Umbilical cord-derived stem cells for tissue therapy: current and future uses

Enhanced angiogenic properties of umbilical cord blood primed by OP9 stromal cells ameliorates neurological deficits in cerebral infarction mouse model

Umbilical cord blood (UCB) transplantation shows proangiogenic effects and contributes to symptom amelioration in animal models of cerebral infarction. However, the effect of specific cell types within a heterogeneous UCB population are still controversial. OP9 is a stromal cell line used as feeder cells to promote the hematoendothelial differentiation of embryonic stem cells. Hence, we investigated the changes in angiogenic properties, underlying mechanisms, and impact on behavioral deficiencies caused by cerebral infarction in UCB co-cultured with OP9 for up to 24 h. In the network formation assay, only OP9 pre-conditioned UCB formed network structures. Single-cell RNA sequencing and flow cytometry analysis showed a prominent phenotypic shift toward M2 in the monocytic fraction of OP9 pre-conditioned UCB. Further, OP9 pre-conditioned UCB transplantation in mice models of cerebral infarction facilitated angiogenesis in the peri-infarct lesions and ameliorated the associated symptoms. In this study, we developed a strong, fast, and feasible method to augment the M2, tissue-protecting, pro-angiogenic features of UCB using OP9. The ameliorative effect of OP9-pre-conditioned UCB in vivo could be partly due to promotion of innate angiogenesis in peri-infarct lesions.

Comprehensive insight into endothelial progenitor cell-derived extracellular vesicles as a promising candidate for disease treatment

Endothelial progenitor cells (EPCs), which are a type of stem cell, have been found to have strong angiogenic and tissue repair capabilities. Extracellular vesicles (EVs) contain many effective components, such as cellular proteins, microRNAs, messenger RNAs, and long noncoding RNAs, and can be secreted by different cell types. The functions of EVs depend mainly on their parent cells. Many researchers have conducted functional studies of EPC-derived EVs (EPC-EVs) and showed that they exhibit therapeutic effects on many diseases, such as cardiovascular disease, acute kidney injury, acute lung injury, and sepsis. In this review article, we comprehensively summarized the biogenesis and functions of EPCs and EVs and the potent role of EPC-EVs in the treatment of various diseases. Furthermore, the current problems and future prospects have been discussed, and further studies are needed to compare the therapeutic effects of EVs derived from various stem cells, which will contribute to the accelerated translation of these applications in a clinical setting.

Safety and Optimization of Metabolic Labeling of Endothelial Progenitor Cells for Tracking

Metabolic labeling is one of the most powerful methods to label the live cell for in vitro and in vivo tracking. However, the cellular mechanisms by modified glycosylation due to metabolic agents are not fully understood. Therefore, metabolic labeling has not yet been widely used in EPC tracking and labeling. In this study, cell functional properties such as proliferation, migration and permeability and gene expression patterns of metabolic labeling agent-treated hUCB-EPCs were analyzed to demonstrate cellular effects of metabolic labeling agents. As the results, 10 μM Ac4ManNAz treatment had no effects on cellular function or gene regulations, however, higher concentration of Ac4ManNAz (>20 μM) led to the inhibition of functional properties (proliferation rate, viability and rate of endocytosis) and down-regulation of genes related to cell adhesion, PI3K/AKT, FGF and EGFR signaling pathways. Interestingly, the new blood vessel formation and angiogenic potential of hUCB-EPCs were not affected by Ac4ManNAz concentration. Based on our results, we suggest 10 μM as the optimal concentration of Ac4ManNAz for in vivo hUCB-EPC labeling and tracking. Additionally, we expect that our approach can be used for understanding the efficacy and safety of stem cell-based therapy in vivo.

Decreased phosphorylation of PDGFR-β impairs the angiogenic potential of expanded endothelial progenitor cells via the inhibition of PI3K/Akt signaling

