Herpes virus entry mediator signaling blockade produces mortality in neonatal sepsis through induced cardiac dysfunction

Introduction

Sepsis remains a major source of morbidity and mortality in neonates, and characterization of immune regulation in the neonatal septic response remains limited. HVEM is a checkpoint regulator which can both stimulate or inhibit immune responses and demonstrates altered expression after sepsis. We hypothesized that signaling via HVEM would be essential for the neonatal response to sepsis, and that therefore blockade of this pathway would improve survival to septic challenge.

Methods

To explore this, neonatal mice were treated with cecal slurry (CS), CS with Anti-HVEM antibody (CS-Ab) or CS with isotype (CS-IT) and followed for 7-day survival. Mice from all treatment groups had thymus, lung, kidney and peritoneal fluid harvested, weighed, and stained for histologic evaluation, and changes in cardiac function were assessed with echocardiography.

Results

Mortality was significantly higher for CS-Ab mice (72.2%) than for CS-IT mice (22.2%). CS resulted in dysregulated alveolar remodeling, but CS-Ab lungs demonstrated significantly less dysfunctional alveolar remodeling than CS alone (MCL 121.0 CS vs. 87.6 CS-Ab), as well as increased renal tubular vacuolization. No morphologic differences in alveolar septation or thymic karyorrhexis were found between CS-Ab and CS-IT. CS-Ab pups exhibited a marked decrease in heart rate (390.3 Sh vs. 342.1 CS-Ab), stroke volume (13.08 CS-IT vs. 8.83 CS-Ab) and ultimately cardiac output (4.90 Sh vs. 3.02 CS-Ab) as well as a significant increase in ejection fraction (73.74 Sh vs. 83.75 CS-Ab) and cardiac strain (40.74 Sh vs. 51.16 CS-Ab) as compared to CS-IT or Sham animals.

Discussion

While receptor ligation of aspects of HVEM signaling, via antibody blockade, appears to mitigate aspects of lung injury and thymic involution, stimulatory signaling via HVEM still seems to be necessary for vascular and hemodynamic resilience and overall neonatal mouse survival in response to this experimental polymicrobial septic insult. This dissonance in the activity of anti-HVEM neutralizing antibody in neonatal animals speaks to the differences in how septic cardiac dysfunction should be considered and approached in the neonatal population.

Timing and cell specificity of senescence drives postnatal lung development and injury

Senescence causes age-related diseases and stress-related injury. Paradoxically, it is also essential for organismal development. Whether senescence contributes to lung development or injury in early life remains unclear. Here, we show that lung senescence occurred at birth and decreased throughout the saccular stage in mice. Reducing senescent cells at this stage disrupted lung development. In mice (<12 h old) exposed to hyperoxia during the saccular stage followed by air recovery until adulthood, lung senescence increased particularly in type II cells and secondary crest myofibroblasts. This peaked during the alveolar stage and was mediated by the p53/p21 pathway. Decreasing senescent cells during the alveolar stage attenuated hyperoxia-induced alveolar and vascular simplification. Conclusively, early programmed senescence orchestrates postnatal lung development whereas later hyperoxia-induced senescence causes lung injury through different mechanisms. This defines the ontogeny of lung senescence and provides an optimal therapeutic window for mitigating neonatal hyperoxic lung injury by inhibiting senescence.

Involvement of miRNA-34a regulated Krüppel-like factor 4 expression in hyperoxia-induced senescence in lung epithelial cells

BACKGROUND

Premature infants, subjected to supplemental oxygen and mechanical ventilation, may develop bronchopulmonary dysplasia, a chronic lung disease characterized by alveolar dysplasia and impaired vascularization. We and others have shown that hyperoxia causes senescence in cultured lung epithelial cells and fibroblasts. Although miR-34a modulates senescence, it is unclear whether it contributes to hyperoxia-induced senescence. We hypothesized that hyperoxia increases miR-34a levels, leading to cellular senescence.

METHODS

We exposed mouse lung epithelial (MLE-12) cells and primary human small airway epithelial cells to hyperoxia (95% O₂/5% CO₂) or air (21% O₂/5% CO₂) for 24 h. Newborn mice (< 12 h old) were exposed to hyperoxia (> 95% O₂) for 3 days and allowed to recover in room air until postnatal day 7. Lung samples from premature human infants requiring mechanical ventilation and control subjects who were not mechanically ventilated were employed.

RESULTS

Hyperoxia caused senescence as indicated by loss of nuclear lamin B1, increased p21 gene expression, and senescence-associated secretory phenotype factors. Expression of miR-34a-5p was increased in epithelial cells and newborn mice exposed to hyperoxia, and in premature infants requiring mechanical ventilation. Transfection with a miR-34a-5p inhibitor reduced hyperoxia-induced senescence in MLE-12 cells. Additionally, hyperoxia increased protein levels of the oncogene and tumor-suppressor Krüppel-like factor 4 (KLF4), which were inhibited by a miR-34a-5p inhibitor. Furthermore, KLF4 knockdown by siRNA transfection reduced hyperoxia-induced senescence.

CONCLUSION

Hyperoxia increases miR-34a-5p, leading to senescence in lung epithelial cells. This is dictated in part by upregulation of KLF4 signaling. Therefore, inhibiting hyperoxia-induced senescence via miR-34a-5p or KLF4 suppression may provide a novel therapeutic strategy to mitigate the detrimental consequences of hyperoxia in the neonatal lung.

Single-cell transcriptomics reveals lasting changes in the lung cellular landscape into adulthood after neonatal hyperoxic exposure

Ventilatory support, such as supplemental oxygen, used to save premature infants impairs the growth of the pulmonary microvasculature and distal alveoli, leading to bronchopulmonary dysplasia (BPD). Although lung cellular composition changes with exposure to hyperoxia in neonatal mice, most human BPD survivors are weaned off oxygen within the first weeks to months of life, yet they may have persistent lung injury and pulmonary dysfunction as adults. We hypothesized that early-life hyperoxia alters the cellular landscape in later life and predicts long-term lung injury. Using single-cell RNA sequencing, we mapped lung cell subpopulations at postnatal day (pnd)7 and pnd60 in mice exposed to hyperoxia (95% O2) for 3 days as neonates. We interrogated over 10,000 cells and identified a total of 45 clusters within 32 cell states. Neonatal hyperoxia caused persistent compositional changes in later life (pnd60) in all five type II cell states with unique signatures and function. Premature infants requiring mechanical ventilation with different durations also showed similar alterations in these unique signatures of type II cell states. Pathologically, neonatal hyperoxic exposure caused alveolar simplification in adult mice. We conclude that neonatal hyperoxia alters the lung cellular landscape in later life, uncovering neonatal programing of adult lung dysfunction.

The pentose phosphate pathway mediates hyperoxia-induced lung vascular dysgenesis and alveolar simplification in neonates

Dysmorphic pulmonary vascular growth and abnormal endothelial cell (EC) proliferation are paradoxically observed in premature infants with bronchopulmonary dysplasia (BPD), despite vascular pruning. The pentose phosphate pathway (PPP), a metabolic pathway parallel to glycolysis, generates NADPH as a reducing equivalent and ribose 5-phosphate for nucleotide synthesis. It is unknown whether hyperoxia, a known mediator of BPD in rodent models, alters glycolysis and the PPP in lung ECs. We hypothesized that hyperoxia increases glycolysis and the PPP, resulting in abnormal EC proliferation and dysmorphic angiogenesis in neonatal mice. To test this hypothesis, lung ECs and newborn mice were exposed to hyperoxia and allowed to recover in air. Hyperoxia increased glycolysis and the PPP. Increased PPP, but not glycolysis, caused hyperoxia-induced abnormal EC proliferation. Blocking the PPP reduced hyperoxia-induced glucose-derived deoxynucleotide synthesis in cultured ECs. In neonatal mice, hyperoxia-induced abnormal EC proliferation, dysmorphic angiogenesis, and alveolar simplification were augmented by nanoparticle-mediated endothelial overexpression of phosphogluconate dehydrogenase, the second enzyme in the PPP. These effects were attenuated by inhibitors of the PPP. Neonatal hyperoxia augments the PPP, causing abnormal lung EC proliferation, dysmorphic vascular development, and alveolar simplification. These observations provide mechanisms and potential metabolic targets to prevent BPD-associated vascular dysgenesis.

