Current Stem Cell Research & Therapy - Volume 8, Issue 1, 2013

Inflammation is a complex defense mechanism characterized by leukocyte migration from the vasculature into damaged tissues and subsequent deposition of extracellular matrix resulting in tissue repair. The inflammatory process is generally categorized into an acute, rapid response, and a persistent but slowly evolving chronic condition, which may progress into inflammatory diseases. An excessive deposition of extracellular matrix leads to overgrowth, hardening, and/or scarring of tissues, defined as fibrosis. The amnion has been used as biomaterial in medicine for over 100 years and has been proven valuable for the treatment of different pathological conditions including wound healing. In light of recent reports, this article will review the effects of the amnion and its cellular components within the inflammatory-fibrotic scenario and the factors described so far that could be involved in these immunomodulatory actions. As proof of principles, we will also discuss pre-clinical and clinical applications of the amnion where advantage has been taken of its anti-inflammatory and anti-fibrotic properties. It is conceivable that the local host environment in which the amnion is placed may have a profound role in influencing the production and function of soluble factors and the shift towards different steps in triggering healing. The healing effect depends on time, dosage, and location of cytokine/growth factor production by the amnion, together with the influence of the host microenvironment. Indeed, determining the specific cascade of events that may define the role of the amnion in a given clinical situation remains a challenge.

Human hepatocyte transplantation is being trialled in lieu of orthotopic liver transplants for patients with acute and chronic liver diseases. Stem cells that can be differentiated into hepatocyte-like cells may replace human hepatocytes that are difficult to source, culture and in critically short supply. Hepatocyte-like cells have been derived from embryonic and adult tissue stem cells using a combination of growth factors and chemical inducers. Stem cells derived from the human placenta have gained interest due to the unlimited supply of placental tissue, minimal issues associated with stem cell retrieval from placental tissue and the large yields of stem cells that can be obtained. Placental stem cells have been characterised and differentiated into hepatocyte-like cells. This review summarises the literature relating to the differentiation of human placental stem cells into hepatocyte-like cells, the characterisation of the differentiated cells, testing the functionality of the hepatocyte-like cells in pre-clinical animal models of liver disease and biomaterials used for culturing and transplantation of these cells into extra-hepatic sites.

Nearly 1.5 million people in the US live with a spinal cord injury (SCI). The cost to the healthcare system is estimated at over $10billion annually likely because over 65% of SCIs occur at the cervical level. Despite medical advances, many SCI patients still experience substantial neurological disability and high dependency with severe loss of motor, sensory and autonomic function. The consensus from a combination of in vivo studies and in vivo models is that mesenchymal or stromal cells, and possibly even neural progenitors, regardless of derivation act through the provision of trophic support and inflammatory modulation. Indeed, they have been found to secrete a wide spectrum of diffusible factors with known roles in both. As such, mesenchymal cells, obtainable from multiple tissues, are ideally suited to addressing many pathophysiological consequences of SCI. Advances in understanding the latter, structural and functional magnetic resonance imaging, image-guided microneurosurgical techniques and transplantable cell biology have enabled the clinical use of cell-based therapies. Of the twenty most recent cell therapy clinical trials for SCI, seven involve adult bone marrow mesenchymal cells and six others umbilical cord cells. This reflects the growing recognition of the clinical potential of perinatal cells. However, a limited understanding of how best to exploit the capabilities of these cells impedes a full-scale clinical deployment. This mini-review focuses on recent developments that are likely to facilitate the targeted application of these cells to treat specific secondary pathophysiological processes.

Cardiomyopathies are still the first cause of death in the world. The identification of resident stem cells, comprising those derived from sub-endocardial stroma, suggests the possible self regeneration of the heart under autocrine/paracrine modulation in the cardiac microenvironment. Nevertheless, because of the limited in vivo regeneration potential of damaged cardiac tissue, the use of drugs and ultimately cardiac transplantation remain the common treatments of heart diseases and defects. The differentiative potential of embryonic and mesenchymal stem cells (MSCs) derived from different tissues (such as bone marrow and adipose tissue) was extensively explored in cell therapy for regenerative medicine. Many groups have been focused, in recent years, on isolation, characterization, and differentiation potential of MSCs derived from perinatal (or extraembryonic) tissues, mainly the placenta and the human umbilical cord. In this review, we summarized recent works about the stemness of Wharton's jelly stromal cells and their potential in cardiac regeneration with favourable use in cell therapy and regenerative medicine. The peculiar features of these cells, as the expression of cardiac-specific transcription factors and immunomodulatory molecules suggest that human umbilical cord may be considered as a reliable alternative source of MSC useful for advanced therapy in cardiac regenerative medicine.

