Erythropoietin protects against necrotizing enterocolitis of newborn rats by the inhibiting nitric oxide formation

The effects of IGF-1 and erythropoietin on apoptosis and telomerase activity in necrotizing enterocolitis model

BACKGROUND

Apoptosis that occurs after hypoxia/reoxygenation (H/R) has an important role in the pathogenesis of necrotizing enterocolitis (NEC). Telomerase activity, showing the regeneration capacity, may also be important in the recovery process. Therefore, we aimed to investigate the effects of insulin-like growth factor-1 (IGF-1) and erythropoietin (EPO) on apoptosis and telomerase activity in an H/R model.

METHODS

Young mice were divided into four groups each containing ten Balb/c mice. Group 1 (H/R) were exposed to H/R; group 2 and group 3 were pretreated with IGF-1 and EPO, respectively, for 7 days before H/R. Group 4 served as control. Intestinal injury was evaluated by histological scoring and assessment of apoptosis was performed by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) test. Proapoptotic and antiapoptotic gene expressions and telomerase activity were analyzed by real-time PCR.

RESULTS

IGF-1- and EPO-treated animals had decreased histological damage and apoptosis, confirmed by TUNEL test and caspase activity. Telomerase activity was increased in these animals in addition to increased expression of antiapoptotic genes. However, proapoptotic gene expressions were not statistically different.

CONCLUSIONS

The protective effects of IGF-1 and EPO in H/R damage may be through increased expression of antiapoptotic genes and increased telomerase activity, especially for IGF-1.

IMPACT

This is a comprehensive study measuring various variables, namely IGF-1, EPO, apoptosis, apoptotic and antiapoptotic genes, and telomerase activity in the NEC model. The intestinal protective effects of IGF-1 and EPO in H/R damage may occur through increased expression of antiapoptotic genes and increased telomerase activity. To the best of our knowledge, telomerase activity has not been investigated in the NEC model before. Regarding our results, novel strategies may be implemented for the early definitive diagnosis, robust preventive measures, and effective treatment modalities for NEC.

Erythropoietin prevents necrotizing enterocolitis in very preterm infants: a randomized controlled trial

Background

Necrotizing enterocolitis (NEC) is one of the most severe complications in very preterm infants, but there are currently no accepted methods to prevent NEC. Studies have shown that erythropoietin (EPO) has the potential to prevent NEC or improve outcomes of preterm NEC. This study aimed to determine whether recombinant human EPO (rhEPO) could protect against NEC in very preterm infants.

Methods

The study was a prospective randomized clinical trial performed among four NICU centers. A total of 1327 preterm infants with gestational age ≤ 32 weeks were admitted to the centers, and 42 infants were excluded leaving 1285 eligible infants to be randomized to the rhEPO or control group. Infants in the rhEPO group were given 500 IU/kg rhEPO intravenously every other day for 2 weeks, while the control group was given the same volume of saline. The primary outcome was the incidence of NEC in very preterm infants at 36 weeks of corrected gestational age.

Results

A total of 1285 infants were analyzed at 36 weeks of corrected age for the incidence of NEC. rhEPO treatment significantly decreased the incidence of NEC (stage I, II and III) (12.0% vs. 17.1%, p = 0.010), especially confirmed NEC (stage II and III) (3.0% vs. 5.4%, p = 0.027). Meanwhile, rhEPO treatment significantly reduced the number of red blood cells transfusion in the confirmed NEC cases (1.2 ± 0.4 vs. 2.7 ± 1.0, p = 0.004). Subgroup analyses showed that rhEPO treatment significantly decreased the incidence of confirmed NEC at gestational age < 28 weeks (p = 0.019), and the incidence of all stages NEC in preterm infants with hemoglobin < 90 g/l (p = 0.000) and 5 min Apgar score > 5 (p = 0.028).

Conclusion

Repeated low-dose rhEPO treatment is beneficial against NEC in very preterm infants.