Survival and Pulmonary Injury After Neonatal Sepsis: PD1/PDL1's Contributions to Mouse and Human Immunopathology

Morbidity and mortality associated with neonatal sepsis remains a healthcare crisis. PD1-/- neonatal mice endured experimental sepsis, in the form of cecal slurry (CS), and showed improved rates of survival compared to wildtype (WT) counterparts. End-organ injury, particularly of the lung, contributes to the devastation set forth by neonatal sepsis. PDL1-/- neonatal mice, in contrast to PD1-/- neonatal mice did not have a significant improvement in survival after CS. Because of this, we focused subsequent studies on the impact of PD1 gene deficiency on lung injury. Here, we observed that at 24 h post-CS (but not at 4 or 12 h) there was a marked increase in pulmonary edema (PE), neutrophil influx, myeloperoxidase (MPO) levels, and cytokine expression sham (Sh) WT mice. Regarding pulmonary endothelial cell (EC) adhesion molecule expression, we observed that Zona occludens-1 (ZO-1) within the cell shifted from a membranous location to a peri-nuclear location after CS in WT murine cultured ECs at 24hrs, but remained membranous among PD1-/- lungs. To expand the scope of this inquiry, we investigated human neonatal lung tissue. We observed that the lungs of human newborns exposed to intrauterine infection had significantly higher numbers of PD1+ cells compared to specimens who died from non-infectious causes. Together, these data suggest that PD1/PDL1, a pathway typically thought to govern adaptive immune processes in adult animals, can modulate the largely innate neonatal pulmonary immune response to experimental septic insult. The potential future significance of this area of study includes that PD1/PDL1 checkpoint proteins may be viable therapeutic targets in the septic neonate.

Increased placental expression of angiotensin-converting enzyme 2, the receptor of SARS-CoV-2, associated with hypoxia in twin anemia-polycythemia sequence (TAPS)

INTRODUCTION

Recent reports suggest SARS-CoV-2, the virus causing COVID-19, may be transmittable from pregnant mother to placenta and fetus, albeit rarely. The efficacy of vertical transmission of SARS-CoV-2 critically depends on the availability of its receptor, ACE2, in the placenta. In the present study, we tested the hypothesis that placental ACE2 expression is oxygenation-dependent by studying the expression of ACE2 and associated cell entry regulators in the monochorionic twin anemia-polycythemia (TAPS) placenta, a model of discordant placental oxygenation.

METHODS

We performed a retrospective comparative immunohistochemical, immunofluorescence and Western blot analysis of ACE2, TMPRSS2 and Cathepsin B expression in anemic and polycythemic territories of TAPS placentas (N = 14).

RESULTS

ACE2 protein levels were significantly higher in the anemic twin territories than in the corresponding polycythemic territories, associated with upregulation of the key ACE2-related cell entry regulators, TMPRSS2 and Cathepsin B, immunolocalized to villous trophoblastic and stromal cells. Cellular colocalization of ACE2 and TMPRSS2, suggestive of functionality of this cell entry axis, was demonstrated by double immunofluorescence studies.

DISCUSSION

Placental hypoxia is associated with upregulation of ACE2 expression, concomitant with increased expression of its key cell entry proteases. ACE2-regulated placental functions, both infection- and non-infection related, may be highly oxygenation-dependent.

Correlation between chorionic plate vascularization and risk of bronchopulmonary dysplasia in extremely preterm infants

INTRODUCTION/OBJECTIVES

The chorionic plate vessels of the placenta are in direct continuity with the fetal vasculature, suggesting chorionic and fetal angiogenesis may be subjected to similar regulatory mechanisms. In this study, we determined the correlation between chorionic plate vascularization and complications of prematurity, focusing on bronchopulmonary dysplasia (BPD) and other conditions with important microvascular components.

METHODS

We performed a clinicoplacental analysis of 127 extremely preterm infants (23-28 weeks gestation). Chorionic plate vascularization was assessed by number and density of perforating chorionic vessels (PCVs). Charts were reviewed for relevant maternal and neonatal data, including respiratory, neurologic and gastrointestinal complications of prematurity.

RESULTS

The placentas displayed marked variability in number (36-523/placenta) and density of PCVs (0.46-3.74 PC V/cm²). The median PCV density of infants with severe BPD was significantly higher than that of infants without BPD (1.51 PC V/cm² versus 1.09 PC V/cm², P < 0.05). Conversely, the frequency of moderate-to-severe BPD was 33% higher in infants with PCV density ≥1.50 PC V/cm² than in those with PCV density <1.50 PC V/cm² (56% versus 40%, P < 0.01). There was no correlation with neonatal neurologic or gastrointestinal complications.

CONCLUSION

Chorionic plate vascularization correlates with frequency and severity of BPD, supporting a vascular basis that in part is antenatal in origin. Quantitative assessment of chorionic plate vascularization may allow early identification of preterm infants at high risk for BPD (proposed threshold: PCV density ≥1.50 PC V/cm²). The lack of correlation between chorionic vascularization and neurologic/gastrointestinal complications suggests these conditions may have less important antenatal and/or vascular contributions.

Stromal cell-derived factor-1 (SDF-1) expression in very preterm human lungs: potential relevance for stem cell therapy for bronchopulmonary dysplasia

Background: The axis formed by CXC chemokine receptor 4 (CXCR4), expressed on mesenchymal stromal cells (MSCs), and stromal cell-derived factor-1 (SDF-1), expressed in recipient organs, is a critical mediator of MSC migration in non-pulmonary injury models. The role and regulation of SDF-1 expression in preterm lungs, of potential relevance for MSC-based cell therapy for bronchopulmonary dysplasia (BPD), is unknown. The aim of this study was to determine the spatiotemporal pattern of CXCR4/SDF-1 expression in lungs of extremely preterm infants at risk for BPD.Methods: Postmortem lung samples were collected from ventilated extremely preterm infants who died between 23 and 29 wks ("short-term ventilated") or between 36 and 39 wks ("long-term ventilated") corrected postmenstrual age. Results were compared with age-matched infants who had lived <12 h or stillborn infants ("early" and "late" controls). CXCR4 and SDF-1 expression was studied by immunohistochemistry, immunofluorescence/confocal microscopy, and qRT-PCR analysis.Results: Compared with age-matched controls without antenatal infection, lungs of early control infants with evidence of intrauterine infection/inflammation showed significant upregulation of SDF-1 expression, localized to the respiratory epithelium, and of CXCR4 expression, localized to stromal cells. Similarly, pulmonary SDF-1 mRNA levels were significantly higher in long-term ventilated ex-premature infants with established BPD than in age-matched controls. The pulmonary vasculature was devoid of SDF-1 expression at all time points. Endogenous CXCR4-positive stromal cells were preferentially localized along the basal aspect of SDF-1-positive bronchial and respiratory epithelial cells, suggestive of functionality of the CXCR4/SDF-1 axis.Conclusions: Incipient and established neonatal lung injury is associated with upregulation of SDF-1 expression, restricted to the respiratory epithelium. Knowledge of the clinical associations, time-course and localization of pulmonary SDF-1 expression may guide decisions about the optimal timing and delivery route of MSC-based cell therapy for BPD.

Discordant placental oxygenation and autophagy in twin anemia-polycythemia sequence (TAPS)

BACKGROUND

(Macro)autophagy is an important process of self-degradation of macromolecules and organelles that ensures cellular homeostasis and energy preservation during stressful conditions. Dysregulated placental autophagy has been implicated in a wide range of pregnancy complications. Recent studies identified hypoxia as a key regulator of trophoblast autophagy in vitro; however, its effects on placental autophagy in vivo remain incompletely understood. In this study, we evaluated the monochorionic twin anemia-polycythemia sequence (TAPS) placenta as model of discordant placental oxygenation to determine the effects of hypoxia on placental autophagy in utero.

METHODS

We performed a retrospective comparative analysis of tissue oxygenation and autophagy in anemic and polycythemic territories of TAPS placentas (N = 12). Archival tissues were subjected to immunohistochemical, immunofluorescence and Western blot analyses of carbonic anhydrase (CA) IX (hypoxia marker) and key autophagy/lysosomal markers.

RESULTS

CAIX protein levels were significantly higher in anemic twin territories than in corresponding polycythemic territories, consistent with relative tissue hypoxia. Anemic placental shares further displayed significantly higher levels of LC3I/II (autophagosome markers) and LAMP1/2 (lysosome markers), associated with upregulated expression of lysosome/autophagosome activity-associated markers, transcription factor EB and cathepsin D. The accumulation of autophagosomes and lysosomes in anemic shares was accompanied by elevated p62 protein expression, suggestive of inhibition of the downstream autophagy pathway.

CONCLUSIONS

TAPS placentas display striking intertwin discordance in tissue oxygenation and autophagic activity and may provide a suitable model for study of the interrelationship between hypoxia, autophagy, and pregnancy outcome in a monochorionic twin setting.

Galectin-3 expression and effect of supplementation in neonatal mice with disseminated Candida albicans infection

BACKGROUND

Invasive candidiasis is an important cause of fungal infections in immunocompromised patients, including premature infants. The S-type lectin, galectin-3 (gal3), is increasingly recognized for its role in antifungal host defense. This study tested the hypothesis that tissue gal3 expression is affected by disseminated infection with Candida albicans and that supplementation with gal3 will provide a benefit in this setting.

METHODS

To determine the expression of gal3 at the tissue level in response to disseminated infection with C. albicans, adult and neonatal mice were infected using previously established models. End points were chosen that reflected substantive tissue fungal burden but before mortality.