Human umbilical cord blood-derived endothelial progenitor cells (EPCs) have been proven to contribute to post-natal angiogenesis, and have been applied in various models of ischemia. However, to date, to the best of our knowledge, there is no available data on the angiogenic properties of EPCs during the process of in vitro expansion. In this study, we expanded EPCs to obtain cells at different passages, and analyzed their cellular properties and angiogenic ability. In the process of expansion, no changes were observed in cell cobblestone-like morphology, apoptotic rate and telomere length. However, the cell proliferative ability was significantly decreased. Additionally, the expression of CD144, CD90 and KDR was significantly downregulated in the later-passage cells. Vascular formation assay in vitro revealed that EPCs at passage 4 and 6 formed more integrated and organized capillary-like networks. In a murine model of hind limb ischemia, the transplantation of EPCs at passage 4 and 6 more effectively promoted perfusion recovery in the limbs on days 7 and 14, and promoted limb salvage and histological recovery. Furthermore, the phosphorylation levels of platelet‑derived growth factor receptor-β (PDGFR-β) were found to be significantly decreased with the in vitro expansion process, accompanied by the decreased activation of the PI3K/Akt signaling pathway. When PDGFR inhibitor was used to treat the EPCs, the differences in the angiogenic potential and migratory ability among the EPCs at different passages were no longer observed; no significant differences were also observed in the levels of phosphorylated PI3K/Akt between the EPCs at different passages following treatment with the inhibitor. On the whole, our findings indicate that the levels of phosphorylated PDGFR-β are decreased in EPCs with the in vitro expansion process, which impairs their angiogenic potential by inhibiting PI3K/Akt signaling. Our findings may aid in the more effective selection of EPCs of different passages for the clinical therapy of ischemic disease.

Neuronal cell reconstruction with umbilical cord blood cells in the brain hypoxia-ischemia

Background: Brain hypoxia-ischemia is a human neonatal injury that is considered a candidate for stem cell therapy. Methods: The possible therapeutic potential of human umbilical cord blood (HUCB) stem cells was evaluated in 14-day-old rats subjected to the right common carotid occlusion, a model of neonatal brain hypoxia-ischemia. Seven days after hypoxia-ischemia, rats received either saline solution or 4 × 10⁵ HUCB cells i.v. Rats in control group did not receive any injection. After two weeks, rats were assessed using two motor tests. Subsequently, rats were scarified for histological and immunohistochemical analyses. Results: Our immunohistochemical findings demonstrated selective migration of the injected HUCB cells to the ischemic area as well as reduction in infarct volume. Seven days after surgery, we found significant recovery in the behavioral performance in the test group (12.7 +/- 0.3) compared to the sham group (10.0 +/-0.05), a trend which continued to day 14 (15.3 ± 0.3 vs. 11.9 ± 0.5, P<0.05). Postural and motor asymmetries at days 7 and 14 in the test group showed a significant decrease in the percentage of right turns in comparison to the sham group (75% and 59% vs. 97% and 96%, P<0.05). Conclusion: The results show the potential of HUCB stem cells in reduction of neurologic deficits associated with neonatal hypoxia-ischemia.

Conditioned medium from umbilical cord mesenchymal stem cells induces migration and angiogenesis

Umbilical cord mesenchymal stem cells (UC-MSCs) have been suggested as a candidate for various clinical applications, however, major limitations include the lack of organ-specific accumulation and low survival rates of transplanted cells. In the present study, it was hypothesized that the paracrine effects of UC‑MSCs may enhance stem cell-based tissue repair and regeneration by promoting the specific homing of stem/progenitor cells and the overall ability to drive them to the damaged area. UC-MSCs-derived conditioned medium (UC-CM) was analyzed using liquid chip and ELISA techniques. In vitro tube formation assays of human umbilical vein endothelial cells (HUVECs) and UC-MSCs were then performed to assess the angiogenic properties of UC-CM. Subsequently, UC-MSCs, HUVECs and fibroblasts were labeled with PKH26 for an in vivo cell migration assay. The expression levels of C-X-C chemokine receptor 4 (CXCR4), C-C chemokine receptor 2 (CCR2) and c-met were determined in the UC-MSCs, HUVECs and fibroblasts using reverse transcription-quantitative polymerase chain reaction and flow cytometry. UC-CM was incubated with or without antibodies, and the contribution of stromal cell-derived factor 1 (SDF-1), monocyte chemotactic protein 1 (MCP-1) and hepatocyte growth factor (HGF) on the migration of cells was investigated in vitro. The results demonstrated that UC-MSCs secreted different cytokines and chemokines, including increased quantities of SDF-1, MCP-1 and HGF, in addition to the angiogenic factors, vascular cell adhesion protein-1, interleukin-8, insulin-like growth factor-1 and vascular endothelial growth factor. The total lengths of the tubes were significantly increased in the UC-MSCs and HUVECs incubated in UC-CM compared with those incubated in Dulbecco's modified Eagle's medium. In vivo cell migration assays demonstrated that UC-CM was a chemotactic stimulus for the UC-MSCs and HUVECs. In vitro Matrigel migration and scratch healing assays demonstrated that UC-CM increased the migration of CXCR4-positive or/and CCR2-positive cells in a dose-dependent manner. In addition, different molecules were screened under antibody-based blocking migration conditions. The data revealed that the SDF-1/CXCR4 and MCP-1/CCR2 axes were involved in the chemoattractive activity of UC-CM and suggested that the effective paracrine factor of UC-CM is a large complex rather than a single factor. The results of the present study supported the hypothesis that UC-MSCs release soluble factors, which may extend the therapeutic applicability of stem cells.