Trial registration The protocol was registered retrospectively at ClinicalTrials.gov (NCT03919500) on April 18, 2019. https://clinicaltrials.gov/ct2/show/NCT03919500

Influence of Growth Factors on the Development of Necrotizing Enterocolitis

Growth factors have important roles in gastrointestinal tract development, maintenance, and response to injury. Various experiments have been used to demonstrate growth factor influence in multiple disease processes. These studies demonstrated enhancement of mucosal proliferation, intestinal motility, immune modulation, and many other beneficial effects. Select growth factors, including epidermal growth factor and heparin-binding epidermal growth factor like growth factor, demonstrate some beneficial effects in experimental and clinical intestinal injury demonstrated in necrotizing enterocolitis. The roles of glucagon-like peptide 2, insulin-like growth factor 1, erythropoietin, growth hormone, and hepatocyte growth factor in necrotizing enterocolitis are summarized in this article.

Epidemiology of Necrotizing Enterocolitis: New Considerations Regarding the Influence of Red Blood Cell Transfusions and Anemia

This article summarizes available evidence on the relationship between red blood cell transfusion and anemia, and necrotizing enterocolitis (NEC). We review recent studies that highlight the uncertainty of the effect of red blood cell transfusion on NEC and the potential role of anemia. We also discuss potential pathophysiologic effects of both red blood cell transfusion and anemia and highlight strategies to prevent anemia and red blood cell transfusion. We also discuss ongoing randomized trials that are likely to provide important new evidence to guide red blood cell transfusion practices.

Red Blood Cell Transfusion in Preterm Infants: Current Evidence and Controversies

The current evidence regarding the indication, advantages and risks of red blood cell transfusion (RBCT) for preterm infants is discussed. This is an important area in Neonatology to be examined given that 90% of extremely low birth weight infants receive RBCT and many controversies remain regarding when to transfuse and the risks of RBCT. The various treatment thresholds and guidelines used are presented and we compare the short-term clinical benefits of liberal and restrictive RBCT in preterm infants; the majority of these are equivocal and sadly long-term outcome data is limited. The latest evidence on how anaemia and blood transfusion affect organ perfusion in preterm infants is presented. This is important when trying to establish the optimal trigger threshold for RBCT in preterm infants, especially because the knowledge about the adaptive physiological responses to anaemia in very low birth weight infants and the effects of RBCT at various levels of anaemia is also inadequate. Further research into the physiological adaptive response to anaemia of varying degrees and to RBCT at different levels of anaemia in preterm infants of different gestational and post-natal ages is needed before we can conclusively guide the optimal timing and trigger thresholds for RBCT in preterm infants.

Cytokines and growth factors in the developing intestine and during necrotizing enterocolitis

Cytokines and growth factors play diverse roles in the uninflamed fetal/neonatal intestinal mucosa and in the development of inflammatory bowel injury during necrotizing enterocolitis (NEC). During gestational development and the early neonatal period, the fetal/premature intestine is exposed to high levels of many "inflammatory" cytokines and growth factors, first via swallowed amniotic fluid in utero and then, after birth, in colostrum and mother's milk. This article reviews the dual, seemingly counter-intuitive roles of cytokines, where these agents play a "trophic" role and promote maturation of the uninflamed mucosa, but can also cause inflammation and promote intestinal injury during NEC.

Study on the inflammatory intervention of erythropoietin on NEC

The aim of this study was to investigate the effect of erythropoietin (EPO) on the inflammatory response and the mechanism analysis of the Τoll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signaling pathway of NEC. A total of 94 patients with necrotizing enterocolitis (NEC) were randomly divided into the control (42 cases) and observation (52 cases) groups, The control group received the standard medical treatment plan, whereas for the observation group this treatment plan was combined with the application of recombinant EPO for intramuscular injection treatment. The clinical effect was subsequently compared. The results showed that the complication and death rates in the observation group were significantly lower than those in the control group with statistically significant differences (P<0.05). Following treatments, the levels of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 in the observation group were significantly lower than those in the control group. The expression levels of mRNA of TLR4 and NF-κB in the observation group were significantly lower than those in the control group, with statistically significant differences (P<0.05). In summary, EPO was able to reduce the levels of inflammatory response of TNF-α and IL-6 through the TLR4/NF-κB signaling pathway, and improve the NEC, thus providing a basis for the clinical treatment of NEC.

