Circulating Stem Cell Populations in Preterm Infants

Abstract

To investigate the association among different circulating stem cell (SC) populations, the levels of selected growth factors and chemokines regulating SC migration in the peripheral blood, and the incidence of retinopathy of prematurity (ROP). Methods: We evaluated 88 participants in this study: 29 preterm infants with ROP, 29 preterm infants without ROP, and 30 healthy full-term infants. Peripheral blood samples collected 10 weeks after delivery were analyzed using flow cytometry, immunofluorescence, realtime reverse transcriptase-polymerase chain reaction, and enzyme-linked immunosorbent assay. The following cell populations were analyzed: (1) lin-CXCR4 ϩ CD45 − (enriched in very small embryonic-like SCs), (2) lin − CXCR4 ϩ CD45 ϩ (enriched in hematopoietic SCs), and (3) CD34 ϩ CD133 ϩ CD144 ϩ (early endothelial progenitor cells) [lin indicates lineage]. The concentrations of vascular endothelial growth factor, basic fibroblast growth factor, hepatocyte growth factor, and stromal cellderived factor 1 were measured in the plasma. Results: The very small embryonic-like SCs and early endothelial progenitor cells expressing neural and endothelial markers were significantly increased in the preterm infants. The number of early endothelial progenitor cells in the peripheral blood was significantly greater in the preterm infants with ROP than in the preterm infants without ROP. An accompanying increase in the concentrations of vascular endothelial growth factor and hepatocyte growth factor was found in the peripheral blood of the preterm infants with ROP. No significant associations were found between hematopoietic SCs and ROP or prematurity. Conclusions: The increased number of early endothelial progenitor cells along with elevated levels of vascular endothelial growth factor and hepatocyte growth factor in preterm infants with ROP suggest that circulating vasculogenic factors may play a role in the development and progression of ROP. The increased number of very small embryonic-like SCs in preterm infants suggests that the development of immature tissues and organs, including the retina, may require a contribution of circulating SCs.

Circulating hematopoietic stem cell count is a valuable predictor of prematurity complications in preterm newborns

“…To analyze distinct stem cell types we selected CD45 - lin - CD184 + and CD45 + lin - CD184 + phenotypes that represent primitive, non-hematopoietic (non-HSC) and hematopoietic (HSC) stem cells, respectively [5,6,17]. Based on our previous reports, and in order to verify whether or not the population of non-HSCs comprise very small embryonic-like stem cells (VSELs), thus we evaluated in parallel the expression of markers common to pluripotent or undifferentiated cells by immunocytofluorescence and qRT-PCR in those cells.…”

“…Receptor CXCR4 (CD184) plays an important role in the mechanisms of HSCs migration and repopulation, in regard to the observation, that murine fetuses lacking this receptor (CXCR4-null model) have multiple defects that are lethal, including impaired BM hematopoiesis [28]. Recently, we were able, not only to confirm the presence of such highly restrictive SCs populations among blood leukocytes, but also to quantitatively determine the absolute numbers of these infrequent cells circulating in the blood of patients with various tissue/organ injuries and disorders [5,6,17]. Of note, the defined CD45 – lin – CD184 + and CD45 + lin – CD184 + SC populations have not been previously evaluated in relatively long-term prospective observation in PB of preterm infants.…”

“…The obtained suspension of CB or PB nucleated cells (NCs) was subjected to immunostaining procedures with murine anti-human monoclonal antibodies, as described previously [5,17]. For linage markers we used antibodies against: CD2 clone RPA-2.10, CD3 clone SK7, CD14 clone MϕP9, CD16 clone 3 G8, CD19 clone HIB19, CD24 clone ML5, CD56 clone NCAM16.2, CD66b clone G10F5, CD235a clone GA-R2 (all from BD Bioscences, San Jose, CA, USA).…”

“…Cell staining for all of the antigens was performed as described previously [17]. The sorted cells were permeabilized (0.1% Triton X-100, 10 min) and stained for β-III-tubulin, Nanog and Oct-4 antigens with anti-human monoclonal antibodies (Abcam, Cambridge, UK) for 1 h at RT, followed by incubation with a secondary antibody conjugated to Texas Red® (Vector Labs, Burlingame, CA, USA).…”

Differential Secretion of Angiopoietic Factors and Expression of MicroRNA in Umbilical Cord Blood from Healthy Appropriate-For-Gestational-Age Preterm and Term Newborns—in Search of Biomarkers of Angiogenesis-Related Processes in Preterm Birth

“…Our group has previously found higher early-and late-EPC counts in umbilical cord blood (UCB) of premature infants compared with full-term neonates [19]. Furthermore, we also reported that elevated numbers of early endothelial progenitor cells in the peripheral blood of preterm neonates were associated with retinal injury [20]. Machalinska et al has also found that in preterm neonates with hypoxic retinopathy, elevated VEGF and IGF-1 blood levels correlated with retinal abnormalities, indicating that these trophic factors may be predictive of abnormal neurodevelopmental outcomes, including retina [21].…”