Skin regeneration: the complexities of translation into clinical practise

The integration of engineering into biological science has resulted in the capacity to provide tissue engineered solutions for tissue damage. Skin regeneration remains the goal of skin repair to reduce the long term consequences of scarring to the individual. A scar is abnormal in its architecture, chemistry and cell phenotype, tissue engineering of scaffolds and cells opens up the potential of tissue regeneration into the future. Tissue engineering solutions have been applied to skin many decades despite technical success the clinical application has been modest. To realise the potential of the developing technologies needs alignment of not only the science and engineering but also the commercial upscaling of production in a safe and regulated framework for clinical use. In addition the education and training for the introduction of new technology within the health system is essential, bringing together the technology and systems for utilisation to optimise the patient outcome. This article is part of a Directed Issue entitled: Regenerative Medicine: The challenge of translation.

CD271 as a marker for mesenchymal stem cells in bone marrow versus umbilical cord blood

CD271 has been applied to isolate mesenchymal stem cells (MSCs) from bone marrow and other tissues. Umbilical cord blood is a unique resource of stem cells and endothelial progenitor cells. Isolation of MSCs from umbilical cord blood, however, has been inefficient and inconsistent. This study was designed to examine the potential application of CD271 as a marker for the isolation of MSCs from umbilical cord blood. CD271+ cells were isolated from umbilical cord blood and bone marrow using CD271 antibody-conjugated microbeads, and characterized in osteogenic, chondrogenic and adipogenic differentiation. CD271+ cells from umbilical cord blood were slow to proliferate compared with those isolated from bone marrow. While CD271+ cells from bone marrow differentiated into osteogenic, chondrogenic and adipogenic lineages, there were no sound indications of differentiation by CD271+ cells from umbilical cord blood under the same differentiation conditions applied to the CD271+ cells from bone marrow. The study also found that bone marrow CD271+ cells remarkably upregulated the expression of chondrogenic genes under chondrogenic differentiation induction. When implanted into bone defects in mice, CD271+ cells from bone marrow regenerated significant bone, but the counterparts in umbilical cord blood formed little bone in the bone defects. In conclusion, CD271 is an efficient marker for MSC isolation from bone marrow but has failed to isolate MSCs from umbilical cord blood. CD271+ cells in bone marrow are particularly chondrogenic. The property of CD271+ cells is unique but varies from different tissues.

Cord blood endothelial progenitor cells as therapeutic and imaging probes

Numerous studies demonstrated that neovascularization processes associated with severe tissue ischemia commonly found in conditions such as cardiovascular disorders and tumor growth occur via angiogenic and vasculogenic mechanisms. Over the past decade, it has been demonstrated that endothelial progenitor cells (EPCs) play a significant role in neo-angiogenic and neovasculogenic processes. Due to their ability to self-renew, circulate, home to the ischemic sites and differentiate into mature endothelial cells, EPCs derived from various sources hold enormous potential to be used as therapeutic agents in pro- or anti-angiogenic strategies for the treatment of ischemic and tumor conditions, respectively. However, the development of EPC-based therapies requires accompanying, noninvasive imaging protocol for in vivo tracking of transplanted cells. Hence, this review focuses on cord blood-derived EPCs and their role in neovascularization with emphasis on the potential use of EPCs as a therapeutic and imaging probe.