Erythropoietin protects epithelial cells from excessive autophagy and apoptosis in experimental neonatal necrotizing enterocolitis

Neonatal necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease of preterm infants. Increased intestinal epithelium permeability is an early event in NEC pathogenesis. Autophagy and apoptosis are induced by multiple stress pathways which may impact the intestinal barrier, and they have been associated with pathogenesis of diverse gastrointestinal diseases including inflammatory bowel disease. Using both in vitro and in vivo models, this study investigates autophagy and apoptosis under experimental NEC stresses. Furthermore this study evaluates the effect of erythropoietin (Epo), a component of breast milk previously shown to decrease the incidence of NEC and to preserve intestinal barrier function, on intestinal autophagy and apoptosis. It was found that autophagy and apoptosis are both rapidly up regulated in NEC in vivo as indicated by increased expression of the autophagy markers Beclin 1 and LC3II, and by evidence of apoptosis by TUNEL and cleaved caspase-3 staining. In the rat NEC experimental model, autophagy preceded the onset of apoptosis in intestine. In vitro studies suggested that Epo supplementation significantly decreased both autophagy and apoptosis via the Akt/mTOR signaling pathway and the MAPK/ERK pathway respectively. These results suggest that Epo protects intestinal epithelium from excessive autophagy and apoptosis in experimental NEC.

Prevention of necrotizing enterocolitis in preterm very low birth weight infants: is it feasible?

Necrotizing enterocolitis (NEC) is still one of the most catastrophic intestinal emergencies in preterm very low-birth weight infants. Primary prevention of NEC should be the priority, since NEC frequently progresses from nonspecific signs, to extensive necrosis within a matter of hours with medical or surgical treatment, making successful treatment and secondary prevention difficult to achieve. Currently available strategies for primary prevention of NEC include antenatal glucocorticosteroids, breast milk feeding, cautious feeding strategy, fluid restriction and probiotics. Nonetheless, based on current research evidence, mixed flora probiotics, and/or breast milk feeding, would appear to be the most effective feasible methods in the prevention of NEC at present.

The role of growth factors in intestinal regeneration and repair in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease resulting in major neonatal morbidity and mortality. The pathology is poorly understood, and the means of preventing and treating NEC are limited. Several endogenous growth factors have been identified as having important roles in intestinal growth as well as aiding intestinal repair from injury or inflammation. In this review, we will discuss several growth factors as mediators of intestinal regeneration and repair as well as potential therapeutic agents for NEC.

Effectiveness of Saccharomyces boulardii in a rat model of colitis

AIM: To investigate the effects of Saccharomyces boulardii (S. boulardii) in an experimental rat model of trinitrobenzene sulfonic acid (TNBS)-induced colitis.

METHODS: Thirty-two Wistar albino female rats were categorized into five groups. On the first day of the study, 50 mg TNBS was administered via a rectal catheter in order to induce colitis in all rats, except those in the control group. For 14 d, the rats were fed a standard diet, without the administration of any additional supplements to either the control or TNBS groups, in addition to 1 mg/kg per day S. boulardii to the S. boulardii group, 1 mg/kg per day methyl prednisolone (MP) to the MP group. The animals in the S. boulardii + MP group were coadministered these doses of S. boulardii and MP. During the study, weight loss, stool consistency, and the presence of obvious blood in the stool were evaluated, and the disease activity index (DAI) for colitis was recorded. The intestines were examined and colitis was macro- and microscopically scored. The serum and tissue levels of tumor necrosis factor-α (TNF-α) and nitric oxide (NO) were determined, and fungemia was evaluated in the blood samples.

