Endothelial colony forming cells and mesenchymal stem cells are enriched at different gestational ages in human umbilical cord blood

Review: Endothelial progenitor cells in pregnancy and obstetric pathologies

Since their discovery, endothelial progenitor cells (EPCs) have generated considerable interest in vascular biology. They are a heterogeneous population of cells that exist in both the fetus and adult, and are mobilized to support de novo vessel formation or encourage vascular health. This review summarizes our understanding of these cells in pregnancy, paying particular attention to their physiological role in placental development and the uterus, alongside their involvement in related obstetric pathologies.

Vulnerability of the developing brain to hypoxic-ischemic damage: contribution of the cerebral vasculature to injury and repair?

As clinicians attempt to understand the underlying reasons for the vulnerability of different regions of the developing brain to injury, it is apparent that little is known as to how hypoxia-ischemia may affect the cerebrovasculature in the developing infant. Most of the research investigating the pathogenesis of perinatal brain injury following hypoxia-ischemia has focused on excitotoxicity, oxidative stress and an inflammatory response, with the response of the developing cerebrovasculature receiving less attention. This is surprising as the presentation of devastating and permanent injury such as germinal matrix-intraventricular haemorrhage (GM-IVH) and perinatal stroke are of vascular origin, and the origin of periventricular leukomalacia (PVL) may also arise from poor perfusion of the white matter. This highlights that cerebrovasculature injury following hypoxia could primarily be responsible for the injury seen in the brain of many infants diagnosed with hypoxic-ischemic encephalopathy (HIE). Interestingly the highly dynamic nature of the cerebral blood vessels in the fetus, and the fluctuations of cerebral blood flow and metabolic demand that occur following hypoxia suggest that the response of blood vessels could explain both regional protection and vulnerability in the developing brain. However, research into how blood vessels respond following hypoxia-ischemia have mostly been conducted in adult models of ischemia or stroke, further highlighting the need to investigate how the developing cerebrovasculature responds and the possible contribution to perinatal brain injury following hypoxia. This review discusses the current concepts on the pathogenesis of perinatal brain injury, the development of the fetal cerebrovasculature and the blood brain barrier (BBB), and key mediators involved with the response of cerebral blood vessels to hypoxia.

Hypoxia-induced angiogenesis: good and evil

The vascular network delivers oxygen (O(2)) and nutrients to all cells within the body. It is therefore not surprising that O(2) availability serves as a primary regulator of this complex organ. Most transcriptional responses to low O(2) are mediated by hypoxia-inducible factors (HIFs), highly conserved transcription factors that control the expression of numerous angiogenic, metabolic, and cell cycle genes. Accordingly, the HIF pathway is currently viewed as a master regulator of angiogenesis. HIF modulation could provide therapeutic benefit for a wide array of pathologies, including cancer, ischemic heart disease, peripheral artery disease, wound healing, and neovascular eye diseases. Hypoxia promotes vessel growth by upregulating multiple pro-angiogenic pathways that mediate key aspects of endothelial, stromal, and vascular support cell biology. Interestingly, recent studies show that hypoxia influences additional aspects of angiogenesis, including vessel patterning, maturation, and function. Through extensive research, the integral role of hypoxia and HIF signaling in human disease is becoming increasingly clear. Consequently, a thorough understanding of how hypoxia regulates angiogenesis through an ever-expanding number of pathways in multiple cell types will be essential for the identification of new therapeutic targets and modalities.

Effect of preeclampsia and intrauterine growth restriction on endothelial progenitor cells in human umbilical cord blood

OBJECTIVES

Endothelial progenitor cells (EPCs) might play important roles in vascular homeostasis. This study evaluated the influence of prematurity, preeclampsia (PE) and intrauterine growth restriction (IUGR) on the EPC population in human umbilical cord blood (CB).

METHODS

CB was obtained from 19 preterm and 27 term deliveries. Mononuclear cells were isolated by gradient centrifugation and subjected to flow cytometry to obtain percentages of CD45(d) CD34+, CD45(d) CD133+, CD 45(d) CD34+ CD133+, and CD45(d) CD34+ CD133+ VEGFR-2+ cells. Clinical data were obtained using chart review.

