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Reactivation of fetal erythropoiesis during the postnatal period
Insights
Hemoglobin F levels in infants do not decrease continuously after birth. Cellular age impacts hemoglobin distribution, showing a bimodal pattern in erythrocytes between 2-4 months.
Area of Science:
- Hematology
- Pediatric Medicine
- Cellular Biology
Background:
- Hemoglobin F (HbF) is the primary hemoglobin during fetal development.
- Postnatal transition involves the switch from HbF to adult hemoglobin (HbA).
- The precise kinetics of HbF decline in infants are not fully understood.
Purpose of the Study:
- To investigate the pattern of hemoglobin F (HbF) disappearance during early infancy.
- To analyze erythrocyte and hemoglobin characteristics across different cellular ages in infants.
- To determine if HbF reduction is a continuous or discontinuous process postnatally.
Main Methods:
- Isopycnic gradient centrifugation was used to separate blood samples into seven cellular age fractions.
- Analysis included erythrocyte and reticulocyte counts, mean cellular volume, and hemoglobin concentration per fraction.
- Blood from adults, umbilical cord, newborns, and infants up to 8 months was studied.
Main Results:
- Erythrocyte distribution showed a bimodal pattern between 2-4 months of postnatal age.
- In infants aged 2-8 months, older erythrocytes did not exhibit the highest HbF concentration, unlike in younger infants.
- This suggests a non-uniform decline in HbF across the erythrocyte population.
Conclusions:
- The postnatal decline of hemoglobin F is not a continuous, uniform process.
- Cellular age plays a significant role in hemoglobin composition during infancy.
- Understanding these dynamics is crucial for pediatric hematology and understanding red blood cell aging.
Abstract:
Using isopycnic gradient centrifugation, blood samples from adults, from umbilical cord, from newborn infants and from infants of different age group up to the age of 8 mo, were separated into seven fractions according to cellular age. We measured the number of erythrocytes and reticulocytes, mean cellular volume, mean cellular hemoglobin concentration, and the concentration of hemoglobin in each of the seven fractions. The distribution of erythrocytes within the gradient during postnatal aging revealed a bimodal distribution between 2-4 mo. Correspondingly, during the age of 2-8 mo the oldest cells did not contain the highest hemoglobin F concentration as was observed in the younger age group. From these data we conclude that the postnatal disappearance of hemoglobin F is not a continuous process.