that are useful for manufacturing cellular products. Platelet-derived growth factor (PDGF) is a major growth factor in PLTs and a potent mitogen in hASCs. To optimize growth conditions, the effects of a combination of growth factors on the promotion of hASC proliferation were investigated. Moreover, PDGF-BB combined with vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) markedly enhanced the viability of hASCs compared with the effects of PDGF-BB alone. Neither VEGF nor HGF had any effect alone. All growth factor receptor inhibitors inhibited cell proliferation. Wound healing assays revealed that VEGF and HGF stimulated PDGF-dependent cell migration. The effects of these growth factors on the activation of their cognate receptors and signaling enzymes were assessed using immunoblotting. Phosphorylation of PDGF receptor (PDGFR)β, VEGF receptor (VEGFR)2 and MET proto-oncogene and receptor tyrosine kinase was induced by PDGF-BB treatment, and was further increased by treatment with PDGF-BB/VEGF and PDGF-BB/HGF. The levels of phospho-ERK1/2 and phospho-p38MAPK were increased by these treatments in parallel. Furthermore, the expression levels of SRY-box transcription factor 2 and peroxisome proliferator-activated receptor g were increased in PDGF-BB-treated cells, and PDGF-BB played a dominant role in spheroid formation. The findings of the present study highlighted that PDGF/PDGFR signaling played a predominant role in the proliferation and migration of hASCs, and suggested that PDGF was responsible for the efficacy of other growth factors when hASCs were cultured with PLTs.

Activation of cell adhesion and migration is an early event of platelet-rich plasma (PRP)-dependent stimulation of human adipose-derived stem/stromal cells

Stem cell therapy is a promising treatment in regenerative medicine. Human adipose-derived stem/stromal cells (hASCs), a type of mesenchymal stem cell, are easy to harvest. In plastic and aesthetic surgery, hASC may be applied in the treatment of fat grafting, wound healing, and scar remodeling. Platelet-rich plasma (PRP) contains various growth factors, including platelet-derived growth factor (PDGF), which accelerates wound healing. We previously reported that PRP promotes the proliferation of hASC via multiple signaling pathways, and we evaluated the effect of PRP on the stimulation of hASC adhesion and migration, leading to the proliferation of these cells. When hASCs were treated with PRP, AKT, ERK1/2, paxillin and RhoA were rapidly activated. PRP treatment led to the formation of F-actin stress fibers. Strong signals for integrin β1, paxillin and RhoA at the cell periphery of RPR-treated cells indicated focal adhesion. PRP promoted cell adhesion and movement of hASC, compared with the control group. Imatinib, an inhibitor of the PDGF receptor tyrosine kinase, inhibited the promotion of PRP-dependent cell migration. PDGF treatment of hASCs also stimulated cell adhesion and migration but to a lesser extent than PRP treatment. PRP promoted the adhesion and the migration of hASC, mediated by the activation of AKT in the integrin signaling pathway. PRP treatment was more effective than PDGF treatment in enhancing cell migration. Thus, the ability of PRPs to promote migration of hASC to enhance cell growth is evident.

Ultrasound-targeted microbubble destruction promotes PDGF-primed bone mesenchymal stem cell transplantation for myocardial protection in acute Myocardial Infarction in rats

BACKGROUND

Ultrasound-targeted microbubble destruction (UTMD) has emerged as a promising strategy for the targeted delivery of bone marrow mesenchymal stem cells (MSCs) to the ischemic myocardium. However, the limited migration capacity and poor survival of MSCs remains a major therapeutic barrier. The present study was performed to investigate the synergistic effect of UTMD with platelet-derived growth factor BB (PDGF-BB) on the homing of MSCs for acute myocardial infarction (AMI).

METHODS

MSCs from male donor rats were treated with PDGF-BB, and a novel microbubble formulation was prepared using a thin-film hydration method. In vivo, MSCs with or without PDGF-BB pretreatment were transplanted by UTMD after inducing AMI in experimental rats. The therapeutic efficacy of PDGF-BB-primed MSCs on myocardial apoptosis, angiogenesis, cardiac function and scar repair was estimated. The effects and molecular mechanisms of PDGF-BB on MSC migration and survival were explored in vitro.

RESULTS

The results showed that the biological effects of UTMD increased the local levels of stromal-derived factor-1 (SDF-1), which promoted the migration of transplanted MSCs to the ischemic region. Compared with UTMD alone, UTMD combined with PDGF-BB pretreatment significantly increased the cardiac homing of MSCs, which subsequently reduced myocardial apoptosis, promoted neovascularization and tissue repair, and increased cardiac function 30 days after MI. The vitro results demonstrated that PDGF-BB enhanced MSC migration and protected these cells from H2O2-induced apoptosis. Mechanistically, PDGF-BB pretreatment promoted MSC migration and inhibited H2O2-induced MSC apoptosis via activation of the phosphatidylinositol 3-kinase/serine-threonine kinase (PI3K/Akt) pathway. Furthermore, crosstalk between PDGF-BB and stromal-derived factor-1/chemokine receptor 4 (SDF-1/CXCR4) is involved in the PI3K/AKT signaling pathway.

CONCLUSION

The present study demonstrated that UTMD combined with PDGF-BB treatment could enhance the homing ability of MSCs, thus alleviating AMI in rats. Therefore, UTMD combined with PDGF-BB pretreatment may offer exciting therapeutic opportunities for strengthening MSC therapy in ischemic diseases.

Growth factors-based beneficial effects of platelet lysate on umbilical cord-derived stem cells and their synergistic use in osteoarthritis treatment

Poor viability of mesenchymal stem cells (MSCs) at the transplanted site often hinders the efficacy of MSCs-based therapy. Platelet lysate (PL) contains rich amounts of growth factors, which benefits cell growth. This study aimed to explore how human PL benefits umbilical cord-derived MSCs (huc-MSCs), and whether they have synergistic potential in osteoarthritis (OA) treatment. As quality control, flow cytometry and specific staining were performed to identify huc-MSCs, and ELISA was used to quantify growth factors in PL. CCK-8 and flow cytometry assays were performed to evaluate the effects of PL on the cell viability and cell cycle progression of huc-MSCs. Wound healing and transwell assays were conducted to assess the migration of huc-MSCs. RNA sequencing, real time PCR, and Western blot assays were conducted to explore the growth factors-based mechanism of PL. The in vitro results showed that PL significantly promoted the proliferation, cell cycle, and migration of huc-MSCs by upregulating relevant genes/proteins and activating beclin1-dependent autophagy via the AMPK/mTOR signaling pathway. The main growth factors (PDGF-AA, IGF-1, TGF-β, EGF, and FGF) contributed to the effects of PL in varying degrees. The in vivo data showed that combined PL and huc-MSCs exerted significant synergistic effect against OA. The overall study determined the beneficial effects and mechanism of PL on huc-MSCs and indicated PL as an adjuvant for huc-MSCs in treating OA. This is the first report on the growth factors-based mechanism of PL on huc-MSCs and their synergistic application. It provides novel knowledge of PLʹs roles and offers a promising strategy for stem cell-based OA therapy by combining PL and huc-MSCs.

