In vitro and in vivo properties of distinct populations of amniotic fluid mesenchymal progenitor cells

Tissue-specific populations from amniotic fluid-derived mesenchymal stem cells manifest variant in vitro and in vivo properties

Amniotic fluid derived mesenchymal stem cells (AFMSCs), shed along the fetal development, exhibit superior multipotency and immunomodulatory properties compared to MSCs derived from other somatic tissues (e.g., bone marrow and fat). However, AFMSCs display heterogeneity due to source ambiguity, making them an underutilized stem cells source for translational clinical trials. Consequently, there is an urgent need to identify a method to purify the AFMSCs for clinical use. We found that the AFMSCs can be categorized into three distinct groups: kidney-specific AFMSCs (AFMSCs-K), lung-specific AFMSCs (AFMSCs-L), and AFMSCs with an undefined tissue source (AFMSCs-X). This classification was based on tissue-specific gene expression pattern of single cell colony. Additionally, we observed that AFMSCs-X, a minority population within the AFMSCs, exhibited the highest multipotency, proliferation, resistance to senescence and immuno-modulation. Our results showed that AFMSCs-X significantly improved survival rates and reduced bacterial colony forming units (CFU) in cecal ligation and puncture (CLP)-induced septic mice. Therefore, our study introduces a novel classification method to enhance the consistency and efficacy of AFMSCs. These subpopulations, originating from different tissue source, may offer a valuable and innovative resource of cells for regenerative medicine purposes.

MFGE-8 identified in fetal mesenchymal-stromal-cell-derived exosomes ameliorates acute hepatic failure pathology

Liver transplantation is the gold-standard therapy for acute hepatic failure (AHF) with limitations related to organ shortage and life-long immunosuppressive therapy. Cell therapy emerges as a promising alternative to transplantation. We have previously shown that IL-10 and Annexin-A1 released by amniotic fluid human mesenchymal stromal cells (AF-MSCs) and their hepatocyte progenitor-like (HPL) or hepatocyte-like (HPL) cells induce liver repair and downregulate systemic inflammation in a CCl4-AHF mouse model. Herein, we demonstrate that exosomes (EXO) derived from these cells improve liver phenotype in CCl4-induced mice and promote oval cell proliferation. LC-MS/MS proteomic analysis identified MEFG-8 in EXO cargo that facilitates rescue of AHF by suppressing PI3K signaling. Administration of recombinant MFGE-8 protein also reduced liver damage in CCl4-induced mice. Clinically, MEFG-8 expression was decreased in liver biopsies from AHF patients. Collectively, our study provides proof-of-concept for an innovative, cell-free, less immunogenic, and non-toxic alternative strategy for AHF.

scRNA-Seq of Cultured Human Amniotic Fluid from Fetuses with Spina Bifida Reveals the Origin and Heterogeneity of the Cellular Content

Amniotic fluid has been proposed as an easily available source of cells for numerous applications in regenerative medicine and tissue engineering. The use of amniotic fluid cells in biomedical applications necessitates their unequivocal characterization; however, the exact cellular composition of amniotic fluid and the precise tissue origins of these cells remain largely unclear. Using cells cultured from the human amniotic fluid of fetuses with spina bifida aperta and of a healthy fetus, we performed single-cell RNA sequencing to characterize the tissue origin and marker expression of cultured amniotic fluid cells at the single-cell level. Our analysis revealed nine different cell types of stromal, epithelial and immune cell phenotypes, and from various fetal tissue origins, demonstrating the heterogeneity of the cultured amniotic fluid cell population at a single-cell resolution. It also identified cell types of neural origin in amniotic fluid from fetuses with spina bifida aperta. Our data provide a comprehensive list of markers for the characterization of the various progenitor and terminally differentiated cell types in cultured amniotic fluid. This study highlights the relevance of single-cell analysis approaches for the characterization of amniotic fluid cells in order to harness their full potential in biomedical research and clinical applications.

Amniotic Fluid-Derived Mesenchymal Stem/Stromal Cell-Derived Secretome and Exosomes Improve Inflammation in Human Intestinal Subepithelial Myofibroblasts

Inflammatory Bowel Diseases (IBDs) are characterized by chronic relapsing inflammation of the gastrointestinal tract. The mesenchymal stem/stromal cell-derived secretome and secreted extracellular vesicles may offer novel therapeutic opportunities in patients with IBD. Thus, exosomes may be utilized as a novel cell-free approach for IBD therapy. The aim of our study was to examine the possible anti-inflammatory effects of secretome/exosomes on an IBD-relevant, in vitro model of LPS-induced inflammation in human intestinal SubEpithelial MyoFibroblasts (SEMFs). The tested CM (Conditioned Media)/exosomes derived from a specific population of second-trimester amniotic fluid mesenchymal stem/stromal cells, the spindle-shaped amniotic fluid MSCs (SS-AF-MSCs), and specifically, their secreted exosomes could be utilized as a novel cell-free approach for IBD therapy. Therefore, we studied the effect of SS-AF-MSCs CM and exosomes on LPS-induced inflammation in SEMF cells. SS-AF-MSCs CM and exosomes were collected, concentrated, and then delivered into the cell cultures. Administration of both secretome and exosomes derived from SS-AF-MSCs reduced the severity of LPS-induced inflammation. Specifically, IL-1β, IL-6, TNF-α, and TLR-4 mRNA expression was decreased, while the anti-inflammatory IL-10 was elevated. Our results were also verified at the protein level, as secretion of IL-1β was significantly reduced. Overall, our results highlight a cell-free and anti-inflammatory therapeutic agent for potential use in IBD therapy.

Perinatal derivatives: How to best validate their immunomodulatory functions

Perinatal tissues, mainly the placenta and umbilical cord, contain a variety of different somatic stem and progenitor cell types, including those of the hematopoietic system, multipotent mesenchymal stromal cells (MSCs), epithelial cells and amnion epithelial cells. Several of these perinatal derivatives (PnDs), as well as their secreted products, have been reported to exert immunomodulatory therapeutic and regenerative functions in a variety of pre-clinical disease models. Following experience with MSCs and their extracellular vesicle (EV) products, successful clinical translation of PnDs will require robust functional assays that are predictive for the relevant therapeutic potency. Using the examples of T cell and monocyte/macrophage assays, we here discuss several assay relevant parameters for assessing the immunomodulatory activities of PnDs. Furthermore, we highlight the need to correlate the in vitro assay results with preclinical or clinical outcomes in order to ensure valid predictions about the in vivo potency of therapeutic PnD cells/products in individual disease settings.

The Potential Clinical Use of Stem/Progenitor Cells and Organoids in Liver Diseases

The liver represents the most important metabolic organ of the human body. It is evident that an imbalance of liver function can lead to several pathological conditions, known as liver failure. Orthotropic liver transplantation (OLT) is currently the most effective and established treatment for end-stage liver diseases and acute liver failure (ALF). Due to several limitations, stem-cell-based therapies are currently being developed as alternative solutions. Stem cells or progenitor cells derived from various sources have emerged as an alternative source of hepatic regeneration. Therefore, hematopoietic stem cells (HSCs), mesenchymal stromal cells (MSCs), endothelial progenitor cells (EPCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are also known to differentiate into hepatocyte-like cells (HPLCs) and liver progenitor cells (LPCs) that can be used in preclinical or clinical studies of liver disease. Furthermore, these cells have been shown to be effective in the development of liver organoids that can be used for disease modeling, drug testing and regenerative medicine. In this review, we aim to discuss the characteristics of stem-cell-based therapies for liver diseases and present the current status and future prospects of using HLCs, LPCs or liver organoids in clinical trials.

