Cellular cardiomyoplasty with human amniotic fluid stem cells: in vitro and in vivo studies

Polycaprolactone/poly L-lactic acid nanofibrous scaffold improves osteogenic differentiation of the amniotic fluid-derived stem cells

Using stem cells is one of the most important determining factors in repairing lesions using regenerative medicine. Obtaining adult stem cells from patients is a perfect choice, but it is worth noting that their differentiation and proliferation potential decreases as the patient ages. For this reason, the use of amniotic fluid stem cells can be one of the excellent alternatives. This research aimed to investigate the osteogenic differentiation potential of the amniotic fluid stem cells while cultured on the polycaprolactone/poly L-lactic acid nanofibrous scaffold. Scaffolds were qualitatively evaluated by a scanning electron microscope, and their hydrophilicity and mechanical properties were studied using contact angle and tensile test, respectively. The biocompatibility and non-toxicity of the nanofibers were also evaluated using viability assay. The osteo-supportive capacity of the nanofibers was examined using alizarin red staining, alkaline phosphatase activity, and calcium release measurement. Finally, the expression level of four important bone-related genes was determined quantitatively. The results demonstrated that the mineralization rate, alkaline phosphatase activity, intracellular calcium, and bone-related genes increased significantly in the cells cultured on the polycaprolactone/poly L-lactic acid scaffold compared to the cells cultured on the tissue culture plate as a control. According to the results, it can be concluded that the polycaprolactone/poly L-lactic acid nanofibrous scaffold surprisingly improved the osteogenic differentiation potential of the amniotic fluid stem cells and, in combination with polycaprolactone/poly L-lactic acid nanofibers could be a promising candidate as bone implants.

Stem Cell-Mediated Angiogenesis in Tissue Engineering Constructs

Angiogenesis has always been a concern in the field of tissue engineering. Poor vascularization of engineered constructs is a problem for the clinical success of these structures. Among the various methods employed to induce angiogenesis, stem cells provide a promising tool for the future. The present review aims to present the application of stem cells in the induction of angiogenesis. Additionally, it summarizes recent advancements in stem cell-mediated angiogenesis of different tissue engineering constructs.

Hypoxia-stressed cardiomyocytes promote early cardiac differentiation of cardiac stem cells through HIF-1α/Jagged1/Notch1 signaling

Hypoxia is beneficial for the differentiation of stem cells transplanted for myocardial injury, but mechanisms underlying this benefit remain unsolved. Here, we report the impact of hypoxia-induced Jagged1 expression in cardiomyocytes (CMs) for driving the differentiation of cardiac stem cells (CSCs). Forced hypoxia-inducible factor 1α (HIF-1α) expression and physical hypoxia (5% O₂) treatment could induce Jagged1 expression in neonatal rat CMs. Pharmacological inhibition of HIF-1α by YC-1 attenuated hypoxia-promoted Jagged1 expression in CMs. An ERK inhibitor (PD98059), but not inhibitors of JNK (SP600125), Notch (DAPT), NF-κB (PTDC), JAK (AG490), or STAT3 (Stattic) suppressed hypoxia-induced Jagged1 protein expression in CMs. c-Kit⁺ CSCs isolated from neonatal rat hearts using a magnetic-activated cell sorting method expressed GATA4, SM22α or vWF, but not Nkx2.5 and cTnI. Moreover, 87.3% of freshly isolated CSCs displayed Notch1 receptor expression. Direct co-culture of CMs with BrdU-labeled CSCs enhanced CSCs differentiation, as evidenced by an increased number of BrdU⁺/Nkx2.5⁺ cells, while intermittent hypoxia for 21 days promoted co-culture-triggered differentiation of CSCs into CM-like cells. Notably, YC-1 and DAPT attenuated hypoxia-induced differentiation. Our results suggest that hypoxia induces Jagged1 expression in CMs primarily through ERK signaling, and facilitates early cardiac lineage differentiation of CSCs in CM/CSC co-cultures via HIF-1α/Jagged1/Notch signaling.

Cardiomyocytes Derived from Human CardiopoieticAmniotic Fluids

Human amniotic fluid (hAF) cells share characteristics of both embryonic and adult stem cells. They proliferate rapidly and can differentiate into cells of all embryonic germ layers but do not form teratomas. Embryoid-bodies obtained from hAF have cardiac differentiation potential, but terminal differentiation to cardiomyocytes (CMs) has not yet been described. Our purpose was to promote cardiac differentiation in hAFcells. Cells were exposed to inducing factors for up to 15 days. Only the subset of hAF cells expressing the multipotency markers SSEA4, OCT4 and CD90 (^{Cardiopoietic}AF cells) responded to the differentiation process by increasing the expression of the cardiac transcription factors Nkx2.5 and GATA4, sarcomeric proteins (cTnT, α-MHC, α-SA), Connexin43 and atrial and ventricular markers. Furthermore, differentiated cells were positive for the calcium pumps CACNA1C and SERCA2a, with approximately 30% of ^{Cardiopoietic}AF-derived CM-like cells responding to caffeine or adrenergic stimulation. Some spontaneous rare beating foci were also observed. In conclusion, we demonstrated that ^{Cardiopoietic}AF cells might differentiate toward the cardiac lineage giving rise to CM-like cells characterized by several cardiac-specific molecular, structural, and functional properties.

