SnapShot: Sensing and Signaling by Cilia.

Primary cilia are cellular appendages that coordinate diverse sensory and signaling activities. They are important for proper mammalian development, adult tissue homeostasis, and vision and odorant detection, and their dysfunction contributes to disease pathology and developmental defects.

Hydrocortisone to Improve Survival without Bronchopulmonary Dysplasia.

BACKGROUND: Bronchopulmonary dysplasia is a prevalent complication after extremely preterm birth. Inflammation with mechanical ventilation may contribute to its development. Whether hydrocortisone treatment after the second postnatal week can improve survival without bronchopulmonary dysplasia and without adverse neurodevelopmental effects is unknown. METHODS: We conducted a trial involving infants who had a gestational age of less than 30 weeks and who had been intubated for at least 7 days at 14 to 28 days. Infants were randomly assigned to receive either hydrocortisone (4 mg per kilogram of body weight per day tapered over a period of 10 days) or placebo. Mandatory extubation thresholds were specified. The primary efficacy outcome was survival without moderate or severe bronchopulmonary dysplasia at 36 weeks of postmenstrual age, and the primary safety outcome was survival without moderate or severe neurodevelopmental impairment at 22 to 26 months of corrected age. RESULTS: We enrolled 800 infants (mean [±SD] birth weight, 715±167 g; mean gestational age, 24.9±1.5 weeks). Survival without moderate or severe bronchopulmonary dysplasia at 36 weeks occurred in 66 of 398 infants (16.6%) in the hydrocortisone group and in 53 of 402 (13.2%) in the placebo group (adjusted rate ratio, 1.27; 95% confidence interval [CI], 0.93 to 1.74). Two-year outcomes were known for 91.0% of the infants. Survival without moderate or severe neurodevelopmental impairment occurred in 132 of 358 infants (36.9%) in the hydrocortisone group and in 134 of 359 (37.3%) in the placebo group (adjusted rate ratio, 0.98; 95% CI, 0.81 to 1.18). Hypertension that was treated with medication occurred more frequently with hydrocortisone than with placebo (4.3% vs. 1.0%). Other adverse events were similar in the two groups. CONCLUSIONS: In this trial involving preterm infants, hydrocortisone treatment starting on postnatal day 14 to 28 did not result in substantially higher survival without moderate or severe bronchopulmonary dysplasia than placebo. Survival without moderate or severe neurodevelopmental impairment did not differ substantially between the two groups. (Funded by the National Institutes of Health; ClinicalTrials.gov number, NCT01353313.).

Impact of neonatal noninvasive resuscitation strategies on lung mechanics, tracheal pressure, and tidal volume in preterm lambs.

This study investigated the relationship between three respiratory support approaches on lung volume recruitment during the first two hours of postnatal life in preterm lambs. We estimated changes in lung aeration, measuring respiratory resistance and reactance by oscillometry at 5 Hz. We also measured intratracheal pressure in subsets of lambs. The first main finding is that sustained inflation (SI) applied noninvasively (Mask SI; n=7) or invasively (endotracheal tube, ETT SI; n=6) led to similar rapid lung volume recruitment (~6 min). In contrast, Mask continuous positive airway pressure (CPAP) without SI (n=6) resuscitation took longer (~30-45 min) to reach similar lung volume recruitment. The second main finding is that, in the first 15 min of postnatal life, the Mask CPAP without SI group closed their larynx during custom ventilator-driven expiration, leading to intratracheal positive end-expiratory pressure of ~17 cmH2O (instead of 8 cmH2O provided by the ventilator). In contrast, the Mask SI group used the larynx to limit inspiratory pressure to ~26 cmH2O (instead of 30 cmH2O provided by the ventilator). These different responses affected tidal volume, being larger in the Mask CPAP without SI group (8.4 ml/Kg, 6.7-9.3 IQR) compared to the Mask SI (5.0 ml/Kg, 4.4-5.2 IQR), and ETT SI groups (3.3 ml/Kg 2.6-3.7 IQR). Distinct physiological responses suggest that spontaneous respiratory activity of the larynx of preterm lambs at birth can uncouple pressure applied by the ventilator to that applied to the lung, leading to unpredictable lung pressure and tidal volumes delivery independently from the ventilator settings.

Can Red Blood Cell and Platelet Transfusions Have a Pathogenic Role in Bronchopulmonary Dysplasia?