Extraembryonic Mesenchymal Stromal/Stem Cells in Liver Diseases: A Critical Revision of Promising Advanced Therapy Medicinal Products

Liver disorders have been increasing globally in recent years. These diseases are associated with high morbidity and mortality rates and impose high care costs on the health system. Acute liver failure, chronic and congenital liver diseases, as well as hepatocellular carcinoma have been limitedly treated by whole organ transplantation so far. But novel treatments for liver disorders using cell-based approaches have emerged in recent years. Extra-embryonic tissues, including umbilical cord, amnion membrane, and chorion plate, contain multipotent stem cells. The pre-sent manuscript discusses potential application of extraembryonic mesenchymal stromal/stem cells, focusing on the management of liver diseases. Extra-embryonic MSC are characterized by robust and constitutive anti-inflammatory and anti-fibrotic properties, indicating as therapeutic agents for inflammatory conditions such as liver fibrosis or advanced cirrhosis, as well as chronic inflammatory settings or deranged immune responses.

Advancing Regenerative Cellular Therapies in Non-Scarring Alopecia

Alopecia or baldness is a common diagnosis in clinical practice. Alopecia can be scarring or non-scarring, diffuse or patchy. The most prevalent type of alopecia is non-scarring alopecia, with the majority of cases being androgenetic alopecia (AGA) or alopecia areata (AA). AGA is traditionally treated with minoxidil and finasteride, while AA is treated with immune modulators; however, both treatments have significant downsides. These drawbacks compel us to explore regenerative therapies that are relatively devoid of adverse effects. A thorough literature review was conducted to explore the existing proven and experimental regenerative treatment modalities in non-scarring alopecia. Multiple treatment options compelled us to classify them into growth factor-rich and stem cell-rich. The growth factor-rich group included platelet-rich plasma, stem cell-conditioned medium, exosomes and placental extract whereas adult stem cells (adipose-derived stem cell-nano fat and stromal vascular fraction; bone marrow stem cell and hair follicle stem cells) and perinatal stem cells (umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs), Wharton jelly-derived MSCs (WJ-MSCs), amniotic fluid-derived MSCs (AF-MSCs), and placental MSCs) were grouped into the stem cell-rich group. Because of its regenerative and proliferative capabilities, MSC lies at the heart of regenerative cellular treatment for hair restoration. A literature review revealed that both adult and perinatal MSCs are successful as a mesotherapy for hair regrowth. However, there is a lack of standardization in terms of preparation, dose, and route of administration. To better understand the source and mode of action of regenerative cellular therapies in hair restoration, we have proposed the "À La Mode Classification". In addition, available evidence-based cellular treatments for hair regrowth have been thoroughly described.

Small Extracellular Vesicles from Human Amniotic Fluid Samples as Promising Theranostics

Since the first evidence that stem cells can provide pro-resolving effects via paracrine secretion of soluble factors, growing interest has been addressed to define the most ideal cell source for clinical translation. Leftover or clinical waste samples of human amniotic fluid obtained following prenatal screening, clinical intervention, or during scheduled caesarean section (C-section) delivery at term have been recently considered an appealing source of mesenchymal progenitors with peculiar regenerative capacity. Human amniotic fluid stem cells (hAFSC) have been demonstrated to support tissue recovery in several preclinical models of disease by exerting paracrine proliferative, anti-inflammatory and regenerative influence. Small extracellular vesicles (EVs) concentrated from the hAFSC secretome (the total soluble trophic factors secreted in the cell-conditioned medium, hAFSC-CM) recapitulate most of the beneficial cell effects. Independent studies in preclinical models of either adult disorders or severe diseases in newborns have suggested a regenerative role of hAFSC-EVs. EVs can be eventually concentrated from amniotic fluid (hAF) to offer useful prenatal information, as recently suggested. In this review, we focus on the most significant aspects of EVs obtained from either hAFSC and hAF and consider the current challenges for their clinical translation, including isolation, characterization and quantification methods.

Therapeutic mesenchymal stromal stem cells: Isolation, characterization and role in equine regenerative medicine and metabolic disorders

Mesenchymal stromal cells (MSC) have become a popular treatment modality in equine orthopaedics. Regenerative therapies are especially interesting for pathologies like complicated tendinopathies of the distal limb, osteoarthritis, osteochondritis dissecans (OCD) and more recently metabolic disorders. Main sources for MSC harvesting in the horse are bone marrow, adipose tissue and umbilical cord blood. While the acquisition of umbilical cord blood is fairly easy and non-invasive, extraction of bone marrow and adipose tissue requires more invasive techniques. Characterization of the stem cells as a result of any isolation method, is also a crucial step for the confirmation of the cells' stemness properties; thus, three main characteristics must be fulfilled by these cells, namely: adherence, expression of a series of well-defined differentiation clusters as well as pluripotency. EVs, resulting from the paracrine action of MSCs, also play a key role in the therapeutic mechanisms mediated by stem cells; MSC-EVs are thus largely implicated in the regulation of proliferation, maturation, polarization and migration of various target cells. Evidence that EVs alone represent a complex network 0involving different soluble factors and could then reflect biophysical characteristics of parent cells has fuelled the importance of developing highly specific techniques for their isolation and analysis. All these aspects related to the functional and technical understanding of MSCs will be discussed and summarized in this review.

A brief very-low oxygen tension regimen is sufficient for the early chondrogenic commitment of human adipose-derived mesenchymal stem cells

PURPOSE

The aim of this study was to evaluate the effects exerted over chondrogenic commitment of human adipose-derived mesenchymal stem cells (ADSCs) by a very low oxygen tension (<1% pO₂).

MATERIALS/METHODS

Cell morphology, mRNA levels of chondrocyte-specific marker genes and the involvement of p38 MAPK signalling were monitored in human ADSCs under a very low oxygen tension.

RESULTS

Cell morphology was significantly changed after two days of hypoxic preconditioning when they featured as elongated spindle-shaped cells. SRY-box containing gene 9, aggrecan and collagen type II mRNA levels were enhanced under severe hypoxic culture conditions. Moreover, the inhibition of p38 MAPK resulted in a substantial reduction in transcription of the above-mentioned specific genes, proving the pivotal role of this pathway in the transcriptional regulation of chondrogenesis.

CONCLUSIONS

Here, we propose a protocol showing the early commitment of stem cells towards the chondrogenic phenotype in only 2 days of culture via a very low hypoxic environment, in the absence of growth factors added in the culture medium.

Cell sheets using human amniotic fluid stem cells reduce tissue fibrosis in murine full-thickness skin wounds

The use of mesenchymal stem cell sheets is a promising strategy for skin regeneration. The injection of dissociated human amniotic fluid stem cells (hAFSCs) was recently found to accelerate cutaneous wound healing with reduced fibrotic scarring, similar to fetal wound healing. However, the use of hAFSCs in applications of cell sheet technology remains limited. The aim of this study was to determine the in vivo efficacy of in vitro-cultured hAFSC sheets in wound healing. The cell sheets were characterized by immunohistochemistry and RT-qPCR and grafted onto full-thickness wounds in BALB/c mice. The wound size was measured, and re-epithelialization, granulation tissue area, and collagen content of the regenerated wound were analyzed histologically. Although the hAFSC sheet contained abundant extracellular matrix molecules and expressed high levels of anti-fibrotic mediators, its grafting did not affect wound closure or the size of the granulation tissue area. In contrast, the organization of type I collagen bundles in the regenerated wound was markedly reduced, while the levels of type III collagen were increased after implantation of the hAFSC sheet. These results suggest that hAFSC sheets can exert anti-fibrotic properties without delaying wound closure.