The therapeutic effect of mesenchymal stromal cells (MSCs) following myocardial infarction (MI) is small. This may be due to differences in cellular sources and donor age, route of administration, in vitro cellular manipulations and the short time course of follow up in many animal studies. Here, we compared MSCs from two different sources (adult bone marrow or Wharton's jelly from umbilical cord) for their long-term therapeutic effect following MI in a rat model to evaluate the effect of donor age. MSCs (or control infusions) were given intravenously 24-48 hr after myocardial ischemia (MI) induced by coronary artery ligation. Cardiac function was assessed by ultrasound at time points starting from before MSC infusion through 68 weeks after MI. A significant improvement in ejection fraction was seen in animals that received MSCs in time points 25 to 31 wks after treatment (p <0.01). These results support previous work that show that MSCs can cause improvement in cardiac function and extend that work by showing that the beneficial effects are durable. To investigate MSCs' cardiac differentiation potential, Wharton's jelly MSCs were co-cultured with fetal or adult bone-derived marrow MSCs. When Wharton's jelly MSCs were co-cultured with fetal MSCs, and not with adult MSCs, myotube structures were observed in two-three days and spontaneous contractions (beating) cells were observed in fiveseven days. The beating structures formed a functional syncytium indicated by coordinated contractions (beating) of independent nodes. Taken together, these results suggest that MSCs given 24-48 hr after MI have a significant and durable beneficial effect more than 25 weeks after MI and that MSC treatment can home to damaged tissue and improve heart function after intravenous infusion 24-48 hrs after MI, and that WJCs may be a useful source for off-the-shelf cellular therapy for MI.

Human umbilical cord stroma-derived mesenchymal stem cells (hUCS-MSCs) are considered as a remarkable and promising stem cell source to be potentially used in cellular therapies. While no graft rejection has been reported in the recipient organism even in xeno-transplantation studies, attenuate tumor cell growth and gene transfers have been experimentally shown. In this study, we have demonstrated a reliable, reproducible and efficient cryopreservation method of hUCS-MSCs resulting in one of the highest cell survival rates reported so far. Conventional, computer-controlled multistep slow freezing (MSSF), and vitrification methods were comparatively tested using cell permeable [dimethylsulfoxide (DMSO), ethylene glycol] and impermeable [trehalose, sucrose, hydroxyethyl starch (HES), human serum albumin] cryoprotectant agents (CPAs). After determining the ice nucleation point for each solution, latent heat evolution was suppressed during freezing, followed by a cooling process to –40°C at 1°C/min or 0.3°C/min. The efficiency of the cryopreservation techniques used was determined by cell viability and proliferation assays, the expression of cell surface markers, cytoskeletal proteins and chromosome alignments. The cell survival rate was found to be highest (87±5%) by MSSF with sucrose (0.1 M) +DMSO (10%) at 1°C/min freezing rate. In this group, no significant difference was noted before and after the cryopreservation in cell morphology, cytokeratin, vimentin, and α-smooth muscle actin profiles and the expressions of CD105, CD90, CD73, CD29 and HLA-DR. Second highest cell survival ratio (85±6%) was obtained in DMSO (10%) alone at 1°C/min freezing rate. Interestingly, poor (18±15%) cell survival rates were obtained after vitrification. Cumulatively, results indicated that MSSF favors the other freezing protocols with an addition of sucrose or DMSO alone depending on the freezing rate used.

Mid-gestation c-KIT+ amniotic fluid stem cells (AFSC) have an intermediate phenotype between embryonic and adult stem cells and are easy to reprogram to pluripotency. We previously showed that 1st trimester AFSC can be reprogrammed to functional pluripotency in a transgene-free approach. Despite both parental populations sharing a common phenotype, expressing CD29, CD44, CD73, CD90, CD105, SSEA4 and OCT4, 2nd trimester AFSC, contrary to 1st trimester cells, do not express NANOG, SSEA3, TRA-1-60 and TRA-1-81, and have slower growth kinetics. Here, we used the Illumina Beadstudio microarray platform to analyse the transcriptome of 1st and 2nd trimester AFSC and show a unique 1st trimester AFSC-specific gene expression signature consisting of 366 genes and a larger set of 603 genes common with hESC compared to 496 genes overlapping between 2nd trimester AFSC and hESC. We conclude that both populations are related but distinct to each other as well as to hESC.

