Heparin-binding epidermal growth factor-like growth factor gene disruption is associated with delayed intestinal restitution, impaired angiogenesis, and poor survival after intestinal ischemia in mice

Protective roles of bioactive peptides during ischemia-reperfusion injury: From bench to bedside

Ischemia-reperfusion (I/R) is a well-known pathological condition which may lead to disability and mortality. I/R injury remains an unresolved and complicated situation in a number of clinical conditions, such as cardiac arrest with successful reanimation, as well as ischemic events in brain and heart. Peptides have many attractive advantages which make them suitable candidate drugs in treating I/R injury, such as low toxicity and immunogenicity, good solubility property, distinct tissue distribution pattern, and favorable pharmacokinetic profile. An increasing number of studies indicate that peptides could protect against I/R injury in many different organs and tissues. Peptides also face several therapeutic challenges that limit their clinical application. In this review, we present the mechanisms of action of peptides in reducing I/R injury, as well as further discuss modification strategies to improve the functional properties of bioactive peptides.

Hydrogen sulfide improves intestinal recovery following ischemia by endothelial nitric oxide-dependent mechanisms

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter that has vasodilatory properties. It may be a novel therapy for intestinal ischemia-reperfusion (I/R) injury. We hypothesized that 1) H₂S would improve postischemic survival, mesenteric perfusion, mucosal injury, and inflammation compared with vehicle and 2) the benefits of H₂S would be mediated through endothelial nitric oxide. C57BL/6J wild-type and endothelial nitric oxide synthase knockout (eNOS KO) mice were anesthetized, and a midline laparotomy was performed. Intestines were eviscerated, the small bowel mesenteric root identified, and baseline intestinal perfusion was determined using laser Doppler. Intestinal ischemia was established by temporarily occluding the superior mesenteric artery. Following ischemia, the clamp was removed, and the intestines were allowed to recover. Either sodium hydrosulfide (2 nmol/kg or 2 µmol/kg NaHS) in PBS vehicle or vehicle only was injected into the peritoneum. Animals were allowed to recover and were assessed for mesenteric perfusion, mucosal injury, and intestinal cytokines. P values < 0.05 were significant. H₂S improved mesenteric perfusion and mucosal injury scores following I/R injury. However, in the setting of eNOS ablation, there was no improvement in these parameters with H₂S therapy. Application of H₂S also resulted in lower levels of intestinal cytokine production following I/R. Intraperitoneal H₂S therapy can improve mesenteric perfusion, intestinal mucosal injury, and intestinal inflammation following I/R. The benefits of H₂S appear to be mediated through endothelial nitric oxide-dependent pathways.NEW & NOTEWORTHY H₂S is a gaseous mediator that acts as an anti-inflammatory agent contributing to gastrointestinal mucosal defense. It promotes vascular dilation, mucosal repair, and resolution of inflammation following intestinal ischemia and may be exploited as a novel therapeutic agent. It is unclear whether H₂S works through nitric oxide-dependent pathways in the intestine. We appreciate that H₂S was able to improve postischemic recovery of mesenteric perfusion, mucosal integrity, and inflammation. The beneficial effects of H₂S appear to be mediated through endothelial nitric oxide-dependent pathways.

A spectrum of intestinal injury models in neonatal mice

PURPOSE

To compare the degree of necrotizing enterocolitis (NEC)-like damage under different stress conditions in neonatal mice.

METHODS

5-day-old C57BL/6 mice were assigned to: (A) breastfed and no stress factors; (B) breastfed+maternal separation (3 h daily); (C) breastfed+hypoxia+lipopolysaccharide (LPS-4 mg/kg/day); (D) hyperosmolar formula+hypoxia+LPS. Mice were killed at 9 days of life. Ileum and colon were stained for hematoxylin/eosin and blindly assessed. A scoring ≥2 was considered NEC. Data were compared using one-way ANOVA and reported as median (range).

RESULTS

Ileum-Mucosal injury was mild in group B (0.0-1). Hypoxia+LPS induced greater injury in group C (1.6, 1-2.5; p < 0.0001 to B) and D (2, 0.5-3.5; p < 0.0001 to B). There were no differences between group C and D (p = n.s.). There were no cases of NEC in group A or B, whereas NEC was present in 36 % group C and 68 % group D mice. Colon-a similar degree of mucosal injury was observed among group B (2, 1-3), C (1.7, 0-3) and D (1.5, 1-3; p = n.s.). NEC was present in 75 % of group B, 50 % of group C and 86 % of group D.

CONCLUSION

These models establish a spectrum of intestinal injury and are useful to investigate the variability of neonatal intestinal diseases, such as NEC.

Human mesenchymal stromal cells decrease mortality after intestinal ischemia and reperfusion injury

BACKGROUND

Cellular therapy is a novel treatment option for intestinal ischemia. Bone marrow-derived mesenchymal stromal cells (BMSCs) have previously been shown to abate the damage caused by intestinal ischemia/reperfusion (I/R) injury. We therefore hypothesized that (1) human BMSCs (hBMSCs) would produce more beneficial growth factors and lower levels of proinflammatory mediators compared to differentiated cells, (2) direct application of hBMSCs to ischemic intestine would decrease mortality after injury, and (3) decreased mortality would be associated with an altered intestinal and hepatic inflammatory response.

