Human amniotic mesenchymal cells have some characteristics of cardiomyocytes

Mesenchymal stromal cells from human perinatal tissues: From biology to cell therapy

Cell-based regenerative medicine is of growing interest in biomedical research. The role of stem cells in this context is under intense scrutiny and may help to define principles of organ regeneration and develop innovative therapeutics for organ failure. Utilizing stem and progenitor cells for organ replacement has been conducted for many years when performing hematopoietic stem cell transplantation. Since the first successful transplantation of umbilical cord blood to treat hematological malignancies, non-hematopoietic stem and progenitor cell populations have recently been identified within umbilical cord blood and other perinatal and fetal tissues. A cell population entitled mesenchymal stromal cells (MSCs) emerged as one of the most intensely studied as it subsumes a variety of capacities: MSCs can differentiate into various subtypes of the mesodermal lineage, they secrete a large array of trophic factors suitable of recruiting endogenous repair processes and they are immunomodulatory.Focusing on perinatal tissues to isolate MSCs, we will discuss some of the challenges associated with these cell types concentrating on concepts of isolation and expansion, the comparison with cells derived from other tissue sources, regarding phenotype and differentiation capacity and finally their therapeutic potential.

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

Human amniotic fluid stem cells (hAFSCs) derived from second-trimester amniocentesis were evaluated for the therapeutic potential of cardiac repair. Whether hAFSCs can be differentiated into cardiomyogenic cells and toward the maturation of endothelial cell lineage was investigated in vitro using mimicking differentiation milieu. Employing an immune-suppressed rat model with experimental myocardial infarction, an intramyocardial injection was conducted with a needle directly into the peri-infarct areas. There were three treatment groups: sham, saline, and hAFSCs (n > or = 10). When cultured with rat neonatal cardiomyocytes or in endothelial growth medium-2 enriched with vascular endothelial growth factor, hAFSCs were differentiated into cardiomyocyte-like cells and cells of endothelial lineage, respectively. After 4 weeks, hAFSC-treated animals showed a preservation of the infarcted thickness, an attenuation of left ventricle remodeling, a higher vascular density, and thus an improvement in cardiac function, when compared with the saline injection group. Survival and proliferation of the transplanted hAFSCs were revealed by immunohistochemical staining. Expressions of the cardiac-specific markers such as Nkx2.5, alpha-actinin, and cardiac Troponin T were observed in the transplanted hAFSCs. Additionally, Cx43 was clearly expressed at the borders of the transplanted/transplanted and host/transplanted cells, an indication of enhancement of cell connection. The results demonstrated that hAFSCs induce angiogenesis, have cardiomyogenic potential, and may be used as a new cell source for cellular cardiomyoplasty.

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.

Osteogenic differentiation of intact human amniotic membrane

Tissue engineering strategies usually require cell isolation and combination with a suitable biomaterial. Human amniotic membrane (AM) represents a natural two-layered sheet comprising cells with proven stem cell characteristics. In our approach, we evaluated the differentiation potential of AM in toto with its sessile stem cells as alternative to conventional approaches requiring cell isolation and combination with biomaterials. For this, AM-biopsies were differentiated in vitro using two osteogenic media compared with control medium (CM) for 28 days. Mineralization and osteocalcin expression was demonstrated by (immuno)histochemistry. Alkaline phosphatase (AP) activity, calcium contents and mRNA expression of RUNX2, AP, osteopontin, osteocalcin, BMP-2 (bone morphogenetic protein), and BMP-4 were quantified and AM viability was evaluated. Under osteogenic conditions, AM-biopsies mineralized successfully and by day 28 the majority of cells expressed osteocalcin. This was confirmed by a significant rise in calcium contents (up to 27.4 ± 6.8 mg/dl d28), increased AP activity, and induction of RUNX2, AP, BMP-2 and BMP-4 mRNA expression. Relatively high levels of viability were retained, especially in osteogenic media (up to 78.3 ± 19.0% d14; 62.9 ± 22.3% d28) compared to CM (42.2 ± 15.2% d14; 35.1 ± 8.6% d28). By this strategy, stem cells within human AM can successfully be driven along the osteogenic pathways while residing within their natural environment.

Xenografted human amniotic membrane-derived mesenchymal stem cells are immunologically tolerated and transdifferentiated into cardiomyocytes

RATIONALE

Amniotic membrane is known to have the ability to transdifferentiate into multiple organs and is expected to stimulate a reduced immunologic reaction.

OBJECTIVE

Determine whether human amniotic membrane-derived mesenchymal cells (hAMCs) can be an ideal allograftable stem cell source for cardiac regenerative medicine.

METHODS AND RESULTS

We established hAMCs. After cardiomyogenic induction in vitro, hAMCs beat spontaneously, and the calculated cardiomyogenic transdifferentiation efficiency was 33%. Transplantation of hAMCs 2 weeks after myocardial infarction improved impaired left ventricular fractional shortening measured by echocardiogram (34+/-2% [n=8] to 39+/-2% [n=11]; P<0.05) and decreased myocardial fibrosis area (18+/-1% [n=9] to 13+/-1% [n=10]; P<0.05), significantly. Furthermore hAMCs transplanted into the infarcted myocardium of Wistar rats were transdifferentiated into cardiomyocytes in situ and survived for more than 4 weeks after the transplantation without using any immunosuppressant. Immunologic tolerance was caused by the hAMC-derived HLA-G expression, lack of MHC expression of hAMCs, and activation of FOXP3-positive regulatory T cells. Administration of IL-10 or progesterone, which is known to play an important role in feto-maternal tolerance during pregnancy, markedly increased HLA-G expression in hAMCs in vitro and, surprisingly, also increased cardiomyogenic transdifferentiation efficiency in vitro and in vivo.

CONCLUSIONS

Because hAMCs have a high ability to transdifferentiate into cardiomyocytes and to acquire immunologic tolerance in vivo, they can be a promising cellular source for allograftable stem cells for cardiac regenerative medicine.

Toward cell therapy using placenta-derived cells: disease mechanisms, cell biology, preclinical studies, and regulatory aspects at the round table

Among the many cell types that may prove useful to regenerative medicine, mounting evidence suggests that human term placenta-derived cells will join the list of significant contributors. In making new cell therapy-based strategies a clinical reality, it is fundamental that no a priori claims are made regarding which cell source is preferable for a particular therapeutic application. Rather, ongoing comparisons of the potentiality and characteristics of cells from different sources should be made to promote constant improvement in cell therapies, and such comparisons will likely show that individually tailored cells can address disease-specific clinical needs. The principle underlying such an approach is resistance to the notion that comprehensive characterization of any cell type has been achieved, neither in terms of phenotype nor risks-to-benefits ratio. Tailoring cell therapy approaches to specific conditions also requires an understanding of basic disease mechanisms and close collaboration between translational researchers and clinicians, to identify current needs and shortcomings in existing treatments. To this end, the international workshop entitled "Placenta-derived stem cells for treatment of inflammatory diseases: moving toward clinical application" was held in Brescia, Italy, in March 2009, and aimed to harness an understanding of basic inflammatory mechanisms inherent in human diseases with updated findings regarding biological and therapeutic properties of human placenta-derived cells, with particular emphasis on their potential for treating inflammatory diseases. Finally, steps required to allow their future clinical application according to regulatory aspects including good manufacturing practice (GMP) were also considered. In September 2009, the International Placenta Stem Cell Society (IPLASS) was founded to help strengthen the research network in this field.