Advances in perinatal stem cells research: a precious cell source for clinical applications

Perinatal tissues possess numerous types of stem (stromal) cells, which are considered effective candidates for cell therapy. These tissues possess common characteristics of both embryonic and adult stem cells, and cell therapists have begun to use perinatal stem cells to treat several diseases. Despite their benefits, these cells are considered biological waste and usually discarded after delivery. This review highlights the characteristics and potential clinical applications in regenerative medicine of perinatal stem cell sources - cord blood hematopoietic stem cells, umbilical cord mesenchymal stem cells, amniotic membrane stem cells, amniotic fluid stem cells, amniotic epithelial cells and chorionic mesenchymal stem cells.

Human Adipose-Derived and Amniotic Fluid-Derived Stem Cells: A Preliminary In Vitro Study Comparing Myogenic Differentiation Capability

Background

Around the world, disabilities due to musculoskeletal disorders have increased and are a major health problem worldwide. In recent years, stem cells have been considered to be powerful tools for musculoskeletal tissue engineering. Human adipose-derived stem cells (hADSCs) and amniotic fluid-derived stem cells (hAFSCs) undergo typical differentiation process into cells of mesodermal origin and can be used to treat muscular system diseases. The aim of the present study was to compare the biological characteristic of stem cells isolated from different human tissues (adipose tissue and amniotic fluid) with respect to myogenic capacity and skeletal and smooth muscle differentiation under the same conditions.

Material/Methods

hAFSCs and hADSCs were isolated during standard medical procedures and widely characterized by specific markers expression and differentiation potential. Both cell types were induced toward smooth and striated muscles differentiation, which was assessed with the use of molecular techniques.

Results

For phenotypic characterization, both stem cell types were assessed for the expression of OCT-4, SOX2, CD34, CD44, CD45, and CD90. Muscle-specific markers appeared in both stem cell types, but the proportion of positive cells showed differences depending on the experimental conditions used and the source from which the stem cells were isolated.

Conclusions

In this study, we demonstrated that hADSCs and hAFSCs have different capability of differentiation toward both muscle types. However, hADSCs seem to be a better source for myogenic protocols and can promote skeletal and smooth muscle regeneration through either direct muscle differentiation or by paracrine mechanism.

Fetal and perinatal stem cells in cardiac regeneration: Moving forward to the paracrine era

Cardiovascular disease (CD) is a major burden for Western society. Regenerative medicine has provided encouraging results, yet it has not addressed the focal defects causing CD and mainly related to the inefficient repair programme of the heart. In this scenario, stem cells have been broadly investigated and their paracrine effect proposed as a possible working strategy to boost endogenous mechanisms of repair and regeneration from within the cardiac tissue. The scientific community is now focusing on identifying the most effective stem cell secretome, as the whole of bioactive factors and extracellular vesicles secreted by stem cells and endowed with regenerative potential. Indeed, the adult stem cell-paracrine potential for cardiac regeneration have been widely analyzed with positive outcome. Nevertheless, low yield, invasive sampling and controversial self-renewal may limit adult stem cell application. On the contrary, fetal and perinatal stem cells, which can be easily isolated from leftover sample via prenatal screening during gestation or as clinical waste material after birth, can offer an ideal alternative. These broadly multipotent immature progenitors share features with both adult and embryonic stem cells, show high self-renewal, but they are not tumorigenic neither cause any ethical concern. While fetal and perinatal stem cells demonstrated to improve cardiac function when injected in the injured heart, the comprehensive characterization of their secretome for future applications is still at its infancy. In this review, we will discuss the paracrine potential of the fetal and perinatal stem cell secretome to provide cardiac repair and resurge the dormant mechanisms of cardiac regeneration for future therapy.

The transplantation of Akt-overexpressing amniotic fluid-derived mesenchymal stem cells protects the heart against ischemia-reperfusion injury in rabbits

Amniotic fluid-derived mesenchymal stem cells (AFMSCs) are an attractive cell source for applications in regenerative medicine, due to characteristics such as proliferative capacity and multipotency. In addition, Akt, a serine‑threonine kinase, maintains stem cells by promoting viability and proliferation. Whether the transplantation of Akt-overexpressing AFMSCs protects the heart against ischemia‑reperfusion (I/R) injury has yet to be elucidated. Accordingly, the Akt gene was overexpressed in AFMSCs using lentiviral transduction, and Akt‑AFMSCs were transplanted into the ischemic myocardium of rabbits prior to reperfusion. Any protective effects resulting from this procedure were subsequently sought after three weeks later. A histological examination revealed that there was a decrease in intramyocardial inflammation and ultrastructural damage, and an increase in capillary density and in the levels of GATA binding protein 4, connexin 43 and cardiac troponin T in the Akt‑AFMSC group compared with the control group. A significant decrease in cardiomyocyte apoptosis, accompanying an increase in phosphorylated Akt and B‑cell lymphoma 2 (Bcl-2) and a decrease in caspase‑3, was also observed. Furthermore, the left ventricular function was markedly augmented in the Akt‑AFMSC group compared with the control group. These observations suggested that the protective effect of AFMSCs may be due to the delivery of secreted cytokines, promotion of neoangiogenesis, prevention of cardiomyocyte apoptosis, transdifferentiation into cardiomyocytes and promotion of the viability of AFMSCs, which are assisted by Akt gene modification. Taken together, the results of the present study have indicated that transplantation of Akt-AFMSCs is able to alleviate myocardial I/R injury and improve cardiac function.