METHODS

Adult hBMSCs and keratinocytes were cultured on polystyrene flasks. For in vitro experiments, cells were exposed to tumor necrosis factor, lipopolysaccharides, or 2% oxygen for 24 h. Supernatants were then analyzed for growth factors and chemokines by multiplex assay. For in vivo experiments, 8- to 12-wk-old male C57Bl6J mice were anesthetized and underwent a midline laparotomy. Experimental groups were exposed to temporary superior mesenteric artery occlusion for 60 min. Immediately after ischemia, 2 × 10(6) hBMSCs or keratinocytes in phosphate-buffered saline were placed into the peritoneal cavity. Animals were then closed and allowed to recover for 6 h (molecular/histologic analysis) or 7 d (survival analysis). After 6-h reperfusion, animals were euthanized. Intestines and livers were harvested and analyzed for inflammatory chemokines, growth factors, and histologic changes.

RESULTS

hBMSCs expressed higher levels of human interleukin (IL) 6, IL-8, vascular endothelial growth factor (VEGF), and epidermal growth factor and lower levels of IL-1, IL-3, IL-7, and granulocyte-monocyte colony-stimulating factor after stimulation. In vivo, I/R resulted in significant mortality (70% mortality), whereas application of hBMSCs after ischemia decreased mortality to 10% in a dose-dependent fashion (P = 0.004). Keratinocyte therapy offered no improvements in mortality above I/R. Histologic profiles were equivalent between ischemic groups, regardless of the application of hBMSCs or keratinocytes. Cellular therapy yielded significantly decreased murine intestinal levels of soluble activin receptor-like kinase 1, betacellulin, and endothelin, whereas increasing levels of eotaxin, monokine induced by gamma interferon (MIG), monocyte chemoattractant protein 1, IL-6, granulocyte colony-stimulating factor (G-CSF), and interferon gamma-induced protein 10 (IP-10) from ischemia were appreciated. hBMSC therapy yielded significantly higher expression of murine intestinal VEGF and lower levels of intestinal MIG compared to keratinocyte therapy. Application of hBMSCs after ischemia yielded significantly lower murine levels of hepatic MIG, IP-10, and G-CSF compared to keratinocyte therapy.

CONCLUSIONS

Human BMSCs produce multiple beneficial growth factors. Direct application of hBMSCs to the peritoneal cavity after intestinal I/R decreased mortality by 60%. Improved outcomes with hBMSC therapy were not associated with improved histologic profiles in this model. hBMSC therapy was associated with higher VEGF in intestines and lower levels of proinflammtory MIG, IP-10, and G-CSF in liver tissue after ischemia, suggesting that reperfusion with hBMSC therapy may alter survival by modulating the systemic inflammatory response to ischemia.

HB-EGF augments the ability of mesenchymal stem cells to attenuate intestinal injury

BACKGROUND

We have previously demonstrated that heparin-binding EGF-like growth factor (HB-EGF) and mesenchymal stem cell (MSC) administration protect the intestines from ischemia/reperfusion (I/R) injury in vivo, with amniotic fluid-derived MSC (AF-MSC) being more efficacious than bone marrow-derived MSC (BM-MSC). The goal of the current study was to determine whether the protective effects of HB-EGF were from direct effects on MSC or via alternative mechanisms.

METHODS

Murine MSC were transfected with an HB-EGF plasmid or control plasmid by electroporation. Mice were subjected to segmental intestinal I/R injury and received either BM-MSC or AF-MSC either with or without exogenous HB-EGF, or BM-MSC or AF-MSC that endogenously over-expressed HB-EGF. MSC engraftment, intestinal histologic injury, and intestinal permeability were quantified.

RESULTS

There was increased MSC engraftment into injured compared to uninjured intestine. HB-EGF increased AF-MSC engraftment into injured intestine. Administration of HB-EGF and MSC improved intestinal histology and intestinal permeability after I/R injury, with AF-MSC being most efficacious. The effect of HB-EGF on MSC was similar when the growth factor was administered exogenously, or when it was overexpressed endogenously.

CONCLUSIONS

The effect of HB-EGF on AF-MSC was similar with both exogenous administration and endogenous overexpression of the growth factor, implying that HB-EGF has a direct effect on AF-MSC. This information may assist in guiding potential future AF-MSC-based therapies for patients at risk of intestinal ischemic injuries.

CXCL5 is required for angiogenesis, but not structural adaptation after small bowel resection

PURPOSE

Intestinal adaptation is the compensatory response to massive small bowel resection (SBR) and characterized by lengthening of villi and deepening of crypts, resulting in increased mucosal surface area. Previous studies have demonstrated increased villus capillary blood vessel density after SBR, suggesting a role for angiogenesis in the development of resection-induced adaptation. Since we have previously shown enhanced expression of the proangiogenic chemokine CXCL5 after SBR, the purpose of this study was to determine the effect of disrupted CXCL5 expression on intestinal adaptation.