In vitro and in vivo study of human amniotic fluid-derived stem cell differentiation into myogenic lineage

Recent findings have shown that amniotic fluid (AF) could be a putative new source of multipotent stem cells (SC). We investigated whether these human SC could efficiently differentiate into myogenic lineage in vitro and integrate in vivo skeletal muscle in severe combined immunodeficiency (SCID) mice. C/kit immunomagnetic-sorted AF (AF c/kit+) SC were characterized by immunocytochemistry and Southern blotting for myogenic markers (desmin, MyoD). In vitro, AF c/kit+ SC phenotypic conversion into myogenic cells was assayed by myogenic-specific induction media. AF c/kit+ SC without ex vivo manipulation were transplanted into the tibialis anterior (TA) of (SCID) mice. Acquisition of a myogenic-like phenotype (desmin, MyoD) in AF c/kit+ SC was observed after culture in myogenic-specific induction media. In vivo, transplanted AF c/kit+ SC showed an engraftment in the skeletal muscle of SCID mice, but with unexpected tubular glandular tissue-like differentiation. Importantly, no immuno-rejection, inflammatory response or tumorigenicity of these cells was found. Within these experimental conditions, AF c/kit+ SC were able to differentiate into myogenic cells in vitro, but not in vivo after their transplantation into the skeletal muscle of SCID mice. Because AF c/kit+ SC survived and differentiated into tubular gland-like cells after their transplantation in the TA, an ex vivo engagement in myogenic pathway prior their transplantation could favor their differentiation into myogenic cells in vivo.

Alternative sources of adult stem cells: human amniotic membrane

Human amniotic membrane is a highly promising cell source for tissue engineering. The cells thereof, human amniotic epithelial cells (hAEC) and human amniotic mesenchymal stromal cells (hAMSC), may be immunoprivileged, they represent an early developmental status, and their application is ethically uncontroversial. Cell banking strategies may use freshly isolated cells or involve in vitro expansion to increase cell numbers. Therefore, we have thoroughly characterized the effect of in vitro cultivation on both phenotype and differentiation potential of hAEC. Moreover, we present different strategies to improve expansion including replacement of animal-derived supplements by human platelet products or the introduction of the catalytic subunit of human telomerase to extend the in vitro lifespan of amniotic cells. Characterization of the resulting cultures includes phenotype, growth characteristics, and differentiation potential, as well as immunogenic and immunomodulatory properties.

Mesenchymal stem cells: emerging therapy for Duchenne muscular dystrophy

Multipotent cells that can give rise to bone, cartilage, fat, connective tissue, and skeletal and cardiac muscle are termed mesenchymal stem cells. These cells were first identified in the bone marrow, distinct from blood-forming stem cells. Based on the embryologic derivation, availability, and various pro-regenerative characteristics, research exploring their use in cell therapy shows great promise for patients with degenerative muscle diseases and a number of other conditions. In this review, the authors explore the potential for mesenchymal stem cell therapy in the emerging field of regenerative medicine with a focus on treatment for Duchenne muscular dystrophy.

Naive rat amnion-derived cell transplantation improved left ventricular function and reduced myocardial scar of postinfarcted heart

Stem cells contained in the amniotic membrane may be useful for cellular repair of the damaged heart. Previously, we showed that amnion-derived cells (ADCs) express embryonic stem cell surface markers and pluripotent stem cell-specific transcription factor genes. These ADCs also possess the potential for mesoderm (cardiac) lineage differentiation. In the present study we investigated whether untreated naive ADC transplantation into the injured left ventricular (LV) myocardium is beneficial as a cell-based cardiac repair strategy in a rat model. ADCs were isolated from Lewis rat embryonic day 14 amniotic membranes. FACS analysis revealed that freshly isolated ADCs contained stage-specific embryonic antigen-1 (SSEA-1), Oct-4-positive cells, and mesenchymal stromal cells, while hematopoietic stem cell marker positive cells were absent. Reverse transcription-PCR revealed that naive ADCs expressed cardiac and vascular specific genes. We injected freshly isolated ADCs (2 x 10(6) cells suspended in PBS, ADC group) into acutely infarcted LV myocardium produced by proximal left coronary ligation. PBS was injected in postinfarction controls (PBS group). Cardiac function was assessed at 2 and 6 weeks after injection. ADC treatment attenuated LV dilatation and sustained LV contractile function at 2 and 6 weeks in comparison to PBS controls (p < 0.05, ANOVA). LV peak systolic pressure and maximum dP/dt of ADC-treated heart were higher and LV end-diastolic pressure and negative dP/dt were lower than in PBS controls (p < 0.05). Histological assessment revealed that infarcted myocardium of the ADC-treated group had less fibrosis, thicker ventricular walls, and increased capillary density (p < 0.05). The fate of injected ADCs was confirmed using ADCs derived from EGFP(+) transgenic rats. Immunohistochemistry at 6 weeks revealed that EGFP(+) cells colocalized with von Willebrand factor, alpha-smooth muscle actin, or cardiac troponin-I. Our results suggest that naive ADCs are a potential cell source for cellular cardiomyoplasty.

Amniotic stem cells for cellular cardiomyoplasty: promises and premises

Cellular cardiomyoplasty is undergoing intensive investigation as a new form of therapy for severely damaged hearts. Among several cell types, mesenchymal stem cells (MSCs) have been proposed as a potential cell source. MSC can be found in adult tissues or in fetal tissues like the umbilical chord blood, amniotic membrane, or amniotic fluid (AF). AF-MSCs have properties intermediate between embryonic and adult MSC, which make them particularly attractive for cellular regeneration. It has been shown that MSC could differentiate in cardiomyocytes-like cells in vitro. In some animal models, it has also been shown that transplanted MSC could engraft and show some cardiomyocytes-like characteristics. Since MSC do not express HLA-DR and present in vitro and in vivo immunosuppressive properties, they can be envisioned to be used in allogenic cellular cardiomyoplasty. Based on these promises, MSC from adult donors are currently used in small safety and feasibility trials. No clinical trial using AF-MSC has been performed yet. Still, the exact role of true cell repopulation and in situ cardiomyocytes differentiation versus pure paracrine effect after cell transplantation is currently much debated. Cellular cardiomyoplasty is a fascinating new area of investigation in regenerative medicine. Although considerable knowledge has been gained over the last decade on the use of MSC as a potential stem cell (SC) source, many issues remain unsolved. Because of several limitations in animal models, clinical studies in highly selected patients balancing the risks and benefits are required. In that regard, MSCs obtained from the fetal AF are a potential new source of SCs that need to be further investigated for cellular cardiomyoplasty.

