Robin K. Ohls

TGF-β2 Suppresses Macrophage Cytokine Production and Mucosal Inflammatory Responses in the Developing Intestine

BACKGROUND & AIMS Premature neonates are predisposed to necrotizing enterocolitis (NEC), an idiopathic, inflammatory bowel necrosis. We investigated whether NEC occurs in the preterm intestine due to incomplete noninflammatory differentiation of intestinal macrophages, which increases the risk of a severe mucosal inflammatory response to bacterial products. METHODS We compared inflammatory properties of human/murine fetal, neonatal, and adult intestinal macrophages. To investigate gut-specific macrophage differentiation, we next treated monocyte-derived macrophages with conditioned media from explanted human fetal and adult intestinal tissues. Transforming growth factor-β (TGF-β) expression and bioactivity were measured in fetal/adult intestine and in NEC. Finally, we used wild-type and transgenic mice to investigate the effects of deficient TGF-β signaling on NEC-like inflammatory mucosal injury. RESULTS Intestinal macrophages in the human preterm intestine (fetus/premature neonate), but not in full-term neonates and adults, expressed inflammatory cytokines. Macrophage cytokine production was suppressed in the developing intestine by TGF-β, particularly the TGF-β(2) isoform. NEC was associated with decreased tissue expression of TGF-β(2) and decreased TGF-β bioactivity. In mice, disruption of TGF-β signaling worsened NEC-like inflammatory mucosal injury, whereas enteral supplementation with recombinant TGF-β(2) was protective. CONCLUSIONS Intestinal macrophages progressively acquire a noninflammatory profile during gestational development. TGF-β, particularly the TGF-β(2) isoform, suppresses macrophage inflammatory responses in the developing intestine and protects against inflammatory mucosal injury. Enterally administered TGF-β(2) protected mice from experimental NEC-like injury.

Recombinant erythropoietin compared with erythrocyte transfusion in the treatment of anemia of prematurity

To assess the risks and benefits of erythropoietin versus erythrocyte transfusion in the treatment of the anemia of prematurity, we randomly assigned 19 anemic preterm infants (birth weight 988 +/- 227 gm; gestational age 27.6 +/- 1.2 weeks; age 41 +/- 15 days; all values mean +/- SD) to receive either transfusion or subcutaneously administered erythropoietin (200 units/kg every other day for 10 doses). In the 10 erythropoietin recipients, corrected reticulocyte counts increased from 2% +/- 1% to 7% +/- 2% (p less than 0.001) and hematocrits increased from 27% +/- 2% to 30% +/- 4% (p less than 0.05). In the nine infants who underwent transfusion, reticulocyte counts did not increase, but hematocrits increased from 28% +/- 4% to 41% +/- 2% after initial transfusion (p less than 0.001) and had decreased to 34% +/- 5% by day 20. Signs attributed to anemia (tachycardia, apnea with bradycardia, and poor weight gain) declined in both the erythropoietin recipients and those who underwent transfusion. However, five of nine infants who underwent transfusion had symptoms within 10 to 14 days and were given further transfusions. Marrow aspiration performed after 7 to 10 days of treatment showed that infants receiving erythropoietin had greater percentages of erythropoietic precursors (p less than 0.01), greater concentrations of mature erythroid progenitors (p less than 0.001), and higher cycling rates of erythroid progenitors (p less than 0.001). The percentage of mature stored neutrophils in marrow was lower in the erythropoietin group than in the transfusion group, resulting in an inverse myeloid/erythroid ratio (0.5:1 vs 6.2:1; p less than 0.001). After 20 days, absolute blood neutrophil counts were lower in the erythropoietin recipients (1.8 +/- 0.9 x 10(3) cells/microliters) than in the infants who underwent transfusion (3.9 +/- 1.9 x 10(3) cells/microliters; p less than 0.05). Administration of erythropoietin thus stimulated erythropoiesis and relieved signs attributed to anemia; the significance of the relative neutropenia remains to be determined. We conclude that erythropoietin administration offers promise as an alternative to erythrocyte transfusion in neonates with symptomatic anemia of prematurity.

