Activin A contributes to the development of hyperoxia-induced lung injury in neonatal mice.

BACKGROUND: Bronchopulmonary dysplasia (BPD) is one of the leading causes of morbidity and mortality in babies born prematurely, yet there is no curative treatment. In recent years, a number of inhibitors against TGFß signaling have been tested for their potential to prevent neonatal injury associated with hyperoxia, which is a contributing factor of BPD. In this study, we assessed the contribution of activin A-a member of the TGFß superfamily-to the development of hyperoxia-induced lung injury in neonatal mice. METHODS: We placed newborn C57Bl6 mouse pups in continuous hyperoxia (85% O2) to mimic many aspects of BPD including alveolar simplification and pulmonary inflammation. The pups were administered activin A receptor type IIB-Fc antagonist (ActRIIB-Fc) at 5 mg/kg or follistatin at 0.1 mg/kg on postnatal days 4, 7, 10, and 13. RESULTS: Treatment with ActRIIB-Fc and follistatin protected against hyperoxia-induced growth retardation. ActRIIB-Fc also reduced pulmonary leukocyte infiltration, normalized tissue: airspace ratio and increased septal crest density. These findings were associated with reduced phosphorylation of Smad3 and decreased matrix metalloproteinase (MMP)-9 activity. CONCLUSION: This study suggests that activin A signaling may contribute to the pathology of bronchopulmonary dysplasia.

Human amnion epithelial cells reduce fetal brain injury in response to intrauterine inflammation.

Intrauterine infection, such as occurs in chorioamnionitis, is a principal cause of preterm birth and is a strong risk factor for neurological morbidity and cerebral palsy. This study aims to examine whether human amnion epithelial cells (hAECs) can be used as a potential therapeutic agent to reduce brain injury induced by intra-amniotic administration of lipopolysaccharide (LPS) in preterm fetal sheep. Pregnant ewes underwent surgery at approximately 110 days of gestation (term is approx. 147 days) for implantation of catheters into the amniotic cavity, fetal trachea, carotid artery and jugular vein. LPS was administered at 117 days; hAECs were labeled with carboxyfluorescein succinimidyl ester and administered at 0, 6 and 12 h, relative to LPS administration, into the fetal jugular vein, trachea or both. Control fetuses received an equivalent volume of saline. Brains were collected 7 days later for histological assessment of brain injury. Microglia (Iba-1-positive cells) were present in the brain of all fetuses and were significantly increased in the cortex, subcortical and periventricular white matter in fetuses that received LPS, indicative of inflammation. Inflammation was reduced in fetuses that received hAECs. In LPS fetuses, the number of TUNEL-positive cells was significantly elevated in the cortex, periventricular white matter, subcortical white matter and hippocampus compared with controls, and reduced in fetuses that received hAECs in the cortex and periventricular white matter. Within the fetal brains studied there was a significant positive correlation between the number of Iba-1-immunoreactive cells and the number of TUNEL-positive cells (R(2) = 0.19, p < 0.001). The administration of hAECs protects the developing brain when administered concurrently with the initiation of intrauterine inflammation.

Human amnion epithelial cells modulate hyperoxia-induced neonatal lung injury in mice.

BACKGROUND AIMS: Human amnion epithelial cells (hAECs) prevent pulmonary inflammation and injury in fetal sheep exposed to intrauterine lipopolysaccharide. We hypothesized that hAECs would similarly mitigate hyperoxia-induced neonatal lung injury. METHODS: Newborn mouse pups were randomized to either normoxia (inspired O2 content (FiO2) = 0.21, n = 60) or hyperoxia (FiO2 = 0.85, n = 57). On postnatal days (PND) 5, 6 and 7, hAECs or sterile saline (control) was administered intraperitoneally. All animals were assessed at PND 14. RESULTS: Hyperoxia was associated with lung inflammation, alveolar simplification and reduced postnatal growth. Administration of hAECs to hyperoxia-exposed mice normalized body weight and significantly attenuated some aspects of hyperoxia-induced lung injury (mean linear intercept and septal crest density) and inflammation (interleukin-1α, interleukin-6, transforming growth factor-ß and platelet-derived growth factor-ß). However, hAECs did not significantly alter changes to alveolar airspace volume, septal tissue volume, tissue-to-airspace ratio, collagen content or leukocyte infiltration induced by hyperoxia. CONCLUSIONS: Intraperitoneal administration of hAECs to neonatal mice partially reduced hyperoxia-induced lung inflammation and structural lung damage. These observations suggest that hAECs may be a potential therapy for neonatal lung disease.

Human amnion epithelial cells reduce ventilation-induced preterm lung injury in fetal sheep.

OBJECTIVE: The objective of the study was to explore whether human amnion epithelial cells (hAECs) can mitigate ventilation-induced lung injury. STUDY DESIGN: An established in utero ovine model of ventilation-induced lung injury was used. At day 110 of gestation, singleton fetal lambs either had sham in utero ventilation (IUV) (n = 4), 12 hours of IUV alone (n = 4), or 12 hours of IUV and hAEC administration (n = 5). The primary outcome, structural lung injury, was assessed 1 week later. RESULTS: Compared with sham controls, IUV alone was associated with significant lung injury: increased collagen (P = .03), elastin (P = .02), fibrosis (P = .02), and reduced secondary-septal crests (P = .009). This effect of IUV was significantly mitigated by the administration of hAECs: less collagen (P = .03), elastin (P = .04), fibrosis (P = .02), normalized secondary-septal crests (P = .02). The hAECs were immunolocalized within the fetal lung and had differentiated into type I and II alveolar cells. CONCLUSION: The hAECs mitigate ventilation-induced lung injury and differentiated into alveolar cells in vivo.