Phenotypic shift of human amniotic epithelial cells in culture is associated with reduced osteogenic differentiation in vitro

BACKGROUND

Amniotic membrane is a highly promising cell source for tissue engineering. Being part of the placenta, this tissue is abundantly available. It can be processed easily to yield large amounts of epithelial and mesenchymal cells that have shown broad differentiation potential. For tissue-engineering purposes, cells may be applied either directly after isolation from the tissue or after a period of in vitro expansion to obtain higher cell numbers. In order to investigate the advantages and drawbacks of these strategies we compared freshly isolated and cultivated human amniotic epithelial cells (hAEC) regarding their surface antigen (Ag) expression profile and osteogenic differentiation capacity.

METHODS

Expression of surface Ag that are characteristic for mesenchymal stromal and embryonic stem cells was analyzed by flow cytometry. Different protocols for osteogenic and adipogenic differentiation were compared.

RESULTS

We have demonstrated that expression of surface Ag changes dramatically during cultivation of hAEC. While not or only weakly expressed on primary isolates, the mesenchymal markers CD13, CD44, CD49e, CD54, CD90 and CD105 are strongly up-regulated during in vitro propagation. In contrast, expression of the embryonic markers TRA-1-60 and TRA-1-81, but not SSEA-4, rapidly decreases upon cultivation. This phenotypic shift is associated with a reduction in osteogenic differentiation.

DISCUSSION

Our results suggest that phenotypic alterations of hAEC during in vitro cultivation might be responsible for a functional reduction of the differentiation potential, which has to be considered for the potential application of these cells in regenerative medicine.

Novel sources of fetal stem cells: where do they fit on the developmental continuum?

The recent isolation of fetal stem cells from several sources either at the early stages of development or during the later trimesters of gestation, sharing similar growth kinetics and expressing pluripotency markers, provides strong support to the notion that these cells may be biologically closer to embryonic stem cells, actually representing intermediates between embryonic stem cells and adult mesenchymal stem cells, regarding proliferation rates and plasticity features, and thus able to confer an advantage over postnatal mesenchymal stem cells derived from conventional adult sources such as bone marrow. This conclusion has been strengthened by the different pattern of growth potential between the two stage-specific types of sources, as assessed by transcriptomic and proteomic analysis. A series of recent studies regarding the numerous novel features of fetal stem cells has reignited our interest in the field of stem-cell biology and in the possibilities for the eventual repair of damaged organs and the generation of in vitro tissues on biomimetic scaffolds for transplantation. These studies, employing elegant approaches and novel technologies, have provided new insights regarding the nature and the potential of fetal stem cells derived from placenta, amniotic fluid, amnion or umbilical cord. In this update, we highlight the major progression that has occurred in fetal stem-cell biology and discuss the most important areas for future investigation in the field of regenerative medicine.

Mesenchymal stem cell: present challenges and prospective cellular cardiomyoplasty approaches for myocardial regeneration

Myocardial ischemia and cardiac dysfunction have been known to follow ischemic heart diseases (IHDs). Despite a plethora of conventional treatment options, their efficacies are associated with skepticism. Cell therapies harbor a promising potential for vascular and cardiac repair, which is corroborated by adequate preclinical evidence. The underlying objectives behind cardiac regenerative therapies subsume enhancing angiomyogenesis in the ischemic myocardium, ameliorating cellular apoptosis, regenerating the damaged myocardium, repopulating the lost resident myocardial cells (smooth muscle, cardiomyocyte, and endothelial cells), and finally, decreasing fibrosis with a consequent reduction in ventricular remodeling. Although-cell based cardiomyoplasty approaches have an immense potential, their clinical utilization is limited owing to the increased need for better candidates for cellular cardiomyoplasty, better routes of delivery, appropriate dose for efficient engraftment, and better preconditioning or genetic-modification strategies for the progenitor and stem cells. Mesenchymal stem cells (MSCs) have emerged as powerful candidates in mediating myocardial repair owing to their unique properties of multipotency, transdifferentiation, intercellular connection with the resident cardiomyocytes via connexin 43 (Cx43)-positive gap junctions in the myocardium, and most important, immunomodulation. In this review, we present an in-depth discussion on the complexities associated with stem and progenitor cell therapies, the potential of preclinical approaches involving MSCs for myocardial repair, and an account of the past milestones and ongoing MSC-based trials in humans.

Amniotic membrane patching promotes ischemic rat heart repair

The amniotic membrane has long been applied for wound healing and treatment of ophthalmological disorders, even though the mechanisms underlying its actions remain to be clarified. Recently, cells derived from fetal membranes of human term placenta have raised strong interest in regenerative medicine for their stem cell potential and immunomodulatory features. Our study aimed to investigate the possible utility of amniotic membrane to limit postischemic cardiac injury. A fragment of human amniotic membrane was applied onto the left ventricle of rats that had undergone ischemia through left anterior descending coronary artery ligation. Echocardiographic assessment of morphological and functional cardiac parameters was then performed over a 3-month period. We demonstrated that application of an amniotic membrane fragment onto ischemic rat hearts could significantly reduce postischemic cardiac dysfunction. The amniotic membrane-treated rats showed higher preservation of cardiac dimensions and improved cardiac contractile function in terms of higher left ventricle ejection fraction, fractional shortening, and wall thickening. These improvements were apparent by day 7 after application of the amniotic membrane, persisted for at least 2 months, and occurred independently of cardiac injury severity. No engraftment of amniotic cells was detected into host cardiac tissues. Our results suggest that use of amniotic membrane may constitute a convenient vehicle for supplying cells that produce cardioprotective soluble factors, and reinforce the notion that this tissue constitutes a cell source with clinical potential that has yet to be completely revealed.

Fetal tissue engineering

Attempts at harnessing the prospective benefits of the therapeutic use of fetal cells or tissues date many decades before the modern era of transplantation. The first reported transplantation of human fetal tissue took place in 1922. Fetal cells or tissues also have been used as helpful investigational tools since the 1930s. Still, it was only in the last three decades that fetal tissue transplantation in people has started to lead to favorable outcomes, yet by and large anecdotally. This article offers an outlook on a relatively new dimension in fetal cell-based therapies, namely the engineering of tissues in the laboratory, along with its prospective applications.