RESULTS

No differences in gal3 were detected in tissues of adult animals relative to uninfected controls. In neonatal animals, gal3 concentration was lower in the spleen of infected animals compared to uninfected. Pretreatment of neonatal mice with recombinant gal3 was associated with reduced mortality and reduced fungal burden in the kidney, spleen, and lung at 24 h following infection.

CONCLUSION

These findings suggest that gal3 has an active role in host defense against candidiasis and that neonatal animals can benefit from supplementation with this lectin in the setting of disseminated candidiasis.

Ovotesticular Disorder of Sex Development (Ovotestis) in Simpson-Golabi-Behmel Syndrome: Expansion of the Clinical Spectrum

Simpson-Golabi-Behmel syndrome type I (SGBS, OMIM312870), caused by defects of the GPC3 and GPC4 genes on chromosome Xq26, is an X-linked recessive macrosomia/multiple congenital anomaly disorder characterized by somatic overgrowth, coarse facial features, variable congenital anomalies, increased tumor risk, and mild-to-moderate neurodevelopmental anomalies. We report the postmortem findings in 3 second-trimester male siblings with SGBS who displayed ambiguous genitalia (in all 3) and gonadal dysgenesis (ovotestis) (in 1), thus expanding the SGBS spectrum to include these disorders of sex development.

Pathology of Neonatal Non- albicans Candidiasis: Autopsy Study and Literature Review

INTRODUCTION/OBJECTIVES

Non- albicans Candida species such as Candida parapsilosis and Candida glabrata have emerged as prevalent pathogens in premature infants. The aim of this study was to systematically delineate the histopathologic findings in neonatal non- albicans candidiasis.

METHODS

We performed a retrospective clinicopathologic analysis of extremely premature (23-28 weeks' gestation) infants diagnosed with invasive candidiasis. Archival autopsy tissues were subjected to periodic acid-Schiff, methenamine-silver and anti- Candida (immuno)histochemical stains, as well as dual anti- Candida and anti-cytokeratin or anti-CD31 immunofluorescence assays. In addition, we studied the prevalence of intestinal Candida colonization in a consecutive autopsy series of extremely premature infants.

RESULTS

Based on positive postmortem blood and/or lung cultures, invasive candidiasis (3 non- albicans and 11 Candida albicans) was diagnosed in 14 of the 187 extremely premature infants examined between 1995 and 2017. In contrast to the well-known inflammatory and tissue-destructive phenotype of congenital C. albicans infection, invasive non- albicans candidiasis/candidemia caused by C. parapsilosis and C. glabrata was inconspicuous by routine hematoxylin-eosin-based histopathologic analysis despite a heavy fungal presence detected in intestines, lungs, and blood by targeted (immuno)histochemical assays. Intestinal colonization by Candida species was identified in 16 of the 26 (61%) extremely premature neonates who had lived for at least 1 week, as assessed by anti- Candida immunostaining.

CONCLUSION

Invasive neonatal non- albicans candidiasis/candidemia appears to have no distinct histopathologic signature. Based on the notoriously low sensitivity of fungal blood cultures and the observed high frequency of Candida intestinal colonization (>50%), it is likely that non- albicans candidiasis/candidemia may be underdiagnosed in (deceased) preterm infants. Routine inclusion of targeted (immuno)histochemical fungal detection strategies in the perinatal autopsy may lead to deeper insight into the prevalence and clinical relevance of neonatal non- albicans candidiasis.

Occult Massive Visceral Fat Necrosis Following Therapeutic Hypothermia for Neonatal Encephalopathy

Therapeutic hypothermia (head or whole-body cooling) improves survival and neurodevelopmental outcome in term newborns with moderate-to-severe encephalopathy. Hypothermia treatment is well tolerated; the most common side effect is thrombocytopenia. In about 1% of infants, focal subcutaneous fat necrosis has been reported. We describe a case of clinically unsuspected massive visceral fat necrosis in a term infant with Apgar score 0 at 1 min ("resuscitated apparently stillborn" infant) who was treated with therapeutic hypothermia for 72 h and expired on the 25th day of life following a neonatal course complicated by severe encephalopathy, pulmonary artery hypertension, persistent thrombocytopenia, hypoglycemia, and severe basal ganglia-thalamic abnormalities on magnetic resonance imaging. Postmortem examination revealed extensive visceral (brown) fat necrosis, involving thoracic, abdominal, and retroperitoneal adipose tissue, with distinctive sparing of the subcutaneous (white) fat. The fulminant-yet clinically occult-visceral fat necrosis seen in this case suggests that (lesser degrees of) fat necrosis may go unrecognized in hypoxic-ischemic newborns, especially in those treated with hypothermia, and underscores the importance of close monitoring of encephalopathic newborns both in the short and long terms for complications of fat necrosis (hypercalcemia and nephrocalcinosis).

Soft agar-based selection of spontaneously transformed rat prostate epithelial cells with highly tumorigenic characteristics

The critical molecular and cellular mechanisms involved in the development and progression of prostate cancer remain elusive. In this report, we demonstrate that normal rat prostate epithelial cells (PEC) undergo spontaneous transformation at high passage (p > 85) evidenced by the acquisition of anchorage independent growth when plated on soft agar and tumorigenicity when injected into immunodeficient mice. In addition, we also report the discovery of a minor subpopulation of spontaneously transformed PEC derived from high passage PEC with the ability to migrate through a layer of 1% agar and form expanding colonies on the underlying plastic substratum. Comparison of these soft agar invasive (SAI) cells with low (p < 35), mid (p36-84) and high passage (p > 85) PEC identified marked differences in cell morphology, proliferation and motility. The SAI subpopulation was more tumorigenic than the high passage anchorage independent cultures from which they were isolated, as manifested by a decreased latency period and an increase in the size of tumors arising in immunodeficient mice. In contrast, low and mid passage cells were unable to grow on soft agar and failed to form tumors when injected into immunodeficient mice. Screening with antibody-based signaling arrays identified several differences in the altered expression levels of signaling proteins between SAI-derived cells and low or high passage PEC, including the up-regulation of EGFR and MAPK-related signaling pathways in SAI-selected cells. In summary, these studies suggest that the SAI assay selects for a novel, highly tumorigenic subpopulation of transformed cells that may represent an early step in the progression of slow growing prostatic carcinomas into more rapidly growing and aggressive tumors.

Redness discordance in monochorionic twin placentas: Correlation with clinical and placental findings

INTRODUCTION/OBJECTIVES

Recent studies suggest redness (color) discordance of the placental basal plate may be a marker for twin anemia-polycythemia sequence (TAPS), a recently described complication of diamniotic-monochorionic twinning characterized by marked intertwin hemoglobin (Hb) discordance in the absence of oligohydramnios-polyhydramnios. In this study, we determined the clinicoplacental and choriovascular correlates of basal plate color discordance in monochorionic twin placentas, and assessed its value as postnatal indicator of TAPS.

METHODS

We performed a clinicoplacental analysis of 100 consecutive non-TTTS diamniotic-monochorionic twin placentas with available photographic documentation of the basal plate. Basal plate redness was quantified by computer-assisted analysis of digital images and expressed as intertwin color difference ratio (CDR).

RESULTS

The CDR ranged between 1.00 and 3.58 (median CDR: 1.14; 90^th %ile: 1.98). Compared to twins with low CDR (N = 90), twins with high CDR (≥2.0; N = 10) had significantly higher hemoglobin difference (11.25 g/dL versus 2.55 g/dL) and significantly fewer and smaller artery-to-artery (AA) and artery-to-vein (AV) anastomoses. Apgar scores and birth weights were equivalent in both groups. Among the 10 twin sets with high CDR, six (60%) qualified as TAPS, as defined by intertwin Hb difference >8 g/dL and absent or very small AA and AV anastomoses. Conversely, 6 of 8 (75%) twin sets with TAPS had a CDR ≥ 2.0.

CONCLUSION

Intertwin CDR correlates with intertwin hemoglobin difference and chorionic angioarchitecture. A CDR value ≥ 2.0 (the 90%ile value for CDR derived from the present cohort) has high specificity (96%), but relatively low positive predictive value (60%) as indicator of TAPS, as currently defined.