Glial cell line-derived neurotrophic factor induced the differentiation of amniotic fluid-derived stem cells into vascular endothelial-like cells in vitro

Amniotic fluid-derived stem cells (AFSCs) are a novel source of stem cells that are isolated and cultured from second trimester amniocentesis. Glial cell line-derived neurotrophic factor (GDNF) acts as a tissue morphogen and regulates stem cell proliferation and differentiation. This study investigated the effect of an adenovirus-mediated GDNF gene, which was engineered into AFSCs, on the cells' biological properties and whether GDNF in combination with AFSCs can be directionally differentiated into vascular endothelial-like cells in vitro. AFSCs were isolated and cultured using the plastic adherence method in vitro and identified by the transcription factor Oct-4, which is the primary marker of pluripotent stem cells. AFSCs were efficiently transfected by a GFP-labeled plasmid system of an adenovirus vector carrying the GDNF gene (Ad-GDNF-GFP). Transfected AFSCs stably expressed GDNF. Transfected AFSCs were cultured in endothelial growth medium-2 containing vascular endothelial growth factor. After 1 week, AFSCs were positive for von Willebrand factor (vWF) and CD31, which are markers of endothelial cells, and the recombinant GDNF group was significantly higher than undifferentiated controls and the GFP only group. These results demonstrated that AFSCs differentiated into vascular endothelial-like cells in vitro, and recombinant GDNF promoted differentiation. The differentiation-induced AFSCs may be used as seed cells to provide a new manner of cell and gene therapies for transplantation into the vascular injury site to promote angiogenesis.

A Mini Overview of Isolation, Characterization and Application of Amniotic Fluid Stem Cells

Amniotic fluid represents rich sources of stem cells that can be used in treatments for a wide range of diseases. Amniotic fluid- stem cells have properties intermediate between embryonic and adult mesenchymal stem cells which make them particularly attractive for cellular regeneration and tissue engineering. Furthermore, scientists are interested in these cells because they come from the amniotic fluid that is routinely discarded after birth. In this review we give a brief introduction of amniotic fluid followed by a description of the cells present within this fluid and aim to summarize the all existing isolation methods, culturing, characterization and application of these cells. Finally, we elaborate on the differentiation and potential for these cells to promote regeneration of various tissue defects, including fetal tissue, the nervous system, heart, lungs, kidneys, bones, and cartilage in the form of table.

Mesenchymal Stem Cells from Wharton's Jelly and Amniotic Fluid

The discovery of mesenchymal stem cells (MSCs) in perinatal sources, such as the amniotic fluid (AF) and the umbilical connective tissue, the so-called Wharton's jelly (WJ), has transformed them into promising stem cell grafts for the application in regenerative medicine. The advantages of AF-MSCs and WJ-MSCs over adult MSCs, such as bone marrow-derived mesenchymal stem cells (BM-MSCs), include their minimally invasive isolation procedure, their more primitive cell character without being tumourigenic, their low immunogenicity and their potential autologous application in congenital disorders and when cryopreserved in adulthood. This chapter gives an overview of the biology of AF-MSCs and WJ-MSCs, and their regenerative potential based on the results of recent preclinical and clinical studies. In the end, open questions concerning the use of WJ-MSCs and AF-MSCs in regenerative medicine will be emphasized.

Stem Cells and Progenitor Cells for Tissue-Engineered Solutions to Congenital Heart Defects

Synthetic patches and fixed grafts currently used in the repair of congenital heart defects are nonliving, noncontractile, and not electrically responsive, leading to increased risk of complication, reoperation, and sudden cardiac death. Studies suggest that tissue-engineered patches made from living, functional cells could grow with the patient, facilitate healing, and help recover cardiac function. In this paper, we review the research into possible sources of cardiomyocytes and other cardiac cells, including embryonic stem cells, induced pluripotent stem cells, mesenchymal stem cells, adipose-derived stem cells, umbilical cord blood cells, amniotic fluid-derived stem cells, and cardiac progenitor cells. Each cell source has advantages, but also has technical hurdles to overcome, including heterogeneity, functional maturity, immunogenicity, and pathogenicity. Additionally, biomaterials used as patch materials will need to attract and support desired cells and induce minimal immune responses.

Amniotic fluid-derived stem cells demonstrate limited cardiac differentiation following small molecule-based modulation of Wnt signaling pathway

Amniotic fluid-derived stem cells (AFSC) are a promising cell source for regenerative medicine and cardiac tissue engineering. However, a non-xenotropic differentiation protocol has not been established for cardiac differentiation of AFSC. We tested a small molecule-based modulation of Wnt signaling for directed cardiac differentiation of AFSC. Cells were treated with inhibitors of glycogen synthase kinase 3 and Wnt production and secretion in a time-dependent and sequential manner, as has been demonstrated successful for cardiac differentiation of embryonic and induced pluripotent stem cells. Cells were then analyzed for gene and protein expression of markers along the cardiac lineage at multiple days during the differentiation protocol. At the midpoint of the differentiation, an increase in the percentage of AFSC expressing Islet-1, a transcription factor found in cardiac progenitor cells, and Nkx-2.5, a cardiac transcription factor, was observed. After a 15 d differentiation, a subpopulation of AFSC upregulated protein expression of smooth muscle actin, myosin light chain-2, and troponin I, all indicative of progression down a cardiac lineage. AFSC at the end of the differentiation also demonstrated organization of connexin 43, a key component of gap junctions, to cell membranes. However, no organized sarcomeres or spontaneous contraction were observed. These results demonstrate that small molecule-based modulation of Wnt signaling alone is not sufficient to generate functional cardiomyocytes from AFSC, though an upregulation of genes and proteins common to cardiac lineage cells was observed.