Human amniotic mesenchymal cells differentiate into chondrocytes

Recently, cartilage diseases have been treated by auto- or allogenic chondrocyte transplantation. However, such treatments are limited by the necessity of having a large amount of cells for transplantation, the risk of rejection, and donor shortage. Since the human amnion is immune-privileged tissue suitable for allotransplantation, the potential of human amniotic mesenchymal cells (HAMc) to differentiate into chondrocytes was assessed. The expression of gene encoding transcription factors SOXs and bone morphogenetic proteins (BMPs) as well as BMP receptors were assessed. Chondrocyte phenotype was characterized by positive expression of the cartilage marker genes collagen type II and aggrecan by RT-PCR, collagen type II protein were analyzed by immunofluorescence analysis. HAMc expressed chondrocyte-related genes, including SOXs, BMPs, as well as BMP receptors. Collagen type II and aggrecan were detected after the induction of chondrogenesis with BMP-2. HAMc, transplanted into noncartilage tissue of mice with BMP-2, or implanted with collagen-scaffold into the defects generated in a rat's bone, underwent morphological changes with deposition of collagen type II. These results showed that HAMc have the potential to differentiate into chondrocytes in vitro and in vivo, suggesting that they have therapeutic potential for the treatment of damaged or diseased cartilage.

Amniotic membrane and amniotic fluid-derived cells: potential tools for regenerative medicine?

Human amniotic membranes and amniotic fluid have attracted increasing attention in recent years as a possible reserve of stem cells that may be useful for clinical application in regenerative medicine. Many studies have been conducted to date in terms of the differentiation potential of these cells, with several reports demonstrating that cells from both the amniotic fluid and membrane display high plasticity. In addition, cells from the amniotic membrane have also been shown to display immunomodulatory characteristics both in vivo and in vitro, which could make them useful in an allotransplantation setting. Here, we provide an overview comparing the latest findings regarding the stem characteristics of cells from both the amniotic membrane and amniotic fluid, as well as on the potential utility of these cells for future clinical application in regenerative medicine.

Preferential expansion of human umbilical cord blood-derived CD34-positive cells on major histocompatibility complex-matched amnion-derived mesenchymal stem cells

BACKGROUND

We previously found in a murine hematopoietic system that hematopoietic stem cells show high differentiation and proliferation capacity on bone marrow-derived mesenchymal stem cells/stromal cells (microenvironment) with "self" major histocompatibility complex (MHC).

DESIGN AND METHODS

We examined whether amnion-derived adherent cells have the characteristics of mesenchymal stem cells, and whether these adherent cells can support the proliferation of umbilical cord blood-derived lineage-negative and CD34-positive cells (Lin(-)CD34(+) cells) obtained from the same fetus to a greater extent than those derived from other fetuses.

RESULTS

Culture-expanded amnion-derived adherent cells expressed mesenchymal stem cell markers and HLA-ABC molecules and could differentiate into osteoblasts, adipocytes and chondrocyte-like cells, indicating that the cells have the characteristics of mesenchymal stem cells. The Lin(-)CD34(+) cells purified from the frozen umbilical cord blood were strongly positive for HLA-ABC, and contained a large number of hematopoietic stem cells. When the Lin(-)CD34(+) cells were cultured on the autologous (MHC-matched) or MHC-mismatched amnion-derived adherent cells in short-term assays (hematopoietic stem cell-proliferation) and long-term culture-initiating cell assays, greater expansion of the Lin(-)CD34(+) cells was observed in the MHC-matched combination than in MHC-mismatched combinations. The concentration of granulocyte-macrophage colony-stimulating factor in the culture supernatants of the long-term culture-initiating cell assays was significantly higher in the MHC-matched combination than in MHC-mismatched combinations.

CONCLUSIONS

IT is likely that a MHC restriction exists between hematopoietic stem cells and mesenchymal stem cells/stromal cells in the human hematopoietic system and that granulocute-macropage colony-stimulating factor contributes to some extent to the preferential hematopoiesis-supporting ability of the MHC-matched amnion-derived adherent cells.

The influence of various storage conditions on cell viability in amniotic membrane

Up to now freeze-dried, gamma-sterilised or glycerol-preserved amniotic membranes (AMs) have widely been used in the field of ophthalmology and wound care (e.g. leg ulcers, burns). After some preservation processes in use, like freeze-drying or glycerol-preserving, the cells in the AM are no longer viable. Within this study we evaluated the influence of different short-term and long-term storage conditions on cell viability in AM. Therefore AMs from cesarean section placentae were washed and biopsied to evaluate the microbiological status and to determine the viability of the tissue. Additionally, viability under various storage conditions was examined by assessment of mitochondrial activity. Preservation included temperatures above and below 0 degrees C as well as various media compositions. As expected, cell viability in amnion decreases during storage, in fact the effect was more pronounced when stored frozen, but the higher viability of amnion obtained by storage above 0 degrees C with medium is associated with the limitation to a short period of storage of about 28 days. The evaluated preservation methods are the basis for future non-clinical in-vivo studies in which the possible benefit of amnion as a viable biomaterial in wound healing will be investigated.

Comparative characterization of cultured human term amnion epithelial and mesenchymal stromal cells for application in cell therapy

Emerging evidence suggests human amnion tissue as a valuable source of two distinct types of pluripotent cells, amnion epithelial cells (hAECs) and mesenchymal stromal cells (hAMSCs), for applications in cell replacement therapy. For some approaches, it may be necessary to culture and differentiate these cells before they can be transplanted. No systematic attempt has been yet made to determine the quantity and quality of amnion cells after isolation and culture. We looked at amnion cell isolates from 27 term placentas. Following our optimized protocol, primary yields were 6.3 x 10(6) hAECs and 1.7 x 10(6) hAMSCs per gram amnion. All 27 cases gave vital cultures of hAMSCs, while one third of cases (9 of 27) failed to give adherent cultures of hAECs. Primary cultures contained significantly more proliferating than apoptotic cells (hAECs: 16.4% vs. 4.0%; hAMSCs: 9.5% vs. 2.4%). Neither hAECs nor hAMSCs were clonogenic. They showed slow proliferation that almost stopped beyond passage 5. Microscopic follow-up revealed that hAEC morphology gradually changed towards mesenchymal phenotype over several passages. Flow cytometric characterization of primary cultures showed expression of mesenchymal progenitor markers CD73, CD90, CD105, and CD166, as well as the embryonic stem cell markers SSEA-3 and -4 on both amnion cell types. These profiles were grossly maintained in secondary cultures. Reverse transcriptase-PCR analysis exhibited transcripts of Oct-3/4 and stem cell factor in primary and secondary cultures of all cases, but no telomerase reverse transcriptase. Immunocytochemistry confirmed translation into Oct-3/4 protein in part of hAEC cultures, but not in hAMSCs. Further, both amnion cell types stained for CD90 and SSEA-4. Osteogenic induction studies with amnion cells from four cases showed significantly stronger differentiation of hAECs than hAMSCs; this capacity to differentiate greatly varied between cases. In conclusion, hAECs and hAMSCs in culture exhibit and maintain a similar marker profile of mesenchymal progenitors. hAECs were found as a less reliable source than hAMSCs and altered morphology during subculture.