RESULTS

Percentages of EPCs were comparable between preterm and term cord blood. CD45(d) CD34+ CD133+ cells were significantly decreased in CB samples obtained from women with PE (n = 14) [0.01, (0.00-2.6), [median, (range)], as compared to those without PE (n = 32) [1.74 (0.00-3.1)] (p = 0.005). CD45(d) CD133+ CD34- cells were significantly increased in presence of PE [0.43, (0.06-1.38)], (p = 0.002). CD45(d) CD34+ CD133+ cells were significantly decreased in presence of IUGR, with no change in CD45(d) CD133+ CD34- cells. Differences in EPC types associated with PE and IUGR were present only in term CB.

CONCLUSIONS

Exposure to PE and IUGR is associated with significant changes in EPC population. Future studies are needed to explore the clinical impact of observed changes.

Vascular progenitor cell mobilization

Blood vessel formation plays a key role in both physiologic and pathologic tissue growth and healing. Thus, a thorough understanding of the mechanisms underlying neovascularization will translate into innovative clinical treatment strategies for a wide variety of disease processes. Vascular precursor/progenitor cell populations have been isolated from several different tissue types and have a rich potential for use in vascular regenerative strategies. Furthermore, levels of circulating endothelial progenitor cells (EPC) have been shown to correlate with outcomes in cardiovascular and vascular diseases. Treatment with EPC has been shown to improve functional outcomes following cardiac and peripheral vascular ischemia. Recent studies have also demonstrated a role for EPC in pediatric disease processes such as retinopathy of prematurity and bronchopulmonary dysplasia. In addition, many of the drugs utilized to treat vascular disease impact EPC mobilization and function. Importantly, the type of vascular injury appears to dictate the mechanism of neovascularization, highlighting the importance of carefully selected vascular regenerative strategies.

A switch toward angiostatic gene expression impairs the angiogenic properties of endothelial progenitor cells in low birth weight preterm infants

Low birth weight (LBW) is associated with increased risk of cardiovascular diseases at adulthood. Nevertheless, the impact of LBW on the endothelium is not clearly established. We investigate whether LBW alters the angiogenic properties of cord blood endothelial colony forming cells (LBW-ECFCs) in 25 preterm neonates compared with 25 term neonates (CT-ECFCs). We observed that LBW decreased the number of colonies formed by ECFCs and delayed the time of appearance of their clonal progeny. LBW dramatically reduced LBW-ECFC capacity to form sprouts and tubes, to migrate and to proliferate in vitro. The angiogenic defect of LBW-ECFCs was confirmed in vivo by their inability to form robust capillary networks in Matrigel plugs injected in nu/nu mice. Gene profile analysis of LBW-ECFCs demonstrated an increased expression of antiangiogenic genes. Among them, thrombospondin 1 (THBS1) was highly expressed at RNA and protein levels in LBW-ECFCs. Silencing THBS1 restored the angiogenic properties of LBW-ECFCs by increasing AKT phosphorylation. The imbalance toward an angiostatic state provide a mechanistic link between LBW and the impaired angiogenic properties of ECFCs and allows the identification of THBS1 as a novel player in LBW-ECFC defect, opening new perspectives for novel deprogramming agents.

Mesenchymal stem-cell-based therapy for the older patient

Bone-marrow aspirate-derived mesenchymal stem cells (MSCs) form a core element of the vast majority of adherent, autologous stem-cell-based therapeutic clinical trials. This article explores the existing literature to determine if proposed MSC-based autologous cell therapy is suitable for use in an elderly patient population. Within the review a number of questions are asked: does the bone-marrow aspirate mononuclear cell (MNC) number, the frequency of MSC colony forming units or their proliferative potential correlate with age? Does disease state have an additional impact? Are immunophenotypes, molecular profiles or differentiation capacity linked to donor age? The answers to the above questions are essential for determining the appropriateness of elderly patients as donors and recipients for autologous MSC-based trials. Taken together, MSC yield, MNC number and proliferative potential all decrease with age while differentiation potential appears unchanged. The retention of differentiation capacity suggests that the elderly patient may be suitable for MSC-based therapy; however, only when isolation protocols are tailored in an individual-specific manner to correct for decreases in MNC number and MSC yield.

Pathogenesis and treatment of bronchopulmonary dysplasia

PURPOSE OF REVIEW

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of infancy affecting mostly premature infants with significant morbidity and mortality. Improved survival of very immature infants has led to increased numbers of infants with this disorder. Acute and chronic lung injury and impaired postnatal lung growth are thought to be responsible for the development of BPD. Whereas changes in clinical practice have improved the clinical course and outcomes for infants with BPD, over the past decade, the overall incidence of BPD has not changed. This review will describe the prenatal and postnatal factors that contribute to the pathogenesis of BPD as well as current and experimental therapies for treatment of BPD.