Injectable cell constructs fabricated via culture on a thermoresponsive methylcellulose hydrogel system for the treatment of ischemic diseases

Cell transplantation via direct intramuscular injection is a promising therapy for patients with ischemic diseases. However, following injections, retention of transplanted cells in engrafted areas remains problematic, and can be deleterious to cell-transplantation therapy. In this Progress Report, a thermoresponsive hydrogel system composed of aqueous methylcellulose (MC) blended with phosphate-buffered saline is constructed to grow cell sheet fragments and cell bodies for the treatment of ischemic diseases. The as-prepared MC hydrogel system undergoes a sol-gel reversible transition upon heating or cooling at ≈32 °C. Via this unique property, the grown cell sheet fragments (cell bodies) can be harvested without using proteolytic enzymes; consequently, their inherent extracellular matrices (ECMs) and integrative adhesive agents remain well preserved. In animal studies using rats and pigs with experimentally created myocardial infarction, the injected cell sheet fragments (cell bodies) become entrapped in the interstices of muscular tissues and adhere to engraftment sites, while a minimal number of cells exist in the group receiving dissociated cells. Moreover, transplantation of cell sheet fragments (cell bodies) significantly increases vascular density, thereby improving the function of an infarcted heart. These experimental results demonstrate that cell sheet fragments (cell bodies) function as a cell-delivery construct by providing a favorable ECM environment to retain transplanted cells locally and consequently, improving the efficacy of therapeutic cell transplantation.

Effects of naringin on the proliferation and osteogenic differentiation of human amniotic fluid-derived stem cells

Human amniotic fluid-derived stem cells (hAFSCs) are a novel cell source for generating osteogenic cells to treat bone diseases. Effective induction of osteogenic differentiation from hAFSCs is critical to fulfil their therapeutic potential. In this study, naringin, the main active compound of Rhizoma drynariae (a Chinese herbal medicine), was used to stimulate the proliferation and osteogenic differentiation of hAFSCs. The results showed that naringin enhanced the proliferation and alkaline phosphatase activity (ALP) of hAFSCs in a dose-dependent manner in the range 1-100 µg/ml, while an inhibition effect was observed at 200 µg/ml. Consistently, the calcium content also increased with naringin concentration up to 100 µg/ml. The enhanced osteogenic differentiation of hAFSCs by naringin was further confirmed by the dose-dependent upregulation of marker genes, including osteopontin (OPN) and Collagen I from RT-PCR analysis. The increased osteoprotegerin (OPG) expression and minimal expression of receptor activator of nuclear factor-κB ligand (RANKL) suggested that naringin also inhibited osteoclastogenesis of hAFSCs. In addition, the gene expressions of bone morphogenetic protein 4 (BMP4), runt-related transcription factor 2 (RUNX2), β-catenin and Cyclin D1 also increased significantly, indicating that naringin promotes the osteogenesis of hAFSCs via the BMP and Wnt-β-catenin signalling pathways. These results suggested that naringin can be used to upregulate the osteogenic differentiation of hAFSCs, which could provide an attractive and promising treatment for bone disorders. Copyright © 2014 John Wiley & Sons, Ltd.

Human amniotic-fluid-derived stem cells: a unique source for regenerative medicine

INTRODUCTION

The first application of tissue engineering was based on the use of differentiated cells from the adult organism, which was associated with an invasiveness and high risk of diseased cells' transplantation. Over the years, the range of available cell populations for tissue engineering has widened.

AREAS COVERED

We review the comprehensive information concerning the characteristic features of amniotic-fluid-derived stem cells (AFSCs). We also review the potential applications of these cells in clinical practice.

EXPERT OPINION

AFSCs hold promise for the future treatment of many incurable diseases. However, such cell-based therapies have some limitations, and there are questions relating to the use of stem cells, which should be carefully analyzed before translation of these cells into clinical practice.

Curculigoside improves osteogenesis of human amniotic fluid-derived stem cells

Curculigoside, a phenolic glycoside, is the main active compound of Curculigo orchioides (Amaryllidaceae, rhizome). C. orchioides is a traditional Chinese herbal medicine and has been commonly used to treat orthopedic disorders and bone healing in Asia. This study evaluated the effect of curculigoside on osteogenic differentiation of human amniotic fluid-derived stem cells (hAFSCs). The results showed that curculigoside stimulated alkaline phosphatase activity and calcium deposition of hAFSCs during osteogenic differentiation in a dose-dependent manner (1-100 μg/mL), while the effects were reduced at the higher concentration of 200 μg/mL. From reverse transcriptase-polymerase chain reaction analysis, the osteogenic genes osteopontin (OPN) and Collagen I were upregulated with curculigoside treatment (1-100 μg/mL). Concurrently, the ratio of osteoprotegerin (OPG) to receptor activator of nuclear factor kappa-B ligand (RANKL) was increased, indicating the inhibition of osteoclastogenesis by curculigoside. Moreover, the role of Wnt/β-catenin signaling during curculigoside treatment was revealed by the upregulation of β-catenin and Cyclin D1. In summary, curculigoside improved osteogenesis and inhibited osteoclastogenesis of hAFSCs, suggesting its potential use to regulate hAFSC osteogenic differentiation for treating bone disorders.