Synaptic effects of estrogen

The concept that estradiol may act as a local neuromodulator in the brain, rapidly affecting connectivity and synaptic function, has been firmly established by research over the last 30 years. De novo synthesis of estradiol within the brain as well as signaling mechanisms mediating responses to the hormone have been demonstrated, along with morphological evidence indicating rapid changes in synaptic input following increases in local estradiol levels. These rapid synaptic effects may play important roles in both physiological and pathophysiological responses to changes in circulating hormone levels, as well as in neurodegenerative disease. How local effects of estradiol on synaptic plasticity are integrated into changes in the overall activity of neural networks in the brain, however, remains a subject that is only incompletely understood.

Exogenous Signaling Molecules Released from Aptamer-Functionalized Hydrogels Promote the Survival of Mesenchymal Stem Cell Spheroids

Mesenchymal stem cells (MSCs) have a very low survival rate after in vivo delivery, which limits their great promise for treating human diseases. Various strategies have been studied to overcome this challenge. However, an overlooked but important potential is to apply exogenous signaling molecules as biochemical cues to promote MSC survival, presumably because it is well-known that MSCs themselves can release a variety of potent signaling molecules. Thus, the purpose of this work was to examine and understand whether the release of exogenous signaling molecules from hydrogels can promote the survival of MSC spheroids. Our data show that more vascular endothelial growth factor (VEGF) but not platelet-derived growth factor BB (PDGF-BB) were released from MSC spheroids in comparison with 2D cultured MSCs. Aptamer-functionalized fibrin hydrogel (aFn) could release exogenous VEGF and PDGF-BB in a sustained manner. PDGF-BB-loaded aFn promoted MSC survival by ∼70% more than VEGF-loaded aFn under the hypoxic condition in vitro. Importantly, PDGF-BB-loaded aFn could double the survival rate of MSC spheroids in comparison with VEGF-loaded aFn during the one-week test in vivo. Therefore, this work demonstrated that defined exogenous signaling molecules (e.g., PDGF-BB) can function as biochemical cues for promoting the survival of MSC spheroids in vivo.

In vitro study of cartilage tissue engineering using human adipose-derived stem cells induced by platelet-rich plasma and cultured on silk fibroin scaffold

BACKGROUND

Cartilage tissue engineering is a promising technique for repairing cartilage defect. Due to the limitation of cell number and proliferation, mesenchymal stem cells (MSCs) have been developed as a substitute to chondrocytes as a cartilage cell-source. This study aimed to develop cartilage tissue from human adipose-derived stem cells (ADSCs) cultured on a Bombyx mori silk fibroin scaffold and supplemented with 10% platelet-rich plasma (PRP).

METHODS

Human ADSCs and PRP were characterized. A silk fibroin scaffold with 500 μm pore size was fabricated through salt leaching. ADSCs were then cultured on the scaffold (ADSC-SS) and supplemented with 10% PRP for 21 days to examine cell proliferation, chondrogenesis, osteogenesis, and surface marker expression. The messenger ribonucleic acid (mRNA) expression of type 2 collagen, aggrecan, and type 1 collagen was analysed. The presence of type 2 collagen confirming chondrogenesis was validated using immunocytochemistry. The negative and positive controls were ADSC-SS supplemented with 10% foetal bovine serum (FBS) and ADSC-SS supplemented with commercial chondrogenesis medium, respectively.

RESULTS

Cells isolated from adipose tissue were characterized as ADSCs. Proliferation of the ADSC-SS PRP was significantly increased (p < 0.05) compared to that of controls. Chondrogenesis was observed in ADSC-SS PRP and was confirmed through the increase in glycosaminoglycans (GAG) and transforming growth factor-β1 (TGF-β1) secretion, the absence of mineral deposition, and increased surface marker proteins on chondrogenic progenitors. The mRNA expression of type 2 collagen in ADSC-SS PRP was significantly increased (p < 0.05) compared to that in the negative control on days 7 and 21; however, aggrecan was significantly increased on day 14 compared to the controls. ADSC-SS PRP showed stable mRNA expression of type 1 collagen up to 14 days and it was significantly decreased on day 21. Confocal analysis showed the presence of type 2 collagen in the ADSC-SS PRP and positive control groups, with high distribution outside the cells forming the extracellular matrix (ECM) on day 21.

CONCLUSION

Our study showed that ADSC-SS with supplemented 10% PRP medium can effectively support chondrogenesis of ADSCs in vitro and promising for further development as an alternative for cartilage tissue engineering in vivo.

Transforming Growth Factor β-Activated Kinase 1 Regulates Mesenchymal Stem Cell Proliferation Through Stabilization of Yap1/Taz Proteins

Bone marrow-derived mesenchymal stem cells (BMMSCs) are multipotent stem cells capable of differentiation into a variety of cell types, proliferation, and production of clinically useful secretory factors. These advantages make BMMSCs highly useful for cell transplantation therapy. However, the molecular network underlying BMMSC proliferation remains poorly understood. Here, we showed that TGFβ-activated kinase 1 (Tak1) is a critical molecule that regulates the activation of cell cycling and that Tak1 inhibition leads to quiescence in BMMSCs both in vivo and in vitro. Mechanistically, Tak1 was phosphorylated by growth factor stimulations, allowing it to bind and stabilize Yap1/Taz, which could then be localized to the nucleus. We also demonstrated that the quiescence induction by inhibiting Tak1 increased oxidized stress tolerance and improved BMMSC engraftment in intramuscular and intrabone marrow cell transplantation models. This study reveals a novel pathway controlling BMMSC proliferation and suggests a useful method to improve the therapeutic effect of BMMSC transplantation. Stem Cells 2019;37:1595-1605.

Activated platelet-rich plasma improves cartilage regeneration using adipose stem cells encapsulated in a 3D alginate scaffold

In the current study, the effect of superimposing platelet-rich plasma (PRP) on different culture mediums in a three-dimensional alginate scaffold encapsulated with adipose-derived mesenchymal stem cells for cartilage tissue repair is reported. The three-dimensional alginate scaffolds with co-administration of PRP and/or chondrogenic supplements had a significant effect on the differentiation of adipose mesenchymal stem cells into mature cartilage, as assessed by an evaluation of the expression of cartilage-related markers of Sox9, collagen II, aggrecan and collagen, and glycosaminoglycan assays. For in vivo studies, following induction of osteochondral lesion in a rabbit model, a high degree of tissue regeneration in the alginate plus cell group (treated with PRP plus chondrogenic medium) compared with other groups of cell-free alginate and untreated groups (control) were observed. After 8 weeks, in the alginate plus cell group, functional chondrocytes were observed, which produced immature matrix, and by 16 weeks, the matrix and hyaline-like cartilage became completely homogeneous and integrated with the natural surrounding cartilage in the defect site. Similar effect was also observed in the subchondral bone. The cell-free scaffolds formed fibrocartilage tissue, and the untreated group did not form a continuous cartilage over the defect by 16 weeks.