Amniotic fluid mesenchymal stromal cells from early stages of embryonic development have higher self-renewal potential

Amniotic fluid (AF) is a rich source of mesenchymal stromal cells (MSCs) that have the ability to differentiate into multiple lineages rendering them a promising and powerful tool for regenerative medicine. However, information regarding the differences among AFMSCs derived from different gestational stages is limited. In the present study, AFMSCs derived from 125 pregnant rats at four embryonic day (E) stages (E12, E15, E18, and E21) were isolated and cultured. The primary E15 cells were the smallest in size and the easiest to culture and usually grew in a spherical shape that resembled the growth morphology of embryonic stem cells (ESCs). Once adhered, the E12 and E15 AFMSCs grew faster and could be passaged more than 60 times while still maintaining a continuous proliferative state; however, AFMSCs derived from E18 and E21 could normally be maintained for only 10 passages. To identify the possible reasons for this difference, RT-qPCR was used to examine several genes associated with self-renewal ability and cell origin. The Sox2 expression levels indicated that AFMSCs from E12 and E15 possessed stronger self-renewal capability. The K19, Col2A1, FGF5, AFP, and SPC expression levels indicated there were mixed-population cells co-existing in the AFMSC culture. In conclusion, E15 cells were easier to culture than E12 cells, could be passaged more often, and had a higher Sox2 expression than E18 or E21 cells. The E15-derived AFMSCs had higher viability and proliferative capacity than cells from the later stages. Therefore, AF cells from the early stages could be a good choice for exploring potential treatments involving AFMSCs.

A comparative analysis of immunomodulatory genes in two clonal subpopulations of CD90+ amniocytes isolated from human amniotic fluid

OBJECT

Immunosuppressive and immunomodulatory activity of mesenchymal stem cells derived from different sources, such as placental membranes, umbilical cord, and amniotic fluid has been proved. The heterogeneous nature of human amniocytes have been confirmed due to different clonal subpopulations found in amniotic fluid. The aim of this study was to investigate a 17-gene panel of immunomodulatory markers in two clonal subpopulations of CD90⁺ amniocytes, divided based on morphology into epithelioid and fibroblastoid cells.

METHOD

Semi-quantitative RT-PCR was used to study the expression of the chosen genes. Flow cytometry analysis confirmed the non-hematopoietic mesenchymal origin of isolated cells, based on lacking the hematopoietic marker of CD31, and the presence of mesenchymal marker of CD90 (both on more than 90% of cells).

RESULTS

Our results showed that besides growth characteristics, the two cell groups were different in expressional profile, so that, fibroblastoid clones displayed higher level of immunosuppression genes as well as mesenchymal surface marker of CD90 compared to epithelioid ones. Our previous investigation on these clones showed that epithelioid cells have a more potential to express the pluripotency genes. It seems there is an inverse relationship between genes associated with immunosuppression and pluripotency.

CONCLUSION

Although many reports have been published regarding the immunosuppressive properties of fetal stem cells, but few studies to date have explained whether the stemness state of human amniocytes may affect their immunosuppressive potential. Further study on amniocytes, which often has self-renewal ability and high immunomodulatory potential, can help to understand the details of this relationship.

Investigating the expression of pluripotency-related genes in human amniotic fluid cells: A semi-quantitative comparison between different subpopulations, from primary to cultured amniocytes

Various classifications have been proposed for human amniotic subpopulations, including classification of spindle-shaped (SS) and round-shaped (RS) cells, as well as the more referred triple-category of epithelioid (E-type) cells, amniotic fluid-specific (AF-type) cells and fibroblastoid (F-type) cells. The present study aims to investigate these amniotic subpopulations regarding the expression of some stem cell markers, including OCT4, NANOG, SOX2, C-KIT (CD117), C-MYC, KLF4, and THY1 (CD90). Flow cytometry was performed to characterize the isolated clonal subpopulations for a hematopoietic and a mesenchymal marker using PE-CD31 and FITC-CD90, respectively. A semi-quantitative RT-PCR analysis was carried out on the isolates in the second half of their lifespan when the cells were at the stationary phase of the growth curve. Characterization of isolated cells demonstrated that all clones including both epithelioid and fibroblastoid cells, had mesenchymal, not hematopoietic, lineage. RT-PCR analysis also revealed a higher expression of the target genes in epithelioid cells. Furthermore, the expression pattern of the genes and their correlations were remarkably different between primary- and long term-cultured amniocytes. Taken together, our results showed that the primary-cultured cells express the stemness genes equally, whereas the long term-cultured amniocytes exhibited a highly variable manner in the expression pattern of the genes. Diverse derivation site of amniocytes and individual genetic background can potentially explain the observed variation in the expression level of the target genes. These can also explain why amniocytes differ in many respects observed in our study, including survival rate, plastic adhesion, and growth characteristics.

Bovine tongue epithelium-derived cells: A new source of bovine mesenchymal stem cells

Mesenchymal stem cells (MSCs) possess the ability to differentiate into multiple cell lineages, and thus, confer great potential for use in regenerative medicine and biotechnology. In the present study, we attempted to isolate and characterize bovine tongue tissue epithelium-derived MSCs (boT-MSCs) and investigate the culture conditions required for long-term culturing of boT-MSCs. boT-MSCs were successfully isolated by the collagenase digestion method and their proliferative capacity was maintained for up to 20 or more passages. We observed a significant increase in the proliferation of boT-MSCs during the 20 consecutive passages under low-glucose Dulbecco’s modified Eagle’s medium culture condition among the three culture conditions. These boT-MSCs presented pluripotency markers (octamer-binding transcription factor 3/4 (Oct3/4) and sex determining region Y-box2 (Sox2)) and cell surface markers, which included CD13, CD29, CD44, CD73, CD90, CD105, CD166, and major histocompatibility complex (MHC) class I (MHC-I) but not CD11b, CD14, CD31, CD34, CD45, CD80, CD86, CD106, CD117, and MHC-II at third passage. Moreover, these boT-MSCs could differentiate into mesodermal (adipocyte, osteocyte, and chondrocyte) cell lineages. Thus, the present study suggests that the tongue of bovines could be used as a source of bovine MSCs.

Therapeutic Potential of Amniotic Fluid Derived Mesenchymal Stem Cells Based on their Differentiation Capacity and Immunomodulatory Properties

BACKGROUND

Amniotic Fluid Derived Mesenchymal Stem Cells (AF-MSCs) are adult, fibroblast- like, self-renewable, multipotent stem cells. During the last decade, the therapeutic potential of AF-MSCs, based on their huge differentiation capacity and immunomodulatory characteristics, has been extensively explored in animal models of degenerative and inflammatory diseases.

OBJECTIVE

In order to describe molecular mechanisms responsible for the therapeutic effects of AFMSCs, we summarized current knowledge about phenotype, differentiation potential and immunosuppressive properties of AF-MSCs.

METHODS

An extensive literature review was carried out in March 2018 across several databases (MEDLINE, EMBASE, Google Scholar), from 1990 to present. Keywords used in the selection were: "amniotic fluid derived mesenchymal stem cells", "cell-therapy", "degenerative diseases", "inflammatory diseases", "regeneration", "immunosuppression". Studies that emphasized molecular and cellular mechanisms responsible for AF-MSC-based therapy were analyzed in this review.

RESULTS

AF-MSCs have huge differentiation and immunosuppressive potential. AF-MSCs are capable of generating cells of mesodermal origin (chondrocytes, osteocytes and adipocytes), neural cells, hepatocytes, alveolar epithelial cells, insulin-producing cells, cardiomyocytes and germ cells. AF-MSCs, in juxtacrine or paracrine manner, regulate proliferation, activation and effector function of immune cells. Due to their huge differentiation capacity and immunosuppressive characteristic, transplantation of AFMSCs showed beneficent effects in animal models of degenerative and inflammatory diseases of nervous, respiratory, urogenital, cardiovascular and gastrointestinal system.

CONCLUSION

Considering the fact that amniotic fluid is obtained through routine prenatal diagnosis, with minimal invasive procedure and without ethical concerns, AF-MSCs represents a valuable source for cell-based therapy of organ-specific or systemic degenerative and inflammatory diseases.