RESULTS: The mean DAI scores for the MP and S. boulardii + MP groups was significantly lower than the TNBS group (3.69 ± 0.61 vs 4.46 ± 0.34, P = 0.018 and 3.77 ± 0.73 vs 4.46 ± 0.34, P = 0.025, respectively). While no significant differences between the TNBS and the S. boulardii or MP groups could be determined in terms of serum NO levels, the level of serum NO in the S. boulardii + MP group was significantly higher than in the TNBS and S. boulardii groups (8.12 ± 4.25 μmol/L vs 3.18 ± 1.19 μmol/L, P = 0.013; 8.12 ± 4.25 μmol/L vs 3.47 ± 1.66 μmol/L, P = 0.012, respectively). The tissue NO levels in the S. boulardii, MP and S. boulardii + MP groups were significantly lower than the TNBS group (16.62 ± 2.27 μmol/L vs 29.72 ± 6.10 μmol/L, P = 0.002; 14.66 ± 5.18 μmol/L vs 29.72 ± 6.10 μmol/L, P = 0.003; 11.95 ± 2.34 μmol/L vs 29.72 ± 6.10 μmol/L, P = 0.002, respectively). The tissue NO levels in the S. boulardii, MP and S. boulardii + MP groups were similar. The mean serum and tissue TNF-α levels were determined to be 12.97 ± 18.90 pg/mL and 21.75 ± 15.04 pg/mL in the control group, 18.25 ± 15.44 pg/mL and 25.27 ± 11.95 pg/mL in the TNBS group, 20.59 ± 16.15 pg/mL and 24.39 ± 13.06 pg/mL in the S. boulardii group, 9.05 ± 5.13 pg/mL and 24.46 ± 10.85 pg/mL in the MP group, and 13.95 ± 10.17 pg/mL and 24.26 ± 10.37 pg/mL in the S. boulardii + MP group. Significant differences in terms of the levels of serum and tissue TNF-α and the macroscopic and microscopic scores were not found between the groups. S. boulardii fungemia was not observed in any of the rats. However, Candida fungemia was detected in one rat (14%) in the TNBS group, two rats (28%) in the S. boulardii group, three rats (50%) in the MP group, and three rats (42%) in S. boulardii + MP group.

CONCLUSION: S. boulardii does not demonstrate considerable effects on the DAI, pathological scores, or cytokine levels but does decrease the tissue NO levels.

The influence of EPO and hypothermia on the kidneys of rats after perinatal asphyxia

The aim of this study was to determine the effects of erythropoietin (EPO), moderate hypothermia, and a combination thereof on the kidneys of newborn rats damaged during perinatal asphyxia. An animal model of perinatal asphyxia (Wistar rats) was used in which after birth, newborn rats were divided into four groups of 15 animals each: G1, rats exposed only to asphyxia; G2, rats exposed to asphyxia and hypothermia (rectal temperature 32°C) and which received EPO (darbepoetin alpha) intraperitoneally; G3, rats exposed to asphyxia and hypothermia; G4, rats exposed to asphyxia and which received EPO. The rats were sacrificed on the 7th day of life and histopathological evaluation of kidneys was performed. Damage to the proximal tubules was significantly higher in group G1 rats than in groups G2, G3, and G4 rats (p < 0.01). Damage to the distal tubules was found only in group G1 rats. Histological changes in the proximal tubules were more prominent than in the distal tubules (p < 0.01). The immature glomeruli zone was less expressed in group G4 rats than in groups G1, G2, and G3 rats (p < 0.01). Based on these results, we conclude that EPO and hypothermia, as well as the combination thereof, have a protective effect on rats' kidneys damaged during perinatal asphyxia.

Erythropoietin protects intestinal epithelial barrier function and lowers the incidence of experimental neonatal necrotizing enterocolitis

The impermeant nature of the intestinal barrier is maintained by tight junctions (TJs) formed between adjacent intestinal epithelial cells. Disruption of TJs and loss of barrier function are associated with a number of gastrointestinal diseases, including neonatal necrotizing enterocolitis (NEC), the leading cause of death from gastrointestinal diseases in preterm infants. Human milk is protective against NEC, and the human milk factor erythropoietin (Epo) has been shown to protect endothelial cell-cell and blood-brain barriers. We hypothesized that Epo may also protect intestinal epithelial barriers, thereby lowering the incidence of NEC. Our data demonstrate that Epo protects enterocyte barrier function by supporting expression of the TJ protein ZO-1. As immaturity is a key factor in NEC, Epo regulation of ZO-1 in the human fetal immature H4 intestinal epithelial cell line was examined and demonstrated Epo-stimulated ZO-1 expression in a dose-dependent manner through the PI3K/Akt pathway. In a rat NEC model, oral administration of Epo lowered the incidence of NEC from 45 to 23% with statistical significance. In addition, Epo treatment protected intestinal barrier function and prevented loss of ZO-1 at the TJs in vivo. These effects were associated with elevated Akt phosphorylation in the intestine. This study reveals a novel role of Epo in the regulation of intestinal epithelial TJs and barrier function and suggests the possible use of enteral Epo as a therapeutic agent for gut diseases.