Adipose-Derived Stromal Vascular Fraction Cells and Platelet-Rich Plasma: Basic and Clinical Implications for Tissue Engineering Therapies in Regenerative Surgery

Cell-based therapy and regenerative medicine offer a paradigm shift in regard to various diseases causing loss of substance or volume and tissue or organ damage. Recently, many authors have focused their attention on mesenchymal stem cells for their capacity to differentiate into many cell lineages. The most widely studied types are bone marrow mesenchymal stem cells and adipose derived stem cells (ADSCs), which display similar results. Based on the literature, we believe that the ADSCs offer advantages because of lower morbidity during the harvesting procedure. Additionally, platelet-rich plasma can be used in this field for its ability to stimulate tissue regeneration. The aim of this chapter is to describe ADSC preparation and isolation procedures, preparation of platelet-rich plasma, and the application of ADSCs in regenerative plastic surgery. We also discuss the mechanisms and future role of ADSCs in cell-based therapy and tissue engineering.

The role of stem cells in anti-aging medicine

Aging is the result of two overlapping processes, "intrinsic" and "extrinsic." Intrinsic structural changes occur as a consequence of physiologic aging and are genetically determined; extrinsic relates to exposure to harmful events and habits, like smoking, bad diet, alcohol consumption, lack of sleep, stress, sun exposure, environmental pollution, etc. Aging may be decelerated by improving bad habits or treating signs of aging with various esthetic methods, food supplements, and antioxidants. It is believed that we cannot stop aging entirely due to the intrinsic part, which leads to irreversible cell damage, as well as tissue and organ damage due to their limited ability to regenerate. Stem cells and their ability to exhibit telomerase activity, to self-renew, and to differentiate into all three embryonic tissues challenges aging as a process, which is not inevitable and can even possibly be reversed. Stem cells can promote regeneration of aged tissues and organs by replacing apoptotic and necrotic cells with healthy ones. In addition, they can have antiinflammatory and antiapoptotic properties by paracrine-secreting growth factors and cytokines on the site of administration. Autologous adipose-derived stem cells are the most promising because they can be easily harvested in huge numbers with minimally invasive liposuction and, as such, represent a powerful tool in anti-aging and regenerative medicine. In this contribution, the author discusses their properties and application in clinical practice.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

The Effects of Platelet-Derived Growth Factor-BB on Bone Marrow Stromal Cell-Mediated Vascularized Bone Regeneration

Regenerative medicine for bone tissue mainly depends on efficient recruitment of endogenous or transplanted stem cells to guide bone regeneration. Platelet-derived growth factor (PDGF) is a functional factor that has been widely used in tissue regeneration and repair. However, the short half-life of PDGF limits its efficacy, and the mechanism by which PDGF regulates stem cell-based bone regeneration still needs to be elucidated. In this study, we established genetically modified PDGF-B-overexpressing bone marrow stromal cells (BMSCs) using a lentiviral vector and then explored the mechanism by which PDGF-BB regulates BMSC-based vascularized bone regeneration. Our results demonstrated that PDGF-BB increased osteogenic differentiation but inhibited adipogenic differentiation of BMSCs via the extracellular signal-related kinase 1/2 (ERK1/2) signaling pathway. In addition, secreted PDGF-BB significantly enhanced human umbilical vein endothelial cell (HUVEC) migration and angiogenesis via the phosphatidylinositol 3 kinase (PI3K)/AKT and ERK1/2 signaling pathways. We evaluated the effect of PDGF-B-modified BMSCs on bone regeneration using a critical-sized rat calvarial defect model. Radiography, micro-CT, and histological analyses revealed that PDGF-BB overexpression improved BMSC-mediated angiogenesis and osteogenesis during bone regeneration. These results suggest that PDGF-BB facilitates BMSC-based bone regeneration by enhancing the osteogenic and angiogenic abilities of BMSCs.

Histone demethylase JMJD6 regulates cellular migration and proliferation in adipose-derived mesenchymal stem cells

BACKGROUND

Adipose-derived mesenchymal stem cells (ADSCs) have been extensively explored as a promising therapeutic agent due to their differentiation, proliferation and migration abilities. The epigenetic mechanisms that regulate the fate of mesenchymal stem cells (MSCs) have been described in detail. However, the epigenetic modulation of ADSCs proliferation and migration is poorly understood.

METHODS

The present study examined histone demethylases roles and expression by RT-PCR, as well as through siRNA screening and ChIP-qPCR assay. Cellular proliferation and migration assays were employed in shRNA-mediated JMJD6 knockdown and control ADSCs. PDE1C inhibition studies were conducted to confirm its role in JMJD6-mediated epigenetic regulation of ADSCs.

RESULTS

The data demonstrate that the histone demethylase JMJD6 plays a critical role in regulating the proliferation and migration of ADSCs by removing H4R3me2a at the promoter regions of PDEC1 and suppressing PDEC1 expression. Importantly, the depletion of JMJD6 in ADSCs significantly increased cellular proliferation and motility, which was associated with increases in PDE1C expression and decreases in the levels of both cAMP and cGMP. The increase in proliferation and migration was reversed by treatment with a PDE1C inhibitor, suggesting that JMJD6 attenuates the proliferation and migration of ADSCs as an epigenetic regulator and PDE1C partially contributes to the JMJD6-mediated regulation.

CONCLUSIONS

Taken together, our results indicate for the first time that JMJD6 plays an important role in the regulation of ADSCs proliferation and migration through the modulation of PDE1C expression.

Platelet-rich plasma enhances the proliferation of human adipose stem cells through multiple signaling pathways

BACKGROUND

Platelet-rich plasma (PRP) is an autologous blood product that contains a high concentration of several growth factors. Platelet-derived growth factor (PDGF)-BB is a potential mitogen for human adipose-derived stem cells (hASCs). PRP stimulates proliferation of hASCs; however, the signaling pathways activated by PRP remain unclear.

METHODS

hASCs were cultured with or without PRP or PDGF-BB, and proliferation was assessed. hASCs were also treated with PRP or PDGF-BB with or without imatinib, which is a PDGF receptor tyrosine kinase inhibitor, or sorafenib, which is a multikinase inhibitor. Inhibition of cell proliferation was examined using anti-PDGF antibody (Abcam, Cambridge, UK), by cell counting. We assessed the effects of inhibitors of various protein kinases such as ERK1/2, JNK, p38, and Akt on the proliferation of hASCs.