Intra-pancreatic tissue-derived mesenchymal stromal cells: a promising therapeutic potential with anti-inflammatory and pro-angiogenic profiles

Background

Human pancreata contain many types of cells, such as endocrine islets, acinar, ductal, fat, and mesenchymal stromal cells (MSCs). MSCs are important and shown to have a promising therapeutic potential to treat various disease conditions.

Methods

We investigated intra-pancreatic tissue-derived (IPTD) MSCs isolated from tissue fractions that are routinely discarded during pancreatic islet isolation of human cadaveric donors. Furthermore, whether pro-angiogenic and anti-inflammatory properties of these cells could be enhanced was investigated.

Results

IPTD-MSCs were expanded in GMP-compatible CMRL-1066 medium supplemented with 5% human platelet lysate (hPL). IPTD-MSCs were found to be highly pure, with > 95% positive for CD90, CD105, and CD73, and negative for CD45, CD34, CD14, and HLA-DR. Immunofluorescence staining of pancreas tissue demonstrated the presence of CD105⁺ cells in the vicinity of islets. IPTD-MSCs were capable of differentiation into adipocytes, chondrocytes, and osteoblasts in vitro, underscoring their multipotent features. When these cells were cultured in the presence of a low dose of TNF-α, gene expression of tumor necrosis factor alpha-stimulated gene-6 (TSG-6) was significantly increased, compared to control. In contrast, treating cells with dimethyloxallyl glycine (DMOG) (a prolyl 4-hydroxylase inhibitor) enhanced mRNA levels of nuclear factor erythroid 2-related factor 2 (NRF2) and vascular endothelial growth factor (VEGF). Interestingly, a combination of TNF-α and DMOG stimulated the optimal expression of all three genes in IPTD-MSCs. Conditioned medium of IPTD-MSCs treated with a combination of DMOG and TNF-α contained higher levels of pro-angiogenic (VEGF, IL-6, and IL-8) compared to controls, promoting angiogenesis of human endothelial cells in vitro. In contrast, levels of MCP-1, a pro-inflammatory cytokine, were reduced in the conditioned medium of IPTD-MSCs treated with a combination of DMOG and TNF-α.

Conclusions

The results demonstrate that IPTD-MSCs reside within the pancreas and can be separated as part of a standard islet-isolation protocol. These IPTD-MSCs can be expanded and potentiated ex vivo to enhance their anti-inflammatory and pro-angiogenic profiles. The fact that IPTD-MSCs are generated in a GMP-compatible procedure implicates a direct clinical application.

Functional secretome analysis reveals Annexin-A1 as important paracrine factor derived from fetal mesenchymal stem cells in hepatic regeneration

BACKGROUND

Human mesenchymal stem/stromal cells (MSCs) and their secreted molecules exert beneficial effects in injured tissues by promoting tissue regeneration and angiogenesis and by inhibiting inflammation and fibrosis. We have previously demonstrated that the therapeutic activity of fetal MSCs derived from amniotic fluid (AF-MSCs) and their hepatic progenitor-like cells (HPL) is mediated by paracrine effects in a mouse model of acute hepatic failure (AHF).

METHODS

Herein, we have combined proteomic profiling of the AF-MSCs and HPL cell secretome with ex vivo and in vivo functional studies to identify specific soluble factors, which underpin tissue regeneration in AHF.

FINDINGS

The anti-inflammatory molecule Annexin-A1 (ANXA1) was detected at high levels in both AF-MSC and HPL cell secretome. Further functional analyses revealed that the shRNA-mediated knock-down of ANXA1 in MSCs (shANXA1-MSCs) decreased their proliferative, clonogenic and migratory potential, as well as their ability to differentiate into HPL cells. Liver progenitors (oval cells) from AHF mice displayed reduced proliferation when cultured ex vivo in the presence of conditioned media from shANXA1-MSCs compared to control MSCs secretome. Intra-hepatic delivery of conditioned media from control MSCs but not shANXA1-MSCs reduced liver damage and circulating levels of pro-inflammatory cytokines in AHF.

INTERPRETATION

Collectively, our study uncovers secreted Annexin-A1 as a novel effector of MSCs in liver regeneration and further underscores the potential of cell-free therapeutic strategies for liver diseases. FUND: Fondation Santé, GILEAD Asklipeios Grant, Fellowships of Excellence - Siemens, IKY, Reinforcement of Postdoctoral Researchers, IKY.

Amniotic Fluid Cells, Stem Cells, and p53: Can We Stereotype p53 Functions?

In recent years, great interest has been devoted to finding alternative sources for human stem cells which can be easily isolated, ideally without raising ethical objections. These stem cells should furthermore have a high proliferation rate and the ability to differentiate into all three germ layers. Amniotic fluid, ordinarily discarded as medical waste, is potentially such a novel source of stem cells, and these amniotic fluid derived stem cells are currently gaining a lot of attention. However, further information will be required about the properties of these cells before they can be used for therapeutic purposes. For example, the risk of tumor formation after cell transplantation needs to be explored. The tumor suppressor protein p53, well known for its activity in controlling Cell Prolif.eration and cell death in differentiated cells, has more recently been found to be also active in amniotic fluid stem cells. In this review, we summarize the major findings about human amniotic fluid stem cells since their discovery, followed by a brief overview of the important role played by p53 in embryonic and adult stem cells. In addition, we explore what is known about p53 in amniotic fluid stem cells to date, and emphasize the need to investigate its role, particularly in the context of cell tumorigenicity.

Down-regulated WDR35 contributes to fetal anomaly via regulation of osteogenic differentiation

BACKGROUND

Autosomal recessive disorder is closely correlated with congenital fetal malformation. The mutation of WDR35 may lead to short rib-polydactyly syndrome (SRP), asphyxiating thoracic dystrophy (ATD, Jeune syndrome) and Ellis van Creveld syndrome. The purpose of this study is to investigate the role of WDR35 in fetal anomaly.

RESULTS

The fetuses presented malformation with abnormal head shape, cardiac dilatation, pericardial effusion, and non-displayed left pulmonary artery and left lung. After the detection of genomic DNA (gDNA) in amniotic fluid cells (AFC), chromosomal rearrangement was found in arr[hg19] 2p25.3p23.3. It was revealed through multiple PCR-DHPLC that MYCN, WDR35, LPIN1, ODC1, KLF11 and NBAS contained duplicated copy numbers in 2p25.3p23.3. AF-MSCs were mostly positive for CD44, CD105, negative for CD34 and CD14. Western Blot test showed that WDR35-encoded protein was decreased in the patients' AFC compared to that in normal pregnant women. In the patients' amniotic fluid-derived mesenchymal stem cells (AF-MSCs), WDR35 overexpression could repair cilia formation, and the overexpression of WDR35 or Gli2 could significantly enhance ALP activity and expressions of osteogenic differentiation marker genes, including RUNXE2, OCN, BSP and ALP. However, WDR35 silencing in C3H10T1/2 cells could remarkably inhibit cilia formation and osteogenic differentiation. This inhibitory effect could be attenuated by Gli2 overexpression.

CONCLUSIONS

The results demonstrated that copy number variation (CNV) of WDR35 may lead to skeletal dysplasia and fetal anomaly, and that down-regulated WDR35 may damage the cilia formation and sequentially indirectly regulate Gli signal, which would eventually result in negative regulation of osteogenic differentiation.