OBJECTIVE: To evaluate whether transfusions in infants born preterm contribute to the pathogenesis of bronchopulmonary dysplasia (BPD). STUDY DESIGN: We conducted a multihospital, retrospective study seeking associations between red blood cell or platelet transfusions and BPD. We tabulated all transfusions administered from January 2018 through December 2022 to infants born ≤29 weeks or <1000 g until 36 weeks postmenstrual age and compared those with BPD grade. We performed a sensitivity analysis to assess the possibility of a causal relationship. We then determined whether each transfusion was compliant with restrictive guidelines, and we estimated effects fewer transfusions might have on future BPD incidence. RESULTS: Eighty-four infants did not develop BPD and 595 did; 352 developed grade 1 (mild), 193 grade 2 (moderate), and 50 grade 3 (severe). Transfusions were given at <36 weeks to 7% of those who did not develop BPD, 46% who did, and 98% who developed severe BPD. For every transfusion the odds of developing BPD increased by a factor of 2.27 (95% CI, 1.59-3.68; P < .001). Sensitivity analyses suggested that transfusions might contribute to BPD. Fifty-seven percent of red blood cell transfusions and 68% of platelet transfusions were noncompliant with new restrictive guidelines. Modeling predicted that complying with restrictive guidelines could reduce the transfusion rate by 20%-30% and the moderate to severe BPD rate by ∼4%-6%. CONCLUSIONS: Transfusions were associated with BPD incidence and severity. Lowering transfusion rates to comply with current restrictive guidelines might result in a small but meaningful reduction in BPD rates.

Effect of Early vs Late Inguinal Hernia Repair on Serious Adverse Event Rates in Preterm Infants: A Randomized Clinical Trial.

Importance: Inguinal hernia repair in preterm infants is common and is associated with considerable morbidity. Whether the inguinal hernia should be repaired prior to or after discharge from the neonatal intensive care unit is controversial. Objective: To evaluate the safety of early vs late surgical repair for preterm infants with an inguinal hernia. Design, Setting, and Participants: A multicenter randomized clinical trial including preterm infants with inguinal hernia diagnosed during initial hospitalization was conducted between September 2013 and April 2021 at 39 US hospitals. Follow-up was completed on January 3, 2023. Interventions: In the early repair strategy, infants underwent inguinal hernia repair before neonatal intensive care unit discharge. In the late repair strategy, hernia repair was planned after discharge from the neonatal intensive care unit and when the infants were older than 55 weeks' postmenstrual age. Main Outcomes and Measures: The primary outcome was occurrence of any prespecified serious adverse event during the 10-month observation period (determined by a blinded adjudication committee). The secondary outcomes included the total number of days in the hospital during the 10-month observation period. Results: Among the 338 randomized infants (172 in the early repair group and 166 in the late repair group), 320 underwent operative repair (86% were male; 2% were Asian, 30% were Black, 16% were Hispanic, 59% were White, and race and ethnicity were unknown in 9% and 4%, respectively; the mean gestational age at birth was 26.6 weeks [SD, 2.8 weeks]; the mean postnatal age at enrollment was 12 weeks [SD, 5 weeks]). Among 308 infants (91%) with complete data (159 in the early repair group and 149 in the late repair group), 44 (28%) in the early repair group vs 27 (18%) in the late repair group had at least 1 serious adverse event (risk difference, -7.9% [95% credible interval, -16.9% to 0%]; 97% bayesian posterior probability of benefit with late repair). The median number of days in the hospital during the 10-month observation period was 19.0 days (IQR, 9.8 to 35.0 days) in the early repair group vs 16.0 days (IQR, 7.0 to 38.0 days) in the late repair group (82% posterior probability of benefit with late repair). In the prespecified subgroup analyses, the probability that late repair reduced the number of infants with at least 1 serious adverse event was higher in infants with a gestational age younger than 28 weeks and in those with bronchopulmonary dysplasia (99% probability of benefit in each subgroup). Conclusions and Relevance: Among preterm infants with inguinal hernia, the late repair strategy resulted in fewer infants having at least 1 serious adverse event. These findings support delaying inguinal hernia repair until after initial discharge from the neonatal intensive care unit. Trial Registration: ClinicalTrials.gov Identifier: NCT01678638.

Accuracy and processing time of kidney volume measurement methods in rodents polycystic kidney disease models: superiority of semiautomated kidney segmentation.