Intravenous administration of human umbilical cord blood-mononuclear cells dose-dependently relieve neurologic deficits in rat intracerebral hemorrhage model

Human umbilical cord blood (HUCB) is now considered as a valuable source for stem cell-based therapies. Previous studies showed that intravascular injection of the HUCB significantly improves neurological functional recovery in a model of intracerebral hemorrhage (ICH). To extend these findings, we examined the behavioral recovery and injured volume in the presence of increasing doses of human umbilical cord blood derived mononuclear cells (HUC-MCs) after intracerebral hemorrhage in rats. The experimental ICH was induced by intrastriatal administration of bacterial collagenase IV in adult rats. One day after the surgery, the rats were randomly divided into 4 groups to receive intravenously either BrdU positive human UC-MCs (4 × 10(6), 8 × 10(6) and 16 × 10(6) cells in 1 ml saline, n=10, respectively) as treated groups or the same amount of saline as lesion group (n=10). There was also one group (control n=10) that received only the vehicle solution of collagenase. The animals were evaluated for 14 days with modified limb placing and corner turn tests. The transplanted human UC-MCs were also detected by immunohistochemistry with labeling of BrdU. Two weeks after infusion, there was a significant recovery in the behavioral performance when 4 × 10(6) or more UC-MCs were delivered (P<0.05-0.001). Injured volume measurements disclosed an inverse relationship between UC-MCs dose and damage reaching significance at the higher UC-MCs doses. Moreover, human UC-MCs were localized by immunohistochemistry only in the injured area. Intravenously transplanted UC-MCs can accelerate the neurological function recovery of ICH rat and diminish the striatum lesion size by demonstrating a dose relationship between them.

Tissue engineering of skin

Each one of us is a self-organizing mass of multiple cell types. From fertilization of the embryo our tissue structures develop until an adult morphology is achieved. At that point our capacity for self-organization is directed to maintaining that morphology in the face of the insults of our daily life and the processes of aging. When a given insult overwhelms our capacity to repair by regeneration the result is scar repair.

Distinct phenotypes and regenerative potentials of early endothelial progenitor cells and outgrowth endothelial progenitor cells derived from umbilical cord blood

The capability of postnatal neovascularization makes circulating endothelial progenitor cells (EPCs) promising for regenerative medicine and tissue engineering. Using EPCs isolated from umbilical cord blood, this study aimed to clarify the transition of functional properties from early EPCs (e-EPCs) to outgrowth EPCs (og-EPCs) for potential applications in regenerative medicine. Mononuclear cells were collected from umbilical cord blood via density gradient centrifugation and further negatively selected by CD45. EPCs were sorted from mononuclear cells by the expression of CD34. e-EPCs (7 days of culture) and og-EPCs (3 weeks of culture) were characterized by morphology, intake of acetylated low-density lipoprotein, vessel-cord formation, cell surface phenotype and the expression of angiogenic genes. e-EPCs and og-EPCs were also compared for osteogenic differentiation under the stimulation of BMP-2. Chemotaxis by SDF-1 was compared among og-EPCs and the first- and second-day attached e-EPCs. Based on the expression of angiogenic genes, e-EPCs possessed few angiogenic properties in vitro and og-EPCs were angiogenic. e-EPCs, however, expressed significant CXCR4 and migrated toward the SDF-1 gradient. og-ECPs did not express CXCR4 and showed no response to SDF-1. During culture, gaining an angiogenic phenotype by og-EPCs is associated with the loss of homing potential. These contrast properties determine different potentials of e-EPCs and og-EPCs in regenerative medicine.

Human cord blood transplantation in a neonatal rat model of hypoxic-ischemic brain damage: functional outcome related to neuroprotection in the striatum

Human umbilical cord blood mononuclear cells (HUCB) have been shown to have a therapeutic role in different models of central nervous system (CNS) damage, including stroke. We evaluated the possible therapeutic potential of HUCB in P7 rats submitted to the Rice-Vannucci model of neonatal hypoxic-ischemic (HI) brain damage. Our results demonstrated that intraperitoneal transplantation of HUCB, 3 h after the HI insult, resulted in better performance in two developmental sensorimotor reflexes, in the first week after the injury. We also showed a neuroprotective effect in the striatum, and a decrease in the number of activated microglial cells in the cerebral cortex of treated animals. We suggest that HUCB transplantation might rescue striatal neurons from cell death after a neonatal HI injury resulting in better functional recovery.