Human amniotic fluid stem cells have a unique potential to accelerate cutaneous wound healing with reduced fibrotic scarring like a fetus

Adult wound healing can result in fibrotic scarring (FS) characterized by excess expression of myofibroblasts and increased type I/type III collagen expression. In contrast, fetal wound healing results in complete regeneration without FS, and the mechanism remains unclear. Amniotic fluid cells could contribute to scar-free wound healing, but the effects of human amniotic fluid cells are not well characterized. Here, we determined the effect of human amniotic fluid stem cells (hAFS) on FS during wound healing. Human amniotic fluid was obtained by amniocentesis at 15-17 weeks of gestation. CD117-positive cells were isolated and defined as hAFS. hAFS (1 × 10⁶) suspended in PBS or cell-free PBS were injected around wounds created in the dorsal region of BALB/c mice. Wound size was macroscopically measured, and re-epithelialization in the epidermis, granulation tissue area in the dermis and collagen contents in the regenerated wound were histologically analyzed. The ability of hAFS to engraft in the wound was assessed by tracking hAFS labeled with PKH-26. hAFS fulfilled the minimal criteria for mesenchymal stem cells. hAFS injection into the wound accelerated wound closure via enhancement of re-epithelialization with less FS. The process was characterized by lower numbers of myofibroblasts and higher expression of type III collagen. Finally, transplanted hAFS were clearly observed in the dermis until day 7 implying that hAFS worked in a paracrine manner. hAFS can function in a paracrine manner to accelerate cutaneous wound healing, producing less FS, a process resembling fetal wound healing.

Identification and Characterization of a Stem Cell-Like Population in Bovine Milk: A Potential New Source for Regenerative Medicine in Veterinary

Milk is a complex fluid required for development, nutrition and immunological protection to the newborn offspring. Interestingly, latest finding proved the presence of novel stem cell population in human milk with multilineage differentiation potential. Given that little is known about cellular milk content in other mammalian species such as bovine, the purpose of our study was to isolate and characterize a potential stem cell-like population in bovine milk. In detail, we first analyzed the phenotype of the isolated cells able to grow in plastic adherence and then their capability to differentiate into osteogenic, chondrogenic, and adipogenic lineages. Bovine milk stem cells (bMSCs) resulted plastic adherent and showed a heterogeneous population with epithelial and spindle-shaped cells. Successively, their immunophenotype indicated that bovine milk cells were positive for the typical epithelial markers E-cadherin, cytokeratin-14, cytokeratin-18, and smooth muscle actin. Notably, a subset (30%-40%), constantly observed in purified milk cells, showed the typical mesenchymal surface antigens CD90, CD73, and CD105. Furthermore, the same percentage of bMSCs expressing CD90, CD73, and CD105 presented the stemness markers SOX2 and OCT4 translocated in their nuclei. Finally, our data showed that bMSCs were able to differentiate into osteoblasts, chondroblasts, and adipocytes. In addition, the flow cytometry analysis revealed the presence of a subpopulation of events characterized by typical extracellular vesicles (EVs, size 0.1-1 μm), which did not contain nuclei and were positive for the same markers identified on the surface of bMSCs (CD73, CD90, and CD105), and thus might be considered milk cell-derived EVs. In conclusion, our data suggest that bovine milk is an easily available source of multipotent stem cells able to differentiate into multiple cell lineages. These features can open new possibilities for development biology and regenerative medicine in veterinary area to improving animal health.

Human Amniotic Fluid Stem Cells: Therapeutic Potential for Perinatal Patients with Intractable Neurological Disease

Mesenchymal stem cells (MSCs) have generated great interest in the fields of regenerative medicine and immunotherapy because of their unique biological properties. Among MSCs, amniotic fluid stem cells (AFS) have a number of characteristics that make them attractive candidates for tissue engineering and cell replacement strategies, particularly for perinatal medicine. If various neonatal conditions, including birth asphyxia, preterm birth, and congenital abnormalities, which result in long-lasting severe impairments, could be predicted during pregnancy, it would allow collection of small samples of amniotic fluid cells by amniocentesis. In vitro culture of these autologous AFS during pregnancy would make them available for use soon after birth. Hypoxic-ischemic encephalopathy (HIE) and myelomeningocele (MMC) are neonatal conditions that cause permanent neurological disability, for which the treatment options are extremely limited. Experiments using animal models of HIE and MMC and human clinical trials have demonstrated that MSCs, including AFS, have beneficial effects on the central nervous system through paracrine influences, indicating that autologous AFS treatment may be applicable for intractable neurological diseases, including HIE and MMC, during the perinatal period. In this review, we focus on recent research related to the therapeutic potential of AFS for perinatal neurological diseases such as HIE and MMC.

Amniotic fluid stem cell exosomes: Therapeutic perspective

It is widely accepted that the therapeutic potential of stem cells can be largely mediated by paracrine factors, also included into exosomes. Thus, stem cell-derived exosomes represent a major therapeutic option in regenerative medicine avoiding, if compared to stem cells graft, abnormal differentiation and tumor formation. Exosomes derived from mesenchymal stem cells (MSC) induce damaged tissue repair, and can also exert immunomodulatory effects on the differentiation, activation and function of different lymphocytes. Therefore, MSC exosomes can be considered as a potential treatment for inflammatory diseases and also an ideal candidate for allogeneic therapy due to their low immunogenicity. Amniotic fluid stem cells (AFSCs) are broadly multipotent, can be expanded in culture, and can be easily cryopreserved in cellular banks. In this study, morphology, phenotype, and protein content of exosomes released into amniotic fluid in vivo and from AFSC during in vitro culture (conditioned medium) were examined. We found that AFSC-derived exosomes present different molecules than amniotic fluid ones, some of them involved in immunomodulation, such transforming growth factor beta and hepatic growth factors. The immunomodulatory effect of AFSC's exosomes on peripheral blood mononuclear cells stimulated with phytohemagglutinin was compared to that of the supernatant produced by such conditioned media deprived of exosomes. We present evidence that the principal effect of AFSC conditioned media (without exosomes) is the induction of apoptosis in lymphocytes, whereas exposure to AFSC-derived exosomes decreases the lymphocyte's proliferation, supporting the hypothesis that the entire secretome of stem cells differently affects immune-response. © 2017 BioFactors, 44(2):158-167, 2018.

Neuroprotection of the hypoxic-ischemic mouse brain by human CD117+CD90+CD105+ amniotic fluid stem cells

Human amniotic fluid contains two morphologically-distinct sub-populations of stem cells with regenerative potential, spindle-shaped (SS-hAFSCs) and round-shaped human amniotic fluid stem cells (RS-hAFSCs). However, it is unclear whether morphological differences correlate with functionality, and this lack of knowledge limits their translational applications. Here, we show that SS-hAFSCs and RS-hAFSCs differ in their neuro-protective ability, demonstrating that a single contralateral injection of SS-hAFSCs into hypoxic-ischemic P7 mice conferred a 47% reduction in hippocampal tissue loss and 43–45% reduction in TUNEL-positive cells in the hippocampus and striatum 48 hours after the insult, decreased microglial activation and TGFβ1 levels, and prevented demyelination. On the other hand, RS-hAFSCs failed to show such neuro-protective effects. It is possible that SS-hAFSCs exert their neuroprotection via endoglin-dependent inhibition of TGFβ1 signaling in target cells. These findings identify a sub-population of CD117⁺CD90⁺CD105⁺ stem cells as a promising source for the neuro-protection of the developing brain.

Therapeutic Potential of Secreted Molecules Derived from Human Amniotic Fluid Mesenchymal Stem/Stroma Cells in a Mice Model of Colitis

Inflammatory bowel diseases (IBDs) are the result of pathological immune responses due to environmental factors or microbial antigens into a genetically predisposed individual. Mainly due to their trophic properties, a mounting interest is focused on the use of human mesenchymal stem/stromal cells (hMSCs) to treat IBD disease in animal models. The aim of the study is to test whether the secreted molecules, derived from a specific population of second trimester amniotic fluid mesenchymal stem/stromal cells, the spindle-shaped MSCs (SS-AF-MSCs), could be utilized as a novel therapeutic, cell free approach for IBD therapy. Induction of colitis was achieved by oral administration of dextran sulphate sodium (DSS) (3 % w/v in tap water), for 5 days, to 8-week-old NOD/SCID mice. The progression of colitis was assessed on a daily basis through recording the body weight, stool consistency and bleeding. Conditioned media (CM) derived from SS-AF-MSCs were collected, concentrated and then delivered intraperitoneally into DSS treated mice. To evaluate and determine the inflammatory cytokine levels, histopathological approach was applied. Administration of CM derived from SS-AF-MSCs cells reduced the severity of colitis in mice. More importantly, TGFb1 protein levels were increased in the mice received CM, while TNFa and MMP2 protein levels were decreased, respectively. Accordingly, IL-10 was significantly increased in mice received CM, whereas TNFa and IL-1b were decreased at mRNA level. Our results demonstrated that CM derived from SS-AF-MSCs cells is able to ameliorate DSS-induced colitis in immunodeficient colitis mouse model, and thus, it has a potential for use in IBD therapy.