RESULTS

The proliferation was remarkably promoted in cells treated with either 1% PRP or 10 ng/ml PDGF-BB, and both imatinib and sorafenib inhibited this proliferation. Anti-PDGF antibody (0.5 and 2 μg/ml) significantly decreased the proliferation of hASCs compared with control. PRP-mediated hASC proliferation was blocked by inhibitors of ERK1/2, Akt, and JNK, but not by an inhibitor of p38.

CONCLUSIONS

PRP promotes hASC proliferation, and PDGF-BB in PRP plays a major role in inducing the proliferation of hASCs. PRP promotes hASC proliferation via ERK1/2, PI3K/Akt, and JNK signaling pathways.

Off-label use of adipose-derived stem cells

Background

Adipose-derived stem cells (ASCs) have a broad range of clinical applications. The ease of cell harvest and high yield with minimal donor-site morbidity makes adipose tissue an ideal source of stem cells. Further, the multi-lineage potential of these cells present significant opportunities within the field of tissue engineering, with studies successfully demonstrating their ability to produce a range of tissue types.

Materials and methods

Literature review of publications on the use of ASCs, in the context of current European and US regulations.

Results

According to European and US regulations, many clinical trials reported in literature to date could be considered off-label.

Conclusion

In Europe, clinical trials involving cultured ASCs and/or the use of collagenase, which causes changes in the structural and functional properties of stem cells, and/or ASCs application in non-homologous tissue, should be considered off-label. ASCs should be non-cultured, isolated mechanically, and used only in the subcutaneous tissue.

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Adipose-derived stem cells hold enormous potential in different fields of regenerative medicine and stem cell therapy.

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According to European and US regulations, many clinical trials reported in literature could be considered off-label.

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In Europe, ASCs should be non-cultured, isolated mechanically, and used only in the subcutaneous tissue.

Dual-delivery of FGF-2/CTGF from Silk Fibroin/PLCL-PEO Coaxial Fibers Enhances MSC Proliferation and Fibrogenesis

The success of mesenchymal stem cell transplantation is highly dependent on their survival and controlled fate regulation. This study demonstrates that dual-delivery of connective tissue growth factor (CTGF) and fibroblast growth factor 2 (FGF-2) from a core-shell fiber of Silk Fibroin/poly(L-lactic acid-co-ε-caprolactone)-polyethylene oxide (SF/PLCL-PEO) enhanced fibrogenic lineage differentiation of MSCs. The core-shell structure was confirmed by transmission electron microscopy (TEM), fluorescence microscopy and attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. A sequential release of FGF-2 and CTGF was successfully achieved in this manner. FGF-2 plays an important role in stem cell proliferation and, meanwhile when accompanied with CTGF, has a slightly additive effect on fibrogenic differentiation of MSCs, whereas CTGF promotes fibrogenesis and alleviates osteogenesis, chondrogenesis and adipogenesis.

Explant culture: An advantageous method for isolation of mesenchymal stem cells from human tissues

Mesenchymal stem cell (MSC) research progressively moves towards clinical phases. Accordingly, a wide range of different procedures were presented in the literature for MSC isolation from human tissues; however, there is not yet any close focus on the details to offer precise information for best method selection. Choosing a proper isolation method is a critical step in obtaining cells with optimal quality and yield in companion with clinical and economical considerations. In this concern, current review widely discusses advantages of omitting proteolysis step in isolation process and presence of tissue pieces in primary culture of MSCs, including removal of lytic stress on cells, reduction of in vivo to in vitro transition stress for migrated/isolated cells, reduction of price, processing time and labour, removal of viral contamination risk, and addition of supporting functions of extracellular matrix and released growth factors from tissue explant. In next sections, it provides an overall report of technical highlights and molecular events of explant culture method for isolation of MSCs from human tissues including adipose tissue, bone marrow, dental pulp, hair follicle, cornea, umbilical cord and placenta. Focusing on informative collection of molecular and methodological data about explant methods can make it easy for researchers to choose an optimal method for their experiments/clinical studies and also stimulate them to investigate and optimize more efficient procedures according to clinical and economical benefits.

Serum-free culturing of human mesenchymal stem cells with immobilized growth factors

Growth factors were immobilized with photo-reactive gelatin and used for serum-free human mesenchymal stem cell (hMSC) culturing.

Low Dose Cadmium Inhibits Proliferation of Human Renal Mesangial Cells via Activation of the JNK Pathway

Cadmium (Cd) is a heavy metal and environmental pollutant. The kidney is the principal target organ of Cd exposure. Previously, we found that low concentration of Cd damages the integrity of the glomerular filtration barrier. However, little is known about the effects of Cd on renal mesangial cells, which provide structural support for the glomerular capillary loops and regulate intraglomerular blood flow. In this study, human renal mesangial cells (HRMCs) were cultured in the presence of serum and treated with 4 μM Cd. We found that Cd activates the c-Jun N-terminal kinase (JNK) pathway, and increases the protein levels of c-Jun and c-Fos. Cd treatment also induces a decrease in proliferation and an increase in apoptosis of HRMCs, but only the decrease in HRMC proliferation was reversed by pretreatment with SP600125, an inhibitor of the JNK pathway. In addition, Cd does not change the expression of α-smooth muscle actin and platelet-derived growth factor receptor-β, the markers of mesangial cells, or the alignment of the filamentous actin (F-actin) cytoskeleton of HRMCs. Our data indicate that the JNK pathway mediates the inhibitory effects of Cd on HRMC proliferation.

Defocused low-energy shock wave activates adipose tissue-derived stem cells in vitro via multiple signaling pathways

BACKGROUND AIMS

We found defocused low-energy shock wave (DLSW) could be applied in regenerative medicine by activating mesenchymal stromal cells. However, the possible signaling pathways that participated in this process remain unknown. In the present study, DLSW was applied in cultured rat adipose tissue-derived stem cells (ADSCs) to explore its effect on ADSCs and the activated signaling pathways.

METHODS

After treating with DLSW, the cellular morphology and cytoskeleton of ADSCs were observed. The secretions of ADSCs were detected. The expressions of ADSC surface antigens were analyzed using flow cytometry. The expressions of proliferating cell nuclear antigen and Ki67 were analyzed using western blot. The expression of CXCR2 and the migrations of ADSCs in vitro and in vivo were detected. The phosphorylation of selected signaling pathways with or without inhibitors was also detected.

RESULTS

DLSW did not change the morphology and phenotype of ADSCs, and could promote the secretion, proliferation and migration of ADSCs. The phosphorylation levels were significantly higher in mitogen-activated protein kinases (MAPK) pathway, phosphoinositide 3-kinase (PI-3K)/AKT pathway and nuclear factor-kappa B (NF-κB) signaling pathway but not in Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway. Furthermore, ADSCs were not activated by DLSW after adding the inhibitors of these pathways simultaneously.