METHODS

CXCL5 knockout (KO) and C57BL/6 wild type (WT) mice were subjected to either a 50% proximal SBR or sham operation. Ileal tissue was harvested on postoperative day 7. To assess for adaptation, villus height and crypt depth were measured. Submucosal capillary density was measured by CD31 immunohistochemistry.

RESULTS

Both CXCL5-KO and WT mice demonstrated normal structural features of adaptation. Submucosal capillary density increased in the WT but not in the KO mice following SBR.

CONCLUSION

CXCL5 is required for increased intestinal angiogenesis during resection-induced adaptation. Since adaptive villus growth occurs despite impaired CXCL5 expression and enhanced angiogenesis, this suggests that the growth of new blood vessels is not needed for resection-induced mucosal surface area expansion following massive SBR.

Heparin-binding epidermal growth factor-like growth factor restores Wnt/β-catenin signaling in intestinal stem cells exposed to ischemia/reperfusion injury

BACKGROUND

We have previously demonstrated that heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) protects the intestines from injury in several different experimental animal models. In the current study, we investigated whether the ability of HB-EGF to protect the intestines from ischemia/reperfusion (I/R) injury was related to its effects on Wnt/β-catenin signaling in intestinal stem cells (ISC).

METHODS

Lucien-rich repeat-containing G-protein-coupled receptor 5 (LGR5)-enhanced green fluorescent protein (EGFP) transgenic (TG) mice with fluorescently labeled ISC, as well as the same mice treated with intraluminal HB-EGF or genetically engineered to overexpress HB-EGF, were exposed to segmental mesenteric artery occlusion (sMAO) to the terminal ilium. Wnt/β-catenin signaling was evaluated using immunofluorescent staining and Western blotting.

RESULTS

LGR5 expression and Wnt/β-catenin signaling in the ISC of the terminal ilium of LGR5-EGFP TG mice was significantly reduced 24 hours after sMAO. Intraluminal administration of HB-EGF or HB-EGF overexpression in these mice led to preservation of LGR5 expression and Wnt/β-catenin signaling.

CONCLUSION

These data show that HB-EGF preserves Wnt/β-catenin signaling in ISC after I/R injury.

The role of epidermal growth factor in prevention of oxidative injury and apoptosis induced by intestinal ischemia/reperfusion in rats

Intestinal ischemia/reperfusion is a major problem which may lead to multiorgan failure and death. The aim of the study was to evaluate the effects of epidermal growth factor (EGF) on apoptosis, cell proliferation, oxidative stress and the antioxidant system in intestinal injury induced by ischemia/reperfusion in rats and to determine if EGF can ameliorate these toxic effects. Intestinal ischemia/reperfusion injury was produced by causing complete occlusion of the superior mesenteric artery for 60 min followed by a 60-min reperfusion period. Animals received intraperitoneal injections of 150 μg/kg human recombinant EGF 30 min prior to the mesenteric ischemia/reperfusion. Mesenteric ischemia/reperfusion caused degeneration of the intestinal mucosa, inhibition of cell proliferation, stimulation of apoptosis and oxidative stress in the small intestine of rats. In the ischemia/reperfusion group, lipid peroxidation was stimulated accompanied by increased intestinal catalase and glutathione peroxidase activities, however, glutathione levels and superoxide dismutase activities were markedly decreased. EGF treatment to rats with ischemia/reperfusion prevented the ischemia/reperfusion-induced oxidative injury by reducing apoptosis and lipid peroxidation, and by increasing antioxidant enzyme activities. These results demonstrate that EGF has beneficial antiapoptotic and antioxidant effects on intestinal injury induced by ischemia/reperfusion in rats.

Heparin-binding EGF-like growth factor (HB-EGF) therapy for intestinal injury: Application and future prospects

Throughout the past 20 years, we have been investigating the potential therapeutic roles of heparin-binding EGF-like growth factor (HB-EGF), a member of the epidermal growth factor family, in various models of intestinal injury including necrotizing enterocolitis (NEC), intestinal ischemia/reperfusion (I/R) injury, and hemorrhagic shock and resuscitation (HS/R). Our studies have demonstrated that HB-EGF acts as an effective mitogen, a restitution-inducing reagent, a cellular trophic factor, an anti-apoptotic protein and a vasodilator, via its effects on various cell types in the intestine. In the current paper, we have reviewed the application and therapeutic effects of HB-EGF in three classic animal models of intestinal injury, with particular emphasis on its protection of the intestines from NEC. Additionally, we have summarized the protective functions of HB-EGF on various target cells in the intestine. Lastly, we have provided a brief discussion focusing on the future development of HB-EGF clinical applications for the treatment of various forms of intestinal injury including NEC.

