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.

Kinetics of Circulating Progenitor Cells and Chemotactic Factors in Full-Term Neonates with Encephalopathy: Indications of Participation in the Endogenous Regenerative Process

“…It seems that the devastating event initially inhibits this chemoattractant, but in the following days, the regeneration mechanisms rebound: damaged brain tissue triggers SDF-1 release, as shown by a correlation between early brain injury markers and later SDF-1 levels (hypothesis C). This is consistent with studies on adults [ 52 , 94 , 95 ], where increased SDF-1 is observed after tissue injury, but the related pattern in neonates is far more complicated [ 35 , 54 , 110 ], making the correlation between SDF-1 and CPCs difficult to interpret [ 53 , 70 ]. It is interesting that in preclinical models of brain injury, SDF-1 levels were elevated for much longer in adult animals [ 92 , 93 ] in contrast to models of neonatal brain injury, indicating a much shorter therapeutic window in neonates [ 7 ].…”

“…This could be due to a different chemotactic axis and/or a different role of lEPCs, e.g., neo-angiogenesis in the penumbra. In previous studies on premature neonates, low EPCs were found in “stress” conditions, such as gestational diabetes, preeclampsia, chorioamnionitis, sepsis, necrotizing enterocolitis, and bronchopulmonary dysplasia [ 54 , 60 , 66 , 68 , 70 , 111 , 112 ], but these observations were not consistent among studies [ 113 ].…”

Kinetics of Circulating Progenitor Cells and Chemotactic Factors in Full-Term Neonates with Encephalopathy: Indications of Participation in the Endogenous Regenerative Process

“…It seems that the devastating event initially inhibits this chemoattractant, but in the following days, the regeneration mechanisms rebound: damaged brain tissue triggers SDF-1 release, as shown by a correlation between early brain injury markers and later SDF-1 levels (hypothesis C). This is consistent with studies on adults [ 52 , 94 , 95 ], where increased SDF-1 is observed after tissue injury, but the related pattern in neonates is far more complicated [ 35 , 54 , 110 ], making the correlation between SDF-1 and CPCs difficult to interpret [ 53 , 70 ]. It is interesting that in preclinical models of brain injury, SDF-1 levels were elevated for much longer in adult animals [ 92 , 93 ] in contrast to models of neonatal brain injury, indicating a much shorter therapeutic window in neonates [ 7 ].…”

“…This could be due to a different chemotactic axis and/or a different role of lEPCs, e.g., neo-angiogenesis in the penumbra. In previous studies on premature neonates, low EPCs were found in “stress” conditions, such as gestational diabetes, preeclampsia, chorioamnionitis, sepsis, necrotizing enterocolitis, and bronchopulmonary dysplasia [ 54 , 60 , 66 , 68 , 70 , 111 , 112 ], but these observations were not consistent among studies [ 113 ].…”

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.…”

Beyond brain injury biomarkers: chemoattractants and circulating progenitor cells as biomarkers of endogenous rehabilitation effort in preterm neonates with encephalopathy

“…Additionally, in this study, SDF-1 levels were increased in full-term newborns compared to preterms, but this has not reached statistical significance, in accordance to other researchers ( 103 , 104 ). Machalinska et al ( 107 ) have found increased levels in full-term neonates at the 10th week of life. We also observed positive (but not constant) correlations of SDF-1 levels with CPCs, that are indicative of its role as a chemoattractant.…”

“…In our study, brain injury was correlated positively with SDF-1 [i.e., presenting a role of chemotaxis after injury, as seen in adult models ( 57 , 102 )] in full-term neonates (data not shown) and in preterms only after day 9 of life. More studies are needed for a conclusive theory ( 103 , 104 , 107 ). Additionally, in this study, SDF-1 levels were increased in full-term newborns compared to preterms, but this has not reached statistical significance, in accordance to other researchers ( 103 , 104 ).…”

Kinetics of Circulating Progenitor Cells and Chemotactic Factors in Full-Term Neonates with Encephalopathy: Indications of Participation in the Endogenous Regenerative Process