Menaquinone-4 enhances osteogenic potential of human amniotic fluid mesenchymal stem cells cultured in 2D and 3D dynamic culture systems

Menaquinones, also known as Vitamin K2 family, regulate calcium homeostasis in a 'bone-vascular cross-talk' and recently received particular attention for their positive effect on bone formation. Given that the correlation between menaquinones and bone metabolism to date is still unclear, the objective of our study was to investigate the possible role of menaquinone-4 (MK-4), an isoform of the menaquinones family, in the modulation of osteogenesis. For this reason, we used a model of human amniotic fluid mesenchymal stem cells (hAFMSCs) cultured both in two-dimensional (2D) and three-dimensional (3D; RCCS™bioreactor) in vitro culture systems. Furthermore, to mimic the 'bone remodelling unit' in vitro, hAFMSCs were co-cultured in the 3D system with human monocyte cells (hMCs) as osteoclast precursors. The results showed that in a conventional 2D culture system, hAFMSCs were responsive to the MK-4, which significantly improved the osteogenic process through γ-glutamyl carboxylase-dependent pathway. The same results were obtained in the 3D dynamic system where MK-4 treatment supported the osteoblast-like formation promoting the extracellular bone matrix deposition and the expression of the osteogenic-related proteins (alkaline phosphatase, osteopontin, collagen type-1 and osteocalcin). Notably, when the hAFMSCs were co-cultured in a 3D dynamic system with the hMCs, the presence of MK-4 supported the cellular aggregate formation as well as the osteogenic function of hAFMSCs, but negatively affected the osteoclastogenic process. Taken together, our results demonstrate that MK-4 supported the aggregate formation of hAFMSCs and increased the osteogenic functions. Specifically, our data could help to optimize bone regenerative medicine combining cell-based approaches with MK-4 treatment.

Term amniotic fluid: an unexploited reserve of mesenchymal stromal cells for reprogramming and potential cell therapy applications

BACKGROUND

Mesenchymal stromal cells (MSCs) are currently being evaluated in numerous pre-clinical and clinical cell-based therapy studies. Furthermore, there is an increasing interest in exploring alternative uses of these cells in disease modelling, pharmaceutical screening, and regenerative medicine by applying reprogramming technologies. However, the limited availability of MSCs from various sources restricts their use. Term amniotic fluid has been proposed as an alternative source of MSCs. Previously, only low volumes of term fluid and its cellular constituents have been collected, and current knowledge of the MSCs derived from this fluid is limited. In this study, we collected amniotic fluid at term using a novel collection system and evaluated amniotic fluid MSC content and their characteristics, including their feasibility to undergo cellular reprogramming.

METHODS

Amniotic fluid was collected at term caesarean section deliveries using a closed catheter-based system. Following fluid processing, amniotic fluid was assessed for cellularity, MSC frequency, in-vitro proliferation, surface phenotype, differentiation, and gene expression characteristics. Cells were also reprogrammed to the pluripotent stem cell state and differentiated towards neural and haematopoietic lineages.

RESULTS

The average volume of term amniotic fluid collected was approximately 0.4 litres per donor, containing an average of 7 million viable mononuclear cells per litre, and a CFU-F content of 15 per 100,000 MNCs. Expanded CFU-F cultures showed similar surface phenotype, differentiation potential, and gene expression characteristics to MSCs isolated from traditional sources, and showed extensive expansion potential and rapid doubling times. Given the high proliferation rates of these neonatal source cells, we assessed them in a reprogramming application, where the derived induced pluripotent stem cells showed multigerm layer lineage differentiation potential.

CONCLUSIONS

The potentially large donor base from caesarean section deliveries, the high yield of term amniotic fluid MSCs obtainable, the properties of the MSCs identified, and the suitability of the cells to be reprogrammed into the pluripotent state demonstrated these cells to be a promising and plentiful resource for further evaluation in bio-banking, cell therapy, disease modelling, and regenerative medicine applications.

TGFβ-induced osteogenic potential of human amniotic fluid stem cells via CD73-generated adenosine production

The human amniotic fluid stem cell (hAFSC) population consists of two morphologically distinct subtypes, spindle-shaped and round-shaped cells (SS-hAFSCs and RS-hAFSCs). Whilst SS-hAFSCs are routinely expanded in mesenchymal-type (MT) conditions, we previously showed that they acquire broader differentiation potential when cultured under embryonic-type (ET) conditions. However, the effects of culture conditions on RS-hAFSCs have not been determined. Here, we show that culturing RS-hAFSCs under ET conditions confers faster proliferation and enhances the efficiency of osteogenic differentiation of the cells. We show that this occurs via TGFβ-induced activation of CD73 and the associated increase in the generation of extracellular adenosine. Our data demonstrate that culture conditions are decisive for the expansion of hAFSCs and that TGFβ present in ET conditions causes the phenotype of RS-hAFSCs to revert to an earlier state of stemness. Cultivating RS-hAFSCs in ET conditions with TGFβ may therefore increase their therapeutic potential for clinical applications.

Highly potent stem cells from full-term amniotic fluid: A realistic perspective

Amniotic fluid (AF) is now known to harbor highly potent stem cells, making it an excellent source for cell therapy. However, most of the stem cells isolated are from AF of mid-term pregnancies in which the collection procedure involves an invasive technique termed amniocentesis. This has limited the access in getting the fluid as the technique imposes certain level of risks to the mother as well as to the fetus. Alternatively, getting AF from full-term pregnancies or during deliveries would be a better resolution. Unfortunately, very few studies have isolated stem cells from AF at this stage of gestation, the fluid that is merely discarded. The question remains whether full-term AF harbors stem cells of similar potency as of the stem cells of mid-term AF. Here, we aim to review the prospect of having this type of stem cells by first looking at the origin and contents of AF particularly during different gestation period. We will then discuss the possibility that the AF, at full term, contains a population of highly potent stem cells. These stem cells are distinct from, and probably more potent than the AF mesenchymal stem cells (AF-MSCs) isolated from full-term AF. By comparing the studies on stem cells isolated from mid-term versus full-term AF from various species, we intend to address the prospect of having highly potent amniotic fluid stem cells from AF of full-term pregnancies in human and animals.

miR-26a Mediates Adipogenesis of Amniotic Fluid Mesenchymal Stem/Stromal Cells via PTEN, Cyclin E1, and CDK6

Recent findings indicate that microRNAs (miRNAs) are critical for the regulatory network of adipogenesis in human mesenchymal stem/stromal cells (MSCs). Fetal MSCs derived from amniotic fluid (AF-MSCs) represent a population of multipotent stem cells characterized by a wide range of differentiation properties that can be applied in cell-based therapies. In this study, miRNA microarray analysis was performed to assess miRNA expression in terminal differentiated AF-MSCs into adipocyte-like cells (AL cells). MiR-26a was identified in high expression levels in AL cells indicating a critical role in the process of adipogenesis. Overexpression of miR-26a in AF-MSCs led to significant induction of their adipogenic differentiation properties that were altered after miR-26a inhibition. We have demonstrated that miR-26a regulates adipogenesis through direct inhibition of PTEN, which in turn promotes activation of Akt pathway. Also, miR-26a modulates cell cycle during adipogenesis by interacting with Cyclin E1 and CDK6. These results point to the regulatory role of miR-26a and its target genes PTEN, Cyclin E1, and CDK6 in adipogenic differentiation of AF-MSCs, providing a basis for understanding the mechanisms of fat cell development and obesity.