Measurement of total kidney volume (TKV) using magnetic resonance imaging (MRI) is a valuable approach for monitoring disease progression in autosomal dominant polycystic kidney disease (PKD) and is becoming more common in preclinical studies using animal models. Manual contouring of kidney MRI areas [i.e., manual method (MM)] is a conventional, but time-consuming, way to determine TKV. We developed a template-based semiautomatic image segmentation method (SAM) and validated it in three commonly used PKD models: Cys1cpk/cpk mice, Pkd1RC/RC mice, and Pkhd1pck/pck rats (n = 10 per model). We compared SAM-based TKV with that obtained by clinical alternatives including the ellipsoid formula-based method (EM) using three kidney dimensions, the longest kidney length method (LM), and MM, which is considered the gold standard. Both SAM and EM presented high accuracy in TKV assessment in Cys1cpk/cpk mice [interclass correlation coefficient (ICC) ≥ 0.94]. SAM was superior to EM and LM in Pkd1RC/RC mice (ICC = 0.87, 0.74, and <0.10 for SAM, EM, and LM, respectively) and Pkhd1pck/pck rats (ICC = 0.59, <0.10, and <0.10, respectively). Also, SAM outperformed EM in processing time in Cys1cpk/cpk mice (3.6 ± 0.6 vs. 4.4 ± 0.7 min/kidney) and Pkd1RC/RC mice (3.1 ± 0.4 vs. 7.1 ± 2.6 min/kidney, both P < 0.001) but not in Pkhd1PCK/PCK rats (3.7 ± 0.8 vs. 3.2 ± 0.5 min/kidney). LM was the fastest (∼1 min) but correlated most poorly with MM-based TKV in all studied models. Processing times by MM were longer for Cys1cpk/cpk mice, Pkd1RC/RC mice, and Pkhd1pck.pck rats (66.1 ± 7.3, 38.3 ± 7.5, and 29.2 ± 3.5 min). In summary, SAM is a fast and accurate method to determine TKV in mouse and rat PKD models.NEW & NOTEWORTHY Total kidney volume (TKV) is a valuable readout in preclinical studies for autosomal dominant and autosomal recessive polycystic kidney diseases (ADPKD and ARPKD). Since conventional TKV assessment by manual contouring of kidney areas in all images is time-consuming, we developed a template-based semiautomatic image segmentation method (SAM) and validated it in three commonly used ADPKD and ARPKD models. SAM-based TKV measurements were fast, highly reproducible, and accurate across mouse and rat ARPKD and ADPKD models.

A mouse model of BBS identifies developmental and homeostatic effects of BBS5 mutation and identifies novel pituitary abnormalities.

Primary cilia are critical sensory and signaling compartments present on most mammalian cell types. These specialized structures require a unique signaling protein composition relative to the rest of the cell to carry out their functions. Defects in ciliary structure and signaling result in a broad group of disorders collectively known as ciliopathies. One ciliopathy, Bardet-Biedl syndrome (BBS; OMIM 209900), presents with diverse clinical features, many of which are attributed to defects in ciliary signaling during both embryonic development and postnatal life. For example, patients exhibit obesity, polydactyly, hypogonadism, developmental delay and skeletal abnormalities along with sensory and cognitive deficits, but for many of these phenotypes it is uncertain, which are developmental in origin. A subset of BBS proteins assembles into the core BBSome complex, which is responsible for mediating transport of membrane proteins into and out of the cilium, establishing it as a sensory and signaling hub. Here, we describe two new mouse models for BBS resulting from a targeted LacZ gene trap allele (Bbs5-/-) that is a predicted congenital null mutation and conditional (Bbs5flox/flox) allele of Bbs5. Bbs5-/- mice develop a complex phenotype consisting of increased pre-weaning lethality craniofacial and skeletal defects, ventriculomegaly, infertility and pituitary anomalies. Utilizing the conditional allele, we show that the male fertility defects, ventriculomegaly and pituitary abnormalities are only present when Bbs5 is disrupted prior to postnatal day 7, indicating a developmental origin. In contrast, mutation of Bbs5 results in obesity, independent of the age of Bbs5 loss.

Prioritized polycystic kidney disease drug targets and repurposing candidates from pre-cystic and cystic mouse Pkd2 model gene expression reversion.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is one of the most prevalent monogenic human diseases. It is mostly caused by pathogenic variants in PKD1 or PKD2 genes that encode interacting transmembrane proteins polycystin-1 (PC1) and polycystin-2 (PC2). Among many pathogenic processes described in ADPKD, those associated with cAMP signaling, inflammation, and metabolic reprogramming appear to regulate the disease manifestations. Tolvaptan, a vasopressin receptor-2 antagonist that regulates cAMP pathway, is the only FDA-approved ADPKD therapeutic. Tolvaptan reduces renal cyst growth and kidney function loss, but it is not tolerated by many patients and is associated with idiosyncratic liver toxicity. Therefore, additional therapeutic options for ADPKD treatment are needed. METHODS: As drug repurposing of FDA-approved drug candidates can significantly decrease the time and cost associated with traditional drug discovery, we used the computational approach signature reversion to detect inversely related drug response gene expression signatures from the Library of Integrated Network-Based Cellular Signatures (LINCS) database and identified compounds predicted to reverse disease-associated transcriptomic signatures in three publicly available Pkd2 kidney transcriptomic data sets of mouse ADPKD models. We focused on a pre-cystic model for signature reversion, as it was less impacted by confounding secondary disease mechanisms in ADPKD, and then compared the resulting candidates' target differential expression in the two cystic mouse models. We further prioritized these drug candidates based on their known mechanism of action, FDA status, targets, and by functional enrichment analysis. RESULTS: With this in-silico approach, we prioritized 29 unique drug targets differentially expressed in Pkd2 ADPKD cystic models and 16 prioritized drug repurposing candidates that target them, including bromocriptine and mirtazapine, which can be further tested in-vitro and in-vivo. CONCLUSION: Collectively, these results indicate drug targets and repurposing candidates that may effectively treat pre-cystic as well as cystic ADPKD.