Synergistic effects of HB-EGF and mesenchymal stem cells in a murine model of intestinal ischemia/reperfusion injury

BACKGROUND

We have previously demonstrated that heparin-binding EGF-like growth factor (HB-EGF) administration protects the intestines from ischemia/reperfusion (I/R) injury in vivo. We have also shown that HB-EGF promotes mesenchymal stem cell (MSC) proliferation and migration in vitro. The goals of the current study were to examine the effects of HB-EGF and both bone marrow (BM)- and amniotic fluid (AF)-derived MSC on intestinal I/R injury in vivo.

MATERIALS AND METHODS

MSC were isolated from pan-EGFP mice, expanded, and purified. Pluripotency was confirmed by induced differentiation. Mice were subjected to terminal ileum I/R and received either: (1) no therapy; (2) HB-EGF; (3) BM-MSC; (4) HB-EGF+BM-MSC; (5) AF-MSC; or (6) HB-EGF+AF-MSC. MSC engraftment, histologic injury, and intestinal permeability were quantified.

RESULTS

There was increased MSC engraftment into injured compared to uninjured intestine for all experimental groups, with significantly increased engraftment for AF-MSC+HB-EGF compared to AF-MSC alone. Administration of HB-EGF and MSC improved intestinal histology and intestinal permeability after I/R injury. The greatest improvement was with combined administration of HB-EGF+AF-MSC.

CONCLUSIONS

Both HB-EGF alone and MSC alone can protect the intestines from I/R injury, with synergistic efficacy occurring when HB-EGF and AF-MSC are administered together.

Essential roles of heparin-binding epidermal growth factor-like growth factor in the brain

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a member of the EGF family of growth factors, which interacts with the EGF receptor to exert mitogenic activity for various types of cells. Through its interactions with various molecules, it is involved in diverse biological processes, including wound healing, blast implantation, and tumor formation. At the same time, HB-EGF is widely expressed in the central nervous system, including the hippocampus and cerebral cortex, and is considered to play pivotal roles in the developing and adult nervous system. Because HB-EGF protein levels in the brain are much higher than those of TGF-α and EGF, it is possible that HB-EGF serves as a major physiologic ligand for the EGF receptor (ErbB1) within the central nervous system. Recent studies indicate that HB-EGF contributes to the neuronal survival and proliferation of glial/stem cells. HB-EGF also promotes the survival of dopaminergic neurons, an action mediated by mitogen-activated protein kinase (MAPK) as well as by the Akt signaling pathway. In this review, we discuss recent findings on the implications of HB-EGF in higher brain functions of the central nervous system.

Heparin-binding epidermal growth factor-like growth factor and mesenchymal stem cells act synergistically to prevent experimental necrotizing enterocolitis

BACKGROUND

We have shown that administration of heparin-binding EGF (epidermal growth factor)-like growth factor (HB-EGF) protects the intestines from experimental necrotizing enterocolitis (NEC). We have also demonstrated that systemically administered mesenchymal stem cells (MSC) can engraft into injured intestines. This study investigated the effects of HB-EGF on MSC in vitro, and whether MSC and HB-EGF can act synergistically to prevent NEC in vivo.

STUDY DESIGN

In vitro, the effect of HB-EGF on MSC proliferation, migration, and apoptosis was determined. In vivo, rat pups received MSC either intraperitoneally (IP) or intravenously (IV). Pups were assigned to 1 of 7 groups: Group 1, breast-fed; Group 2, experimental NEC; Group 3, NEC+HB-EGF; Group 4, NEC+MSC IP; Group 5, NEC+HB-EGF+MSC IP; Group 6, NEC+MSC IV; or Group 7, NEC+HB-EGF+MSC IV. Mesechymal stem cell engraftment, histologic injury, intestinal permeability, and mortality were determined.

RESULTS

Heparin-binding EGF-like growth factor promoted MSC proliferation and migration, and decreased MSC apoptosis in vitro. In vivo, MSC administered IV had increased engraftment into NEC-injured intestine compared with MSC administered IP (p < 0.05). Heparin binding EGF-like growth factor increased engraftment of IP-administered MSC (p < 0.01) and IV-administered MSC (p < 0.05). Pups in Groups 3 to 7 had a decreased incidence of NEC compared with nontreated pups (Group 2), with the lowest incidence in pups treated with HB-EGF+MSC IV (p < 0.01). Pups in Group 7 had a significantly decreased incidence of intestinal dilation and perforation, and had the lowest intestinal permeability, compared with other treatment groups (p < 0.01). Pups in all experimental groups had significantly improved survival compared with pups exposed to NEC, with the best survival in Group 7 (p < 0.05).

CONCLUSIONS

Heparin-binding EGF-like growth factor and MSC act synergistically to reduce injury and improve survival in experimental NEC.

Heparin-binding epidermal growth factor-like growth factor improves intestinal barrier function and reduces mortality in a murine model of peritonitis

BACKGROUND

The morbidity and mortality associated with bacterial peritonitis remain high. Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is a potent intestinal cytoprotective agent. The aim of this study was to evaluate the effect of HB-EGF in a model of murine peritonitis.