Amniotic fluid as a source of pluripotent and multipotent stem cells for organ regeneration

PURPOSE OF REVIEW

Amniotic fluid, due to its contact to the fetus during development, is considered an important diagnostic tool to evaluate the health status of the fetus during pregnancy. However, amniotic fluid also contains a heterogeneous cellular population that can be safely collected by amniocentesis and easily cultured. Many different cell types have been found within amniotic fluid and currently some of them are being tested for their possible use for cellular therapy.

RECENT FINDINGS

Potential of pluripotent and multipotent cells isolated from the amniotic fluid has been tested and in-vitro differentiations toward various cell types have been successfully performed. Furthermore, in-vivo studies are highlighting the benefits and mechanisms of amniotic fluid cells for therapy, with particular focus on kidney and lung diseases.

SUMMARY

Amniotic fluid may represent a precious source for easily and safely retrievable cell types that may be used for regenerative medicine purposes.

Formation of functional gap junctions in amniotic fluid-derived stem cells induced by transmembrane co-culture with neonatal rat cardiomyocytes

Amniotic fluid-derived stem cells (AFSC) have been reported to differentiate into cardiomyocyte-like cells and form gap junctions when directly mixed and cultured with neonatal rat ventricular myocytes (NRVM). This study investigated whether or not culture of AFSC on the opposite side of a Transwell membrane from NRVM, allowing for contact and communication without confounding factors such as cell fusion, could direct cardiac differentiation and enhance gap junction formation. Results were compared to shared media (Transwell), conditioned media and monoculture media controls. After a 2-week culture period, AFSC did not express cardiac myosin heavy chain or troponin T in any co-culture group. Protein expression of cardiac calsequestrin 2 was up-regulated in direct transmembrane co-cultures and media control cultures compared to the other experimental groups, but all groups were up-regulated compared with undifferentiated AFSC cultures. Gap junction communication, assessed with a scrape-loading dye transfer assay, was significantly increased in direct transmembrane co-cultures compared to all other conditions. Gap junction communication corresponded with increased connexin 43 gene expression and decreased phosphorylation of connexin 43. Our results suggest that direct transmembrane co-culture does not induce cardiomyocyte differentiation of AFSC, though calsequestrin expression is increased. However, direct transmembrane co-culture does enhance connexin-43-mediated gap junction communication between AFSC.

DNA methylation patterns of imprinting centers for H19, SNRPN, and KCNQ1OT1 in single-cell clones of human amniotic fluid mesenchymal stem cell

OBJECTIVE

To test the hypothesis that human amniotic fluid mesenchymal stem cells contain a unique epigenetic signature in imprinting centers of H19, SNRPN, and KCNQ1OT1 during in vitro cell culture.

MATERIALS AND METHODS

By bisulfite genomic sequencing, we analyzed the imprinting centers of three imprinted genes (including H19, SNRPN, and KCNQ1OT/) in a total of six single-cell clones of human amniotic fluid mesenchymal stem cells at cell passages 7, 8, 9, and 10 during in vitro cell culture.

RESULTS

The imprinting centers of H19 and KCNQ1OT1 showed hypermethylation at passage 7 in all single-cell clones of human amniotic fluid mesenchymal stem cells, and there was no significant change in DNA methylation patterns during in vitro cell culture. The imprinting centers of SNRPN showed variable methylation patterns at passage 7 in six single-cell clones, and DNA methylation patterns varied during in vitro cell culture from passages 8 to 10.

CONCLUSION

In conclusion, human amniotic fluid mesenchymal stem cells contain a unique epigenetic signature during in vitro cell culture. H19 and KCNQ1OT1 possessed a substantial degree of hypermethylation status, and variable DNA methylation patterns of SNRPN was observed during in vitro cell culture of human amniotic fluid mesenchymal stem cells. Our results urge further understanding of epigenetic status of human amniotic fluid mesenchymal stem cells before it is applied in cell replacement therapy.

Amniotic fluid-derived stem cells for cardiovascular tissue engineering applications

Recent research has demonstrated that a population of stem cells can be isolated from amniotic fluid removed by amniocentesis that are broadly multipotent and nontumorogenic. These amniotic fluid-derived stem cells (AFSC) could potentially provide an autologous cell source for treatment of congenital defects identified during gestation, particularly cardiovascular defects. In this review, the various methods of isolating, sorting, and culturing AFSC are compared, along with techniques for inducing differentiation into cardiac myocytes and endothelial cells. Although research has not demonstrated complete and high-yield cardiac differentiation, AFSC have been shown to effectively differentiate into endothelial cells and can effectively support cardiac tissue. Additionally, several tissue engineering and regenerative therapeutic approaches for the use of these cells in heart patches, injection after myocardial infarction, heart valves, vascularized scaffolds, and blood vessels are summarized. These applications show great promise in the treatment of congenital cardiovascular defects, and further studies of isolation, culture, and differentiation of AFSC will help to develop their use for tissue engineering, regenerative medicine, and cardiovascular therapies.

Human amniotic fluid stem cell-derived muscle progenitor cell therapy for stress urinary incontinence

The most promising treatment for stress urinary incontinence can be a cell therapy. We suggest human amniotic fluid stem cells (hAFSCs) as an alternative cell source. We established the optimum in vitro protocol for the differentiation from hAFSCs into muscle progenitors. These progenitors were transplanted into the injured urethral sphincter and their therapeutic effect was analyzed. For the development of an efficient differentiation system in vitro, we examined a commercial medium, co-culture and conditioned medium (CM) systems. After being treated with CM, hAFSCs were effectively developed into a muscle lineage. The progenitors were integrated into the host urethral sphincter and the host cell differentiation was stimulated in vivo. Urodynamic analysis showed significant increase of leak point pressure and closing pressure. Immunohistochemistry revealed the regeneration of circular muscle mass with normal appearance. Molecular analysis observed the expression of a larger number of target markers. In the immunogenicity analysis, the progenitor group had a scant CD8 lymphocyte. In tumorigenicity, the progenitors showed no teratoma formation. These results suggest that hAFSCs can effectively be differentiated into muscle progenitors in CM and that the hAFSC-derived muscle progenitors are an accessible cell source for the regeneration of injured urethral sphincter.