RECENT FINDINGS

The factors that contribute to the pathogenesis of BPD are well described; however, recent studies have better defined how these factors modulate lung growth. Inflammation, proinflammatory cytokines and altered angiogenic gene signaling contribute to lung injury and impair prenatal and postnatal lung growth resulting in BPD; however, to date no therapy has been identified that potently and consistently prevents or reverses their effects on lung growth. We will discuss the cell signaling pathways affected in BPD and current therapies available for modulating these pathways.

SUMMARY

Despite current advances in neonatal care, BPD remains a heavy burden on healthcare resources. New treatments directed at either reducing lung injury or improving lung growth are under study.

Human umbilical cord blood-derived mononuclear cell transplantation: case series of 30 subjects with hereditary ataxia

Background

The differential diagnosis for hereditary ataxia encompasses a variety of diseases characterized by both autosomal dominant and recessive inheritance. There are no curative treatments available for these neurodegenerative conditions. This open label treatment study used human umbilical cord blood-derived mononuclear cells (CBMC) combined with rehabilitation training as potential disease modulators.

Methods

30 patients suffering from hereditary ataxia were treated with CBMCs administered systemically by intravenous infusion and intrathecally by either cervical or lumbar puncture. Primary endpoint measures were the Berg Balance Scale (BBS), serum markers of immunoglobulin and T-cell subsets, measured at baseline and pre-determined times post-treatment.

Results

A reduction of pathological symptoms and signs was shown following treatment. The BBS scores, IgG, IgA, total T cells and CD3+CD4 T cells all improved significantly compared to pre-treatment values (P < 0.01~0.001). There were no adverse events.

Conclusion

The combination of CBMC infusion and rehabilitation training may be a safe and effective treatment for ataxia, which dramatically improves patients' functional symptoms. These data support expanded double blind, placebo-controlled studies for these treatment modalities.

Engineering blood vessels using stem cells: innovative approaches to treat vascular disorders

Vascular disease is the leading cause of mortality in the USA, providing the impetus for new treatments and technologies. Current therapies rely on the implantation of stents or grafts to treat injured blood vessels. However, these therapies may be immunogenic or may incompletely recover the functional integrity of the vasculature. In light of these shortcomings, cell-based therapies provide new treatment options to heal damaged areas with more suitable substitutes. Current clinical trials employing stem cell-based therapies involve the transfusion of harvested endothelial progenitor cells. While the results from these trials have been encouraging, utilizing tissue-engineered approaches could yield technologically advanced solutions. This article discusses engineered stem cell-based therapies from three angles: the differentiation of adult stem cells, such as mesenchymal stem cells and endothelial progenitor cells, into vascular lineages; investigation of human embryonic stem cells and induced pluripotent stem cells as inexhaustible sources of vascular cells; and tissue-engineering approaches, which incorporate these vascular progenitor cells into biomimetic scaffolds to guide regeneration. The optimal solution to vascular disease lies at the interface of these technologies--embedding differentiated cells into engineered scaffolds to impart precise control over vascular regeneration.

Translating research into clinical scale manufacturing of mesenchymal stromal cells

It sounds simple to obtain sufficient numbers of cells derived from fetal or adult human tissues, isolate and/or expand the stem cells, and then transplant an appropriate number of these cells into the patient at the correct location. However, translating basic research into routine therapies is a complex multistep process which necessitates product regulation. The challenge relates to managing the expected therapeutic benefits with the potential risks and to balance the fast move to clinical trials with time-consuming cautious risk assessment. This paper will focus on the definition of mesenchymal stromal cells (MSCs), and challenges and achievements in the manufacturing process enabling their use in clinical studies. It will allude to different cellular sources, special capacities of MSCs, but also to current regulations, with a special focus on accessory material of human or animal origin, like media supplements. As cellular integrity and purity, formulation and lot release testing of the final product, validation of all procedures, and quality assurance are of utmost necessity, these topics will be addressed.