Human fetal membranes: a source of stem cells for tissue regeneration and repair?

The ability of stem cells to differentiate into multiple cell lineages has ushered in exciting possibilities for stem cell based therapies that would be used to regenerate and repair damaged tissues and organs. Stem cells isolated from the embryo, fetus, adult and also the umbilical cord and placenta are being widely tested. Recent studies show that human fetal membranes also harbour cells with stem cell like properties. The amnion and chorion contain stromal cells that display characteristics and differentiation potential similar to that of adult, bone marrow derived mesenchymal stem cells. Amniotic epithelial cells share some of the features of pluripotent embryonic stem cells and multipotent mesenchymal stem cells and differentiate into multiple cell lineages in vitro. Amniotic epithelial cells also produce numerous substances that could augment tissue regeneration and repair. This review will focus on the stem cell like properties of stromal and epithelial cells derived from human fetal membranes and their potential use in stem cell based therapies.

Human amnion-derived mesenchymal stem cells are a potential source for uterine stem cell therapy

OBJECTIVES

Human amnion is an easy-to-obtain novel source of human mesenchymal stem cells, which poses little or no ethical dilemmas. We have previously shown that human amnion-derived mesenchymal (HAM) cells exhibit certain mesenchymal stem cell-like characteristics with respect to expression of stem cell markers and differentiation potentials.

MATERIALS AND METHODS

In this study, we further characterized HAM cells' potential for in vivo therapeutic application.

RESULTS

Flow cytometric analyses of HAM cells show that they express several stem cell-related cell surface markers, including CD90, CD105, CD59, CD49d, CD44 and HLA-ABC, but not CD45, CD34, CD31, CD106 or HLA-DR. HAM cells at the 10th passage showed normal karyotype. More interestingly, the AbdB-like HOXA genes HOXA9, HOXA10 and HOXA11 that are expressed in the mesenchyme of the developing female reproductive tract and pregnant uteri are also expressed in HAM cells, suggesting similarities between these two mesenchymal cell types. Progesterone receptor is also highly expressed in HAM cells and expression of genes or proteins in HAM cells could be manipulated with the aid of lentivirus technology or cell-permeable peptides. To test potentials of HAM cells for in vivo application, we introduced enhanced green fluorescence protein (EGFP)-expressing HAM cells to mice by intrauterine infusion (into uteri) or by intravenous injection (into the circulation). Presence of EGFP-expressing cells within the uterine mesenchyme after intrauterine infusion or in lungs after intravenous injection was noted within 1-4 weeks.

CONCLUSIONS

Collectively, these results suggest that HAM cells are a potential source of mesenchymal stem cells with therapeutic potential.

Placenta-derived stem cells: new hope for cell therapy?

An urgent current need in regenerative medicine is that of identifying a plentiful, safe and ethically acceptable stem cell source for the development of therapeutic strategies to restore functionality in damaged or diseased organs and tissues. In this context, human term placenta represents a prime candidate, as it is available in nearly unlimited supply, is ethically problem-free and easily procured. Placental cells display differentiation capacity toward all three germ layers, while also displaying immunomodulatory effects, therefore supporting the possibility that they could be applied in an allogeneic transplantation setting. Although promising data have been reported to date, further study is required to fully characterize the differentiation potential of placenta-derived cells and to identify their possible clinical applications. Here, we provide a snapshot of current knowledge regarding the potential of cells from the amniotic membrane of human term placenta to address current shortcomings in the field of regenerative medicine.

Successful vitrification of human amnion-derived mesenchymal stem cells

BACKGROUND

A cryopreservation protocol for human amnion-derived mesenchymal stem cells (HAMs) is required because these cells cannot survive for long periods in culture. The aim of this study was to determine whether vitrification is a useful freezing method for storage of HAMs.

METHODS

HAMs were cryopreserved using vitrification method. The morphology and viability of thawed HAMs was evaluated by Trypan Blue staining. The expression of several embryonic stem cell (ESC) markers was evaluated using flow cytometry, RT-PCR and immunocytochemistry. Von Kossa, Oil Red O and Alcian Blue staining were used to asses the differentiation potential of thawed HAMs.

RESULTS

The post-thawing viability of HAMs was 84.3 +/- 3.2% (Mean +/- SD, n = 10). The thawed HAMs showed morphological characteristics indistinguishable from the non-vitrified fresh HAMs. The expression of surface antigens (strong positive for CD44, CD49d, CD59, CD90, CD105 and HLA-ABC; weak positive for HLA-G; negative for CD31, CD34, CD45, CD106, CD117 and HLA-DR) and the expression of ESC markers [CK18, fibroblast growth factor-5, GATA-4, neural cell adhesion molecule, Nestin, Oct-4, stem cell factor, HLA-ABC, Vimentin, bone morphogenetic protein (BMP) 4, hepatocyte nuclear factor 4 alpha (HNF-4 alpha), Pax-6, alpha-fetoprotein, Brachyury, BMP-2, TRA-1-60, stage-specific embryonic antigen (SSEA-3, SSEA-4)] were maintained in the vitrified-thawed HAMs. The thawed HAMs retained ability to differentiate into osteoblasts, adipocytes and chondrocytes under appropriate culture conditions.

CONCLUSIONS

Our results suggest that vitrification is a reliable and effective method for cryopreservation of HAMs.

Ex vivo characteristics of human amniotic membrane-derived stem cells

Cells were isolated from four human amniotic membranes, and their biological characteristics analyzed during ex vivo expansion. Morphologically homogenous populations of fibroblast-like cells were obtained from the second or third passage. Under the appropriate culture conditions, these human amniotic membrane-derived mesenchymal cells (HAM) were shown to differentiate into adipocytes, osteocytes, chondrocytes and neuronal cells, as visualized by Oil Red O, von Kossa, alcian blue, anti-Neu N, and anti-Gal C antibody staining, respectively. Immunophenotype analysis of HAM cells revealed the presence of antigens for SSEA-3, SSEA-4, collagen type-I, -II, -III, -IV, -XII, fibronectin, alpha-SMA, vimentin, desmin, cytokeratin18 (CK18), HCAM-1, fibroblast surface protein, and human leukocyte antigen (HLA) ABC. ICAM-1 protein was weakly detectable, and proteins of TRA-1-60, VCAM-1, von Willebrand factor, PECAM-1, and HLA DR were not detected. HAM cells reached senescence after 14.5+/-0.9 passages, over a period of 146.8+/-8.9 days, and underwent an average of 36.9 4.7 population doublings. RT-PCR analysis showed that all four HAM cell lines consistently expressed genes of Oct-4, Rex-1, SCF, NCAM, nestin, BMP-4, GATA-4, HNF-4alpha, vimentin, and CK18, regardless of the passage number. The genes of Brachyury, FGF-5, Pax-6, and BMP2 were never expressed. Strikingly, alpha-fetoprotein (alphaFP), HLA ABC, and HLA DR genes were expressed in an earlier passage but not expressed in later passages. Telomerase activity of two HAM lines was discernable upon the third passage. These observations strongly suggest that HAM might be immune-privileged and, thus, advantageous as therapeutic cells.