Efficacy and cost analysis of treating very low birth weight infants with erythropoietin during their first two weeks of life: A randomized, placebo-controlled trial

OBJECTIVE We hypothesized that using a higher dose of erythropoietin (Epo) and starting treatment on the first day of life would reduce the transfusion requirements of ventilator-dependent and non-ventilator-dependent very low birth weight (VLBW) infants. Moreover, we hypothesized that this treatment would be cost-effective. METHODS We randomly assigned 20 ill newborn VLBW infants to receive either Epo (200 units/kg per day) or placebo during their first 2 weeks of life. The caregivers were unaware of the treatment assignments, and erythrocyte transfusions were administered according to hematocrit and signs of anemia. RESULTS On day 1, reticulocyte counts and hematocrits were similar in the two groups. During the subsequent 2 weeks, reticulocyte counts of the placebo recipients fell significantly below those of the Epo recipients, but hematocrits in the two groups did not differ. More transfusions were received by the placebo recipients (mean = 1.4 per patient) than by the Epo recipients (mean = 0.2 per patient; p < 0.01). No adverse effects of Epo were noted, and the costs in the placebo group exceeded those in the Epo group. CONCLUSIONS We conclude that administration of Epo to VLBW infants during the first 2 weeks of life results in fewer transfusions and is cost-effective.

Pharmacokinetics and effectiveness of recombinant erythropoietin administered to preterm infants by continuous infusion in total parenteral nutrition solution

OBJECTIVES To compare the pharmacokinetics and effectiveness of continuously administered recombinant erythropoietin (Epo) in total parenteral nutrition (TPN) solution with daily subcutaneously administered Epo. METHODS Forty preterm infants in the first 72 hours of life were randomly assigned to receive Epo (200 units/kg per day for 10 consecutive days), either subcutaneously (20 infants, 1051 +/- 40 gm, 28.3 +/- 0.4 weeks of gestation; mean +/- SEM), or added daily to their TPN fluids (20 infants, 1028 +/- 36 gm, 27.9 +/- 0.4 weeks of gestation). Both groups received iron supplementation (1 mg/kg per day iron dextran in the TPN solution). Absolute reticulocyte counts and complete blood cell counts with differentials were measured, and transfusions and phlebotomy losses were recorded. Pharmacokinetics were determined in the first 16 infants. RESULTS In the infants who received Epo subcutaneously, the elimination half-life was 17.6 +/- 4.4 hours on day 3 and 11.2 +/- 1.5 hours on day 10; the volume of distribution was 802 +/- 190 ml/kg on day 3 and 1330 +/- 243 m/kg on day 10. Serum Epo concentrations were higher on day 3 than on day 10 for both groups (subcutaneous: 400 +/- 64 mU/ml vs 177 +/- 29 mU/m, p <0.05; TPN: 395 +/- 64 vs 194 +/- 41 mU/ml, p <0.05). Clearance did not differ between the two groups with regard to route of administration and increased significantly from days 3 to 10 in both groups. Reticulocyte counts were similar in both groups. There were no differences between groups in the number of transfusions given, and the overall decline in hematocrit was similar. No adverse effects of Epo were noted in either group. CONCLUSIONS Adding Epo to the TPN solution in this population results in similar Epo concentrations, clearance, and effectiveness as subcutaneous dosing.

Existence, Functional Impairment, and Lung Repair Potential of Endothelial Colony-Forming Cells in Oxygen-Induced Arrested Alveolar Growth