Cord blood transplantation and stem cell regenerative potential

The past 20 years of experience with umbilical cord blood transplantation have demonstrated that cord blood is effective in the treatment of a spectrum of diseases, including hematological malignancies, bone marrow failure, hemoglobinopathies, and inborn errors of metabolism. Cord blood can be obtained with ease and then safely cryopreserved for either public or private use without loss of viability. As compared to other unrelated donor cell sources, cord blood transplantation allows for greater human leukocyte antigen disparity without a corresponding increase in graft-vs.-host disease. Moreover, cord blood has a lower risk of transmitting infections by latent viruses and is less likely to carry somatic mutations than other adult cells. Recently, multiple populations of stem cells with primitive stem cell properties have been identified from cord blood. Meanwhile, there is an increasing interest in applying cord blood mononuclear cells or enriched stem cell populations to regenerative therapies. Accumulating evidence has suggested functional improvements after cord blood transplantation in various animal models for treatments of cardiac infarction, diabetes, neurological diseases, etc. In this review, we will summarize the most recent updates on clinical applications of cord blood transplantation and the promises and limitations of cell-based therapies for tissue repair and regeneration.

Endothelial colony-forming cells and mesenchymal stem cells from ECMO circuits of term infants

OBJECTIVE

Endothelial progenitor cells (EPCs) have been examined in numerous adult diseases and have been suggested as a cellular-based therapy. However, there are no reports describing EPCs being isolated from newborn peripheral blood.

STUDY DESIGN

Endothelial colony-forming cells (ECFCs), a subtype of EPCs, were isolated from blood collected from 12 neonatal extracorporeal membrane oxygenation (ECMO) circuits.

RESULT

ECFCs were isolated in all samples. We unexpectedly isolated a distinctly different colony of mesenchymal stem cells (MSCs) in seven samples. Both cell types expressed the expected endothelial or mesenchymal cell surface antigens.

CONCLUSION

To our knowledge, this is the first report of ECFCs and MSCs isolated from peripheral blood of critically ill term newborns. Both cells types may be mobilized in response to critical illness or to the ECMO circuit. Further studies evaluating the role of stem cells in various newborn conditions are warranted.

Human endothelial stem/progenitor cells, angiogenic factors and vascular repair

Neovascularization or new blood vessel formation is of utmost importance not only for tissue and organ development and for tissue repair and regeneration, but also for pathological processes, such as tumour development. Despite this, the endothelial lineage, its origin, and the regulation of endothelial development and function either intrinsically from stem cells or extrinsically by proangiogenic supporting cells and other elements within local and specific microenvironmental niches are still not fully understood. There can be no doubt that for most tissues and organs, revascularization represents the holy grail for tissue repair, with autologous endothelial stem/progenitor cells, their proangiogenic counterparts and the products of these cells all being attractive targets for therapeutic intervention. Historically, a great deal of controversy has surrounded the identification and origin of cells and factors that contribute to revascularization, the use of such cells or their products as biomarkers to predict and monitor tissue damage and repair or tumour progression and therapeutic responses, and indeed their efficacy in revascularizing and repairing damaged tissues. Here, we will review the role of endothelial progenitor cells and of supporting proangiogenic cells and their products, principally in humans, as diagnostic and therapeutic agents for wound repair and tissue regeneration.

Increased migration by stimulation of thymidine phosphorylase in endothelial cells of different origin

Thymidine phosphorylase (TP) catalyzes the phosphorylytic cleavage of thymidine to thymine and deoxyribose-1-phosphate. The latter may be involved in the angiogenic stimulation of TP. In the present study, we investigated whether thymidine and deoxyribose (dR) could stimulate angiogenesis in vitro of two types of endothelial cells (isolated from umbilical veins (HUVEC) and endothelial colony forming cells (ECFC)), and whether the stereoisomer L-deoxyribose (L-dR) and the thymidine phosphorylase inhibitor (TPI) could reduce this. Both cell types had a low TP activity. Thymidine increased the migration of both HUVECs and ECFCs, but dR only that of the ECFCs. The invasion was not changed by any of the agents tested. In conclusion, TP may play a role in the migration of HUVECs and ECFCs, but not the invasion.

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.

Safety evaluation of allogeneic umbilical cord blood mononuclear cell therapy for degenerative conditions

Background

The current paradigm for cord blood transplantation is that HLA matching and immune suppression are strictly required to prevent graft versus host disease (GVHD). Immunological arguments and historical examples have been made that the use of cord blood for non-hematopoietic activities such as growth factor production, stimulation of angiogenesis, and immune modulation may not require matching or immune suppression.