Molecular and proteomic characterization of human mesenchymal stem cells derived from amniotic fluid: comparison to bone marrow mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) constitute a population of multipotent adherent cells able to give rise to multiple mesenchymal lineages such as osteoblasts, adipocytes, or chondrocytes. So far, the most common source of MSCs has been the bone marrow (BM); however BM-MSC harvesting and processing exhibits major drawbacks and limitations. Thus, identification and characterization of alternative sources of MSCs are of great importance. In the present study, we isolated and expanded fetal MSCs from second-trimester amniotic fluid (AF). We documented that these cells are of embryonic origin, can differentiate under appropriate conditions into cell types derived from all three germ layers, and express the pluripotency marker Oct-4, the human Nanog protein, and the stage-specific embryonic antigen-4 (SSEA-4). Furthermore, we systematically tested the immunophenotype of cultured MSCs by flow cytometry analysis using a wide variety of markers. Direct comparison of this phenotype to the one derived from cultured BM-MSCs demonstrated that cultured MSCs from both sources exhibit similar expression patterns. Using the two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) approach, we have generated for the first time the protein map of cultured AF-MSCs by identifying 261 proteins, and we compared it directly to that of cultured BM-MSCs. The functional pattern of the identified proteins from both sources was similar. However, cultured AF-MSCs displayed a number of unique proteins related to proliferation and primitive phenotype, which may confer to the distinct features of the two types. Considering the easy access to this new cell source and the yield of expanded MSCs for stem cell research, AF may provide an excellent source of MSCs both for basic research and for potential therapeutic applications.

The potential of amniotic membrane/amnion-derived cells for regeneration of various tissues

Regenerative medicine is a new field based on the use of stem cells to generate biological substitutes and improve tissue functions, restoring damaged tissue with high proliferability and differentiability. It is of interest as a potential alternative to complicated tissue/organ transplantation. Recently, amnion-derived cells have been reported to have multipotent differentiation ability, and these cells have attracted attention as a cell source for cell-transplantation therapy. The amnion possesses considerable advantageous characteristics: the isolated cells can differentiate into all three germ layers; they have low immunogenicity and anti-inflammatory functions; and they do not require the sacrifice of human embryos for their isolation, thus avoiding the current controversies associated with the use of human embryonic stem cells. Moreover, we developed human amniotic cell-sheets using a novel culture surface coated with a noncytotoxic, temperature-responsive elastic protein-based polymer. We also generated a "hyper-dry-amnion", which has already been applied clinically in the ophthalmological field. Compared to cryopreserved fresh amnion, "hyper-dry-amnion" is easy to handle and has started to bring good results to patients. These materials from the amnion are also expected to open a new field in tissue engineering. Thus, amnion, which had been discarded after parturition, has started to be appreciated as an attractive material in the field of regenerative medicine. In this review, the most recent and relevant clinical and experimental data about the use of amniotic membrane and cells derived from it are described.

Concise review: isolation and characterization of cells from human term placenta: outcome of the first international Workshop on Placenta Derived Stem Cells

Placental tissue draws great interest as a source of cells for regenerative medicine because of the phenotypic plasticity of many of the cell types isolated from this tissue. Furthermore, placenta, which is involved in maintaining fetal tolerance, contains cells that display immunomodulatory properties. These two features could prove useful for future cell therapy-based clinical applications. Placental tissue is readily available and easily procured without invasive procedures, and its use does not elicit ethical debate. Numerous reports describing stem cells from different parts of the placenta, using nearly as numerous isolation and characterization procedures, have been published. Considering the complexity of the placenta, an urgent need exists to define, as clearly as possible, the region of origin and methods of isolation of cells derived from this tissue. On March 23-24, 2007, the first international Workshop on Placenta Derived Stem Cells was held in Brescia, Italy. Most of the research published in this area focuses on mesenchymal stromal cells isolated from various parts of the placenta or epithelial cells isolated from amniotic membrane. The aim of this review is to summarize and provide the state of the art of research in this field, addressing aspects such as cell isolation protocols and characteristics of these cells, as well as providing preliminary indications of the possibilities for use of these cells in future clinical applications.

Human amnion mesenchyme harbors cells with allogeneic T-cell suppression and stimulation capabilities

Cells derived from the amniotic membrane of human placenta have been receiving particular attention because of their stem cell potentiality and immunomodulatory properties, which make them an attractive candidate source for cell therapy approaches. In this study, we isolated cells from the mesenchymal region of amnion and identified two subpopulations discordant for expression of the HLA-DR, CD45, CD14, and CD86 cellular markers. We therefore refer to the unfractionated cell population derived from this region as amniotic mesenchymal tissue cells (AMTC). We studied the suppressive and stimulatory characteristics of the unfractionated, HLA-DR-positive, and HLA-DR-negative AMTC populations and demonstrated that all three fail to induce an allogeneic T-cell response. However, unfractionated AMTC, which could inhibit T-cell allogeneic proliferation responses, induced proliferation of T cells stimulated via the T-cell receptor (TcR), in a cell-cell contact setting. We have shown that this stimulatory capacity can be attributed to the HLA-DR-positive AMTC subpopulation. Indeed, even though the HLA-DR-positive AMTC fraction surprisingly failed to induce proliferation of resting allogeneic T cells, they could cause strong proliferation of anti-CD3-primed allogeneic T cells. This stimulatory effect was not observed using the HLA-DR-negative AMTC fraction. The revelation that human amniotic mesenchyme possesses cell populations with both suppressive and stimulatory properties sheds additional light on the immunomodulatory functions of this tissue and may contribute to the clarification of some ongoing controversies associated with mesenchymal stromal cells of other sources, such as the presence of HLA-DR-positive cells and the suppressive versus stimulatory properties of these cells.

Isolation, characterization, and differentiation of stem cells derived from the rat amniotic membrane

Stem-cell-based therapies may offer treatments for a variety of intractable diseases. A fundamental goal in stem-cell biology concerns the characterization of diverse populations that exhibit different potentials, growth capabilities, and therapeutic utilities. We report the characterization of a stem-cell population isolated from tissue explants of rat amniotic membrane. Similar to mesenchymal stem cells, these amnion-derived stem cells (ADSCs) express the surface markers CD29 and CD90, but were negative for the lymphohematopoietic markers CD45 and CD11b. ADSCs exist in culture in a multidifferentiated state, expressing neuroectodermal (neurofilament-M), mesodermal (fibronectin), and endodermal (alpha-1-antitrypsin) genes. To assess plasticity, ADSCs were subjected to a number of culture conditions intended to encourage differentiation into neuroectodermal, mesodermal, and endodermal cell types. ADSCs cultured in a defined neural induction media assumed neuronal morphologies and up-regulated neural-specific genes. Under different conditions, ADSCs were capable of differentiating into presumptive bone and fat cells, indicated by the deposition of mineralized matrix and accumulated lipid droplets, respectively. Moreover, ADSCs cultured in media that promotes liver cell differentiation up-regulated liver-specific genes (albumin) and internalized low-density lipoprotein (LDL), consistent with a hepatocyte phenotype. To determine whether this observed plasticity reflects the presence of true stem cells within the population, we have derived individual clones from single cells. Clonal lines recapitulate the expression pattern of parental ADSC cultures and are multipotent. ADSCs have been cultured for 20 passages without losing their plasticity, suggesting long-term self-renewal. In sum, our data suggest that ADSCs and derived clonal lines are capable of long-term self-renewal and multidifferentiation, fulfilling all the criteria of a stem-cell population.