METHODS

HB-EGF(-/-) knockout (KO) mice and their HB-EGF(+/+) wild-type (WT) counterparts were subjected to sham operation, cecal ligation and puncture (CLP), or CLP with HB-EGF treatment (800 μg/kg IP daily). Villous length, intestinal permeability, intestinal epithelial cell (IEC) apoptosis, bacterial load in peritoneal fluid (PF) and mesenteric lymph nodes (MLN), inflammatory cytokine levels, and survival were determined.

RESULTS

After exposure to CLP, HB-EGF KO mice had significantly shorter villi (1.37 ± 0.13 vs 1.96 ± 0.4 relative units; P < .03), increased intestinal permeability (17.01 ± 5.18 vs 11.50 ± 4.67 nL/min/cm2; P < .03), increased IEC apoptotic indices (0.0093 ± 0.0033 vs 0.0016 ± 0.0014; P < .01), and increased bacterial counts in PF (25,313 ± 17,558 vs 11,955 ± 6,653 colony forming units [CFU]/mL; P < .05) and MLN (19,009 ± 11,200 vs 5,948 ± 2,988 CFU/mL/g; P < .01) compared with WT mice. Administration of HB-EGF to WT and HB-EGF KO mice exposed to CLP led to significantly increased villous length and decreased intestinal permeability, IEC apoptosis and bacterial counts in MLN (P < .05). Survival of HB-EGF KO mice subjected to CLP was significantly improved with administration of HB-EGF (P < .05).

CONCLUSION

HB-EGF gene KO increases susceptibility to peritonitis-induced intestinal injury, which can be reversed by administration of HB-EGF. These results support a protective role of HB-EGF in peritonitis-induced sepsis.

Heparin-binding epidermal growth factor-like growth factor protects mesenchymal stem cells

BACKGROUND

We have previously demonstrated that mesenchymal stem cell (MSC) administration protects the intestines from injury in a mouse model of intestinal ischemia/reperfusion injury. We have also shown that heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a potent intestinal cytoprotective agent in vivo that can protect the intestines by way of its effects on stem cells. The goal of the present study was to examine the effects of HB-EGF on both amniotic fluid (AF)- and bone marrow (BM)-derived MSCs in vitro.

METHODS

MSCs were isolated from the AF and BM of pan-EGFP mice, grown in MSC-specific culture medium, and purified by sequential passages according to their adherence properties. Pluripotency was confirmed by induced differentiation. After incubation of MSCs with HB-EGF, proliferation was quantified using the CyQuant cell proliferation assay kit under normoxic and anoxic conditions. Chemotaxis was quantified using the CHEMICON QCM cell migration kit, and apoptosis was determined using caspase-3 immunohistochemistry after exposure of the MSCs to anoxic stress.

RESULTS

AF-MSCs and BM-MSCs showed significantly increased proliferation and migration in response to HB-EGF. HB-EGF significantly protected AF-MSCs and BM-MSCs from anoxia-induced apoptosis. The proliferative and anti-apoptotic effects of HB-EGF were even more pronounced in AF-MSCs than in BM-MSCs.

CONCLUSIONS

These results have demonstrated that HB-EGF acts as a mitogenic and chemotactic agent for MSCs that protects MSCs from injury. These findings could have important implications for future experiments designed to use MSCs to protect the intestines from injury.

Angiogenesis in peritoneal dialysis

Long-term exposure to peritoneal dialysis fluid induces morphological alterations, including angiogenesis, leading to a loss of ultrafiltration (UF) capacity. We discuss the effect of different factors in peritoneal dialysis (PD) on angiogenesis. In addition, we describe the process of angiogenesis and the possible role of different cell types in the peritoneum upon PD contributing to new blood vessel formation. Furthermore, we review several interventions used in our rat PD exposure model to decrease angiogenesis in PD. Moreover, we show new data on the use of sunitinib to inhibit angiogenesis in this rat model. Although various interventions seem to be promising, well-randomised clinical trials showing absolute prevention of angiogenesis and UF failure are, yet, still missing. To make real progress in PD treatment, the aim should be to prevent angiogenesis as well as peritoneal fibrosis and PD-induced inflammation.

Mice overexpressing the gene for heparin-binding epidermal growth factor-like growth factor (HB-EGF) have increased resistance to hemorrhagic shock and resuscitation

BACKGROUND

The aim of the current study was to determine whether overexpression of heparin-binding epidermal growth factor-like growth factor (HB-EGF) could protect the intestines from injury after hemorrhagic shock and resuscitation in mice.

METHODS

Hemorrhagic shock and resuscitation was induced in HB-EGF transgenic and wild type mice. Cross-reacting material 197 (5 mg/kg) was administered to a subset of HB-EGF transgenic mice to block the overexpressed HB-EGF. Intestinal histologic injury scores, intestinal epithelial cell apoptosis indices, and gut barrier function were determined. The Student t test and 1-way analysis of variance were employed to compare the differences between groups.