CONCLUSIONS

Our results demonstrated for the first time that DLSW could activate ADSCs through MAPK, PI-3K/AKT and NF-κB signaling pathways. Combination of DLSW and agonists targeting these pathways might improve the efficacy of ADSCs in regenerative medicine in the future.

Dihydroartemisinin transiently activates the JNK/SAPK signaling pathway in endothelial cells

Artemisinin and its derivatives are well-known anti-malaria drugs and in the early stages of research for cancer treatment. Dihydroartemisinin (DHA), a more water-soluble derivative of artemisinin, has demonstrated strong anti-angiogenic activity. The purpose of the present study was to investigate the underlying molecular mechanisms of the effect of DHA on angiogenesis. Human umbilical vein endothelial cells (HUVECs) treated with DHA were examined for apoptosis and activation of the c-Jun N-terminal kinase (JNK) signaling pathway, one of the major mitogen-activated protein kinase cascades. It was observed that 20 µM DHA induces transient activation of JNK in HUVECs. DHA also elevates the expression of cyclooxygenase-2 and matrix metalloproteinase-13, which is abolished by treatment with the JNK inhibitor SP600125. Although DHA persistently increases inhibitor of κB-α protein and thus inhibits nuclear factor-κB signaling, it does not affect apoptosis or caspase 3/9 activities in HUVECs. The present study provides key information for understanding the effects of DHA on endothelial cells, which is required for investigating its potential for clinic application as a chemotherapeutic agent.

Gamma-secretase Inhibitor Prevents Proliferation and Migration of Ductus Arteriosus Smooth Muscle Cells through the Notch3-HES1/2/5 Pathway

Patent ductus arteriosus (PDA) can cause morbidity and mortality in neonates. Vascular remodeling, characterized by proliferation and migration of smooth muscle cells (SMCs), is an essential process for postnatal DA closure. Notch signaling is an important mediator of vascular remodelling but its role in DA is unkonwn. We investigated the effects and underlying mechanisms of γ-secretase inhibitor DAPT, a Notch signaling inhibitor on angiotensin II (Ang II)-induced proliferation and migration of DASMCs. Proliferation and migration of DASMCs cultured from neonatal Wistar rats were induced by Ang II, with or without DAPT pre-treatment. In addition, potential underlying mechanisms including cell cycle progression, Ca(2+) influx, reactive oxygen species (ROS) production, signal transduction of MAPK and Akt, and Notch receptor with its target gene pathway were examined. We found that DAPT inhibited Ang II-induced DASMCs proliferation and migration dose dependently. DAPT also arrested the cell cycle progression in the G0/G1-phase, and attenuated calcium overload and ROS production caused by Ang II. Moreover, DAPT inhibited nuclear translocation of Notch3 receptor intracellular domain, with decreased expression of its down-stream genes including HES1, HES2 and HES5. Finally, Ang II-activated ERK1/2, JNK and Akt were also counteracted by DAPT. In conclusion, DAPT inhibits Ang II-induced DASMCs proliferation and migration. These effects are potentially mediated by decreased calcium influx, reduced ROS production, and down-regulation of ERK1/2, JNK and Akt, through the Notch3-HES1/2/5 pathway. Therefore, Notch signaling has a role in DA remodeling and may provide a target pathway for therapeutic intervention of PDA.

Analysis of migration rate and chemotaxis of human adipose-derived mesenchymal stem cells in response to LPS and LTA in vitro

Mesenchymal stem cells (MSC) are able to stimulate the regeneration of injured tissue. Since bacterial infections are common complications in wound healing, bacterial pathogens and their components come into direct contact with MSC. The interaction with bacterial structures influences the proliferation, differentiation and migratory activity of the MSC, which might be of relevance during regeneration. Studies on MSC migration in response to bacterial components have shown different results depending on the cell type. Here, we analyzed the migration rate and chemotaxis of human adipose-derived MSC (adMSC) in response to the basic cell-wall components lipopolysaccharide (LPS) of Gram-negative bacteria and lipoteichoic acid (LTA) of Gram-positive bacteria in vitro. To this end, we used transwell and scratch assays, as well as a specific chemotaxis assay combined with live-cell imaging. We found no significant influence of LPS or LTA on the migration rate of adMSC in transwell or scratch assays. Furthermore, in the µ-slide chemotaxis assay, the stimulation with LPS did not exert any chemotactic effect on adMSC.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Functional regulation of adipose-derived stem cells by PDGF-D

Platelet-derived growth factor-D (PDGF-D) was recently identified, and acts as potent mitogen for mesenchymal cells. PDGF-D also induces cellular transformation and promotes tumor growth. However, the functional role of PDGF-D in adipose-derived stem cells (ASCs) has not been identified. Therefore, we primarily investigated the autocrine and paracrine roles of PDGF-D in this study. Furthermore, we identified the signaling pathways and the molecular mechanisms involved in PDGF-D-induced stimulation of ASCs. It is of interest that PDGF-B is not expressed, but PDGF-D and PDGF receptor-β are expressed in ASCs. PDGF-D showed the strongest mitogenic effect on ASCs, and PDGF-D regulates the proliferation and migration of ASCs through the PI3K/Akt pathways. PDGF-D also increases the proliferation and migration of ASCs through generation of mitochondrial reactive oxygen species (mtROS) and mitochondrial fission. mtROS generation and fission were mediated by p66Shc phosphorylation, and BCL2-related protein A1 and Serpine peptidase inhibitor, clade E, member 1 mediated the proliferation and migration of ASCs. In addition, PDGF-D upregulated the mRNA expression of diverse growth factors such as vascular endothelial growth factor A, fibroblast growth factor 1 (FGF1), FGF5, leukemia inhibitory factor, inhibin, beta A, interleukin 11, and heparin-binding EGF-like growth factor. Therefore, the preconditioning of PDGF-D enhanced the hair-regenerative potential of ASCs. PDGF-D-induced growth factor expression was attenuated by a pharmacological inhibitor of mitogen-activated protein kinase pathway. In summary, PDGF-D is highly expressed by ASCs, where it acts as a potent mitogenic factor. PDGF-D also upregulates growth factor expression in ASCs. Therefore, PDGF-D can be considered a novel ASC stimulator, and used as a preconditioning agent before ASC transplantation.

Adipose-derived stromal vascular fraction cells and platelet-rich plasma: basic and clinical evaluation for cell-based therapies in patients with scars on the face

BACKGROUND

Actually, autologous fat grafts have many clinical applications in breast surgery, facial rejuvenation, buttock augmentation, and Romberg syndrome as well as a treatment of liposuction sequelae.

OBJECTIVE

The aim of this article was to describe the preparation and isolation procedures for stromal vascular fraction (SVF), the preparation of platelet-rich plasma (PRP), and the clinical application in the treatment of the scar on the face.