Methods

114 patients suffering from non-hematopoietic degenerative conditions were treated with non-matched, allogeneic cord blood. Doses of 1-3 × 10⁷ cord blood mononuclear cells per treatment, with 4-5 treatments both intrathecal and intravenously were performed. Adverse events and hematological, immunological, and biochemical parameters were analyzed for safety evaluation.

Results

No serious adverse effects were reported. Hematological, immunological, and biochemical parameters did not deviate from normal ranges as a result of therapy.

Conclusion

The current hematology-based paradigm of need for matching and immune suppression needs to be revisited when cord blood is used for non-hematopoietic regenerative purposes in immune competent recipients.

Low birth weight infants and the developmental programming of hypertension: a focus on vascular factors

Low birth weight infants, in particular those born preterm, have been shown to develop increased arterial blood pressure and hypertension at adulthood. Three main systems are involved in the developmental programming of hypertension: the kidney, the neuroendocrine system, and the vascular tree. This review focuses on vascular dysfunction and discusses clinical and experimental evidence that relates low birth weight and the risk for hypertension at adulthood. Recent studies demonstrate an impairment of vascular structure and function. Both arterial vessels, through altered arterial stiffness and endothelium-dependent vasodilation, and the capillary bed, through microvascular rarefaction, are involved in the early pathogenesis of hypertension. The key role of the endothelium, as shown by altered vasodilatation, angiogenesis, endothelial progenitor cells, and microparticle number and function, is discussed as a possible explanatory mechanism.

Optimization of the culturing conditions of human umbilical cord blood-derived endothelial colony-forming cells under xeno-free conditions applying a transcriptomic approach

Establishment of fetal bovine serum (FBS)-free cell culture conditions is essential for transplantation therapies. Blood-derived endothelial colony-forming cells (ECFCs) are potential candidates for regenerative medicine applications. ECFCs were isolated from term umbilical cord blood units and characterized by flow cytometry, capillary formation and responsiveness to cytokines. ECFCs were expanded under standard, FBS-containing endothelial medium, or transferred to chemically defined endothelial media without FBS. Microarray expression profiling was applied to compare the transcriptome profiles in FBS-containing versus FBS-free culture. ECFC outgrowth in standard medium was successful in 92% of cord blood units. The karyotype of expanded ECFCs remained normal. Without FBS, ECFC initiation and expansion failed. Modest proliferation, changes in cell morphology and organization and cell death have been observed after passaging. Gene ontology analysis revealed a broad down-regulation of genes involved in cell cycle progression and up-regulation of genes involved in stress response and apoptosis. Interestingly, genes participating in lipid biosynthesis were markedly up-regulated. Detection of several endothelial cell-specific marker genes showed the maintenance of the endothelial cell characteristics during serum-free culture. Although ECFCs maintain their endothelial characteristics during serum-free culturing, they could not be expanded. Additional supply of FBS-free media with lipid concentrates might increase the ECFC survival.

Hypoxia-inducible factor-1-dependent mechanisms of vascularization and vascular remodelling

The vascular system delivers oxygen and nutrients to every cell in the vertebrate organism. Hypoxia-inducible factor 1 (HIF-1) is a master regulator of hypoxic/ischaemic vascular responses, driving transcriptional activation of hundreds of genes involved in vascular reactivity, angiogenesis, arteriogenesis, and the mobilization and homing of bone marrow-derived angiogenic cells. This review will focus on the pivotal role of HIF-1 in vascular homeostasis, the involvement of HIF-1 in vascular diseases, and recent advances in targeting HIF-1 for therapy in preclinical models.

Endothelial progenitor cells: their potential in the placental vasculature and related complications

Endothelial progenitor cells (EPCs) have received significant attention in recent times. A role for EPCs has been suggested in a range of pathologies and some recent studies of EPCs in pregnancy have been published. This review provides a guide to the confusing field of EPCs. Attention is paid to their phenotyping, as although elementary this remains a highly debated topic. The current understanding of different subtypes and physiological role of EPCs in the placenta, fetus and adult are also considered. An overview is given as to role of EPC's in the pathophysiology of different disease states and the possible therapeutic and diagnostic applications expected from EPC-related research in obstetrics.