Mortality in Congenital Diaphragmatic Hernia: A Multicenter Registry Study of Over 5000 Patients Over 25 Years.

OBJECTIVE: To determine if risk-adjusted survival of patients with CDH has improved over the last 25 years within centers that are long-term, consistent participants in the CDH Study Group (CDHSG). SUMMARY BACKGROUND DATA: The CDHSG is a multicenter collaboration focused on evaluation of infants with CDH. Despite advances in pediatric surgical and intensive care, CDH mortality has appeared to plateau. Herein, we studied CDH mortality rates amongst long-term contributors to the CDHSG. METHODS: We divided registry data into 5-year intervals, with Era 1 (E1) beginning in 1995, and analyzed multiple variables (operative strategy, defect size, and mortality) to assess evolution of disease characteristics and severity over time. For mortality analyses, patients were risk stratified using a validated prediction score based on 5-minute Apgar (Apgar5) and birth weight. A risk-adjusted, observed to expected (O:E) mortality model was created using E1 as a reference. RESULTS: 5203 patients from 23 centers with >22years of participation were included. Birth weight, Apgar5, diaphragmatic agenesis, and repair rate were unchanged over time (all P > 0.05). In E5 compared to E1, minimally invasive and patch repair were more prevalent, and timing of diaphragmatic repair was later (all P < 0.01). Overall mortality decreased over time: E1 (30.7%), E2 (30.3%), E3 (28.7%), E4 (26.0%), E5 (25.8%) ( P = 0.03). Risk-adjusted mortality showed a significant improvement in E5 compared to E1 (OR 0.78, 95% CI 0.62-0.98; P = 0.03). O:E mortality improved over time, with the greatest improvement in E5. CONCLUSIONS: Risk-adjusted and observed-to-expected CDH mortality have improved over time.

Higher or Lower Hemoglobin Transfusion Thresholds for Preterm Infants.

BACKGROUND: Limited data suggest that higher hemoglobin thresholds for red-cell transfusions may reduce the risk of cognitive delay among extremely-low-birth-weight infants with anemia. METHODS: We performed an open, multicenter trial in which infants with a birth weight of 1000 g or less and a gestational age between 22 weeks 0 days and 28 weeks 6 days were randomly assigned within 48 hours after delivery to receive red-cell transfusions at higher or lower hemoglobin thresholds until 36 weeks of postmenstrual age or discharge, whichever occurred first. The primary outcome was a composite of death or neurodevelopmental impairment (cognitive delay, cerebral palsy, or hearing or vision loss) at 22 to 26 months of age, corrected for prematurity. RESULTS: A total of 1824 infants (mean birth weight, 756 g; mean gestational age, 25.9 weeks) underwent randomization. There was a between-group difference of 1.9 g per deciliter (19 g per liter) in the pretransfusion mean hemoglobin levels throughout the treatment period. Primary outcome data were available for 1692 infants (92.8%). Of 845 infants in the higher-threshold group, 423 (50.1%) died or survived with neurodevelopmental impairment, as compared with 422 of 847 infants (49.8%) in the lower-threshold group (relative risk adjusted for birth-weight stratum and center, 1.00; 95% confidence interval [CI], 0.92 to 1.10; P = 0.93). At 2 years, the higher- and lower-threshold groups had similar incidences of death (16.2% and 15.0%, respectively) and neurodevelopmental impairment (39.6% and 40.3%, respectively). At discharge from the hospital, the incidences of survival without severe complications were 28.5% and 30.9%, respectively. Serious adverse events occurred in 22.7% and 21.7%, respectively. CONCLUSIONS: In extremely-low-birth-weight infants, a higher hemoglobin threshold for red-cell transfusion did not improve survival without neurodevelopmental impairment at 22 to 26 months of age, corrected for prematurity. (Funded by the National Heart, Lung, and Blood Institute and others; TOP ClinicalTrials.gov number, NCT01702805.).