Isolation, Characterization, Cryopreservation of Human Amniotic Stem Cells and Differentiation to Osteogenic and Adipogenic Cells

Human stem cells and progenitor cells can be used to treat cancer and replace dysfunctional cells within a tissue or organ. The objective of this study was to identify the appropriate cells type in regenerative medicine and targeted therapy. As an alternative to embryonic and bone marrow stem cells, we examined human amniotic fluid stem cells (hAFSCs), one of the potential source of multipotent stem cells isolated from both cell pellet (using single-stage method), and supernatant of human amniotic fluid. Source of isolation and unique property of the cells emphasize that these cells are one of the promising new tools in therapeutic field. Double sources for isolation and availability of the left over samples in diagnostic laboratory at the same time have less legal and ethical concerns compared with embryonic stem cell studies. Cells were isolated, cultured for 18^th passage for 6 months and characterized using qPCR and flow cytometry. Cells showed good proliferative ability in culture condition. The cells successfully differentiated into the adipogenic and osteogenic lineages. Based on these findings, amniotic fluid can be considered as an appropriate and convenient source of human amniotic fluid stem cells. These cells provide potential tools for therapeutic applications in the field of regenerative medicine. To get a better understanding of crosstalk between Oct4/NANOG with osteogenesis and adipogenesis, we used network analysis based on Common Targets algorithm and Common Regulators algorithm as well as subnetwork discovery based on gene set enrichment. Network analysis highlighted the possible role of MIR 302A and MIR let-7g. We demonstrated the high expression of MIR 302A and low expression of MIR let7g in hAFSCs by qPCR.

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.

Human Amniotic Fluid Mesenchymal Stem Cells from Second- and Third-Trimester Amniocentesis: Differentiation Potential, Molecular Signature, and Proteome Analysis

Human amniotic fluid stem cells have become an attractive stem cell source for potential applications in regenerative medicine and tissue engineering. The aim of this study was to characterize amniotic fluid-derived mesenchymal stem cells (AF-MSCs) from second- and third-trimester of gestation. Using two-stage protocol, MSCs were successfully cultured and exhibited typical stem cell morphological, specific cell surface, and pluripotency markers characteristics. AF-MSCs differentiated into adipocytes, osteocytes, chondrocytes, myocytes, and neuronal cells, as determined by morphological changes, cell staining, and RT-qPCR showing the tissue-specific gene presence for differentiated cell lineages. Using SYNAPT G2 High Definition Mass Spectrometry technique approach, we performed for the first time the comparative proteomic analysis between undifferentiated AF-MSCs from late trimester of gestation and differentiated into myogenic, adipogenic, osteogenic, and neurogenic lineages. The analysis of the functional and expression patterns of 250 high abundance proteins selected from more than 1400 demonstrated the similar proteome of cultured and differentiated AF-MSCs but the unique changes in their expression profile during cell differentiation that may help the identification of key markers in differentiated cells. Our results provide evidence that human amniotic fluid of second- and third-trimester contains stem cells with multilineage potential and may be attractive source for clinical applications.

Stem cells from human amniotic fluid exert immunoregulatory function via secreted indoleamine 2,3-dioxygenase1

Although human amniotic fluid does contain different populations of foetal-derived stem cells, scanty information is available on the stemness and the potential immunomodulatory activity of in vitro expanded, amniotic fluid stem cells. By means of a methodology unrequiring immune selection, we isolated and characterized different stem cell types from second-trimester human amniotic fluid samples (human amniotic fluid stem cells, HASCs). Of those populations, one was characterized by a fast doubling time, and cells were thus designated as fHASCs. Cells maintained their original phenotype under prolonged in vitro passaging, and they were able to originate embryoid bodies. Moreover, fHASCs exhibited regulatory properties when treated with interferon (IFN)-γ, including induction of the immunomodulatory enzyme indoleamine 2,3-dioxygenase 1 (IDO1). On coculture with human peripheral blood mononuclear cells, IFN-γ-treated fHASCs caused significantly decreased T-cell proliferation and increased frequency in CD4(+)  CD25(+)  FOXP3(+) regulatory T cells. Both effects required an intact IDO1 function and were cell contact-independent. An unprecedented finding in our study was that purified vesicles from IFN-γ-treated fHASCs abundantly expressed the functional IDO1 protein, and those vesicles were endowed with an fHASC-like regulatory function. In vivo, fHASCs were capable of immunoregulatory function, promoting allograft survival in a mouse model of allogeneic skin transplantation. This was concurrent with the expansion of CD4(+)  CD25(+)  Foxp3(+) T cells in graft-draining lymph nodes from recipient mice. Thus fHASCs, or vesicles thereof, may represent a novel opportunity for immunoregulatory maneuvers both in vitro and in vivo.

Human Adipose Stem Cells: From Bench to Bedside

Stem cell-based therapies for repair and regeneration of different tissues are becoming more important in the treatment of several diseases. Adult stem cells currently symbolize the most available source of cell progenitors for tissue engineering and repair and can be harvested using minimally invasive procedures. Moreover, mesenchymal stem cells (MSCs), the most widely used stem cells in stem cell-based therapies, are multipotent progenitors, with capability to differentiate into cartilage, bone, connective, muscle, and adipose tissue. So far, bone marrow has been regarded as the main source of MSCs. To date, human adult adipose tissue may be the best suitable alternative source of MSCs. Adipose stem cells (ASCs) can be largely extracted from subcutaneous human adult adipose tissue. A large number of studies show that adipose tissue contains a biologically and clinically interesting heterogeneous cell population called stromal vascular fraction (SVF). The SVF may be employed directly or cultured for selection and expansion of an adherent population, so called adipose-derived stem cells (ASCs). In recent years, literature based on data related to SVF cells and ASCs has augmented considerably: These studies have demonstrated the efficacy and safety of SVF cells and ASCs in vivo in animal models. On the basis of these observations, in several countries, various clinical trials involving SVF cells and ASCs have been permitted. This review aims at summarizing data regarding either ASCs cellular biology or ASCs-based clinical trials and at discussing the possible future clinical translation of ASCs and their potentiality in cell-based tissue engineering.

Molecular and phenotypic characterization of human amniotic fluid-derived cells: a morphological and proteomic approach

Mesenchymal Stem Cells derived from Amniotic Fluid (AFMSCs) are multipotent cells of great interest for regenerative medicine. Two predominant cell types, that is, Epithelial-like (E-like) and Fibroblast-like (F-like), have been previously detected in the amniotic fluid (AF). In this study, we examined the AF from 12 donors and observed the prevalence of the E-like phenotype in 5, whereas the F-like morphology was predominant in 7 samples. These phenotypes showed slight differences in membrane markers, with higher CD90 and lower Sox2 and SSEA-4 expression in F-like than in E-like cells; whereas CD326 was expressed only in the E-like phenotype. They did not show any significant differences in osteogenic, adipogenic or chondrogenic differentiation. Proteomic analysis revealed that samples with a predominant E-like phenotype (HC1) showed a different profile than those with a predominant F-like phenotype (HC2). Twenty-five and eighteen protein spots were differentially expressed in HC1 and HC2 classes, respectively. Of these, 17 from HC1 and 4 from HC2 were identified by mass spectrometry. Protein-interaction networks for both phenotypes showed strong interactions between specific AFMSC proteins and molecular chaperones, such as preproteasomes and mature proteasomes, both of which are important for cell cycle regulation and apoptosis. Collectively, our results provide evidence that, regardless of differences in protein profiling, the prevalence of E-like or F-like cells in AF does not affect the differentiation capacity of AFMSC preparations. This may be valuable information with a view to the therapeutic use of AFMSCs.