Background— Bronchopulmonary dysplasia and emphysema are life-threatening diseases resulting from impaired alveolar development or alveolar destruction. Both conditions lack effective therapies. Angiogenic growth factors promote alveolar growth and contribute to alveolar maintenance. Endothelial colony-forming cells (ECFCs) represent a subset of circulating and resident endothelial cells capable of self-renewal and de novo vessel formation. We hypothesized that resident ECFCs exist in the developing lung, that they are impaired during arrested alveolar growth in experimental bronchopulmonary dysplasia, and that exogenous ECFCs restore disrupted alveolar growth. Methods and Results— Human fetal and neonatal rat lungs contain ECFCs with robust proliferative potential, secondary colony formation on replating, and de novo blood vessel formation in vivo when transplanted into immunodeficient mice. In contrast, human fetal lung ECFCs exposed to hyperoxia in vitro and neonatal rat ECFCs isolated from hyperoxic alveolar growth–arrested rat lungs mimicking bronchopulmonary dysplasia proliferated less, showed decreased clonogenic capacity, and formed fewer capillary-like networks. Intrajugular administration of human cord blood–derived ECFCs after established arrested alveolar growth restored lung function, alveolar and lung vascular growth, and attenuated pulmonary hypertension. Lung ECFC colony- and capillary-like network-forming capabilities were also restored. Low ECFC engraftment and the protective effect of cell-free ECFC-derived conditioned media suggest a paracrine effect. Long-term (10 months) assessment of ECFC therapy showed no adverse effects with persistent improvement in lung structure, exercise capacity, and pulmonary hypertension. Conclusions— Impaired ECFC function may contribute to arrested alveolar growth. Cord blood–derived ECFC therapy may offer new therapeutic options for lung diseases characterized by alveolar damage.

Resting-state functional connectivity differences in premature children

We examine the coherence in the spontaneous brain activity of sleeping children as measured by the blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) signals. The results are described in terms of resting-state networks (RSN) and their properties. More specifically, in this study we examine the effect of severe prematurity on the spatial location of the visual, temporal, motor, basal ganglia, and the default mode networks, the temporal response properties of each of these networks, and the functional connectivity between them. Our results suggest that the anatomical locations of the RSNs are well developed by 18 months of age and their spatial locations are not distinguishable between premature and term born infants at 18 months or at 36 months, with the exception of small spatial differences noted in the basal ganglia area and the visual cortex. The two major differences between term and pre-term children were present at 36 but not 18 months and include: (1) increased spectral energy in the low frequency range (0.01–0.06 Hz) for pre-term children in the basal ganglia component, and (2) stronger connectivity between RSNs in term children. We speculate that children born very prematurely are vulnerable to injury resulting in weaker connectivity between resting-state networks by 36 months of age. Further work is required to determine whether this could be a clinically useful tool to identify children at risk of developmental delay related to premature birth.

Current Controversies in the Management of the Anemia of Prematurity

Preterm infants, especially those with extremely low birth weight (ELBW) are exposed to frequent blood draws as part of their care in the neonatal intensive care unit. ELBW infants develop the anemia of prematurity (AOP), a hypo-proliferative anemia marked by inadequate production of erythropoietin (Epo). Treatment of AOP includes red blood cell transfusions, which are given to preterm infants based on indications and guidelines (hematocrit/hemoglobin levels, ventilation and oxygen need, apneas and bradycardias, poor weight gain) that are relatively non-specific. In this article we review recent studies evaluating transfusion guidelines, discuss ways to decrease phlebotomy losses and examine the use of red cell growth factors such as Epo in preventing and treating anemia in preterm infants.

THE USE OF ERYTHROPOIETIN IN NEONATES

Although much information has been accumulated about the clinical use of Epo in preterm infants, many questions remain unanswered. The evolution of clinical practice in the care of extremely ill, preterm infants continues to affect the number of transfusions required during hospitalization. Decreasing phlebotomy losses and instituting standardized transfusion guidelines have both been shown significantly to decrease the transfusion requirements of preterm infants. The administration of Epo likely decreases transfusion need even further; however, the direct impact of each of these actions has not been studied prospectively. It is likely that the combination of instituting rigorous and standardized transfusion guidelines, decreasing phlebotomy losses, and the appropriate use of Epo will have the greatest impact in decreasing transfusion requirements in all preterm and term neonates, regardless of the cause of their anemia.