Florid Intussusceptive-like Microvascular Dysangiogenesis in a Preterm Lung

The cellular mechanisms underlying the microvascular dysangiogenesis of bronchopulmonary dysplasia (chronic lung disease of the newborn) remain largely undetermined. We report unusual pulmonary vascular findings in a 27-week-gestation male newborn who died on the second day of life from intractable respiratory failure, following a pregnancy complicated by prolonged membrane rupture and persistent severe oligohydramnios. As expected, postmortem examination revealed pulmonary hypoplasia (lung/body weight ratio: 2.23%; 10th percentile for 27 weeks: 2.59%). In addition, lung microscopy revealed complex networks of non-sprouting, tortuous, and bulbously dilated capillaries, randomly distributed in widened airspace septa. Anti-smooth muscle actin immunohistochemistry demonstrated immunoreactive central densities within capillary lumina, suggestive of intravascular pillar formation. The plexus-forming, non-sprouting type of angiogenesis and apparent transluminal pillar formation are consistent with intussusceptive ("longitudinal splitting") angiogenesis. In concordance with previous observations made in human fetal lung xenografts, these findings support the notion that human postcanalicular lungs have the capacity to switch from sprouting to non-sprouting, intussusceptive-like angiogenesis, possibly representing an adaptive response activated by hemodynamic flow alterations and/or hypoxia. The possible relationship between the intussusceptive-like vascular changes observed in this case and the microvascular dysangiogenesis characteristic of bronchopulmonary dysplasia remains to be determined.

Effects of human umbilical cord blood mononuclear cells on respiratory system mechanics in a murine model of neonatal lung injury

BACKGROUND

Mononuclear cells (MNCs) have well-documented beneficial effects in a wide range of adult pulmonary diseases. The effects of human umbilical cord blood-derived MNCs on neonatal lung injury, highly relevant for potential autologous application in preterm newborns at risk for bronchopulmonary dysplasia (BPD), remain incompletely established. The aim of this study was to determine the long-term morphologic and functional effects of systemically delivered MNCs in a murine model of neonatal lung injury.

MATERIALS AND METHODS

MNCs from cryopreserved cord blood (1 × 10⁶ cells per pup) were given intravenously to newborn mice exposed to 90% O₂ from birth; controls received cord blood total nucleated cells (TNCs) or granular cells, or equal volume vehicle buffer (sham controls). In order to avoid immune rejection, we used SCID mice as recipients. Lung mechanics (flexiVent™), engraftment, growth, and alveolarization were evaluated eight weeks postinfusion.

RESULTS

Systemic MNC administration to hyperoxia-exposed newborn mice resulted in significant attenuation of methacholine-induced airway hyperreactivity, leading to reduction of central airway resistance to normoxic levels. These bronchial effects were associated with mild improvement of alveolarization, lung compliance, and elastance. TNCs had no effects on alveolar remodeling and were associated with worsened methacholine-induced bronchial hyperreactivity. Granular cell administration resulted in a marked morphologic and functional emphysematous phenotype, associated with high mortality. Pulmonary donor cell engraftment was sporadic in all groups.

CONCLUSIONS

These results suggest that cord blood MNCs may have a cell type-specific role in therapy of pulmonary conditions characterized by increased airway resistance, such as BPD and asthma. Future studies need to determine the active MNC subtype(s), their mechanisms of action, and optimal purification methods to minimize granular cell contamination.

Intussusceptive-like angiogenesis in human fetal lung xenografts: Link with bronchopulmonary dysplasia-associated microvascular dysangiogenesis?

BACKGROUND

Human fetal lung xenografts display an unusual pattern of non-sprouting, plexus-forming angiogenesis that is reminiscent of the dysmorphic angioarchitecture described in bronchopulmonary dysplasia (BPD). The aim of this study was to determine the clinicopathological correlates, growth characteristics and molecular regulation of this aberrant form of graft angiogenesis.

METHODS

Fetal lung xenografts, derived from 12 previable fetuses (15 to 22 weeks' gestation) and engrafted in the renal subcapsular space of SCID-beige mice, were analyzed 4 weeks posttransplantation for morphology, vascularization, proliferative activity and gene expression.

RESULTS

Focal plexus-forming angiogenesis (PFA) was observed in 60/230 (26%) of xenografts. PFA was characterized by a complex network of tortuous nonsprouting vascular structures with low endothelial proliferative activity, suggestive of intussusceptive-type angiogenesis. There was no correlation between the occurrence of PFA and gestational age or time interval between delivery and engraftment. PFA was preferentially localized in the relatively hypoxic central subcapsular area. Microarray analysis suggested altered expression of 15 genes in graft regions with PFA, of which 7 are known angiogenic/lymphangiogenic regulators and 5 are known hypoxia-inducible genes. qRT-PCR analysis confirmed significant upregulation of SULF2, IGF2, and HMOX1 in graft regions with PFA.

CONCLUSION

These observations in human fetal lungs ex vivo suggest that postcanalicular lungs can switch from sprouting angiogenesis to an aberrant intussusceptive-type of angiogenesis that is highly reminiscent of BPD-associated dysangiogenesis. While circumstantial evidence suggests hypoxia may be implicated, the exact triggering mechanisms, molecular regulation and clinical implications of this angiogenic switch in preterm lungs in vivo remain to be determined.

Evidence of Placental Hypoxia in Maternal Sleep Disordered Breathing

Sleep disordered breathing (SDB) represents a spectrum of disorders, including habitual snoring and obstructive sleep apnea (OSA). Sleep disordered breathing is characterized by chronic intermittent hypoxia, airflow limitation, and recurrent arousals, which may lead to tissue hypoperfusion, hypoxia, and inflammation. In this study, we aimed to examine whether SDB during pregnancy was associated with histopathologic evidence of chronic placental hypoxia and/or uteroplacental underperfusion. The placentas of women with OSA (n  =  23) and habitual snoring (n  =  78) as well as nonsnorer controls (n  =  47) were assessed for histopathologic and immunohistochemical markers of chronic hypoxia and uteroplacental underperfusion. Fetal normoblastemia was significantly more prevalent in SDB placentas than in those of nonsnorer controls (34.6% and 56.5% in snorers and OSA, respectively, versus 6.4% in controls). Expression of the tissue hypoxia marker carbonic anhydrase IX (CAIX) was more common in OSA placentas than controls (81.5% and 91.3% in snorers and OSA, respectively, versus 57.5% in controls). Adjusting for confounders such as body mass index, diabetes mellitus, or chronic hypertension did not alter the results. The uteroplacental underperfusion scores were similar among the 3 groups. Our findings suggest that SDB during pregnancy is associated with fetoplacental hypoxia, as manifested by fetal normoblastemia and increased placental carbonic anhydrase IX immunoreactivity. The clinical implications and underlying mechanisms remain to be determined.

Extensive placental choriovascular infiltration by maturing myeloid cells in down syndrome-associated transient abnormal myelopoiesis

Transient abnormal myelopoiesis (TAM), a clonal proliferation of predominantly megakaryocytic precursor cells, affects 4%-10% of newborns with Down syndrome. Approximately 20%-30% of TAM survivors are at risk of development of acute myeloid leukemia (myeloid leukemia associated with Down syndrome, ML-DS). We report unusual placental findings in a female infant with trisomy 21 born at 38 weeks of gestation. In line with previous descriptions of placental pathology in infants with TAM, abundant blast-like cells were present in the lumen of chorionic and stem villous vessels. In addition, there was multifocal extensive infiltration of the wall of chorionic vessels by maturing myeloid cells in a pattern reminiscent of TAM- or leukemia-associated systemic infiltration. The clinical significance of this unusual choriovascular involvement of the placenta in TAM is undetermined.

Examination of the twin placenta

Twin birth rates have increased dramatically over the past three decades, and twins currently account for 3% of all pregnancies. Twin pregnancies of any type are at risk for prematurity. In addition, monochorionic twin pregnancies (25-30% of all twin pregnancies) are predisposed to a specific set of complications, including twin-to-twin transfusion syndrome (TTTS), twin reversed arterial perfusion syndrome (TRAP), malformations, and intertwin growth discordance. This article reviews the basic mechanisms underlying the twinning process, the relationship between zygosity and chorionicity, and the various types of twinning. We describe the major complications of monochorionic twinning in association with their reported placental characteristics (or lack thereof). Finally, a rational, evidence-based approach to examination of the twin placenta is presented. It is essential for the pathologist to understand the value, strengths, and limitations of examination of the twin placenta in order to provide a meaningful clinicopathological correlation in complicated (monochorionic) twin pregnancies.

Xenotransplantation models to study the effects of toxicants on human fetal tissues

Many diseases that manifest throughout the lifetime are influenced by factors affecting fetal development. Fetal exposure to xenobiotics, in particular, may influence the development of adult diseases. Established animal models provide systems for characterizing both developmental biology and developmental toxicology. However, animal model systems do not allow researchers to assess the mechanistic effects of toxicants on developing human tissue. Human fetal tissue xenotransplantation models have recently been implemented to provide human-relevant mechanistic data on the many tissue-level functions that may be affected by fetal exposure to toxicants. This review describes the development of human fetal tissue xenotransplant models for testis, prostate, lung, liver, and adipose tissue, aimed at studying the effects of xenobiotics on tissue development, including implications for testicular dysgenesis, prostate disease, lung disease, and metabolic syndrome. The mechanistic data obtained from these models can complement data from epidemiology, traditional animal models, and in vitro studies to quantify the risks of toxicant exposures during human development.