Erythropoietin protects severe haemorrhagic shock-induced organ damage in conscious rats

OBJECTIVE

Erythropoietin (EPO) has pleiotropic cytoprotective actions. We investigated the effects of EPO on the physiopathology and cytokine levels after haemorrhagic shock (HS) in conscious rats.

METHODS

Rats received an intravenous injection of 300 U/kg EPO over 10 min followed by HS via withdrawal of 60% of total blood volume from a femoral arterial catheter (6 ml/100 g body weight) over 30 min. Mean arterial pressure (MAP) and heart rate (HR) were monitored continuously for 18 h after the start of blood withdrawal. Levels of biochemical parameters, including haemoglobin, GOT, GPT, BUN, creatinine (Cr), LDH, CPK, and lactate were measured at 30 min before the induction of HS and 0, 1, 3, 6, 9, 12, and 18 h after HS. Cytokine levels, including TNF-alpha and IL-6, in serum were measured at 1, 9, and 18 h after HS. The kidneys, liver, lungs, and small intestine were removed for pathology assessment at 48 h after HS.

RESULTS

HS significantly increased HR, blood GOT, GPT, BUN, Cr, LDH, CPK, lactate, TNF-alpha, and IL-6 levels and decreased haemoglobin and MAP in rats. Pre-treatment with EPO improved survival rate, preserved the MAP, decreased the tachycardia and markers of organ injury, suppressed the release of TNF-alpha and IL-6 after HS in rats.

CONCLUSION

Pre-treatment with EPO suppresses the release of serum TNF-alpha and IL-6, along with decreasing the levels of markers of organ injury associated with HS, with such actions ameliorating HS-induced organ damage in rats.

Erythropoietin (EPO) influences colonic anastomotic healing in a rat model by modulating collagen metabolism

INTRODUCTION

Anastomotic failure is one of the most frequent complications in abdominal surgery. During anastomotic healing. the strength of the intestinal tissue nearby is closely related to the accumulation of collagen in interlinked scar tissue. This in turn is influenced, among other things, by single groups of matrixmetalloproteinases, especially collagenases (MMP-1, -8, and -13) and gelatinases (MMP-2 and -9). EPO is known to induce the expression of tissue-inhibitor-of-matrixmetalloproteinases-1 (TIMP-1) and thereby to down-regulate MMPs.

MATERIALS AND METHODS

We used a rat as an experimental model and applied a high dose of EPO (5U/g BW s.c.), one dose 24 h before operation (as pre-conditioning) and one dose directly after performing a colonic anastomosis. After 3 and after 5 d, respectively, immunohistochemical stainings for MMP-2, -8, and -9 as well as TIMP-1 were carried out and evaluated semiquantitatively for each layer of the colonic wall. Sirius-red staining and cross-polarization microscopy were evaluated and the collagen I/III ratio calculated. Anastomotic and colonic tissue distal to the anastomosis were used to determine collagen content.

RESULTS

We found increased bursting pressure 5 d post-surgery after applying erythropoietin. It was thus shown that EPO influences collagen metabolism and changes the collagen I/III ratio in the colon distal to the anastomosis. The evaluation of immunohistochemistry did not show the expected ubiquitous up-regulation of TIMP-1 and down-regulation of MMPs. Nevertheless, correlations between TIMP-1, MMP-8, and collagen I/III ratio could only be established after the application of EPO.

CONCLUSION

Contrary to our hypothesis, the picture of TIMP-1 and of the regulation of the MMPs after the application of EPO is not as clear as expected. EPO improves anastomotic bursting strength and the correlation of TIMP-1, MMP-8, and collagen type I/III ratio can only be seen after the application of EPO.

Activated protein C reduces intestinal injury in an experimental model of necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis is a devastating intestinal disease of premature infants. Although activated protein C (APC) is well defined as a physiologic anticoagulant, emerging data suggest that it also has cytoprotective, antiinflammatory, and antiapoptotic properties. There is no study on active protein C administration for necrotizing enterocolitis in animal models.