Cognitive Outcomes of Preterm Infants Randomized to Darbepoetin, Erythropoietin, or Placebo

BACKGROUND: We previously reported decreased transfusions and donor exposures in preterm infants randomized to Darbepoetin (Darbe) or erythropoietin (Epo) compared with placebo. As these erythropoiesis-stimulating agents (ESAs) have shown promise as neuroprotective agents, we hypothesized improved neurodevelopmental outcomes at 18 to 22 months among infants randomized to receive ESAs. METHODS: We performed a randomized, masked, multicenter study comparing Darbe (10 μg/kg, 1×/week subcutaneously), Epo (400 U/kg, 3×/week subcutaneously), and placebo (sham dosing 3×/week) given through 35 weeks’ postconceptual age, with transfusions administered according to a standardized protocol. Surviving infants were evaluated at 18 to 22 months’ corrected age using the Bayley Scales of Infant Development III. The primary outcome was composite cognitive score. Assessments of object permanence, anthropometrics, cerebral palsy, vision, and hearing were performed. RESULTS: Of the original 102 infants (946 ± 196 g, 27.7 ± 1.8 weeks’ gestation), 80 (29 Epo, 27 Darbe, 24 placebo) returned for follow-up. The 3 groups were comparable for age at testing, birth weight, and gestational age. After adjustment for gender, analysis of covariance revealed significantly higher cognitive scores among Darbe (96.2 ± 7.3; mean ± SD) and Epo recipients (97.9 ± 14.3) compared with placebo recipients (88.7 ± 13.5; P = .01 vs ESA recipients) as was object permanence (P = .05). No ESA recipients had cerebral palsy, compared with 5 in the placebo group (P < .001). No differences among groups were found in visual or hearing impairment. CONCLUSIONS: Infants randomized to receive ESAs had better cognitive outcomes, compared with placebo recipients, at 18 to 22 months. Darbe and Epo may prove beneficial in improving long-term cognitive outcomes of preterm infants.

A Randomized, Masked, Placebo-Controlled Study of Darbepoetin Alfa in Preterm Infants

BACKGROUND: A novel erythropoiesis stimulating agent (ESA), darbepoetin alfa (Darbe), increases hematocrit in anemic adults when administered every 1 to 3 weeks. Weekly Darbe dosing has not been evaluated in preterm infants. We hypothesized that infants would respond to Darbe by decreasing transfusion needs compared with placebo, with less-frequent dosing than erythropoietin (Epo). METHODS: Preterm infants 500 to 1250 g birth weight and ≤48 hours of age were randomized to Darbe (10 μg/kg, 1 time per week subcutaneously), Epo (400 U/kg, 3 times per week subcutaneously) or placebo (sham dosing) through 35 weeks’ gestation. All received supplemental iron, folate, and vitamin E, and were transfused according to protocol. Transfusions (primary outcome), complete blood counts, absolute reticulocyte counts (ARCs), phlebotomy losses, and adverse events were recorded. RESULTS: A total of 102 infants (946 ± 196 g, 27.7 ± 1.8 weeks’ gestation, 51 ± 25 hours of age at first dose) were enrolled. Infants in the Darbe and Epo groups received significantly fewer transfusions (P = .015) and were exposed to fewer donors (P = .044) than the placebo group (Darbe: 1.2 ± 2.4 transfusions and 0.7 ± 1.2 donors per infant; Epo: 1.2 ± 1.6 transfusions and 0.8 ± 1.0 donors per infant; placebo: 2.4 ± 2.9 transfusions and 1.2 ± 1.3 donors per infant). Hematocrit and ARC were higher in the Darbe and Epo groups compared with placebo (P = .001, Darbe and Epo versus placebo for both hematocrit and ARCs). Morbidities were similar among groups, including the incidence of retinopathy of prematurity. CONCLUSIONS: Infants receiving Darbe or Epo received fewer transfusions and fewer donor exposures, and fewer injections were given to Darbe recipients. Darbepoetin and Epo successfully serve as adjuncts to transfusions in maintaining red cell mass in preterm infants.