Intranasal versus intraperitoneal delivery of human umbilical cord tissue-derived cultured mesenchymal stromal cells in a murine model of neonatal lung injury

Clinical trials investigating mesenchymal stromal cell (MSC) therapy for bronchopulmonary dysplasia have been initiated; however, the optimal delivery route and functional effects of MSC therapy in newborns remain incompletely established. We studied the morphologic and functional effects of intranasal versus i.p. MSC administration in a rodent model of neonatal lung injury. Cultured human cord tissue MSCs (0.1, 0.5, or 1 × 10(6) cell per pup) were given intranasally or i.p. to newborn severe combined immunodeficiency-beige mice exposed to 90% O2 from birth; sham controls received an equal volume of phosphate-buffered saline. Lung mechanics, engraftment, lung growth, and alveolarization were evaluated 8 weeks after transplantation. High-dose i.p. MSC administration to newborn mice exposed to 90% O2 resulted in the restoration of normal lung compliance, elastance, and pressure-volume loops (tissue recoil). Histologically, high-dose i.p. MSC administration was associated with alveolar septal widening, suggestive of interstitial matrix modification. Intranasal MSC or lower-dose i.p. administration had no significant effects on lung function or alveolar remodeling. Pulmonary engraftment was rare in all the groups. These findings suggest that high-dose systemic administration of human cultured MSCs can restore normal compliance in neonatally injured lungs, possibly by paracrine modulation of the interstitial matrix. Intranasal delivery had no obvious pulmonary effects.

Xenotransplantation of human fetal adipose tissue: a model of in vivo adipose tissue expansion and adipogenesis

Obesity during childhood and beyond may have its origins during fetal or early postnatal life. At present, there are no suitable in vivo experimental models to study factors that modulate or perturb human fetal white adipose tissue (WAT) expansion, remodeling, development, adipogenesis, angiogenesis, or epigenetics. We have developed such a model. It involves the xenotransplantation of midgestation human WAT into the renal subcapsular space of immunocompromised SCID-beige mice. After an initial latency period of approximately 2 weeks, the tissue begins expanding. The xenografts are healthy and show robust expansion and angiogenesis for at least 2 months following transplantation. Data and cell size and gene expression are consistent with active angiogenesis. The xenografts maintain the expression of genes associated with differentiated adipocyte function. In contrast to the fetal tissue, adult human WAT does not engraft. The long-term viability and phenotypic maintenance of fetal adipose tissue following xenotransplantation may be a function of its autonomous high rates of adipogenesis and angiogenesis. Through the manipulation of the host mice, this model system offers the opportunity to study the mechanisms by which nutrients and other environmental factors affect human adipose tissue development and biology.

Lethal hypoplasia and developmental anomalies of the lungs in a newborn with intrauterine adrenal hemorrhage and cerebral infarcts: a proposed pulmonary disruption sequence

We report a case of a 31-week-gestation male newborn who died soon after birth from intractable respiratory failure and persistent pulmonary hypertension. The pregnancy had been complicated by intermittent bleeding between 13 and 20 weeks' gestation, attributed to peripheral placental separation, as well as bilateral fetal adrenal hemorrhage, first detected at 17 weeks' gestation. Postmortem examination revealed small, calcified adrenal glands as well as several remote cerebral and cerebellar infarcts. The lungs were hypoplastic (lung weight/body weight ratio: 1.64%; 10th percentile for 28-36 weeks' gestation: 2.27%) and distorted by exaggerated lobulation. Microscopically, the lungs exhibited several developmental anomalies, including focal acinar dysgenesis suggestive of arrested development in the pseudoglandular stage of development (8-16 weeks' gestation) (mainly in the upper lobes), and features of bronchial obstruction, including focal lobular hyperplasia and microcystic maldevelopment (mainly in the lower lobes). The adrenal and cerebral findings were consistent with a severe early-gestation hypoxic-ischemic insult, likely related to peripheral placental separation and chronic abruption. The co-occurrence and timing of these well-recognized hypoxic lesions provide further evidence that certain developmental lung anomalies, such as focal acinar dysplasia, focal lobular hyperplasia, and microcystic maldevelopment, may, at least in some cases, have a hypoxic/ischemic etiology.

Postmortem lung volume/body weight standards for term and preterm infants

Assessment of lung growth is a critical component of the perinatal autopsy. Increased lung liquid content may lead to overestimation of lung growth based on (wet) lung weight. In contrast, lung volume is not influenced by intraalveolar lung liquid. Our aim was to establish age-specific reference values for postmortem lung volume/BW in preterm and term infants. We performed a retrospective analysis of fetuses/infants (16-41 weeks' gestation) without (N = 134) or with (N = 79) risk factors for pulmonary hypoplasia. Lungs were inflated at standardized pressure and volumes determined by water immersion method. Lung volume increased 11-fold between 16 and 41 weeks' gestation, concomitant with a 16-fold increase in BW. Mean lung volume/BW remained constant at 33-34 ml/kg between 16 and 31 weeks' gestation and decreased to 23.4 ml/kg at term. Lung volume/BW of infants with severe risk factors (renal anomalies, diaphragmatic hernia) was significantly lower than age-matched standards. In this group, all fetuses/infants diagnosed as having lung hypoplasia by lung volume/BW also had lung hypoplasia LW/BW standards. However, in infants with "softer" risk factors (rupture of membranes, chromosomal anomalies), 5/26 cases diagnosed with lung hypoplasia based on lung volume/BW had normal LW/BW ratios. In these discrepant cases, lung sections showed significant inflammation and edema, likely accounting for increased wet lung weight. In conclusion, we determined age-specific lung volume/BW reference values for preterm and term infants. In selected situations assessment of lung volume/BW may represent a useful complementary tool to LW/BW for postmortem evaluation of lung size.

What-and why-the pathologist should know about twin-to-twin transfusion syndrome

Approximately 20% of all twin pregnancies are monochorionic. Between 9% and 15% of all monochorionic twin gestations are complicated by severe chronic twin-to-twin transfusion syndrome (TTTS), characterized by a gradual shift of blood volume from the donor twin to the recipient twin through placental vascular connections [1 - 3] . The prognosis of severe, untreated chronic TTTS diagnosed in midtrimester fetuses is extremely poor, with mortality rates exceeding 70% [4] . Since publication of the results of the Eurofoetus trial in 2004, laser photocoagulation of the intertwin anastomoses has become accepted as the optimal first-line therapy for severe TTTS diagnosed before 26 weeks of gestation. While laser treatment of vascular communications was initially limited to selected fetal treatment centers, its increasingly widespread use has resulted in the exposure of more pathologists, even in less specialized institutions, to laser-treated placentas. Furthermore, the surge in laser coagulation has revived the general medical, scientific, and public interest in the placental and choriovascular findings in monochorionic twin placentas. The pathologist's understanding of the pathophysiology of TTTS and of TTTS-associated placental pathology, including the findings related to laser ablation of the anastomoses, can be of great benefit to the involved obstetric/neonatal/surgical team and, ultimately, to the patients. In this review, we summarize the current knowledge of the placental contributions to TTTS and other complications of monochorionic twinning and describe the strengths and limitations of placental examination in these settings. It is our expectation that overviews such as this may serve as a template to generate consensus guidelines for standardized and evidence-based pathologic evaluation of monochorionic twin placentas.

Correlation between cord insertion type and chorionic villus vascularization of the co-twin in diamniotic-monochorionic twin pregnancies

BACKGROUND

Recent evidence suggests that cord insertion type of one twin correlates with chorionic plate vascularization of the monochorionic co-twin. Specifically, for twins with paracentral cords, chorionic plate vascularization is significantly greater when the co-twin has a velamentous, rather than paracentral cord insertion.

AIMS

To determine whether this correlation between cord insertion type and vascularization of the co-twin also extends to the deeper chorionic villus tree.

STUDY DESIGN

Morphometric analysis of chorionic villus vascularization in CD31-immunostained sections of a retrospective cohort of gestational age-matched third trimester monochorionic placentas with discordant paracentral/velamentous (PC/V) or concordant paracentral/paracentral (PC/PC) cord insertions.

OUTCOME MEASURES

Vascular numerical density (number of vascular profiles per unit villus stromal area) of intermediate villi (>80 μm diameter) and terminal villi (<80 μm).

RESULTS

For twins with paracentral cord insertion, the vascular numerical density of intermediate villi was significantly higher for twins in a discordant PC/V relationship than for those in a concordant PC/PC relationship (P<0.05), thus replicating previous findings in superficial chorionic vessels. For terminal villi, in contrast, the vascular numerical density of twins with paracentral cords in a PC/V combination was significantly lower than of those in a PC/PC combination, and similar to that of their co-twins with velamentous cord insertion.

CONCLUSIONS

Early placental angiogenesis in monochorionic twin gestations may be influenced by implantation and cord localization of the co-twin. The regulation of terminal villus angiogenesis appears to be dissociated from more proximal villus angiogenesis and independent of cord insertion of the co-twin.