METHODS

Ten patients with burns sequelae (n = 6) and post-traumatic scars (n = 4) were treated with SVF-enhanced autologous fat grafts obtained by the Celution System. Another 10 patients with burns sequelae (n = 5) and post-traumatic scars (n = 5) were treated with fat grafting based on the Coleman technique mixed with 0.5 mL of PRP.To assess the effects of their treatment, the authors compared their results with those of a control group consisting of 10 patients treated with centrifuged fat.

RESULTS

In the patients treated with SVF-enhanced autologous fat grafts, we observed a 63% maintenance of contour restoring after 1 year compared with only 39% of the control group (n = 10) treated with centrifuged fat graft (P < 0.0001). In the patients treated with fat grafting and PRP, we observed a 69% maintenance of contour restoring after 1 year compared with that of the control group (n = 10).

CONCLUSIONS

Autologous fat grafting is a good method for the correction of scars on the face instead of the traditional scar surgical excision.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effects of cytokines and chemokines on migration of mesenchymal stem cells following spinal cord injury

We investigated the effects of cytokines and chemokines and their associated signaling pathways on mesenchymal stem cell migration after spinal cord injury, to determine their roles in the curative effects of mesenchymal stem cells. This study reviewed the effects of tumor necrosis factor-α, vascular endothelial growth factor, hepatocyte growth factor, platelet-derived growth factor, basic fibroblast growth factor, insulin like growth factor-1, stromal cell-derived factor and monocyte chemoattractant protein-1, 3 during mesenchymal stem cell migration to damaged sites, and analyzed the signal transduction pathways involved in their effects on mesenchymal stem cell migration. The results confirmed that phosphatidylinositol 3-kinase/serine/threonine protein kinases and nuclear factor-κB play crucial roles in the migration of mesenchymal stem cells induced by cytokines and chemokines.

Platelet-derived growth factor-BB enhances MSC-mediated cardioprotection via suppression of miR-320 expression

Delivery of bone marrow-derived mesenchymal stem cells (MSCs) to myocardium protects ischemic tissue through the paracrine release of beneficial angiogenic and cytoprotective factors. Platelet-derived growth factor (PDGF)-BB, a potent mitogen of MSCs, is involved in the pathophysiology of ischemic heart disease. However, the role(s) of PDGF in MSC-mediated cardioprotection remains unknown. Here, we found that PDGF treatment of MSCs resulted in rapid activation of both Akt and ERK (central intracellular signal mediators), upregulated VEGF, and induced phosphorylation of the activator protein-1 (AP-1) transcription factor c-Jun. Examination of several microRNA genes having predicted promoter c-Jun-binding sites showed that PDGF treatment resulted in upregulation of miR-16-2 and downregulation of miRs-23b, -27b, and -320b. To examine possible PDGF augmentation of therapeutic potential, we evaluated the effects of PDGF using an ex vivo isolated mouse heart ischemia-reperfusion model. Human MSCs, with or without PDGF preconditioning, were infused into the coronary circulation of isolated mouse hearts. The hearts that received PDGF-treated MSCs exhibited a greater functional recovery compared with naïve MSC-infused hearts, following ischemia-reperfusion injury. This enhanced functional recovery was abolished by overexpression of miR-320, a microRNA we found downregulated by PDGF-activated c-Jun. Overexpression of miR-320 also resulted in upregulation of insulin-like growth factor binding protein (IGFBP) family members, suggesting PDGF "cross talk" with the mitogenic IGF signaling pathway. Collectively, we conclude that PDGF enhances MSC-mediated cardioprotection via a c-Jun/miR-320 signaling mechanism and PDGF MSC preconditioning may be an effective therapeutic strategy for cardiac ischemia.

JNK is necessary for oligodendrocyte precursor cell proliferation induced by the conditioned medium from B104 neuroblastoma cells

The conditioned medium from B104 neuroblastoma cells (B104CM) induces proliferation of oligodendrocyte progenitor cells (OPCs) in vitro. Our previous study showed that phosphorylation of extracellular signal-regulated protein kinase(s), not PI3K or p38, is key to B104CM-induced OPC proliferation. However, whether there are still other signaling pathways that are also involved in B104CM-induced proliferation remains unknown. In the present study, we evaluated the implication of c-Jun N-terminal kinase (JNK) signaling pathway in the B104CM-induced proliferation of OPCs using the specific inhibitor of JNK. We provided convincing evidence for the first time that the phosphorylation of JNK is necessary for OPC proliferation induced by B104CM in vitro. Moreover, the activation of JNK results in subsequent expressions of c-jun, c-fos, and c-myc, which initiates proliferation of OPCs. Collectively, these results suggest that JNK is also necessary for B104CM-induced OPC proliferation.

B-type natriuretic peptide inhibits angiotensin II-induced proliferation and migration of pulmonary arterial smooth muscle cells

Pulmonary vascular remodeling, characterized by disordered proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), is a pathognomonic feature of pulmonary arterial hypertension. Thus, pharmacologic strategy targeting on anti-proliferation and anti-migration of PASMCs may have therapeutic implications for PAH. Here we investigated the effects and underlying mechanisms of B-type natriuretic peptide (BNP) on angiotensin II (Ang II)-induced proliferation and migration of PASMCs. Proliferation and migration of PASMCs cultured from Wistar rats were induced by Ang II, with or without BNP treatment. In addition, potential underlying mechanisms including cell cycle progression, Ca(2+) overload, reactive oxygen species (ROS) production, signal transduction of MAPK and Akt, and the cGMP/PKG pathway were examined. We found that BNP inhibited Ang II-induced PASMCs proliferation and migration dose dependently. BNP could also arrest the cell cycle progression in the G0/G1-phase. In addition, BNP attenuated intracellular calcium overload caused by Ang II. Moreover, Ang II-induced ROS production was mitigated by BNP, with associated down-regulation of NAD(P)H oxidase 1 (Nox1) and reduced mitochondrial ROS production. Finally, Ang II-activated MAPKs and Akt were also counteracted by BNP. Of note, all these effects of BNP were abolished by a PKG inhibitor (Rp-8-Br-PET-cGMPS). In conclusion, BNP inhibits Ang II-induced PASMCs proliferation and migration. These effects are potentially mediated by decreased calcium influx, reduced ROS production by Nox1 and mitochondria, and down-regulation of MAPK and Akt signal transduction, through the cGMP/PKG pathway. Therefore, this study implicates that BNP may have a therapeutic role in pulmonary vascular remodeling.

Adipose-derived stem cells: Implications in tissue regeneration

Adipose-derived stem cells (ASCs) are mesenchymal stem cells (MSCs) that are obtained from abundant adipose tissue, adherent on plastic culture flasks, can be expanded in vitro, and have the capacity to differentiate into multiple cell lineages. Unlike bone marrow-derived MSCs, ASCs can be obtained from abundant adipose tissue by a minimally invasive procedure, which results in a high number of cells. Therefore, ASCs are promising for regenerating tissues and organs damaged by injury and diseases. This article reviews the implications of ASCs in tissue regeneration.