“…It seems that the devastating event initially inhibits this chemoattractant, but in the following days, the regeneration mechanisms rebound: damaged brain tissue triggers SDF-1 release, as shown by a correlation between early brain injury markers and later SDF-1 levels (hypothesis C). This is consistent with studies on adults [ 52 , 94 , 95 ], where increased SDF-1 is observed after tissue injury, but the related pattern in neonates is far more complicated [ 35 , 54 , 110 ], making the correlation between SDF-1 and CPCs difficult to interpret [ 53 , 70 ]. It is interesting that in preclinical models of brain injury, SDF-1 levels were elevated for much longer in adult animals [ 92 , 93 ] in contrast to models of neonatal brain injury, indicating a much shorter therapeutic window in neonates [ 7 ].…”

“…This could be due to a different chemotactic axis and/or a different role of lEPCs, e.g., neo-angiogenesis in the penumbra. In previous studies on premature neonates, low EPCs were found in “stress” conditions, such as gestational diabetes, preeclampsia, chorioamnionitis, sepsis, necrotizing enterocolitis, and bronchopulmonary dysplasia [ 54 , 60 , 66 , 68 , 70 , 111 , 112 ], but these observations were not consistent among studies [ 113 ].…”

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.…”

Beyond brain injury biomarkers: chemoattractants and circulating progenitor cells as biomarkers of endogenous rehabilitation effort in preterm neonates with encephalopathy

“…Additionally, in this study, SDF-1 levels were increased in full-term newborns compared to preterms, but this has not reached statistical significance, in accordance to other researchers ( 103 , 104 ). Machalinska et al ( 107 ) have found increased levels in full-term neonates at the 10th week of life. We also observed positive (but not constant) correlations of SDF-1 levels with CPCs, that are indicative of its role as a chemoattractant.…”

“…In our study, brain injury was correlated positively with SDF-1 [i.e., presenting a role of chemotaxis after injury, as seen in adult models ( 57 , 102 )] in full-term neonates (data not shown) and in preterms only after day 9 of life. More studies are needed for a conclusive theory ( 103 , 104 , 107 ). Additionally, in this study, SDF-1 levels were increased in full-term newborns compared to preterms, but this has not reached statistical significance, in accordance to other researchers ( 103 , 104 ).…”

Kinetics of Circulating Progenitor Cells and Chemotactic Factors in Full-Term Neonates with Encephalopathy: Indications of Participation in the Endogenous Regenerative Process

“…It seems that the devastating event initially inhibits this chemoattractant, but in the following days, the regeneration mechanisms rebound: damaged brain tissue triggers SDF-1 release, as shown by a correlation between early brain injury markers and later SDF-1 levels (hypothesis C). This is consistent with studies on adults [ 52 , 94 , 95 ], where increased SDF-1 is observed after tissue injury, but the related pattern in neonates is far more complicated [ 35 , 54 , 110 ], making the correlation between SDF-1 and CPCs difficult to interpret [ 53 , 70 ]. It is interesting that in preclinical models of brain injury, SDF-1 levels were elevated for much longer in adult animals [ 92 , 93 ] in contrast to models of neonatal brain injury, indicating a much shorter therapeutic window in neonates [ 7 ].…”

“…This could be due to a different chemotactic axis and/or a different role of lEPCs, e.g., neo-angiogenesis in the penumbra. In previous studies on premature neonates, low EPCs were found in “stress” conditions, such as gestational diabetes, preeclampsia, chorioamnionitis, sepsis, necrotizing enterocolitis, and bronchopulmonary dysplasia [ 54 , 60 , 66 , 68 , 70 , 111 , 112 ], but these observations were not consistent among studies [ 113 ].…”

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.…”

Beyond brain injury biomarkers: chemoattractants and circulating progenitor cells as biomarkers of endogenous rehabilitation effort in preterm neonates with encephalopathy

“…Additionally, in this study, SDF-1 levels were increased in full-term newborns compared to preterms, but this has not reached statistical significance, in accordance to other researchers ( 103 , 104 ). Machalinska et al ( 107 ) have found increased levels in full-term neonates at the 10th week of life. We also observed positive (but not constant) correlations of SDF-1 levels with CPCs, that are indicative of its role as a chemoattractant.…”

“…In our study, brain injury was correlated positively with SDF-1 [i.e., presenting a role of chemotaxis after injury, as seen in adult models ( 57 , 102 )] in full-term neonates (data not shown) and in preterms only after day 9 of life. More studies are needed for a conclusive theory ( 103 , 104 , 107 ). Additionally, in this study, SDF-1 levels were increased in full-term newborns compared to preterms, but this has not reached statistical significance, in accordance to other researchers ( 103 , 104 ).…”