Ex vivo expanded human cord blood-derived hematopoietic progenitor cells induce lung growth and alveolarization in injured newborn lungs

BACKGROUND

We investigated the capacity of expanded cord blood-derived CD34+ hematopoietic progenitor cells to undergo respiratory epithelial differentiation ex vivo, and to engraft and attenuate alveolar disruption in injured newborn murine lungs in vivo.

METHODS

Respiratory epithelial differentiation was studied in CD34+ cells expanded in the presence of growth factors and cytokines ("basic" medium), in one group supplemented with dexamethasone ("DEX"). Expanded or freshly isolated CD34+ cells were inoculated intranasally in newborn mice with apoptosis-induced lung injury. Pulmonary engraftment, lung growth and alveolarization were studied at 8 weeks post-inoculation.

RESULTS

SP-C mRNA expression was seen in 2/7 CD34+ cell isolates expanded in basic media and in 6/7 isolates expanded in DEX, associated with cytoplasmic SP-C immunoreactivity and ultrastructural features suggestive of type II cell-like differentiation. Administration of expanding CD34+ cells was associated with increased lung growth and, in animals treated with DEX-exposed cells, enhanced alveolar septation. Freshly isolated CD34+ cells had no effect of lung growth or remodeling. Lungs of animals treated with expanded CD34+ cells contained intraalveolar aggregates of replicating alu-FISH-positive mononuclear cells, whereas epithelial engraftment was extremely rare.

CONCLUSION

Expanded cord blood CD34+ cells can induce lung growth and alveolarization in injured newborn lungs. These growth-promoting effects may be linked to paracrine or immunomodulatory effects of persistent cord blood-derived mononuclear cells, as expanded cells showed limited respiratory epithelial transdifferentiation.

Galectin-3 plays an important role in protection against disseminated candidiasis

Recent in vitro studies have implicated galectin-3 as an important receptor in host recognition and response to specific Candida species; however, its role in protection against disseminated candidiasis in vivo has not been evaluated. This study investigated the importance of galectin-3 in host defense against systemic infection with the highly virulent species Candida albicans, and the less virulent species, C. parapsilosis. Mice deficient in galectin-3 (gal3-/-) were more susceptible to infection than wild-type (WT) mice. When infected with C. albicans, gal3-/- mice died significantly faster and exhibited a trend towards increased fungal burden and increased abscess formation in infected brains compared to WT mice. When infected with C. parapsilosis, gal3-/- mice had significantly higher renal fungal burdens and abscess formation compared to WT mice. To evaluate whether galectin-3 may contribute to susceptibility to candidiasis in human infants, galectin-3 levels in sera of newborn infants, a patient population uniquely susceptible to infections with both C. albicans and C. parapsilosis, were compared to serum galectin-3 levels of adults. Galectin-3 levels were significantly lower in newborn infant sera compared to adult sera. These data indicate that galectin-3 plays an important role in a murine model of disseminated candidiasis and suggest a potential mechanism of neonatal susceptibility to these infections.

Ascending Infection: Acute Chorioamnionitis

Acute chorioamnionitis is a major cause of spontaneous preterm birth, accounting for more than 40% of deliveries complicated by preterm premature rupture of membranes or preterm labor. In the majority of cases, especially in preterm births, acute chorioamnionitis is caused by ascending polymicrobial infection. Recent evidence suggests that in some cases acute chorioamnionitis may have a noninfectious cause. In addition to the nonspecific patterns of conventional acute chorioamnionitis, this article describes characteristic inflammatory patterns indicative of a specific infectious cause. Several inflammatory entities of putative immunologic (noninfectious) etiology are addressed, including eosinophilic/T-cell vasculitis and chronic chorioamnionitis.

The human fetal lung xenograft: validation as model of microvascular remodeling in the postglandular lung

BACKGROUND

Coordinated remodeling of epithelium and vasculature is essential for normal postglandular lung development. The value of the human-to-rodent lung xenograft as model of fetal microvascular development remains poorly defined.

AIM

The aim of this study was to determine the fate of the endogenous (human-derived) microvasculature in fetal lung xenografts.

METHODS

Lung tissues were obtained from spontaneous pregnancy losses (14-22 weeks' gestation) and implanted in the renal subcapsular or dorsal subcutaneous space of SCID-beige mice (T, B, and NK-cell-deficient) and/or nude rats (T-cell-deficient). Informed parental consent was obtained. Lung morphogenesis, microvascular angiogenesis, and epithelial differentiation were assessed at 2 and 4 weeks post-transplantation by light microscopy, immunohistochemical, and gene expression studies. Archival age-matched postmortem lungs served as control.

RESULTS

The vascular morphology, density, and proliferation of renal subcapsular grafts in SCID-beige mice were similar to age-matched control lungs, with preservation of the physiologic association between epithelium and vasculature. The microvasculature of subcutaneous grafts in SCID-beige mice was underdeveloped and dysmorphic, associated with significantly lower VEGF, endoglin, and angiopoietin-2 mRNA expression than renal grafts. Grafts at both sites displayed mild airspace dysplasia. Renal subcapsular grafts in nude rats showed frequent infiltration by host lymphocytes and obliterating bronchiolitis-like changes, associated with markedly decreased endogenous angiogenesis.

CONCLUSION

This study demonstrates the critical importance of host and site selection to ensure optimal xenograft development. When transplanted to severely immune suppressed, NK-cell-deficient hosts and engrafted in the renal subcapsular site, the human-to-rodent fetal lung xenograft provides a valid model of postglandular microvascular lung remodeling.

Resilience of the human fetal lung following stillbirth: potential relevance for pulmonary regenerative medicine

Recent advances in pulmonary regenerative medicine have increased the demand for alveolar epithelial progenitor cells. Fetal lung tissues from spontaneous pregnancy losses may represent a neglected, yet ethically and societally acceptable source of alveolar epithelial cells. The aim of this study was to determine the regenerative capacity of fetal lungs obtained from second trimester stillbirths. Lung tissues were harvested from 11 stillborn fetuses (13 to 22 weeks' gestation) at postdelivery intervals ranging from 10 to 41 hours and grafted to the renal subcapsular space of immune-suppressed rats to provide optimal growth conditions. Histology, epithelial and alveolar type II cell proliferation, and surfactant protein-C mRNA expression were studied in preimplantation lung tissues and in xenografts at posttransplantation week 2. All xenografts displayed advanced architectural maturation compared with their respective preimplantation tissues, regardless of gestational age and postdelivery interval. The proliferative activity of the grafts was significantly higher than that of the preimplantation tissues (mean Ki-67 labeling index 26.7%±7.7% versus 14.7%±10.5%; P<.01). The proliferative activity of grafts obtained after a long (>36 hours) postdelivery interval was significantly higher than that of the corresponding preimplantation tissue, and equivalent to that of grafts obtained after a short postdelivery interval (<14 hours). The regenerative capacity of fetal lung tissue was greater at younger (13 to 17 weeks) than at older (19 to 22 weeks) gestational ages. The presence of inflammation/chorioamnionitis did not appear to affect graft regeneration. All grafts studied displayed robust surfactant protein-C mRNA expression. In conclusion, fetal lung tissues from second trimester stillbirths can regain their inherent high regenerative potential following short-term culture, even if harvested more than 36 hours after delivery.

siRNA inhibition of aspartyl-asparaginyl β-hydroxylase expression impairs cell motility, Notch signaling, and fetal growth

Aspartyl-asparaginyl-β-hydroxylase (AAH) regulates cell motility and invasiveness by enhancing Notch signaling. Invasive trophoblastic cells, which mediate placentation, normally express high levels of AAH. Previously, we showed that ethanol-impaired placentation is associated with reduced AAH expression. The present study determines the degree to which inhibition of AAH expression is sufficient to impair functions required for placentation. Immortalized, first trimester-derived, human trophoblastic cells (HTR-8/SVneo) were transfected with siRNA targeting AAH (siRNA-AAH) or no specific sequences (siRNA-Scr) using the Amaxa electroporation system. Directional motility was measured using an ATP luminescence-based assay. For in vivo studies, we microinjected siRNA-AAH or siRNA-Scr directly into the implantation sites (mesometrial triangle) of gestation-day-17, Long Evans pregnant rats, and harvested placentas 24 h later for histologic and molecular studies. siRNA-AAH transfection reduced AAH expression and directional motility in HTR-8/SVneo cells. In vivo delivery of siRNA-AAH reduced AAH expression and mean number of invasive trophoblastic cells at the implantation site. These adverse effects of siRNA-AAH were associated with impaired fetal growth and significantly reduced expression of Notch-signaling network genes. AAH is an important, positive regulator of trophoblastic cell motility, and inhibition of AAH in vivo leads to impaired implantation and fetal growth, and alters Notch-signaling mechanisms, similar to the effects of chronic ethanol exposure.