Functional network analysis of the transcriptomes of mesenchymal stem cells derived from amniotic fluid, amniotic membrane, cord blood, and bone marrow

Using high-density oligonucleotide microarrays and functional network analyses, we examined whether MSCs derived from four different origins exhibited unique gene expression profiles individually and then compared the gene expression profiles of all MSCs with those of fetal organs. Our results indicated that within each group of MSCs from the same origin, the variability of the gene expression levels was smaller than that between groups of different origins. Functional genomic studies revealed the specific roles of MSCs from different origins. Our results suggest that amniotic fluid MSCs may initiate interactions with the uterus by upregulating oxytocin and thrombin receptors. Amniotic membrane MSCs may play a role in maintaining homeostasis of fluid and electrolytes by regulating the networks of endothelin, neprilysin, bradykinin receptors, and atrial natriuretic peptide. Cord blood MSCs may be involved in innate immune systems as the neonatal defense system against the earliest encountered pathogens. Adult bone marrow MSCs may be an important source not only of all blood lineages but also of bone formation. However, in spite of the different gene expression profiles seen in MSCs derived from different origins, a set of core gene expression profiles was preserved in these four kinds of MSCs. The core signature transcriptomes of all MSCs, when contrasted against those of fetal organs, included genes involved in the regulation of extracellular matrix and adhesion, transforming growth factor-beta receptor signaling, and the Wnt signaling pathways. Disclosure of potential conflicts of interest is found at the end of this article.

Tissue engineering from human mesenchymal amniocytes: a prelude to clinical trials

PURPOSE

The surgical treatment of congenital anomalies using tissues engineered from amniotic fluid-derived mesenchymal cells has been validated experimentally. As a prerequisite for testing the clinical feasibility of this therapeutic concept, this study was aimed to expand human mesenchymal amniocytes in the absence of animal products.

METHODS

Human mesenchymal cells were isolated from amniotic fluid samples (n = 12) obtained at 20 to 37 weeks' gestation. Their phenotypic profiles and cell proliferation rates were compared during expansion under 2 different media, containing either fetal bovine serum or allogeneic human AB serum. Statistical analyses were by the 2-sided Wilcoxon signed rank test and linear regression (P < .05).

RESULTS

Mesenchymal cells could be isolated and expanded at any gestational age. There was a greater than 9-fold logarithmic expansion of mesenchymal cells, with no significant differences in the overall proliferation rates based on serum type (P = .94), or gestational age (P = .14). At any passage, cells expanded for up to 50 days remained positive for markers consistent with a multipotent mesenchymal progenitor lineage, regardless of the medium used.

CONCLUSIONS

Human mesenchymal amniocytes retain their progenitor phenotype and can be dependably expanded ex vivo in the absence of animal serum. Clinical trials of amniotic fluid-based tissue engineering are feasible within preferred regulatory guidelines.

5-Azacytidine induces changes in electrophysiological properties of human mesenchymal stem cells

Previously, mouse bone marrow-derived stem cells (MSC) treated with the unspecific DNA methyltransferase inhibitor 5-azacytidine were reported to differentiate into cardiomyocytes. The aim of the present study was to investigate the efficiency of a similar differentiation strategy in human mononuclear cells obtained from healthy bone marrow donors. After 1-3 passages, cultures were exposed for 24 h to 5-azacytidine (3 mciroM) followed by 6 weeks of further culture. Drug treatment did not induce expression of myogenic marker MyoD or cardiac markers Nkx2.5 and GATA-4 and did not yield beating cells during follow-up. In patch clamp experiments, approximately 10-15% of treated and untreated cells exhibited L-type Ca(2+) currents. Almost all cells showed outwardly rectifying K(+) currents of rapid or slow activation kinetics. Mean current amplitude at +60 mV doubled after 6 weeks of treatment compared with time-matched controls. Membrane capacitance of treated cells was significantly larger than in controls 2 weeks after treatment and remained high after 6 weeks. Expression levels of mRNAs for the K(+) channels Kv1.1, Kv1.5, Kv2.1, Kv4.3 and KCNMA1 and for the Ca(2+) channel Ca(v)1.2 were not affected by 5-azacytidine. Treatment with potassium channel blockers tetraethylammonium and clofilium at concentrations shown previously to inhibit rapid or slowly activating K(+) currents of hMSC inhibited proliferation of these cells. Our results suggest that despite the absence of differentiation of hMSC into cardiomyocytes, treatment with 5-azacytidine caused profound changes in current density.

Identification of stem cell marker-positive cells by immunofluorescence in term human amnion

The placenta contains different populations of stem/progenitor cells such as mesenchymal, hematopoietic, trophoblastic and pluripotent stem cells. Although some tissue-specific stem cells are restricted to particular parts of the placenta, the localization of embryonic stem cell-like cells in term human placenta has not been determined. We have used immunofluorescence staining techniques with antibodies to pluripotent stem cell antigens, SSEA-3, SSEA-4, TRA 1-60 and TRA 1-81, and confocal microscopic analysis to identify and localize stem cells within the placenta. Stem cell marker-positive cells were found in amnion but not in choriodecidua, tissues known to contain hematopoietic and trophoblastic stem cells. Amniotic mesenchymal cells did not react with these pluripotent stem cell markers, while all amniotic epithelial cells reacted with at least one antibody. The TRA 1-60 and TRA 1-81 positive cells were solitary and present throughout the surface of amniotic membrane without a specific pattern of distribution, whereas SSEA-3 was negative and SSEA-4 was weakly positive on all amniotic epithelial cells. These data suggest that the human amnion contains stem cell-like cells at different states of differentiation. Human term amnion may be useful source of pluripotent stem cells for regenerative medicine.