Variability for Age at Successful Extubation in Infants with Congenital Diaphragmatic Hernia.

OBJECTIVE: The objective of this study was to characterize clinical factors associated with successful extubation in infants with congenital diaphragmatic hernia. STUDY DESIGN: Using the Children's Hospitals Neonatal Database, we identified infants with congenital diaphragmatic hernia from 2017 to 2020 at 32 centers. The main outcome was age in days at the time of successful extubation, defined as the patient remaining extubated for 7 consecutive days. Unadjusted Kaplan-Meier and multivariable Cox proportional hazards ratio equations were used to estimate associations between clinical factors and the main outcome. Observations occurred through 180 days after birth. RESULTS: There were 840 eligible neonates with a median gestational age of 38 weeks and birth weight of 3.0 kg. Among survivors (n = 693), the median age at successful extubation was 15 days (interquartile range [IQR]: 8-29 days, 95th percentile: 71 days). For nonsurvivors (n = 147), the median age at death was 21 days (IQR: 11-39 days, 95th percentile: 110 days). Center (adjusted hazards ratio: 0.22-15, P < .01), low birth weight, intrathoracic liver position, congenital heart disease, lower 5-minute Apgar score, lower pH upon admission to Children's Hospitals Neonatal Database center, and use of extracorporeal support were independently associated with older age at successful extubation. Tracheostomy was associated with multiple failed extubations. CONCLUSION: Our findings suggest that infants who have not successfully extubated by about 3 months of age may be candidates for tracheostomy with chronic mechanical ventilation or palliation. The variability of timing of successful extubation among our centers supports the development of practice guidelines after validating clinical criteria.

Umbilical cord milking in nonvigorous infants: a cluster-randomized crossover trial.

BACKGROUND: Delayed cord clamping and umbilical cord milking provide placental transfusion to vigorous newborns. Delayed cord clamping in nonvigorous newborns may not be provided owing to a perceived need for immediate resuscitation. Umbilical cord milking is an alternative, as it can be performed more quickly than delayed cord clamping and may confer similar benefits. OBJECTIVE: We hypothesized that umbilical cord milking would reduce admission to the neonatal intensive care unit compared with early cord clamping in nonvigorous newborns born between 35 and 42 weeks' gestation. STUDY DESIGN: This was a pragmatic cluster-randomized crossover trial of infants born at 35 to 42 weeks' gestation in 10 medical centers in 3 countries between January 2019 and May 2021. The centers were randomized to umbilical cord milking or early cord clamping for approximately 1 year and then crossed over for an additional year or until the required number of consented subjects was reached. Waiver of consent as obtained in all centers to implement the intervention. Infants were eligible if nonvigorous at birth (poor tone, pale color, or lack of breathing in the first 15 seconds after birth) and were assigned to umbilical cord milking or early cord clamping according to their birth hospital randomization assignment. The baseline characteristics and outcomes were collected following deferred informed consent. The primary outcome was admission to the neonatal intensive care unit for predefined criteria. The main safety outcome was hypoxic-ischemic encephalopathy. Data were analyzed by the intention-to-treat concept. RESULTS: Among 16,234 screened newborns, 1780 were eligible (905 umbilical cord milking, 875 early cord clamping), and 1730 had primary outcome data for analysis (97% of eligible; 872 umbilical cord milking, 858 early cord clamping) either via informed consent (606 umbilical cord milking, 601 early cord clamping) or waiver of informed consent (266 umbilical cord milking, 257 early cord clamping). The difference in the frequency of neonatal intensive care unit admission using predefined criteria between the umbilical cord milking (23%) and early cord clamping (28%) groups did not reach statistical significance (modeled odds ratio, 0.69; 95% confidence interval, 0.41-1.14). Umbilical cord milking was associated with predefined secondary outcomes, including higher hemoglobin (modeled mean difference between umbilical cord milking and early cord clamping groups 0.68 g/dL, 95% confidence interval, 0.31-1.05), lower odds of abnormal 1-minute Apgar scores (Apgar ≤3, 30% vs 34%, crude odds ratio, 0.72; 95% confidence interval, 0.56-0.92); cardiorespiratory support at delivery (61% vs 71%, modeled odds ratio, 0.57; 95% confidence interval, 0.33-0.99), and therapeutic hypothermia (3% vs 4%, crude odds ratio, 0.57; 95% confidence interval, 0.33-0.99). Moderate-to-severe hypoxic-ischemic encephalopathy was significantly less common with umbilical cord milking (1% vs 3%, crude odds ratio, 0.48; 95% confidence interval, 0.24-0.96). No significant differences were observed for normal saline bolus, phototherapy, abnormal 5-minute Apgar scores (Apgar ≤6, 15.7% vs 18.8%, crude odds ratio, 0.81; 95% confidence interval, 0.62-1.06), or a serious adverse event composite of death before discharge. CONCLUSION: Among nonvigorous infants born at 35 to 42 weeks' gestation, umbilical cord milking did not reduce neonatal intensive care unit admission for predefined criteria. However, infants in the umbilical cord milking arm had higher hemoglobin, received less delivery room cardiorespiratory support, had a lower incidence of moderate-to-severe hypoxic-ischemic encephalopathy, and received less therapeutic hypothermia. These data may provide the first randomized controlled trial evidence that umbilical cord milking in nonvigorous infants is feasible, safe and, superior to early cord clamping.