Alveolar epithelial cell therapy with human cord blood-derived hematopoietic progenitor cells

The role of umbilical cord blood (CB)-derived stem cell therapy in neonatal lung injury remains undetermined. We investigated the capacity of human CB-derived CD34(+) hematopoietic progenitor cells to regenerate injured alveolar epithelium in newborn mice. Double-transgenic mice with doxycycline (Dox)-dependent lung-specific Fas ligand (FasL) overexpression, treated with Dox between embryonal day 15 and postnatal day 3, served as a model of neonatal lung injury. Single-transgenic non-Dox-responsive littermates were controls. CD34(+) cells (1 × 10(5) to 5 × 10(5)) were administered at postnatal day 5 by intranasal inoculation. Engraftment, respiratory epithelial differentiation, proliferation, and cell fusion were studied at 8 weeks after inoculation. Engrafted cells were readily detected in all recipients and showed a higher incidence of surfactant immunoreactivity and proliferative activity in FasL-overexpressing animals compared with non-FasL-injured littermates. Cord blood-derived cells surrounding surfactant-immunoreactive type II-like cells frequently showed a transitional phenotype between type II and type I cells and/or type I cell-specific podoplanin immunoreactivity. Lack of nuclear colocalization of human and murine genomic material suggested the absence of fusion. In conclusion, human CB-derived CD34(+) cells are capable of long-term pulmonary engraftment, replication, clonal expansion, and reconstitution of injured respiratory epithelium by fusion-independent mechanisms. Cord blood-derived surfactant-positive epithelial cells appear to act as progenitors of the distal respiratory unit, analogous to resident type II cells. Graft proliferation and alveolar epithelial differentiation are promoted by lung injury.

Pulmonary dendritic cells in lungs of preterm infants: neglected participants in bronchopulmonary dysplasia?

Preterm infants are at risk for bronchopulmonary dysplasia (BPD), a chronic lung disease characterized by disrupted alveolar remodeling and microvascular dysangiogenesis. The pathogenesis of BPD is multifactorial, with contributions from antenatal and/or postnatal infection and inflammation. The potential role of dendritic cells, critical immune regulatory cells with potent angiogenic activities, remains undetermined. We studied the prevalence and topography of dendritic cells in postmortem lungs of short- and long-term ventilated preterm infants born between 23 and 29 weeks in gestation. Controls were age-matched infants who had lived less than 12 hours. Dendritic cells were identified by anti-DC-SIGN immunohistochemistry and were co-localized with endothelial and smooth muscle cells by double immunofluorescence. Lungs of early and late control infants without evidence of antenatal infection contained scattered DC-SIGN-positive dendritic cells in the peripheral lung parenchyma. Lungs of early control infants with a history of chorioamnionitis/antenatal infection and lungs of short- or long-term ventilated preterm infants showed a dramatic (more than 3-fold) increase in dendritic cells. Double labeling highlighted a close association between dendritic cells and small- or medium-sized pulmonary vessels. In conclusion, we demonstrated that dendritic cells are an integral component of normal postcanalicular lung development. Antenatal infection and ventilation/BPD are associated with significant pulmonary recruitment of dendritic cells. The recently described angiogenic effects of dendritic cells and their intimate association with the pulmonary microvasculature indicate that dendritic cells may participate in BPD-associated dysangiogenesis. Elucidation of the role of this immunovascular axis may lead to novel therapeutic approaches to BPD.

Angiogenesis-related gene expression profiling in ventilated preterm human lungs

Preterm infants exposed to oxygen and mechanical ventilation are at risk for bronchopulmonary dysplasia (BPD), a multifactorial chronic lung disorder characterized by arrested alveolar development and nonsprouting, dysmorphic microvascular angiogenesis. The molecular regulation of this BPD-associated pathological angiogenesis remains incompletely understood. In this study, the authors used focused microarray technology to characterize the angiogenic gene expression profile in postmortem lung samples from short-term ventilated preterm infants (born at 24 to 27 weeks' gestation) and age-matched control infants. Microarray analysis identified differential expression of 13 of 112 angiogenesis-related genes. Genes significantly up-regulated in ventilated lungs included the antiangiogenic genes thrombospondin-1, collagen XVIII alpha-1, and tissue inhibitor of metalloproteinase-1 (TIMP1), as well as endoglin, transforming growth factor-alpha, and monocyte chemoattractant protein-1 (CCL2). Increased expression of thrombospondin-1 in ventilated lungs was verified by real-time polymerase chain reaction (PCR) and immunolocalized primarily to intravascular platelets and fibrin aggregates. Down-regulated genes included proangiogenic angiogenin and midkine, as well as vascular endothelial growth factor (VEGF)-B, VEGF receptor-2, and the angiopoietin receptor TEK/Tie-2. In conclusion, short-term ventilated lungs show a shift from traditional angiogenic growth factors to alternative, often antisprouting regulators. This angiogenic shift may be implicated in the regulation of dysmorphic angiogenesis and, consequently, deficient alveolarization characteristic of infants with BPD.

Effects of Fas-ligand overexpression on alveolar type II cell growth kinetics in perinatal murine lungs

We determined the time-specific effects of FasL overexpression on perinatal alveolar type II cell growth kinetics. To achieve temporal overexpression of respiratory epithelium-specific FasL expression, tetracycline inducible CCSP-rtTA/FasL-TetOp transgenic mice were given doxycycline (Dox) from gestational d 14 (E14) to E19 (antenatal treatment group), from postnatal d 1 (P1) to P7 (postnatal group), or from E14 to P7 (combined antenatal and postnatal group). Antenatal Dox administration induced an increase of pulmonary FasL mRNA levels in double transgenic animals up to >300-fold over single transgenic littermate controls, associated with massive fetal respiratory epithelial apoptosis and excessive postnatal lethality. Although animals from the combined antenatal/postnatal Dox treatment group continued to display evidence of increased apoptosis, there was a paradoxical increase in alveolar type II cell proliferation, resulting in a net increase in type II cell density, elevated pulmonary surfactant protein C levels and improved postnatal survival. Postnatal Dox administration was also associated with increased type II cell density, although FasL up-regulation was more variable. In conclusion, these results, and our previous studies, suggest that FasL signaling has dual timing-dependent proapoptotic and proproliferative effects on postcanalicular type II cell kinetics.

Effects of chemotherapy during pregnancy on the placenta

Whereas the effects of chemotherapy during pregnancy for mother and fetus are well described, its effects on the placenta remain largely undetermined. We performed a retrospective clinicopathologic analysis of the placenta following chemotherapy. Charts were reviewed for type of malignancy, type and timing of chemotherapy, and fetal and pregnancy outcome. Placentas were studied by standard pathologic analysis as well as computer-assisted morphometry and fluorescence in situ hybridization (FISH) analysis. Patients (n = 13) underwent chemotherapy during pregnancy for carcinoma of breast (3), ovary (2), cervix (2), salivary gland (1), lymphoma/leukemia (4), or rhabdomyosarcoma (1). Eleven patients were treated with DNA-active cytotoxic agents during the 2nd and/or 3rd trimesters; their placentas showed nonspecific findings, including villous hypermaturity, distal villous hypoplasia, villous edema, and excessive extravillous trophoblast, and 4/11 (36%) were small-for-age. In one case (rhabdomyosarcoma), the mother was exposed to cytotoxic agents throughout the entire pregnancy. In this case, associated with severe congenital anomalies, the placenta showed striking nuclear pleomorphism of the extravillous trophoblast of the chorion laeve, associated with FISH-demonstrated hyperpolyploidy. One patient was treated with the targeted tyrosine kinase inhibitor, imatinib, in 2 consecutive pregnancies; these placentas showed no specific anomalies. Our findings suggest that chemotherapy during the 1st trimester induces excessive polyploidization of the chorion laeve trophoblast, likely representing an adaptive response to intraamniotic toxins. Second and 3rd trimester exposure to cytotoxic agents may predispose to placental underdevelopment. However, without appropriate controls (untreated patients with equivalent malignancies), the specific effects of chemotherapy in this group are difficult to assess.

Fate and effects of adult bone marrow cells in lungs of normoxic and hyperoxic newborn mice

Cell-based therapy in adult lung injury models is associated with highly variable donor cell engraftment and epithelial reconstitution. The role of marrow-derived cell therapy in neonatal lung injury is largely unknown. In this study, we determined the fate and effects of adult bone marrow cells in a model of neonatal lung injury. Wild-type mice placed in a normoxic or hyperoxic (95% O(2)) environment received bone marrow cells from animals expressing green fluorescent protein (GFP) at Postnatal Day (P)5. Controls received vehicle buffer. Lungs were analyzed between Post-Transplantation (TPX) Day 2 and Week 8. The volume of GFP-immunoreactive donor cells, monitored by stereologic volumetry, remained constant between Post-TPX Weeks 1 and 8 and was similar in normoxic and hyperoxia-exposed recipients. Virtually all marrow-derived cells showed colocalization of GFP and the pan-macrophage marker, F4/80, by double immunofluorescence studies. Epithelial transdifferentiation was not seen. Marrow cell administration had adverse effects on somatic growth and alveolarization in normoxic mice, while no effects were discerned in hyperoxia-exposed recipients. Reexposure of marrow-treated animals to hyperoxia at P66 resulted in significant expansion of the donor-derived macrophage population. In conclusion, intranasal administration of unfractionated bone marrow cells to newborn mice does not achieve epithelial reconstitution, but establishes persistent alveolar macrophage chimerism. The predominantly adverse effects of marrow treatment in newborn lungs are likely due to macrophage-associated paracrine effects. While this model and route of cell therapy may not achieve epithelial reconstitution, the role of selected stem cell populations and/or alternate routes of administration for cell-based therapy in injured newborn lungs deserve further investigation.