Endothelial progenitor cells and cardiovascular cell-based therapies

Since their initial discovery more than a decade ago, bone marrow (BM)-derived circulating endothelial progenitor cells (EPC) have been reported to play a role in postnatal vasculogenesis through vessel regeneration and remodeling. These cells have been reported to mobilize into the blood stream in response to vascular injury, and differentiate into cells expressing a host of endothelial cell (EC) markers in vitro. Because of demonstrable regenerative capacity in animal models of human disease, EPC are thought to represent a novel treatment option for problematic cardiovascular conditions such as myocardial infarction (MI) and peripheral vascular disease (PVD). Various studies have been performed to test the clinical efficacy of EPC in patients with cardiovascular disease (CVD), including the mobilization of EPC with pharmacologic agents in patients with heart disease, and harvesting of cells from the circulation and BM for autologous reinfusion in affected patients. The outcomes of these trials have been mixed and not as robust as predicted from the animal models, partly because of the variation in the definition of human EPC and the resulting heterogeneity in cell populations used in the treatments. This review will decipher a number of published studies that have been conducted to examine cell therapies for treatment of CVD, will attempt to explain why efficacy of treatment with putative EPC has been inconsistent, and predict which aspects of these trials may need to be redesigned for future successful treatment of CVD.

Recovery of multipotent progenitors from the peripheral blood of patients requiring extracorporeal membrane oxygenation support

RATIONALE

Studies have demonstrated that bone marrow-derived cells can be recruited to injured lungs through an unknown mechanism. We hypothesize that marrow progenitors are mobilized into the circulation of patients with cardiac and/or respiratory failure, and may then traffic to and incorporate into the sites of tissue injury.

OBJECTIVES

To determine whether progenitor populations are increased in the blood of patients with severe acute cardiorespiratory failure placed on extracorporeal membrane oxygenation (ECMO).

METHODS

Mononuclear cells from ECMO, umbilical cord, and control blood samples were evaluated in colony-forming assays for hematopoietic, mesenchymal, and epithelial cells. Progenitors were identified by proliferative and differentiative capacities, and confirmed by the expression of lineage-specific markers.

MEASUREMENTS AND MAIN RESULTS

Significantly higher levels of hematopoietic progenitors were observed in ECMO (n = 41) samples than neonatal intensive care unit (n = 16) or pediatric intensive care unit controls (n = 14). Hematopoietic progenitor mobilization increased with time on ECMO support. Mesenchymal progenitors (MSC) were recovered from 18/58 ECMO samples with rapid sample processing (< 4 h) critical to their recovery. MSC were not recovered from normal controls. ECMO-derived MSC had osteogenic, chondrogenic, and adipogenic differentiation potential. The recovery of MSC did not influence survival outcome (61%). Epithelial progenitors were observed in eight ECMO samples but not in control samples. Their presence was associated with a lower survival trend (38%).

CONCLUSIONS

Hematopoietic, mesenchymal, and epithelial progenitors were mobilized into the circulation of patients on ECMO. This may reflect a response to severe cardiopulmonary injury, blood-foreign surface interactions with the ECMO circuit, and/or hemodilution.

Circulating endothelial progenitor cells in preterm infants with bronchopulmonary dysplasia

RATIONALE

The new form of bronchopulmonary dysplasia (BPD) is characterized by lung immaturity with disrupted alveolar and capillary development after extremely premature birth, but the mechanism of impaired lung vascular formation is still not completely understood.

OBJECTIVES

We tested the hypothesis that reduced numbers of circulating endothelial progenitor cells at birth are associated with the development of BPD.

METHODS

We studied ninety-eight preterm infants with gestational age of less than 32 weeks or a birth weight less than 1,500 g. Endothelial colony-forming cells (ECFCs) were assessed by clonogenic analysis in infants for whom cord blood was available. The proportion of circulating endothelial and hematopoietic cells was measured by flow cytometry at birth, at 48 hours, and at 7 days of life.

MEASUREMENTS AND MAIN RESULTS

ECFCs in cord blood were lower in infants who later developed BPD (median [range]: 0.00 [0.00-0.48] vs. 2.00 [0.00-21.87]; P = 0.002). ECFCs decreased with decreasing gestational age (r = 0.41; P = 0.02), but even at extremely low gestational ages, infants with higher numbers of ECFCs were protected from BPD. The endothelial and hematopoietic cell subsets studied by flow cytometry were comparable in infants with and without BPD and rapidly decreased after birth.

CONCLUSIONS

ECFCs are low at extremely low gestational ages and increase during gestation; extremely preterm infants who display lower numbers at birth have an increased risk of developing BPD. Our findings suggest that decreased ECFCs following extremely preterm birth may be associated with the risk for developing lung vascular immaturity characteristic of new BPD.