A Comprehensive Immune Cell Atlas of Cystic Kidney Disease Reveals the Involvement of Adaptive Immune Cells in Injury-Mediated Cyst Progression in Mice.

BACKGROUND: Inducible disruption of cilia-related genes in adult mice results in slowly progressive cystic disease, which can be greatly accelerated by renal injury. METHODS: To identify in an unbiased manner modifier cells that may be influencing the differential rate of cyst growth in injured versus non-injured cilia mutant kidneys at a time of similar cyst severity, we generated a single-cell atlas of cystic kidney disease. We conducted RNA-seq on 79,355 cells from control mice and adult-induced conditional Ift88 mice (hereafter referred to as cilia mutant mice) that were harvested approximately 7 months post-induction or 8 weeks post 30-minute unilateral ischemia reperfusion injury. RESULTS: Analyses of single-cell RNA-seq data of CD45+ immune cells revealed that adaptive immune cells differed more in cluster composition, cell proportion, and gene expression than cells of myeloid origin when comparing cystic models with one another and with non-cystic controls. Surprisingly, genetic deletion of adaptive immune cells significantly reduced injury-accelerated cystic disease but had no effect on cyst growth in non-injured cilia mutant mice, independent of the rate of cyst growth or underlying genetic mutation. Using NicheNet, we identified a list of candidate cell types and ligands that were enriched in injured cilia mutant mice compared with aged cilia mutant mice and non-cystic controls that may be responsible for the observed dependence on adaptive immune cells during injury-accelerated cystic disease. CONCLUSIONS: Collectively, these data highlight the diversity of immune cell involvement in cystic kidney disease.

A transgenic Alx4-CreER mouse to analyze anterior limb and nephric duct development.

BACKGROUND: Genetic tools to study gene function and the fate of cells in the anterior limb bud are very limited. RESULTS: We describe a transgenic mouse line expressing CreERT2 from the Aristaless-like 4 (Alx4) promoter that induces recombination in the anterior limb. Cre induction at embryonic day 8.5 revealed that Alx4-CreERT2 labeled cells using the mTmG Cre reporter contributed to anterior digits I to III as well as the radius of the forelimb. Cre activity is expanded further along the AP axis in the hindlimb than in the forelimb resulting in some Cre reporter cells contributing to digit IV. Induction at later time points labeled cells that become progressively restricted to more anterior digits and proximal structures. Comparison of Cre expression from the Alx4 promoter transgene with endogenous Alx4 expression reveals Cre expression is slightly expanded posteriorly relative to the endogenous Alx4 expression. Using Alx4-CreERT2 to induce loss of intraflagellar transport 88 (Ift88), a gene required for ciliogenesis, hedgehog signaling, and limb patterning, did not cause overt skeletal malformations. However, the efficiency of deletion, time needed for Ift88 protein turnover, and for cilia to regress may hinder using this approach to analyze cilia in the limb. Alx4-CreERT2 is also active in the mesonephros and nephric duct that contribute to the collecting tubules and ducts of the adult nephron. Embryonic activation of the Alx4-CreERT2 in the Ift88 conditional line results in cyst formation in the collecting tubules/ducts. CONCLUSION: Overall, the Alx4-CreERT2 line will be a new tool to assess cell fates and analyze gene function in the anterior limb, mesonephros, and nephric duct.

Early brain and abdominal oxygenation in extremely low birth weight infants.