METHODS

Twenty-one Wistar albino rat pups were divided into 3 groups: group 1 = control; group 2 = hypoxia-reoxygenation and saline; group 3 = hypoxia-reoxygenation and APC (0.2 mg/kg per day) treatment. On the 15th day, hypoxia was induced by placing the pups in a 100% carbon dioxide chamber for 5 minutes. After the hypoxia period, the pups were reoxygenated for 10 minutes with 100% oxygen and returned to their mothers. All pups were killed 4 hours after the hypoxia-reoxygenation period was over. The abdomen was opened, and representative samples of injured areas were taken for histopathologic examination, nitrite levels, apoptosis, and cytokine levels.

RESULTS

On histopathologic examination, injury scores in group 2 animals were found to be significantly higher than in group 3 animals (P = .002). Significantly increased intestinal nitric oxide levels were found in group 2 rats compared with the rats of groups 1 and 3 (P = .001 and P = .001, respectively). The APC treatment was significantly reduced "apoptotic cell death" in the bowel, when compared with vehicle-treated group. The proinflammatory cytokine levels (interleukin [IL]-1beta, tumor necrosis factor [TNF]-alpha, and IL-6) were significantly increased in hypoxia group as compared with control group. The concentration of cytokines, IL-1beta, IL-6, and TNF-alpha was reduced in the APC treatment group.

CONCLUSION

The APC treatment attenuates hypoxia-reoxygenation induced with intestinal injury and decreased apoptotic cell index in this animal model. The protective effect of APC is associated with its ability to reduce the expression of inflammatory cytokines and nitric oxide.

Prevention of necrotising enterocolitis: Year 2004 and beyond

The incidence of necrotising enterocolitis (NEC) has not changed significantly despite the dramatic advances in perinatal-neonatal care. The absolute number of survivors of NEC is expected to rise, as prevention of prematurity, the single most important risk factor for the illness, continues to be difficult. Prevention of NEC has thus become an area of research priority. Given the role of inflammatory mediators in its pathogenesis newer immune modulators are being studied as potential agents for prevention/treatment of NEC. Caution, however, is warranted because the failure of sepsis trials in adults has clearly indicated that the concept of down-regulating the inflammatory response is deceptively simple. Clinical trials of any such promising preventative agent(s) need to be designed carefully and must include long-term neurodevelopmental outcomes as almost an entire population of high-risk preterm neonates will be exposed to their adverse effects. As new frontiers continue to be explored, the proven benefits of simple and safe interventions like antenatal glucocorticoid therapy and the preferential use of breast milk for feeding high-risk neonates must not be forgotten. Given that a single effective agent is unlikely in the near future, utilizing a package of "potentially better practices" seems to be the most appropriate strategy to prevent and minimize NEC.

Is there a role for erythropoietin in neonatal medicine?

Since it was first cloned in 1985, the therapeutic potential of recombinant human erythropoietin in the neonatal hyporegenerative anaemias has been studied-the anaemia of prematurity and haemolytic disease of the newborn. Between 60% and 100% of preterm infants are transfused before three weeks of age, a large proportion receiving more than one transfusion. Blood transfusions are currently also the mainstay of treatment for the hyporegenerative anaemia encountered in neonates with Rhesus disease. Sometimes the situation is complicated by the religious beliefs of the parents. Blood transfusions are associated with numerous risks, from transmission of infection to local injury, and in an effort to minimize these risks Neonatologists have looked to recombinant erythropoietin. Despite an extensive number of studies, there is as yet no clear consensus as to whether the use of recombinant erythropoietin in Neonatal medicine minimizes the need for blood transfusions without risk to the neonate. In this article we review the evidence for and against the use of recombinant erythropoietin in Neonatal medicine.

Necrotizing enterocolitis: A multifactorial disease with no cure

Necrotizing enterocolitis is an inflammatory bowel disease of neonates with significant morbidity and mortality in preterm infants. Due to the multifactorial nature of the disease and limitations in disease models, early diagnosis remains challenging and the pathogenesis elusive. Although preterm birth, hypoxic-ischemic events, formula feeding, and abnormal bacteria colonization are established risk factors, the role of genetics and vasoactive/inflammatory mediators is unclear. Consequently, treatments do not target the specific underlying disease processes and are symptomatic and surgically invasive. Breast-feeding is the most effective preventative measure. Recent advances in the prevention of necrotizing enterocolitis have focused on bioactive nutrients and trophic factors in human milk. Development of new disease models including the aspect of prematurity that consistently predisposes neonates to the disease with multiple risk factors will improve our understanding of the pathogenesis and lead to discovery of innovative therapeutics.