Isolation, characterization, differentiation, and application of adipose-derived stem cells

While bone marrow-derived mesenchymal stem cells are known and have been investigated for a long time, mesenchymal stem cells derived from the adipose tissue were identified as such by Zuk et al. in 2001. However, as subcutaneous fat tissue is a rich source which is much more easily accessible than bone marrow and thus can be reached by less invasive procedures, adipose-derived stem cells have moved into the research spotlight over the last 8 years.Isolation of stromal cell fractions involves centrifugation, digestion, and filtration, resulting in an adherent cell population containing mesenchymal stem cells; these can be subdivided by cell sorting and cultured under common conditions.They seem to have comparable properties to bone marrow-derived mesenchymal stem cells in their differentiation abilities as well as a favorable angiogenic and anti-inflammatory cytokine secretion profile and therefore have become widely used in tissue engineering and clinical regenerative medicine.

The molecular mechanism underlying the proliferating and preconditioning effect of vitamin C on adipose-derived stem cells

Although adipose-derived stem cells (ASCs) show promise for cell therapy, there is a tremendous need for developing ASC activators. In the present study, we investigated whether or not vitamin C increases the survival, proliferation, and hair-regenerative potential of ASCs. In addition, we tried to find the molecular mechanisms underlying the vitamin C-mediated stimulation of ASCs. Sodium-dependent vitamin C transporter 2 (SVCT2) is expressed in ASCs, and mediates uptake of vitamin C into ASCs. Vitamin C increased the survival and proliferation of ASCs in a dose-dependent manner. Vitamin C increased ERK1/2 phosphorylation, and inhibition of the mitogen-activated protein kinase (MAPK) pathway attenuated the proliferation of ASCs. Microarray and quantitative polymerase chain reaction showed that vitamin C primarily upregulated expression of proliferation-related genes, including Fos, E2F2, Ier2, Mybl1, Cdc45, JunB, FosB, and Cdca5, whereas Fos knock-down using siRNA significantly decreased vitamin C-mediated ASC proliferation. In addition, vitamin C-treated ASCs accelerated the telogen-to-anagen transition in C3H/HeN mice, and conditioned medium from vitamin C-treated ASCs increased the hair length and the Ki67-positive matrix keratinocytes in hair organ culture. Vitamin C increased the mRNA expression of HGF, IGFBP6, VEGF, bFGF, and KGF, which may mediate hair growth promotion. In summary, vitamin C is transported via SVCT2, and increased ASC proliferation is mediated by the MAPK pathway. In addition, vitamin C preconditioning enhanced the hair growth promoting effect of ASCs. Because vitamin C is safe and effective, it could be used to increase the yield and regenerative potential of ASCs.

Concentration of PDGF-AB, BB and TGF-β1 as valuable human serum parameters in adipose-derived stem cell proliferation

INTRODUCTION

Human serum (HS) has attributes similar to fetal bovine serum (FBS) in the proliferation and differentiation of human adipose-derived stem cells (hASCs) when compared in vitro. The purpose of this study was to determine what types of HS, with respect to the concentrations of endogenous growth factors, could be made available for hASC proliferation.

METHODS

HS was collected from 2 groups of healthy donor (freshly isolated HS [n=9], and HS preserved for 4 years [n=7]). All sera were isolated with a Cellaid HS isolation device (JMS Co., Ltd, Hiroshima, Japan) and then classified into 3 groups based on the concentrations (high, middle, and low) of platelet-derived growth factor (PDGF)-AB, PDGF-BB, and transforming growth factor-beta 1 (TGF-β1) by means of enzyme-linked immunoassay screening. The hASCs were isolated from subcutaneous fat using a collagenase enzymatic digestion process and were cultured in control media, each supplemented with HS from a different group. Cell numbers were counted on days 2, 4, 7, and 14, and the relationship between cell proliferation and the level of each growth factor was investigated.

RESULTS

The proliferation of hASCs correlated with the concentration of each growth factor. The cut-off points for PDGF-AB, PDGF-BB, and TGF-β1 in HS [necessary for hASC proliferation when compared with FBS] were 10 ng/mL, 1.5 ng/mL, and 15 ng/mL, respectively. There was no correlation between the storage period of HS and the proliferation potential of hASCs.

CONCLUSIONS

These results suggest that the effectiveness of HS on hASC proliferation depends on the concentrations of endogenous PDGFs. In addition, the Cellaid device used in this study allows the simultaneous release of several growth factors from platelets, and our results have shown that it can be used to collect HS for future hASC-based therapies.

The therapeutic potential of bone marrow-derived mesenchymal stromal cells on hepatocellular carcinoma

Mesenchymal stromal cells (MSCs) are more often obtained from adult and extraembryonic tissues, with the latter sources being likely better from a therapeutic perspective. MSCs show tropism towards inflamed or tumourigenic sites. Mechanisms involved in MSC recruitment into tumours are comprehensively analysed, including chemoattractant signalling axes, endothelial adhesion and transmigration. In addition, signals derived from hepatocellular carcinoma (HCC) tumour microenvironment and their influence in MSC tropism and tumour recruitment are dissected, as well as the present controversy regarding their influence on tumour growth and/or metastasis. Finally, evidences available on the use of MSCs and other selected progenitor/stem cells as vehicles of antitumourigenic genes are discussed. A better knowledge of the mechanisms involved in progenitor/stem cell recruitment to HCC tumours is proposed in order to enhance their tumour targeting which may result in improvements in cell-based gene therapy strategies.

Periodontal-ligament-derived stem cells exhibit the capacity for long-term survival, self-renewal, and regeneration of multiple tissue types in vivo

Primary periodontal ligament stem cells (PDLSCs) are known to possess multidifferentiation potential and exhibit an immunophenotype similar to that described for bone-marrow-derived mesenchymal stem cells. In the present study, bromo-deoxyuridine (BrdU)-labeled ovine PDLSCs implanted into immunodeficient mice survived after 8 weeks post-transplantation and exhibited the capacity to form bone/cementum-like mineralized tissue, ligament structures similar to Sharpey's fibers with an associated vasculature. To evaluate self-renewal potential, PDLSCs were recovered from harvested primary transplants 8 weeks post-transplantation that exhibit an immunophenotype and multipotential capacity comparable to primary PDLSCs. The re-derived PDLSCs isolated from primary transplants were implanted into secondary ectopic xenogeneic transplants. Histomorphological analysis demonstrated that four out of six donor re-derived PDLSC populations displayed a capacity to survive and form fibrous ligament structures and mineralized tissues associated with vasculature in vivo, although at diminished levels in comparison to primary PDLSCs. Further, the capacity for long-term survival and the potential role of PDLSCs in dental tissue regeneration were determined using an ovine preclinical periodontal defect model. Autologous ex vivo-expanded PDLSCs that were prelabeled with BrdU were seeded onto Gelfoam(®) scaffolds and then transplanted into fenestration defects surgically created in the periodontium of the second premolars. Histological assessment at 8 weeks post-implantation revealed surviving BrdU-positive PDLSCs associated with regenerated periodontium-related tissues, including cementum and bone-like structures. This is the first report to demonstrate the self-renewal capacity of PDLSCs using serial xenogeneic transplants and provides evidence of the long-term survival and tissue contribution of autologous PDLSCs in a preclinical periodontal defect model.