The Fas system confers protection against alveolar disruption in hyperoxia-exposed newborn mice

The functional significance of the Fas/Fas-ligand (FasL) system in hyperoxia-induced lung injury and alveolar disruption in newborn lungs in vivo remains undetermined. To assess the role of the Fas/FasL system, we compared the effects of hyperoxia (95% O2 from birth to Postnatal Day [P]7) in Fas-deficient lpr mice and wild-type mice. Alveolar disruption was more severe in hyperoxic lpr mice than in wild-type mice. In addition, a transient alveolarization defect was noted in normoxic lpr mice. Hyperoxia induced marked up-regulation of pulmonary Fas expression in wild-type mice, as well as elevated mRNA levels of pro-apoptotic Bax, Bad, and Bak. Pulmonary apoptotic activity was similar in hyperoxic wild-type and lpr mice. In contrast, lung growth and proliferation, assessed by stereologic volumetry and Ki67 proliferation studies, were significantly higher in hyperoxic wild-type mice compared with lpr mice, suggesting the Fas/FasL system has a pro-proliferative role in hyperoxic conditions. Levels of the prosurvival MAPkinase, pERK1/2, were significantly higher in hyperoxic wild-type mice compared with lpr mice, while pAkt levels were similar. These data suggest that the primary role of the Fas/FasL system in hyperoxic newborn lungs is pro-proliferative, rather than pro-apoptotic, and likely mediated through a Fas-ERK1/2 pathway. Fas-induced proliferation and lung growth in hyperoxic newborn lungs may counteract, in part, the detrimental effects of apoptosis mediated by non-Fas pathways, such as pro-apoptotic Bax/Bcl-2 family members. The capacity of the Fas/FasL signaling pathway to mediate protective rather than destructive functions in hyperoxic newborn lungs highlights the versatility of this complex pathway.

Fas-ligand-induced apoptosis of respiratory epithelial cells causes disruption of postcanalicular alveolar development

Premature infants are at risk for bronchopulmonary dysplasia, a complex condition characterized by impaired alveolar development and increased alveolar epithelial apoptosis. The functional involvement of pulmonary apoptosis in bronchopulmonary dysplasia- associated alveolar disruption remains undetermined. The aims of this study were to generate conditional lung-specific Fas-ligand (FasL) transgenic mice and to determine the effects of FasL-induced respiratory epithelial apoptosis on alveolar remodeling in postcanalicular lungs. Transgenic (TetOp)(7)-FasL responder mice, generated by pronuclear microinjection, were bred with Clara cell secretory protein (CCSP)-rtTA activator mice. Doxycycline (Dox) was administered from embryonal day 14 to postnatal day 7, and lungs were studied between embryonal day 19 and postnatal day 21. Dox administration induced marked respiratory epithelium-specific FasL mRNA and protein up-regulation in double-transgenic CCSP-rtTA(+)/(TetOp)(7)-FasL(+) mice compared with single-transgenic CCSP-rtTA(+) littermates. The Dox-induced FasL up-regulation was associated with dramatically increased apoptosis of alveolar type II cells and Clara cells, disrupted alveolar development, decreased vascular density, and increased postnatal lethality. These data demonstrate that FasL-induced alveolar epithelial apoptosis during postcanalicular lung remodeling is sufficient to disrupt alveolar development after birth. The availability of inducible lung-specific FasL transgenic mice will facilitate studies of the role of apoptosis in normal and disrupted alveologenesis and may lead to novel therapeutic approaches for perinatal and adult pulmonary diseases characterized by dysregulated apoptosis.

Endoglin (CD105) up-regulation in pulmonary microvasculature of ventilated preterm infants

RATIONALE

Preterm infants exposed to mechanical ventilation and oxygen are at risk for bronchopulmonary dysplasia (BPD), a multifactorial chronic lung disorder characterized by arrested alveolar development. Studies have described disruption of microvascular development in BPD, characterized by primitive angioarchitectural patterns reminiscent of the canalicular/saccular stages of lung development. The molecular regulation of this BPD-associated dysangiogenesis remains undetermined.

OBJECTIVES

Endoglin (CD105), a hypoxia-inducible transforming growth factor-beta coreceptor, has been implicated as an important regulator of angiogenesis in various neoplastic and nonneoplastic conditions. The aim of this study was to investigate the expression of endoglin and other angiogenesis-related factors in ventilated preterm human lungs.

METHODS

We have studied endoglin protein and mRNA expression in postmortem lungs of short-term and long-term ventilated preterm infants. Control subjects were age-matched infants who had lived for less than 1 hour.

MEASUREMENTS AND MAIN RESULTS

Lungs of short-term ventilated preterm infants showed significant upregulation of endoglin mRNA and protein levels, immunolocalized to the microvasculature. Similar but more variable endoglin upregulation was noted in lungs of long-term ventilated infants with BPD. The mRNA levels of vascular endothelial growth factor, angiopoietin-1, and their respective receptors were significantly lower in ventilated lungs than in age-matched nonventilated control lungs.

CONCLUSIONS

BPD is associated with a shift from traditional angiogenic growth factors (vascular endothelial growth factor, angiopoietin-1) to alternative regulators such as endoglin, which may contribute to BPD-associated microvascular dysangiogenesis.

Intrauterine infection with Klebsiella pneumoniae: report of a case and literature review

We report a case of intrauterine Klebsiella pneumoniae infection that resulted in premature rupture of membranes and fetal demise at 20 weeks' gestation in a pregnancy achieved by in vitro fertilization. Postmortem findings included massive panlobar pneumonia, the presence of abundant gram-negative, rod-shaped bacteria within the pulmonary air spaces and the lumen of the gastrointestinal tract, and fetal lung and blood cultures positive for Klebsiella pneumoniae. The placenta showed severe acute chorioamnionitis associated with a brisk fetal inflammatory response (umbilical cord and chorionic plate vasculitis). Marked pancreatic fibrosis was noted, indicative of a preceding necrotizing pancreatitis. In spite of this fulminant histopathologic evidence of intrauterine infection, the infection was clinically silent. This represents, to our knowledge, the 1st reported case of fatal intrauterine Klebsiella pneumoniae infection fully supported by conclusive fetal and placental histopathological evidence.

Postmortem lung weight/body weight standards for term and preterm infants

Assessment of lung development is a crucial component of the perinatal autopsy, especially in preterm infants. In current pathology practice, the diagnosis of lung hypoplasia in very premature infants (<28 weeks of gestation) is based on a lung weight/body weight ratio (LW/BW) of 1.5% or less. While useful to confirm the presence of marked pulmonary hypoplasia, the 1.5% threshold may be too stringent to detect more subtle degrees of pulmonary hypoplasia, as seen in association with rupture of membranes. The aim of this study was to establish reference values for postmortem LW/BW in preterm and term infants. To this end, we performed a retrospective analysis of fetuses and newborns (16-41 weeks of gestation) without known risk factors for pulmonary hypoplasia. Mean LW/BW ranged between 2.98-3.15% between 16-27 weeks, and decreased to 2.55% by 28-36 weeks and 1.79% at term. The 10th percentile for LW/BW was significantly higher in preterm infants (2.24% between 20-23 weeks, and 2.59% between 24-27 weeks) than in term infants (1.24% at >or=37 weeks, P < 0.01). We then correlated LW/BW of infants with risk factors for pulmonary hypoplasia with the newly established reference values. As expected, mean LW/BW of infants with congenital diaphragmatic hernia or severe renal anomalies was <1.5% (0.98% and 1.40%, respectively). Mean LW/BW of infants with prolonged (> 1 week) rupture of membranes (PROM) was 2.08%. Three of 12 (25%) preterm infants with PROM had pulmonary hypoplasia according to the traditional criteria (LW/BW <1.5%). However, an additional 4/12 (33%) infants with PROM had a LW/BW between 1.5% and the 10th percentile for age (2.2%), indicative of more subtle but potentially relevant pulmonary underdevelopment. In conclusion, we determined LW/BW reference values for preterm and term infants. Correlation of LW/BW with age-matched reference values at postmortem examination represents an invaluable additional tool to evaluate lung growth, particularly in preterm infants.