High-dose erythropoietin inhibits apoptosis and stimulates proliferation in neonatal rat intestine

BACKGROUND

Erythropoietin (Epo) receptors are widely expressed in the small bowel of neonatal rats and evidence suggests Epo has important trophic effects in developing bowel.

OBJECTIVE

To compliment in vitro data, we directly examine in vivo the hypotheses that systemic Epo treatment can promote cell division and enterocyte migration, and arrest apoptosis in the ileum of neonatal rats.

DESIGN

Epo (5000 U/kg s.c.) or vehicle treatments were given to one week old Sprague-Dawley rats (n = 86) along with timed injections of the thymidine analog 5-bromo-2-deoxyuridine (BrdU, 50mg/kg s.c.) to label DNA synthesis and track newly proliferating cells. To characterize the time course of effects, animals were killed at scheduled times from 30 min to 24 h after treatment. BrdU-containing cells were immunostained and counted in intestinal crypts, villi, and muscle wall of ileum. Effects of Epo on apoptosis were analyzed by TUNEL staining. Calibrated measurements were made to determine the density or relative proportion of BrdU- and TUNEL-positive cells.

RESULTS

Systemic high-dose Epo promoted cell division in intestinal smooth muscle and enterocytes, stimulated migration of intestinal epithelial cells, and arrested apoptosis of enterocytes at the villous tips.

CONCLUSION

These data provide in vivo evidence that Epo functions trophically in developing intestine tissues.

Effects of erythropoietin on hyperoxic lung injury in neonatal rats

Pulmonary oxygen toxicity is believed to play a prominent role in the lung injury that leads to the development of bronchopulmonary dysplasia (BPD). To determine whether human recombinant erythropoietin (rhEPO) treatment reduces the risk of developing BPD, we investigated the effect of rhEPO treatment on the histopathologic changes seen in hyperoxia-induced lung injury of BPD. Twenty-five rat pups were divided into four groups: air-exposed control group (n = 5), hyperoxia-exposed placebo group (n = 7), hyperoxia-exposed rhEPO-treated group (n = 6), and air-exposed rhEPO-treated group (n = 7). Measurement of alveolar surface area, quantification of secondary crest formation, microvessel count, evaluation of alveolar septal fibrosis, and smooth muscle actin immunostaining were performed to assess hyperoxia-induced changes in lung morphology. Treatment of hyperoxia-exposed animals with rhEPO resulted in a significant increase in the mean alveolar area, number of secondary crests formed, and the microvessel count in comparison with hyperoxia-exposed placebo-treated animals. There was significantly less fibrosis in rhEPO-treated animals. However, treatment of hyperoxia-exposed animals with rhEPO did not result in a significant change in smooth muscle content compared with hyperoxia-exposed placebo treated animals. Our results suggest treatment with rhEPO during hyperoxia exposure is associated with improved alveolar structure, enhanced vascularity, and decreased fibrosis. Therefore, we conclude that treatment of preterm infants with EPO might reduce the risk of developing BPD.

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Science review: recombinant human erythropoietin in critical illness: a role beyond anemia?

Erythropoiesis usually fails during severe illness because of a blunting of the kidney-erythropoietin (EPO)-bone marrow axis. In this setting, clinical studies have shown that recombinant human erythropoietin (rhEPO), administered in pharmacological amounts, significantly reduces the need for blood transfusions. In addition to the kidney, however, EPO is also produced locally by other tissues in a paracrine-autocrine manner. Here, similar to its role in the bone marrow, EPO rescues cells from apoptosis. Additionally, EPO reduces inflammatory responses, restores vascular autoregulation, and promotes healing. The results of many studies (including a phase II clinical trial in ischemic stroke) demonstrate that rhEPO protects the brain, spinal cord, retina, heart, and kidney from ischemic and other types of injury. Although rhEPO is efficacious in the treatment of EPO-deficient anemia during illness, inadequate effort has been devoted to determining whether direct tissue protection might also result from its administration. Here, we speculate on the potential utility of EPO as a protective cytokine in the context of acute critical illness and suggest key parameters required for a proof-of-concept clinical study.