RESULTS

All mice subjected to hemorrhagic shock and resuscitation had significantly increased intestinal histologic injury scores, apoptosis indices, and intestinal permeability compared with sham-operated mice. Compared with wild type mice, HB-EGF transgenic mice had significantly decreased histologic injury (mean injury grade 2.79 ± 0.84 vs 3.88 ± 1.43, P = .02), apoptosis indices (mean apoptosis index 8.77 ± 5.23 vs 17.91 ± 13.23, P = .03), and mucosal permeability (FITC-dextran 4 clearance 13.06 ± 5.67 vs 20.03 ± 7.81 nL/min/ m(2), P = .02) at 3 hours of reperfusion. HB-EGF transgenic mice subjected to hemorrhagic shock and resuscitation and treated with cross-reacting material 197 had a significantly increased histologic injury (mean injury grade 3.63 ± 1.00 vs 2.79 ± 0.84, P = .04) and mucosal permeability (FITC-dextran 4 clearance 22.87 ± 9.69 vs 13.06 ± 5.67 nL/min/cm2, P = .01) at 3 hours of reperfusion compared with non-cross-reacting material 197 treated transgenic mice, with no significant changes in apoptosis indices. Cross-reacting material 197 did not reverse the decreased apoptosis observed in HB-EGF transgenic mice subjected to hemorrhagic shock and resuscitation, which suggests that mechanisms in addition to decreased apoptosis may be responsible for the intestinal cytoprotective effects of endogenous HB-EGF overexpression.

CONCLUSION

Overexpression of HB-EGF increases resistance to hemorrhagic shock and resuscitation in mice.

Heparin-binding epidermal growth factor-like growth factor overexpression in transgenic mice increases resistance to necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency and the leading surgical cause of death in premature infants. We have shown that administration of exogenous heparin-binding epidermal growth factor-like growth factor (HB-EGF) in mice protects the intestines from experimental NEC. The aim of the current study was to evaluate the effect of gain-of-function of endogenous HB-EGF on susceptibility to NEC.

METHODS

Neonatal HB-EGF transgenic (TG) mice and their wild-type (WT) counterparts were exposed to experimental NEC. An additional group of HB-EGF TG pups were also exposed to NEC, but received the HB-EGF antagonist cross-reacting material 197 (CRM197) injected subcutaneously immediately after birth. To examine gut barrier function, HB-EGF TG and WT pups received intragastric fluorescein isothiocyanate-labeled dextran under basal and stressed conditions, and serum fluorescein isothiocyanate-labeled dextran levels were measured.

RESULTS

Wild-type mice had an incidence of NEC of 54.2%, whereas HB-EGF TG mice had a significantly decreased incidence of NEC of 22.7% (P = .03). Importantly, administration of CRM197 to HB-EGF TG pups significantly increased the incidence of NEC to 65% (P = .004). HB-EGF TG mice had significantly decreased intestinal permeability compared to WT mice both under basal and stressed conditions.

CONCLUSIONS

Our results provide evidence that overexpression of the HB-EGF gene decreases susceptibility to NEC and that administration of the HB-EGF antagonist CRM197 reverses this protective effect.

Heparin-binding EGF-like growth factor protects pericytes from injury

BACKGROUND

We have previously shown that heparin-binding EGF-like growth factor (HB-EGF) promotes angiogenesis and preserves mesenteric microvascular blood flow in several models of intestinal injury. The current study was designed to evaluate the effect of HB-EGF on pericytes, since these cells function to regulate capillary blood flow and new capillary growth.

MATERIALS AND METHODS

C3H/10T1/2 mouse mesenchymal cells were differentiated into pericyte-like cells in vitro using transforming growth factor-β1 (TGF-β1). In addition, primary pericyte cultures were established from rat brain. The effect of HB-EGF on pericyte proliferation was assessed. In addition, cells were stressed by exposure to anoxia, and apoptosis determined. In vivo, we examined the effect of HB-EGF on pericytes in a model of intestinal I/R injury based on superior mesenteric artery occlusion (SMAO) in mice.

RESULTS

Differentiated C3H/10T1/2 cells (pericyte-like cells) demonstrated morphologic characteristics of pericytes, and expressed pericyte specific markers. Addition of HB-EGF led to significant cell proliferation in differentiated pericyte-like cells, even under conditions of anoxic stress. Addition of the EGF receptor inhibitor AG 1478 led to complete inhibition of the proliferative effects of HB-EGF on pericyte-like cells. In addition, HB-EGF protected pericyte-like cells from anoxia-induced apoptosis. In addition, HB-EGF promoted cell proliferation in primary pericyte cultures. In vivo, administration of HB-EGF to mice subjected to intestinal I/R injury led to protection of pericytes from injury.

CONCLUSIONS

These results suggest that HB-EGF may function as a microcirculatory blood flow regulator, at least in part, via its effects on pericytes.