Human amnion epithelial cells as a treatment for inflammation-induced fetal lung injury in sheep.

OBJECTIVE: The purpose of this study was to determine whether human amnion epithelial cells (hAECs) can modulate the pulmonary developmental consequences of intrauterine inflammation in fetal sheep that are exposed to intraamniotic lipopolysaccharide (LPS) injection. STUDY DESIGN: At 117 days' gestation, fetal sheep (n=16) received intraamniotic LPS (20 mg). hAECs were delivered at 0, 6, and 12 hours into the fetal jugular vein (n=4), trachea (n=4), or both (n=4). Controls (n=6) received equivalent administration of saline solution. Lungs were collected at 124 days. RESULTS: Intraamniotic LPS caused pulmonary inflammation and altered lung structure and function. hAECs attenuated changes in lung function and structure that had been induced by LPS: lung volume, 40 cm H2O (P<.05, intravenous+intratracheal hAECs vs LPS), tissue-to-airspace ratio (P<.05, intravenous+intratracheal hAECs vs LPS), and septal crest density (P<.001, all hAEC groups vs LPS). Leukocyte infiltration of the lungs was not reduced by hAECs; however, inflammatory cytokines were reduced (tumor necrosis factor-α, P<.01, vs LPS; interleukin-1b, P<.01, vs LPS; interleukin-6, P<.01 vs LPS). Surfactant protein A and C messenger RNA was increased by LPS, although this was not statistically significant (P>.05 vs control); there were significant increases in all hAEC-treated animals (surfactant protein-A, P<.05 vs LPS; surfactant protein-C, P<.01 vs LPS). CONCLUSION: Human amnion epithelial cells attenuate the fetal pulmonary inflammatory response to experimental intrauterine inflammation and reduce, but (as administered in our study) do not prevent, consequent alterations in lung development.

Evaluating the Impact of Human Amnion Epithelial Cells on Angiogenesis.

The effects of human amnion epithelial cells (hAECs) on angiogenesis remain controversial. It is yet unknown if the presence of inflammation and/or gestational age of hAEC donors have an impact on angiogenesis. In this study, we examined the differences between term and preterm hAECs on angiogenesis in vitro and in vivo. Conditioned media from term hAECs induced the formation of longer huVEC tubules on Matrigel. Both term and preterm hAECs expressed VEGFA, PDGFB, ANGPT1, and FOXC1, which significantly increased after TNFα and IFNγ stimulation. In the presence of TNFα and IFNγ, coculture with term hAECs reduced gene transcription of Tie-2 and Foxc1 in huVECs, while coculture with preterm hAECs increased gene transcription of PDGFRα and PDGFRß and reduced gene transcription of FOXC1 in huVECs. In vivo assessment of angiogenesis using vWF immunostaining revealed that hAEC treatment decreased angiogenesis in a bleomycin model of lung fibrosis but increased angiogenesis in a neonatal model of hyperoxia-induced lung injury. In summary, our findings suggested that the impact of hAECs on angiogenesis may be influenced by the presence of inflammation and underlying pathology.

Human amnion epithelial cells repair established lung injury.

With a view to developing a cell therapy for chronic lung disease, human amnion epithelial cells (hAECs) have been shown to prevent acute lung injury. Whether they can repair established lung disease is unknown. We aimed to assess whether hAECs can repair existing lung damage induced in mice by bleomycin and whether the timing of cell administration influences reparative efficacy. In addition, we aimed to characterize the effect of hAECs on fibroblast proliferation and activation, investigating possible mechanisms of reparative action. hAECs were administered intraperitoneally (IP) either 7 or 14 days after bleomycin exposure. Lungs were assessed 7 days after hAEC administration. Bleomycin significantly reduced body weight and induced pulmonary inflammation and fibrosis at 14 and 21 days. Delivery of hAECs 7 days after bleomycin had no effect on lung injury, whereas delivery of hAECs 14 days after bleomycin normalized lung tissue density, collagen content, and α-SMA production, in association with a reduction in pulmonary leucocytes and lung expression of TGF-ß, PDGF-α, and PDGF-ß. In vitro, hAECs reduced proliferation and activation of primary mouse lung fibroblasts. Our findings suggest that the timing of hAEC administration in the course of lung disease may impact on the ability of hAECs to repair lung injury.

Cell therapy: a novel treatment approach for bronchopulmonary dysplasia.

Bronchopulmonary dysplasia (BPD) is a major cause of substantial lifelong morbidity in preterm infants. Despite a better understanding of the pathophysiology of BPD and significant research effort into its management, there remains today no effective treatment. Cell-based therapy is a novel approach that offers much promise in the prevention and treatment of BPD. Recent research supports a therapeutic role for cell transplantation in the management of a variety of acute and chronic adult and childhood lung diseases, with potential of such therapy to reduce inflammation and prevent acute lung injury. However, considerable uncertainties remain regarding cell therapies before they can be established as safe and effective clinical treatments for BPD. This review summarizes the current literature investigating cell therapies in lung disease, with particular focus on the various types of cells available and their specific properties in the context of a future therapy for BPD.