Different sources of stem cells are considered as a potential source of precursor cells that could improve skeletal muscle regeneration. Under physiological conditions muscle regeneration is based on the satellite cells, i.e. adult muscle precursor cells that are localized between muscle fiber and surrounding basal lamina. These cells remain quiescent but after skeletal muscle injury activate, proliferate, differentiate, and fuse either to form new muscle fibers or reconstruct the damaged ones. As it was shown in many studies few populations of stem cells other than satellite cells are able to support skeletal muscle regeneration. Among them are mesenchymal stem cells (MSCs) that are present in many niches within adult organism and also in fetal tissues, such as human umbilical cord blood (HUCB) or umbilical cord connective tissue, i.e. Wharton's jelly. Thus, MSCs are intensively tested to prove that they are able to differentiate into various cell types, including skeletal myoblasts, and therefore could be useful in regenerative medicine. In our previous study we showed that MSCs isolated from Wharton's jelly expressed pluripotency as well as myogenic markers and were able to undergo myogenic differentiation both in vitro and in vivo. We also analyzed the potential of HUCB cells population which contains not only MSCs but also hematopoietic precursors. Our analyses of whole population of HUCB cells showed that these cells express myogenic regulatory factors, i.e. MyoD, and are able to contribute to skeletal muscle regeneration. In the present study we document that adherent fraction of HUCB cells, i.e. the cells that constitute the subpopulation enriched in MSCs, expresses pluripotency and myogenic markers, and have a positive impact at the regeneration of injured mouse skeletal muscle.

Hepatocyte transplantation is being trialled as an alternative to whole organ transplant for patients with acute liver failure and liver specific metabolic diseases. Due to the scarcity of human hepatocytes, hepatocyte-like cells (HLC) generated from stem cells may become a viable alternative to hepatocyte transplantation. Human amniotic epithelial cells (hAEC) from the placenta have stem cell-like properties and can be differentiated into HLC. Naïve hAEC have low immunogenicity and exert immunomodulatory effects that may facilitate allogeneic transplantation. However, whether the immunogenicity and immunomodulatory properties alter with differentiation into HLC are unknown. We further characterized HLC generated from hAEC, examined changes in human leucocyte antigens (HLA) and co-stimulatory molecules and effects exerted by the HLC on human peripheral blood mononuclear cells (PBMC). HLC derived from hAEC expressed proteins found in hepatocytes, had CYP3A4 drug metabolizing enzyme activity and secreted urea. IFN-γ treatment increased HLA Class IA, Class II and co-stimulatory molecule CD40 expression in the HLC. IFN-γ treated HLC stimulated proliferation of PBMC in one-way mixed lymphocyte reactions and were more immunogenic than undifferentiated hAEC. However, the HLC showed immunomodulatory properties and inhibited mitogen induced PBMC proliferation in vitro. PBMC proliferation may have been inhibited by IL-6, TGF-β1, PGE2 and HLA-G secreted by the HLC. The retention of immunomodulatory properties may enable HLC grafts to survive for longer periods despite the immunogenicity of the HLC.

Rheumatoid arthritis and osteoarthritis are the main diseases that imply an inflammatory process at the joints involving the articular cartilage. Recently, mesenchymal stem cells (MSCs) derived from perinatal tissues were considered good candidates for cellular therapy of musculoskeletal and orthopaedic diseases, since they can differentiate into multiple cell types and are an easily accessible cellular source. Therefore, several protocols exist on the differentiation of mesenchymal stem cells of different origins into osteoblasts and chondrocytes. Another key feature of MSCs is their capacity to modulate the immune system responses in vitro and in vivo. This may have critical outcomes in diseases of the musculoskeletal system where an inflammatory or autoimmune process is at the basis of the main disease. In the present paper, after isolation of MSCs from Wharton's Jelly (WJ-MSCs), we performed the three standard differentiation protocols. The acquisition of the differentiated phenotype was demonstrated by the specific histological stains. As the main objective of this work, we determined the expression of immunomodulatory molecules (by immunohistochemistry and qualitative RT-PCR), both in undifferentiated cells and after differentiation. We demonstrated for the first time that immune-related molecules (as B7-H3/CD276 and HLA-E) which have been characterized in undifferentiated MSCs, are also expressed by the differentiated progeny. This strongly suggests that also after the acquisition of a mature phenotype, WJ-MSCs-derived cells may maintain their immune privilege. This evidence, which deserves much work to be confirmed in vivo and in other MSCs populations, may provide a formal proof of the good results globally achieved with WJMSCs as cellular therapy vehicle.