Applications of amniotic membrane and fluid in stem cell biology and regenerative medicine

The amniotic membrane (AM) and amniotic fluid (AF) have a long history of use in surgical and prenatal diagnostic applications, respectively. In addition, the discovery of cell populations in AM and AF which are widely accessible, nontumorigenic and capable of differentiating into a variety of cell types has stimulated a flurry of research aimed at characterizing the cells and evaluating their potential utility in regenerative medicine. While a major focus of research has been the use of amniotic membrane and fluid in tissue engineering and cell replacement, AM- and AF-derived cells may also have capabilities in protecting and stimulating the repair of injured tissues via paracrine actions, and acting as vectors for biodelivery of exogenous factors to treat injury and diseases. Much progress has been made since the discovery of AM and AF cells with stem cell characteristics nearly a decade ago, but there remain a number of problematic issues stemming from the inherent heterogeneity of these cells as well as inconsistencies in isolation and culturing methods which must be addressed to advance the field towards the development of cell-based therapies. Here, we provide an overview of the recent progress and future perspectives in the use of AM- and AF-derived cells for therapeutic applications.

Human amniotic fluid cells form functional gap junctions with cortical cells

The usage of stem cells is a promising strategy for the repair of damaged tissue in the injured brain. Recently, amniotic fluid (AF) cells have received a lot of attention as an alternative source of stem cells for cell-based therapies. However, the success of this approach relies significantly on proper interactions between graft and host tissue. In particular, the reestablishment of functional brain networks requires formation of gap junctions, as a key step to provide sufficient intercellular communication. In this study, we show that AF cells express high levels of CX43 (GJA1) and are able to establish functional gap junctions with cortical cultures. Furthermore, we report an induction of Cx43 expression in astrocytes following injury to the mouse motor cortex and demonstrate for the first time CX43 expression at the interface between implanted AF cells and host brain cells. These findings suggest that CX43-mediated intercellular communication between AF cells and cortical astrocytes may contribute to the reconstruction of damaged tissue by mediating modulatory, homeostatic, and protective factors in the injured brain and hence warrants further investigation.

Human amniotic fluid-derived c-kit(+) and c-kit (-) stem cells: growth characteristics and some differentiation potential capacities comparison

Amniotic fluid (AF) contains heterogeneous and multipotential cell types. A pure mesenchymal stem cells group can be sorted from AF using flow cytometry. In order to evaluate a possible therapeutic application of these cells, the human AF-derived c-kit(+) stem cells (c-kit(+) AFS) were compared with the c-kit(-) (unselected) stem cells (c-kit(-) AFS). Our findings revealed that the optimal period to obtain c-kit(+) AFS cells was between 16 and 22 weeks of gestation. Following cell sorting, c-kit(+) AFS cells shared similar morphological and proliferative characteristics as the c-kit(-) AFS cells. Both c-kit(+) and c-kit(-) AFS cells had the characteristics of mesenchymal stem cells through surface marker identification by flow cytometric and immunocytochemical analysis. Both c-kit(+) and c-kit(-) AFS cells could differentiate along adipogenic and osteogenic lineages. However, the myocardial differentiation capacity was enhanced in c-kit(+) AFS cells by detecting GATA-4, cTnT, α-actin, Cx43 mRNA and protein expression after myocardial induction; whereas induced c-kit(-) AFS cells were only detected with GATA-4 mRNA and protein expression. The c-kit(+) AFS cells could have potential clinical application for myogenesis in cardiac regenerative therapy.

Evaluation of endothelial cells differentiated from amniotic fluid-derived stem cells

Amniotic fluid holds great promise as a stem cell source, especially in neonatal applications where autologous cells can be isolated and used. This study examined chemical-mediated differentiation of amniotic fluid-derived stem cells (AFSC) into endothelial cells and verified the function of AFSC-derived endothelial cells (AFSC-EC). AFSC were isolated from amniotic fluid obtained from second trimester amnioreduction as part of therapeutic intervention from pregnancies affected with twin-twin transfusion syndrome. Undifferentiated AFSC were of normal karyotype with a subpopulation of cells positive for the embryonic stem cell marker SSEA4, hematopoietic stem cell marker c-kit, and mesenchymal stem cell markers CD29, CD44, CD73, CD90, and CD105. Additionally, these cells were negative for the endothelial marker CD31 and hematopoietic differentiation marker CD45. AFSC were cultured in endothelial growth media with concentrations of vascular endothelial growth factor (VEGF) ranging from 1 to 100 ng/mL. After 2 weeks, AFSC-EC expressed von Willebrand factor, endothelial nitric oxide synthase, CD31, VE-cadherin, and VEGF receptor 2. Additionally, the percentage of cells expressing CD31 was positively correlated with VEGF concentration up to 50 ng/mL, with no increase at higher concentrations. AFSC-EC showed a decrease in stem cells markers c-kit and SSEA4 and were morphologically similar to human umbilical vein endothelial cells (HUVEC). In functional assays, AFSC-EC formed networks and metabolized acetylated low-density lipoprotein, also characteristic of HUVEC. Nitrate levels for AFSC-EC, an indirect measure of nitric oxide synthesis, were significantly higher than undifferentiated controls and significantly lower than HUVEC. These results indicate that AFSC can differentiate into functional endothelial-like cells and may have the potential to provide vascularization for constructs used in regenerative medicine strategies.