Heparin-binding EGF-like growth factor promotes intestinal anastomotic healing

BACKGROUND

We have accumulated multiple lines of evidence supporting the ability of HB-EGF to protect the intestines from injury and to augment the healing of partial-thickness scald burns of the skin. The aim of the current study was to investigate the role of heparin-binding EGF-like growth factor (HB-EGF) in intestinal anastomotic wound healing.

MATERIALS AND METHODS

HB-EGF (-/-) knockout (KO) mice (n=42) and their HB-EGF (+/+) wild type (WT) counterparts (n=33), as well as HB-EGF transgenic (TG) mice (n=26) and their (WT) counterparts (n=27), underwent division and reanastomosis of the terminal ileum. In addition, WT mice (n=21) that received enteral HB-EGF (800 μg/kg) underwent the same operative procedure. Anastomotic bursting pressure was measured at 3 and 6 d postoperatively. Tissue sections were stained with hematoxylin and eosin to assess anastomotic healing, and Picrosirus red to assess collagen deposition. Immunohistochemistry using anti-von Willebrand factor antibodies was performed to assess angiogenesis. Complications and mortality were also recorded.

RESULTS

HB-EGF KO mice had significantly lower bursting pressures, lower healing scores, higher mortality, and higher complication rates postoperatively compared with WT mice. Collagen deposition and angiogenesis were significantly decreased in KO mice compared with WT mice. Conversely, HB-EGF TG mice had increased anastomotic bursting pressure, higher healing scores, lower mortality, lower complication rates, increased collagen deposition, and increased angiogenesis postoperatively compared with WT mice. WT mice that received HB-EGF had increased bursting pressures compared with non-HB-EGF treated mice.

CONCLUSION

Our results demonstrate that HB-EGF is an important factor involved in the healing of intestinal anastomoses.

Epidermal growth factor receptor signaling modulates chemokine (CXC) ligand 5 expression and is associated with villus angiogenesis after small bowel resection

BACKGROUND

Adaptive villus growth after a massive small bowel resection (SBR) is an important response to the loss of intestinal surface area and is regulated via epidermal growth factor receptor (EGFR) signaling. Increased levels of the proangiogenic chemokine ligand 5 (CXCL5) have been found within the adapting bowel in which angiogenesis is increased. We sought to determine whether CXCL5 was expressed specifically in the villus mesenchymal zone (area of increased blood vessel growth) and whether this expression was affected by EGF.

METHODS

C57BL/6J mice were subjected to sham operation (bowel transaction with reanastomosis) or 50% proximal SBR. The remnant intestine was harvested, and the villus lamina propria was isolated by laser capture microdissection. The expression of CXCL5 messenger RNA (mRNA) was analyzed using real-time polymerase chain reaction (RT-PCR). Furthermore, CXCL5 mRNA levels were determined in EGF-stimulated human umbilical vein endothelial cells (HUVECs).

RESULTS

A 2.39-fold increase (P < .05) in CXCL5 mRNA occurred in the lamina propria after SBR. In addition, villus height was found to be related directly to the degree of CXCL5 mRNA (R(2) = 0.97) expression. HUVECs treated with EGF demonstrated a 9-fold increase in CXCL5 mRNA expression.

CONCLUSION

The villus growth observed in resection-induced adaptation is associated with increased expression of the chemokine CXCL5 within the lamina propria. Because EGF enhances CXCL5 expression directly in endothelial cells, EGFR-directed proangiogenic gene expression may be a critical mechanism for adaptive ileal villus growth.

HB-EGF protects the lungs after intestinal ischemia/reperfusion injury

BACKGROUND

Acute respiratory distress syndrome continues to be a major source of morbidity and mortality in critically-ill patients. Heparin binding EGF-like growth factor (HB-EGF) is a biologically active protein that acts as an intestinal cytoprotective agent. We have previously demonstrated that HB-EGF protects the intestines from injury in several different animal models of intestinal injury. In the current study, we investigated the ability of HB-EGF to protect the lungs from remote organ injury after intestinal ischemia/reperfusion (I/R).

METHODS

Mice were randomly assigned to one of the following groups: (1) sham-operated; (2) sham+HB-EGF (1200 microg/kg in 0.6 mL administered by intra-luminal injection at the jejuno-ileal junction immediately after identification of the superior mesenteric artery); (3) superior mesenteric artery occlusion for 45 min followed by reperfusion for 6 h (I/R); or (4) I/R+HB-EGF (1200 microg/kg in 0.6 mL) administered 15 min after vascular occlusion. The severity of acute lung injury was determined by histology, morphometric analysis and invasive pulmonary function testing. Animal survival was evaluated using Kaplan-Meier analysis.

RESULTS

Mice subjected to intestinal I/R injury showed histologic and functional evidence of acute lung injury and decreased survival compared with sham-operated animals. Compared with mice treated with HB-EGF (I/R+HB-EGF), the I/R group had more severe acute lung injury, and decreased survival.