Stem cells derived from human fetal membranes display multilineage differentiation potential

The amnion is the inner of two membranes surrounding the fetus. That it arises from embryonic epiblast cells prior to gastrulation suggests that it may retain a reservoir of stem cells throughout pregnancy. We found that human amniotic epithelial cells (hAECs) harvested from term-delivered fetal membranes express mRNA and proteins present in human embryonic stem cells (hESCs), including POU domain, class 5, transcription factor 1; Nanog homeobox; SRY-box 2; and stage-specific embryonic antigen-4. In keeping with possible stem cell-like activity, hAECs were also clonogenic, and primary hAEC cultures could be induced to differentiate into cardiomyocytic, myocytic, osteocytic, adipocytic (mesodermal), pancreatic, hepatic (endodermal), neural, and astrocytic (neuroectodermal) cells in vitro, as defined by phenotypic, mRNA expression, immunocytochemical, and/or ultrastructural characteristics. However, unlike hESCs, hAECs did not form teratomas upon transplantation into severe combined immunodeficiency mice testes. Last, using flow cytometry we have shown that only a very small proportion of primary hAECs contain class IA and class II human leukocyte antigens (HLAs), consistent with a low risk of tissue rejection. However, following differentiation into hepatic and pancreatic lineages, significant proportions of cells contained class IA, but not class II, HLAs. These observations suggest that the term amnion, an abundant and easily accessible tissue, may be a useful source of multipotent stem cells that possess a degree of immune privilege.

Human amniotic fluid-derived stem cells are rejected after transplantation in the myocardium of normal, ischemic, immuno-suppressed or immuno-deficient rat

Human amniotic fluid-derived stem (AFS) cells, similarly to embryonic stem cells, could possess privileged immunological characteristics suitable for a successful transplantation even in a discordant xenograft system. We investigated whether AFS cells could be fruitfully used in a rat model of myocardial infarction. c-kit immunomagnetic-sorted AFS cells were characterized by flow cytometric analysis and cytospins as well as reverse-transcription polymerase chain reaction, Western blotting and immunocytochemistry for cardiovascular differentiation markers. In vitro, AFS cell phenotypic conversion was assayed by cardiovascular-specific induction media or co-cultured with rat neonatal cardiomyocytes. AFS cells showed mRNAs and/or protein for endothelial (angiopoietin, CD146) and smooth muscle (smoothelin) cells, and cardiomyocyte (Nkx2.5, MLC-2v, GATA-4, beta-MyHC) markers. Acquisition of a cardiomyocyte-like phenotype in rare AFS cells could be seen only in co-cultures with rat neonatal cells. In vivo, AFS cells xenotransplantated in a rat model of myocardial infarction, with or without cyclosporine treatment, or in intact heart from immuno-competent or immuno-deficient animals were acutely rejected due to the different recruitment of recipient CD4(+), CD8(+) T and B lymphocytes, NK cells and macrophages. This reaction is most likely to be linked to expression of B7 co-stimulatory molecules CD80 and CD86 as well as macrophage marker CD68 on AFS cells. Xenotransplanted AFS cells gave also rise in some animals to cell masses in the subendocardium and myocardium suggestive of a process of chondro-osteogenic differentiation. Despite AFS cells in vitro can differentiate to some extent to cells of cardiovascular lineages, their in vivo use in xenotransplantation for cell therapy of myocardial infarction is hampered by their peculiar immunogenic properties and phenotypic instability.

Human first-trimester fetal MSC express pluripotency markers and grow faster and have longer telomeres than adult MSC

The biological properties of stem cells are key to the success of cell therapy, for which MSC are promising candidates. Although most therapeutic applications to date have used adult bone marrow MSC, increasing evidence suggests that MSC from neonatal and mid-gestational fetal tissues are more plastic and grow faster. Fetal stem cells have been isolated earlier in development, from first-trimester blood and hemopoietic organs, raising the question of whether they are biologically closer to embryonic stem cells and thus have advantages over adult bone marrow MSC. In this study, we show that human first-trimester fetal blood, liver, and bone marrow MSC but not adult MSC express the pluripotency stem cell markers Oct-4, Nanog, Rex-1, SSEA-3, SSEA-4, Tra-1-60, and Tra-1-81. In addition, fetal MSC, irrespective of source, had longer telomeres (p < .001), had greater telomerase activity (p < .01), and expressed more human telomerase reverse transcriptase (p < .01). Fetal MSC were also more readily expandable and senesced later in culture than their adult counterparts (p < .01). Compared with adult MSC, first-trimester fetal tissues constitute a source of MSC with characteristics that appear advantageous for cell therapy.

Smad5 determines murine amnion fate through the control of bone morphogenetic protein expression and signalling levels

Smad5 is an intracellular mediator of bone morphogenetic protein (Bmp)signalling. It is essential for primordial germ cell (PGC) development, for the development of the allantois and for amnion closure, as demonstrated by loss of Bmp signalling. By contrast, the appearance of ectopic PGC-like cells and regionalized ectopic vasculogenesis and haematopoiesis in thickened Smad5m1/m1 amnion are amnion defects that have not been associated with loss of Bmp signalling components. We show that defects in amnion and allantois can already be detected at embryonic day (E) 7.5 in Smad5 mutant mice. However, ectopic Oct4-positive (Oct4+)and alkaline phosphatase-positive (AP+) cells appear suddenly in thickened amnion at E8.5, and at a remote distance from the allantois and posterior primitive streak, suggesting a change of fate in situ. These ectopic Oct4+, AP+ cells appear to be Stella negative and hence cannot be called bona fide PGCs. We demonstrate a robust upregulation of Bmp2 and Bmp4 expression, as well as of Erk and Smad activity, in the Smad5 mutant amnion. The ectopic expression of several Bmp target genes in different domains and the regionalized presence of cells of several Bmp-sensitive lineages in the mutant amnion suggest that different levels of Bmp signalling may determine cell fate. Injection of rBMP4 in the exocoelom of wild-type embryos can induce thickening of amnion,mimicking the early amnion phenotype in Smad5 mutants. These results support a model in which loss of Smad5 results paradoxically in gain of Bmp function defects in the amnion.

Human Amniotic Cell Sheet Harvest Using a Novel Temperature-Responsive Culture Surface Coated with Protein-Based Polymer

Human amniotic epithelial (hAE) and mesenchymal (hAM) cells are believed to have the potential to differentiate into various functional cells, such as neurons, hepatocytes, cardiomyocytes, and pancreatic beta cells. However, cell transplantation has been performed by injection of cell suspensions, and thus it is difficult to control shape, size, location, and functions of differentiated cells. To overcome these problems, we developed a novel temperature-responsive culture surface coated with elastic protein-based polymer. By reducing the temperature using a polyvinylidene difluoride (PVDF) membrane, the primary hAE and hAM cell sheet can detach from the coated surface. The recovered cell sheet can be transferred and can re-adhere and re-proliferate on another surface. This represents the first report of harvesting of primary hAE and hAM cell sheets using the novel temperature- responsive polymer. These findings suggest that this new technique of cell sheet detachment from noncytotoxic, highly biocompatible protein-based polymer-coated surfaces may be useful in tissue engineering, as well as in the investigation of hAE and hAM cell sheets for transplantation.