Strategies for future histocompatible stem cell therapy

Stem cell therapy based on the safe and unlimited self-renewal of human pluripotent stem cells is envisioned for future use in tissue or organ replacement after injury or disease. A gradual decline of regenerative capacity has been documented among the adult stem cell population in some body organs during the aging process. Recent progress in human somatic cell nuclear transfer and inducible pluripotent stem cell technologies has shown that patient-derived nuclei or somatic cells can be reprogrammed in vitro to become pluripotent stem cells, from which the three germ layer lineages can be generated, genetically identical to the recipient. Once differentiation protocols and culture conditions can be defined and optimized, patient-histocompatible pluripotent stem cells could be directed towards virtually every cell type in the human body. Harnessing this capability to enrich for given cells within a developmental lineage, would facilitate the transplantation of organ/tissue-specific adult stem cells or terminally differentiated somatic cells to improve the function of diseased organs or tissues in an individual. Here, we present an overview of various experimental cell therapy technologies based on the use of patient-histocompatible stem cells, the pending issues needed to be dealt with before clinical trials can be initiated, evidence for the loss and/or aging of the stem cell pool and some of the possible uses of human pluripotent stem cell-derivatives aimed at curing disease and improving health.

Therapeutic stem-cells for cancer treatment: hopes and hurdles in tactical warfare

As our understanding of stem-cell behaviour rapidly increases, more and more reports suggest that use of stem-cell therapy will extend well beyond regenerative medicine in the near future. Due to their inherent tumoritropic migratory properties, stem cells can serve as vehicles for the delivery of effective, targeted treatment to isolated tumours and to metastatic disease. In vitro, stem cells can readily be engineered by inserting specifically tailored transgenes with antitumour effects to create tumour-seeking therapeutic vehicles. Transgene effects include direct tumour-cell killing, promotion of local immune responses, oncolytic virus production, and prodrug activation schemes. Many of these strategies have been validated in a wide range of studies assessing treatment feasibility or efficacy and establishing methods for real-time monitoring of stem-cell migration and fate in vivo. New insights into avenues for stem-cell sourcing have shortened the probable time to realisation of such treatments for patients. In this Review, we provide an outline of the rationale and status of stem-cell-based treatments for tumours, and we discuss prospects for clinical implementation and the factors crucial for maintaining momentum towards this goal.

Umbilical cord blood transfusions for prevention of progressive brain injury and induction of neural recovery: an immunological perspective

One of the most promising treatments for neurodegenerative diseases appears to be human umbilical cord blood cell transplantation. A variety of studies demonstrate some benefit of this method of treatment in a number of different animal models and case studies. However, before the methodologies and results of these animal studies and case studies can be translated into successful widespread treatments, aspects relating to the immunological properties of the transplanted cells must be considered. In this perspective, we discuss the benefit of the cellular immaturity of these cells with respect to the immune response, and compare cord blood transplantation to blood transfusions, as well as discussing what future studies should entail.

Long-term cultured human umbilical cord neural-like cells transplanted into the striatum of NOD SCID mice

The use of stem cells and other cells as therapies is still in its infancy. One major setback is the limited survival of the grafts, possibly due to immune rejection. Studies were therefore performed with human umbilical cord blood cells (HUCB) to determine the ability of these cells to survive in vivo and the effect of the immune response on their survival by transplantation into the normal striatum of immunodeficient NOD SCID mice. Long-term culture of HUCB cells resulted in several different populations of cells, including one that possessed fine processes and cell bodies that resembled neurons. Their neuronal phenotype was confirmed by immunohistochemical staining for the early neuronal marker TuJ1 and the potentially neural marker Nestin. Five days after cell transplantation of this neuronal phenotype, immunohistochemical staining for human mitochondria confirmed the presence of living HUCB cells in the mouse striatum, with cells localized at the site of injection, expressing early neural and neuronal markers (Nestin and TuJ1) as well as exhibiting neuronal morphology. However, no evidence of surviving cells was apparent 1 month postgrafting. The absence of signs of T cell-mediated rejection, such as CD4 and CD8 lymphocytes and minimal changes in microglia and astrocytes, suggest that cell loss was not due to a T cell-mediated immune response. In conclusion HUCB cells can survive long-term in vitro and undergo neuron-like differentiation. In mice, these cells do not survive a month. This may relate to the differentiated state of the cells transplanted into the unlesioned striatum, rather than T cell-mediated immunological rejection.