Akt- and Erk-mediated regulation of proliferation and differentiation during PDGFRβ-induced MSC self-renewal

Understanding the mechanisms that direct mesenchymal stem cell (MSC) self-renewal fate decisions is a key to most tissue regenerative approaches. The aim of this study here was to investigate the mechanisms of action of platelet-derived growth factor receptor β (PDGFRβ) signalling on MSC proliferation and differentiation. MSC were cultured and stimulated with PDGF-BB together with inhibitors of second messenger pathways. Cell proliferation was assessed using ethynyl-2′-deoxyuridine and phosphorylation status of signalling molecules assessed by Western Blots. To assess differentiation potentials, cells were transferred to adipogenic or osteogenic media, and differentiation assessed by expression of differentiation association genes by qRT-PCR, and by long-term culture assays. Our results showed that distinct pathways with opposing actions were activated by PDGF. PI3K/Akt signalling was the main contributor to MSC proliferation in response to activation of PDGFRβ. We also demonstrate a negative feedback mechanism between PI3K/Akt and PDGFR-β expression. In addition, PI3K/Akt downstream signal cascades, mTOR and its associated proteins p70S6K and 4E-BP1 were involved. These pathways induced the expression of cyclin D1, cyclin D3 and CDK6 to promote cell cycle progression and MSC proliferation. In contrast, activation of Erk by PDGFRβ signalling potently inhibited the adipocytic differentiation of MSCs by blocking PPARγ and CEBPα expression. The data suggest that PDGFRβ-induced Akt and Erk pathways regulate opposing fate decisions of proliferation and differentiation to promote MSC self-renewal. Thus, activation of multiple intracellular cascades is required for successful and sustainable MSC self-renewal strategies.

Reactive oxygen species-responsive miR-210 regulates proliferation and migration of adipose-derived stem cells via PTPN2

Hypoxia enhances the proliferation and migration of adipose-derived stem cells (ASCs) via the generation of reactive oxygen species (ROS). Therefore, this study primarily investigated whether or not ROS generation could regulate microRNA-210 (miR-210) expression, and increase proliferation/migration of ASCs. In addition, we tried to identify the signaling pathways involved in miR-210 upregulation and the direct target genes of miR-210 that mediate these functions. Various sources of ROS generation such as hypoxia, antimycin, rotenone, and platelet-derived growth factor (PDGF)-BB upregulated miR-210 expression, and increased the proliferation/migration of ASCs. There is a positive feed-forward loop between ROS generation and miR-210, and miR-210 itself increases ROS generation by downregulation of iron–sulfur cluster scaffold homolog 2 (ISCU2). Although hypoxia-inducible factor-1α was not involved in miR-210 expression, pharmacological or small interfering RNA (siRNA)-driven inhibition of Akt and ERK1/2 molecules reduced miR-210 expression. Transfection of siRNAs of NF-κB and Elk1 also reduced miR-210 expression, indicating that these signaling pathways mediate miR-210 upregulation. Protein tyrosine phosphatase, non-receptor type 2 (PTPN2) was selected for miR-210 target gene, and it was downregulated by ROS generators or miR-210 mimic treatment. PTPN2 was first proven to be a direct miR-210 target in luciferase activity assay, and pharmacological inhibition or overexpression of PTPN2 regulated the proliferation and migration of ASC. In conclusion, ROS generation from diverse sources induces miR-210 expression in ASCs via PDGFR-β, Akt and ERK pathways. Transcription of miR-210 expression is regulated by NF-κB and Elk1, and miR-210 increases the proliferation and migration of ASCs via ISCU2 and PTPN2 downregulation.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

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

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

Migration of human mesenchymal stem cells under low shear stress mediated by mitogen-activated protein kinase signaling

Human mesenchymal stem cells (hMSCs) are attractive candidates for cell-based tissue repair approaches and have been used as vectors for delivering therapeutic genes to sites of injury. It is believed that hMSCs are able to detect and respond to shear stress due to blood and interstitial fluid flow through mechanotransduction pathways after transplantation. However, information regarding hMSC migration under shear stress and its mechanism is still limited. In this study, we examined the effect of shear stress on hMSC migration and the role of mitogen-activated protein kinases (MAPKs) in their migration. Shear stress between 0.2 and 10 Pa, which was produced by the flow medium, was exerted on fluorescently labeled hMSCs. Cell migration was evaluated using the scratch wound assay, and images were captured using a microscope equipped with a digital 3CCD camera. The results showed that hMSCs subjected to a shear stress of 0.2 Pa caused notably faster wound closure than statically cultured hMSCs, while migration in the 0.5- and 1-Pa shear stress group did not differ significantly from that in the control group. Shear stress >2 Pa markedly inhibited hMSC migration. hMSCs subjected to a shear stress of 0.2 Pa displayed an increase in extracellular signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinases (JNK), and p38 MAPK activation for up to 60 min, while a shear stress of 2 Pa abrogated the activation. JNK and p38 MAPK inhibitors completely abolished the effect of shear stress on hMSC migration, while significant differences were observed between the ERK1/2 inhibitor-treated static control and shear stress groups. Taken together, these results demonstrate that low shear stress effectively induces hMSC migration and that JNK and p38 MAPK play more prominent roles in shear stress-induced migration than ERK1/2.

Concise review: adipose-derived stromal vascular fraction cells and platelet-rich plasma: basic and clinical implications for tissue engineering therapies in regenerative surgery

Cell-based therapy and regenerative medicine offer a paradigm shift in regard to various diseases causing loss of substance or volume and tissue or organ damage. Recently, many authors have focused their attention on mesenchymal stem cells for their capacity to differentiate into many cell lineages. The most widely studied types are bone marrow mesenchymal stem cells and adipose-derived stem cells (ADSCs), which display similar results. Based on the literature, we believe that the ADSCs offer advantages because of lower morbidity during the harvesting procedure. Additionally, platelet-rich plasma can be used in this field for its ability to stimulate tissue regeneration. The aims of this article are to describe ADSC preparation and isolation procedures, preparation of platelet-rich plasma, and the application of ADSCs in regenerative plastic surgery. We also discuss the mechanisms and future role of ADSCs in cell-based therapy and tissue engineering.