Amniotic fluid-derived stem cells in regenerative medicine research

The stem cells isolated from amniotic fluid present an exciting possible contribution to the field of regenerative medicine and amniotic fluid-derived stem (AFS) cells have significant potential for research and therapeutic applications. AFS cells are multipotent, showing the ability to differentiate into cell types from all three embryonic germ layers. They express both embryonic and adult stem cell markers, expand extensively without feeder cells, double in 36 h, and are not tumorigenic. The AFS cells can be maintained for over 250 population doublings and preserve their telomere length and a normal karyotype. They differentiate easily into specific cell lineages and do not require human embryo tissue for their isolation, thus avoiding the current controversies associated with the use of human embryonic stem (ES) cells. The discovery of the AFS cells has been recent, and a great deal of work remains to be performed on the characterization and use of these cells. This review describes the various differentiated lineages that AFS cells can form and the future of these promising new stem cells in regenerative medicine research.

In vitro and in vivo cardiomyogenic differentiation of amniotic fluid stem cells

Cell therapy has developed as a complementary treatment for myocardial regeneration. While both autologous and allogeneic uses have been advocated, the ideal candidate has not been identified yet. Amniotic fluid-derived stem (AFS) cells are potentially a promising resource for cell therapy and tissue engineering of myocardial injuries. However, no information is available regarding their use in an allogeneic context. c-kit-sorted, GFP-positive rat AFS (GFP-rAFS) cells and neonatal rat cardiomyocytes (rCMs) were characterized by cytocentrifugation and flow cytometry for the expression of mesenchymal, embryonic and cell lineage-specific antigens. The activation of the myocardial gene program in GFP-rAFS cells was induced by co-culture with rCMs. The stem cell differentiation was evaluated using immunofluorescence, RT-PCR and single cell electrophysiology. The in vivo potential of Endorem-labeled GFP-rAFS cells for myocardial repair was studied by transplantation in the heart of animals with ischemia/reperfusion injury (I/R), monitored by magnetic resonance imaging (MRI). Three weeks after injection a small number of GFP-rAFS cells acquired an endothelial or smooth muscle phenotype and to a lesser extent CMs. Despite the low GFP-rAFS cells count in the heart, there was still an improvement of ejection fraction as measured by MRI. rAFS cells have the in vitro propensity to acquire a cardiomyogenic phenotype and to preserve cardiac function, even if their potential may be limited by poor survival in an allogeneic setting.

Core-shell cell bodies composed of human cbMSCs and HUVECs for functional vasculogenesis

Rapid induction and creation of functional vascular networks is essential for the success of treating ischemic tissues. The formation of mature and functional vascular networks requires the cooperation of endothelial cells (ECs) and perivascular cells. In the study, we used a thermo-responsive hydrogel system to fabricate core-shell cell bodies composed of cord-blood mesenchymal stem cells (cbMSCs) and human umbilical vascular ECs (HUVECs) for functional vasculogenesis. When seeded on Matrigel, the shelled HUVECs attempted to interact and communicate vigorously with the cored cbMSCs initially. Subsequently, HUVECs migrated out and formed tubular structures; cbMSCs were observed to coalesce around the HUVEC-derived tubes. With time progressing, the tubular networks continued to expand without regression, indicating that cbMSCs might function as perivascular cells to stabilize the nascent networks. In the in vivo study, cbMSC/HUVEC bodies were embedded in Matrigel and implanted subcutaneously in nude mice. At day 7, visible blood-filled vessels were clearly identified within the implant containing cbMSC/HUVEC bodies, indicating that the formed vessels anastomosed with the host vasculature. The cored cbMSCs were stained positive for smooth muscle actin, suggesting that they underwent smooth muscle differentiation and formed microvessels with the shelled HUVECs, as the role of perivascular cells. These data confirm that the formation of mature vessels requires heterotypic cooperation of HUVECs and MSCs. This study provides a new strategy for therapeutic vasculogenesis, by showing the feasibility of using cbMSC/HUVEC bodies to create functional vascular networks.

Perinatal sources of mesenchymal stem cells: Wharton's jelly, amnion and chorion

Recently, stem cell biology has become an interesting topic, especially in the context of treating diseases and injuries using transplantation therapy. Several varieties of human stem cells have been isolated and identified in vivo and in vitro. Ideally, stem cells for regenerative medical application should be found in abundant quantities, harvestable in a minimally invasive procedure, then safely and effectively transplanted to either an autologous or allogenic host. The two main groups of stem cells, embryonic stem cells and adult stem cells, have been expanded to include perinatal stem cells. Mesenchymal stem cells from perinatal tissue may be particularly useful in the clinic for autologous transplantation for fetuses and newborns, and after banking in later stages of life, as well as for in utero transplantation in case of genetic disorders.This review highlights the characteristics and therapeutic potential of three human mesenchymal stem cell types obtained from perinatal sources: Wharton's jelly, the amnion, and the chorion.