BACKGROUND: Extremely low birth weight (ELBW) infants are at risk for end-organ hypoxia and ischemia. Regional tissue oxygenation of the brain and gut as monitored with near-infrared spectroscopy (NIRS) may change with postnatal age, but normal ranges are not well defined. METHODS: A prospective study of ELBW preterm infants utilized NIRS monitoring to assess changes in cerebral and mesenteric saturation (Csat and Msat) over the first week after birth. This secondary study of a multicenter trial comparing hemoglobin transfusion thresholds assessed cerebral and mesenteric fractional tissue oxygen extraction (cFTOE and mFTOE) and relationships with perinatal variables. RESULTS: In 124 infants, both Csat and Msat declined over the first week, with a corresponding increase in oxygen extraction. With lower gestational age, lower birth weight, and 5-min Apgar score ≤5, there was a greater increase in oxygen extraction in the brain compared to the gut. Infants managed with a lower hemoglobin transfusion threshold receiving ≥2 transfusions in the first week had the lowest Csat and highest cFTOE (p < 0.001). CONCLUSION: Brain oxygen extraction preferentially increased in more immature and anemic preterm infants. NIRS monitoring may enhance understanding of cerebral and mesenteric oxygenation patterns and inform future protective strategies in the preterm ELBW population. IMPACT: Simultaneous monitoring of cerebral and mesenteric tissue saturation demonstrates the balance of oxygenation between preterm brain and gut and may inform protective strategies. Over the first week, oxygen saturation of the brain and gut declines as oxygen extraction increases. A low hemoglobin transfusion threshold is associated with lower cerebral saturation and higher cerebral oxygen extraction compared to a high hemoglobin transfusion threshold, although this did not translate into clinically relevant differences in the TOP trial primary outcome. Greater oxygen extraction by the brain compared to the gut occurs with lower gestational age, lower birth weight, and 5-min Apgar score ≤5.

Kidney resident macrophages in the rat have minimal turnover and replacement by blood monocytes.

Kidney resident macrophages (KRMs) are involved in maintaining renal homeostasis and in controlling the pathological outcome of acute kidney injury and cystic kidney disease in mice. In adult mice, KRMs maintain their population through self-renewal with little or no input from the peripheral blood. Despite recent data suggesting that a transcriptionally similar population of KRM-like cells is present across species, the idea that they are self-renewing and minimally dependent on peripheral blood input in other species has yet to be proven due to the lack of an appropriate model and cross-species expression markers. In this study, we used our recently identified cross-species KRM cell surface markers and parabiosis surgery in inbred Lewis rats to determine if rat KRMs are maintained independent of peripheral blood input, similar to their mouse counterparts. Flow cytometry analysis indicated that parabiosis surgery in the rat results in the establishment of chimerism of T/B cells, neutrophils, and monocyte-derived infiltrating macrophages in the blood, spleen, and kidney 3 wk after parabiosis surgery. Analysis of KRMs using the cell surface markers CD81 and C1q indicated that these cells have minimal chimerism and, therefore, receive little input from the peripheral blood. These data indicate that KRM properties are conserved in at least two different species.NEW & NOTEWORTHY In this report, we performed parabiosis surgery on inbred Lewis rats and showed that rat kidney resident macrophages (KRMs), identified using our novel cross-species markers, are minimally dependent on peripheral blood input. Thus, for the first time, to our knowledge, we confirm that a hallmark of mouse KRMs is also present in KRMs isolated from another species.

Early extubation to noninvasive respiratory support of former preterm lambs improves long-term respiratory outcomes.

Invasive mechanical ventilation (IMV) and exposure to oxygen-rich gas during early postnatal life are contributing factors for long-term pulmonary morbidities faced by survivors of preterm birth and bronchopulmonary dysplasia. The duration of IMV that leads to long-term pulmonary morbidities is unknown. We compared two durations of IMV (3 h vs. 6 days) during the first 6-7 days of postnatal life in preterm lambs to test the hypothesis that minimizing the duration of IMV will improve long-term respiratory system mechanics and structural outcomes later in life. Moderately preterm (∼85% gestation) lambs were supported by IMV for either 3 h or 6 days before weaning from all respiratory support to become former preterm lambs. Respiratory system mechanics and airway reactivity were assessed monthly from 1 to 6 mo of chronological postnatal age by the forced oscillation technique. Quantitative morphological measurements were made for smooth muscle accumulation around terminal bronchioles and indices of alveolar formation. Minimizing IMV to 3 h led to significantly better (P < 0.05) baseline respiratory system mechanics and less reactivity to methacholine in the first 3 mo of chronological age (2 mo corrected age), significantly less (P < 0.05) accumulation of smooth muscle around peripheral resistance airways (terminal bronchioles), and significantly better (P < 0.05) alveolarization at the end of 5 mo corrected age compared with continuous IMV for 6 days. We conclude that limiting the duration of IMV following preterm birth of fetal lambs leads to better respiratory system mechanics and structural outcomes later in life.