Isolation and in vitro characterization of bovine amniotic fluid derived stem cells at different trimesters of pregnancy

Amniotic fluid (AF) is a source of multipotent mesenchymal stem cells (MSCs), very promising cells for tissue engineering in clinical application. The aim of this work was to isolate and characterize cells isolated from bovine AF as alternative sources of primitive multipotent stem cells in a species that could be a large-animal model for biomedical and biotechnology researches. Samples were recovered, at slaughterhouse, from 39 pregnant cows at different trimesters of pregnancy and cells were cultured in vitro. At passages (P) 3 and 7 differentiation towards chondrogenic, osteogenic and adipogenic lineages was induced. Flow cytometry analysis for CD90, CD105, CD73, CD44, CD34, CD45 and CD14 was performed, immunocytochemistry (ICC) for Oct4, SSEA4, α-SMA, Vimentin, N- and E- Cadherin and CK and qPCR analysis for OCT4, NANOG and SOX2 were carried out. The cell yield was significantly higher in the first trimester compared to the second and the third one (P < 0.05). Cells were isolated from 25/39 samples and cell population appeared heterogeneous. Two main cell types were identified in samples from all trimesters: round- (RS) and spindle-shaped (SS) cells. 17/25 samples showed both populations (mixed, MX). Both cell types showed MSC-markers and differentiation capability with some variability related to the passages. The SS-population also expressed low levels of stemness markers such as NANOG and SSEA4 but not OCT4. Bovine AF shows a heterogeneous cell population containing also MSCs, multipotent cells that represent an intermediate stage between embryonic stem cells and adult ones.

Do oral bacteria alter the regenerative potential of stem cells? A concise review

Mesenchymal stem cells (MSCs) are widely recognized as critical players in tissue regeneration. New insights into stem cell biology provide evidence that MSCs may also contribute to host defence and inflammation. In case of tissue injury or inflammatory diseases, e.g. periodontitis, stem cells are mobilized towards the site of damage, thus coming in close proximity to bacteria and bacterial components. Specifically, in the oral cavity, complex ecosystems of commensal bacteria live in a mutually beneficial state with the host. However, the formation of polymicrobial biofilm communities with pathogenic properties may trigger an inadequate host inflammatory-immune response, leading to the disruption of tissue homoeostasis and development of disease. Because of their unique characteristics, MSCs are suggested as crucial regulators of tissue regeneration even under such harsh environmental conditions. The heterogeneous effects of bacteria on MSCs across studies imply the complexity underlying the interactions between stem cells and bacteria. Hence, a better understanding of stem cell behaviour at sites of inflammation appears to be a key strategy in developing new approaches for in situ tissue regeneration. Here, we review the literature on the effects of oral bacteria on cell proliferation, differentiation capacity and immunomodulation of dental-derived MSCs.

Xenotransplantation of human adipose-derived stem cells in zebrafish embryos

Zebrafish is a widely used animal model with well-characterized background in developmental biology. The fate of human adipose-derived stem cells (ADSCs) after their xenotransplantation into the developing embryos of zebrafish is unknown. Therefore, human ADSCs were firstly isolated, and then transduced with lentiviral vector system carrying a green fluorescent protein (GFP) reporter gene, and followed by detection of their cell viability and the expression of cell surface antigens. These GFP-expressing human ADSCs were transplanted into the zebrafish embryos at 3.3–4.3 hour post-fertilization (hpf). Green fluorescent signal, the proliferation and differentiation of human ADSCs in recipient embryos were respectively examined using fluorescent microscopy and immunohistochemical staining. The results indicated that human ADSCs did not change their cell viability and the expression levels of cell surface antigens after GFP transduction. Microscopic examination demonstrated that green fluorescent signals of GFP expressed in the transplanted cells were observed in the embryos and larva fish at post-transplantation. The positive staining of Ki-67 revealed the survival and proliferation of human ADSCs in fish larvae after transplantation. The expression of CD105 was observable in the xenotransplanted ADSCs, but CD31 expression was undetectable. Therefore, our results indicate that human ADSCs xenotransplanted in the zebrafish embryos not only can survive and proliferate at across-species circumstance, but also seem to maintain their undifferentiation status in a short term. This xenograft model of zebrafish embryos may provide a promising and useful technical platform for the investigation of biology and physiology of stem cells in vivo.

Comparative proteomic analysis of two distinct stem-cell populations from human amniotic fluid

Human amniotic fluid (AF) contains a variety of stem cells of embryonic and extra-embryonic origins. We characterized two distinct types of stem cells isolated from residual AF material derived from prenatal diagnostic amniocentesis. The two types of cells differed in their morphology and growth kinetics, showing fast (fast human amniotic stem cells; fHASCs) or slow (slow human amniotic stem cells; sHASCs) population-doubling times. Both fHASCs and sHASCs expressed pluripotent stem-cell markers, yet unlike sHASCs, clonogenic fHASCs would generate embryoid bodies and maintain their original phenotype during prolonged in vitro passaging. fHASCs - but not sHASCs - expressed the KLF4, SSEA-4 and CD117 markers. Differential proteomic analysis allowed us to identify the protein patterns specific for either cell type as potentially contributing to their distinct phenotypes. We found thirty-six proteins that were differentially expressed by the two cell types, and those proteins were classified according to their biological and molecular functions. Bioinformatic cluster analysis revealed differential occurrence of cytoskeletal proteins, such as vimentin, F-actin-binding protein, and chloride intracellular channel protein 1. Selected proteins differentially expressed by fHASCs and sHASCs were further characterized by Western blot analysis and confocal microscopy.

Perinatal stem cells: A promising cell resource for tissue engineering of craniofacial bone

In facing the mounting clinical challenge and suboptimal techniques of craniofacial bone defects resulting from various conditions, such as congenital malformations, osteomyelitis, trauma and tumor resection, the ongoing research of regenerative medicine using stem cells and concurrent advancement in biotechnology have shifted the focus from surgical reconstruction to a novel stem cell-based tissue engineering strategy for customized and functional craniofacial bone regeneration. Given the unique ontogenetical and cell biological properties of perinatal stem cells, emerging evidence has suggested these extraembryonic tissue-derived stem cells to be a promising cell source for extensive use in regenerative medicine and tissue engineering. In this review, we summarize the current achievements and obstacles in stem cell-based craniofacial bone regeneration and subsequently we address the characteristics of various types of perinatal stem cells and their novel application in tissue engineering of craniofacial bone. We propose the promising feasibility and scope of perinatal stem cell-based craniofacial bone tissue engineering for future clinical application.

Platelet-rich plasma (PRP) promotes fetal mesenchymal stem/stromal cell migration and wound healing process

Numerous studies have shown the presence of high levels of growth factors during the process of healing. Growth factors act by binding to the cell surface receptors and contribute to the subsequent activation of signal transduction mechanisms. Wound healing requires a complex of biological and molecular events that includes attraction and proliferation of different type of cells to the wound site, differentiation and angiogenesis. More specifically, migration of various cell types, such as endothelial cells and their precursors, mesenchymal stem/stromal cells (MSCs) or skin fibroblasts (DFs) plays an important role in the healing process. In recent years, the application of platelet rich plasma (PRP) to surgical wounds and skin ulcerations is becoming more frequent, as it is believed to accelerate the healing process. The local enrichment of growth factors at the wound after PRP application causes a stimulation of tissue regeneration. Herein, we studied: (i) the effect of autologous PRP in skin ulcers of patients of different aetiology, (ii) the proteomic profile of PRP, (iii) the migration potential of amniotic fluid MSCs and DFs in the presence of PRP extract in vitro, (iv) the use of the PRP extract as a substitute for serum in cultivating AF-MSCs. Considering its easy access, PRP may provide a valuable tool in multiple therapeutic approaches.