Enhancement of cell retention and functional benefits in myocardial infarction using human amniotic-fluid stem-cell bodies enriched with endogenous ECM

Stem cell transplantation may repair the infarcted heart. Despite the encouraging preliminary results, an optimal cell type used and low retention of the transplanted cells remain to be overcome. In this study, a multiwelled methylcellulose hydrogel system was used to cultivate human amniotic-fluid stem cells (hAFSCs) to form spherically symmetric cell bodies for cellular cardiomyoplasty. The grown hAFSC bodies enriched with extracellular matrices (ECM) were xenogenically transplanted in the peri-infarct area of an immune-suppressed rat, via direct intramyocardial injection. Results of bioluminescence imaging and real-time PCR revealed that hAFSC bodies could considerably enhance cell retention and engraftment in short-term and long-term observations, when compared with dissociated hAFSCs. Echocardiography and magnetic resonance imaging showed that the enhanced cell engraftment in the hAFSC-body group could significantly attenuate the progression of heart failure, improve the global function, and increase the regional wall motion. At the infarct, expressions of HGF, bFGF and VEGF were significantly up-regulated, an indication of the significantly increased vessel densities in the hearts treated with hAFSC bodies. The injected hAFSC bodies could undergo differentiation into angiogenic and cardiomyogenic lineages and contribute to functional benefits by direct regeneration. The aforementioned results demonstrate that hAFSC bodies can attenuate cell loss after intramuscular injection by providing an adequate physical size and offering an enriched ECM environment to retain the transplanted cells in the myocardium, thus improving heart function.

Amniotic liquid derived stem cells as reservoir of secreted angiogenic factors capable of stimulating neo-arteriogenesis in an ischemic model

Most urgent health problems are related to a blood vessel formation failure. The use of stem cells from different sources or species for both in vitro and in vivo engineering of endothelium does not necessarily imply their direct commitment towards a vascular phenotype. In the present study, we used human amniotic fluid stem cells (AFSC) to evoke a strong angiogenic response in murine recipients, in terms of host guided-regeneration of new vessels, and we demonstrated that the AFSC secretome is responsible for the vascularising properties of these cells. We indentified in AFSC conditioned media (ACM) pro-angiogenic soluble factors, such as MCP-1, IL-8, SDF-1, VEGF. Our in vitro results suggest that ACM are cytoprotective, pro-differentiative and chemoattractive for endothelial cells. We also tested ACM on a pre-clinical model of hind-limb ischemic mouse, concluding that ACM contain mediators that promote the neo-arteriogenesis, as remodelling of pre-existing collateral arteries to conductance vessels, thus preventing the capillary loss and the tissue necrosis of distal muscles. In line with the current regenerative medicine trend, in the present study we assert the concept that stem cell-secreted mediators can guide the tissue repair by stimulating or recruiting host reparative cells.

The LARGE principle of cellular reprogramming: lost, acquired and retained gene expression in foreskin and amniotic fluid-derived human iPS cells

Human amniotic fluid cells (AFCs) are routinely obtained for prenatal diagnostics procedures. Recently, it has been illustrated that these cells may also serve as a valuable model system to study developmental processes and for application in regenerative therapies. Cellular reprogramming is a means of assigning greater value to primary AFCs by inducing self-renewal and pluripotency and, thus, bypassing senescence. Here, we report the generation and characterization of human amniotic fluid-derived induced pluripotent stem cells (AFiPSCs) and demonstrate their ability to differentiate into the trophoblast lineage after stimulation with BMP2/BMP4. We further carried out comparative transcriptome analyses of primary human AFCs, AFiPSCs, fibroblast-derived iPSCs (FiPSCs) and embryonic stem cells (ESCs). This revealed that the expression of key senescence-associated genes are down-regulated upon the induction of pluripotency in primary AFCs (AFiPSCs). By defining distinct and overlapping gene expression patterns and deriving the LARGE (Lost, Acquired and Retained Gene Expression) Principle of Cellular Reprogramming, we could further highlight that AFiPSCs, FiPSCs and ESCs share a core self-renewal gene regulatory network driven by OCT4, SOX2 and NANOG. Nevertheless, these cell types are marked by distinct gene expression signatures. For example, expression of the transcription factors, SIX6, EGR2, PKNOX2, HOXD4, HOXD10, DLX5 and RAXL1, known to regulate developmental processes, are retained in AFiPSCs and FiPSCs. Surprisingly, expression of the self-renewal-associated gene PRDM14 or the developmental processes-regulating genes WNT3A and GSC are restricted to ESCs. Implications of this, with respect to the stability of the undifferentiated state and long-term differentiation potential of iPSCs, warrant further studies.

Biological characteristics of stem cells from foetal, cord blood and extraembryonic tissues

Foetal stem cells (FSCs) can be isolated during gestation from many different tissues such as blood, liver and bone marrow as well as from a variety of extraembryonic tissues such as amniotic fluid and placenta. Strong evidence suggests that these cells differ on many biological aspects such as growth kinetics, morphology, immunophenotype, differentiation potential and engraftment capacity in vivo. Despite these differences, FSCs appear to be more primitive and have greater multi-potentiality than their adult counterparts. For example, foetal blood haemopoietic stem cells proliferate more rapidly than those found in cord blood or adult bone marrow. These features have led to FSCs being investigated for pre- and post-natal cell therapy and regenerative medicine applications. The cells have been used in pre-clinical studies to treat a wide range of diseases such as skeletal dysplasia, diaphragmatic hernia and respiratory failure, white matter damage, renal pathologies as well as cancers. Their intermediate state between adult and embryonic stem cells also makes them an ideal candidate for reprogramming to the pluripotent status.