CONCLUSION

Our results demonstrate that HB-EGF reduces the severity of acute lung injury after intestinal I/R in mice. These data demonstrate that HB-EGF may be a potential novel systemic anti-inflammatory agent for the prevention of the systemic inflammatory response syndrome (SIRS) after intestinal injury.

Deletion of the heparin-binding epidermal growth factor-like growth factor gene increases susceptibility to necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) is the leading surgical cause of death in premature infants. We have accumulated evidence supporting a role for heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) in protection of the intestines from NEC. The aim of the current study was to evaluate the effect of loss-of-function of endogenous HB-EGF on susceptibility to NEC.

METHODS

Neonatal HB-EGF((-/-)) knockout (KO) mice and their HB-EGF((+/+)) wild-type (WT) counterparts were exposed to experimental NEC. An additional group of HB-EGF KO pups were also exposed to NEC but had HB-EGF added to their formula. To examine gut barrier function, HB-EGF KO and WT pups received intragastric fluorescein isothiocyanate-labeled dextran (FITC dextran) under basal and stressed conditions, and serum FITC dextran levels were measured.

RESULTS

The WT mice had an incidence of NEC of 53%, whereas HB-EGF KO mice had a significantly increased incidence of NEC of 80% (P = .04). Importantly, administration of exogenous HB-EGF to HB-EGF KO pups significantly reduced the incidence of NEC to 45% (P = .04). Heparin-binding EGF KO mice had significantly increased intestinal permeability compared to WT mice under basal and stressed conditions.

CONCLUSIONS

Our results provide evidence that loss of the HB-EGF gene increases susceptibility to NEC and that administration of exogenous HB-EGF reverses this susceptibility.

Antecedents of Bell stage III necrotizing enterocolitis

OBJECTIVE

New biopharmaceuticals hold promise for preventing or treating necrotizing enterocolitis. However, it is unclear whether any such biopharmaceutical that requires enteral administration could be administered using an 'early-treatment' paradigm. This study was undertaken to assess this issue based on data from every case of Bell stage III NEC cared for during the past 7 years at Intermountain Healthcare.

STUDY DESIGN

Patients with Bell stage III NEC were identified from electronic medical record repositories and the diagnosis was validated using operative reports. Electronic and paper records of each patient were then used to identify potential clinical and laboratory antecedents occurring within the 48 h period preceding the diagnosis of NEC.

RESULT

One hundred eighteen patients had Stage III NEC. The earliest recognized antecedents were nonspecific for NEC (apnea/bradycardia, skin mottling and irritability). These were recorded at 2.8+/-2.1, 4.5+/-3.1 and 5.4+/-3.7 (mean+/-s.d.) hours, respectively, before NEC was diagnosed. The most commonly identified gastrointestinal antecedents were blood in the stools, increased abdominal girth and elevated pre-feeding gastric residuals or emesis. These were identified 2.0+/-1.9, 2.8+/-3.1 and 4.9+/-4.0 h before NEC was recognized. Thirty-eight percent had a blood transfusion (18+/-12 h) preceding the NEC. Tachycardia, tachypnea, hypotension and diarrhea were rarely identified as antecedents and no consistent laboratory antecedents were discovered.

CONCLUSION

We judge that an 'early treatment of NEC' paradigm testing any pharmacological agent that must be administered enterally is not feasible. The first recognized antecedents of Bell stage III NEC are nonspecific for gastrointestinal pathology and insufficient time exists for dosing between the first gastrointestinal signs and placement of the gastric decompression tube.

Heparin-binding epidermal growth factor-like growth factor is essential for preservation of gut barrier function after hemorrhagic shock and resuscitation in mice

BACKGROUND

The aim of the current study was to determine the role of heparin-binding (HB) epidermal growth factor (EGF)-like growth factor as a mediator of gut barrier function after hemorrhagic shock and resuscitation (HS/R) in mice.

METHODS

HS/R was induced in HB-EGF knockout (KO) and wild-type (WT) mice. Intestinal histologic injury scores, intestinal epithelial cell apoptosis, and gut barrier function were determined. Statistical analyses were performed using linear mixed models with P<.05 considered significant.

RESULTS

All mice subjected to HS/R had significantly increased intestinal histologic injury scores, apoptosis indices, and intestinal permeability compared with mice subjected to sham operation. Compared with WT mice, HB-EGF KO mice subjected to HS/R had significantly increased histologic injury (mean injury grade, 4.5 +/- 1 vs 2.75 +/- 0.5 at 3 hours of resuscitation; P<.05), increased apoptosis indices (mean apoptosis index, 6.84 +/- 1.95 vs 3.24 +/- 1.00 at 3 hours of resuscitation; P < .05), and increased mucosal permeability (FD4 clearance 78 +/- 18.91 vs 47.75 +/- 8.06 nL/min/cm(2) at 3 hours of resuscitation; P<.05).

CONCLUSION

HB-EGF is essential for the preservation of gut barrier function after HS/R. These findings support the clinical use of HB-EGF in protection of the intestines from disease states associated with intestinal hypoperfusion injury.