Early infiltrating macrophage subtype correlates with late-stage phenotypic outcome in a mouse model of hepatorenal fibrocystic disease.

Hepatorenal fibrocystic disease (HRFCD) is a genetically inherited disorder related to primary cilia dysfunction in which patients display varying levels of fibrosis, bile duct expansion, and inflammation. In mouse models of HRFCD, the phenotype is greatly impacted by the genetic background in which the mutation is placed. Macrophages are a common factor associated with progression of HRFCD and are also strongly influenced by the genetic background. These data led us to hypothesize that macrophage subtypes that change in relation to the genetic background are responsible for the variable phenotypic outcomes in HRFCD. To test this hypothesis, we utilized a mouse model of HRFCD (Ift88Orpk mice) on the C57BL/6 and BALB/c inbred backgrounds that have well-documented differences in macrophage subtypes. Our analyses of infiltrating macrophage subtypes confirm that genetic strain influences the subtype of infiltrating macrophage present during normal postnatal liver development and in Ift88Orpk livers (Ly6clo in C57BL/6 vs Ly6chi in BALB/c). Each infiltrating macrophage subtype was similarly associated with a unique phenotypic outcome as analysis of liver tissue shows that C57BL/6 Ift88Orpk mice have increased bile duct expansion, but reduced levels of fibrosis compared to BALB/c Ift88Orpk livers. RNA sequencing data suggest that the ability to infiltrate macrophage subtypes to influence the phenotypic outcome may be due to unique ligand-receptor signaling between infiltrating macrophages and cilia dysfunctional biliary epithelium. To evaluate whether specific macrophage subtypes cause the observed phenotypic divergence, we analyzed the liver phenotype in BALB/c Ift88Orpk mice on a CCR2-/- background. Unexpectedly, the loss of Ly6chi macrophages, which were strongly enriched in BALB/c Ift88Orpk mice, did not significantly alter liver fibrosis. These data indicate that macrophage subtypes may correlate with HRFCD phenotypic outcome, but do not directly cause the pathology.

Initial Laparotomy Versus Peritoneal Drainage in Extremely Low Birthweight Infants With Surgical Necrotizing Enterocolitis or Isolated Intestinal Perforation: A Multicenter Randomized Clinical Trial.

OBJECTIVE: The aim of this study was to determine which initial surgical treatment results in the lowest rate of death or neurodevelopmental impairment (NDI) in premature infants with necrotizing enterocolitis (NEC) or isolated intestinal perforation (IP). SUMMARY BACKGROUND DATA: The impact of initial laparotomy versus peritoneal drainage for NEC or IP on the rate of death or NDI in extremely low birth weight infants is unknown. METHODS: We conducted the largest feasible randomized trial in 20 US centers, comparing initial laparotomy versus peritoneal drainage. The primary outcome was a composite of death or NDI at 18 to 22 months corrected age, analyzed using prespecified frequentist and Bayesian approaches. RESULTS: Of 992 eligible infants, 310 were randomized and 96% had primary outcome assessed. Death or NDI occurred in 69% of infants in the laparotomy group versus 70% with drainage [adjusted relative risk (aRR) 1.0; 95% confidence interval (CI): 0.87-1.14]. A preplanned analysis identified an interaction between preoperative diagnosis and treatment group (P = 0.03). With a preoperative diagnosis of NEC, death or NDI occurred in 69% after laparotomy versus 85% with drainage (aRR 0.81; 95% CI: 0.64-1.04). The Bayesian posterior probability that laparotomy was beneficial (risk difference <0) for a preoperative diagnosis of NEC was 97%. For preoperative diagnosis of IP, death or NDI occurred in 69% after laparotomy versus 63% with drainage (aRR, 1.11; 95% CI: 0.95-1.31); Bayesian probability of benefit with laparotomy = 18%. CONCLUSIONS: There was no overall difference in death or NDI rates at 18 to 22 months corrected age between initial laparotomy versus drainage. However, the preoperative diagnosis of NEC or IP modified the impact of initial treatment.

Association of Intrapartum Drugs with Spontaneous Intestinal Perforation: A Single-Center Retrospective Review.

OBJECTIVE: Spontaneous intestinal perforation (SIP) occurs commonly in extremely low gestational age newborns (ELGANs; <30 weeks' GA). Early, concurrent neonatal use of indomethacin (Neo_IN) and hydrocortisone (Neo_HC) is a known risk for SIP. Mothers in premature labor often receive indomethacin (Mat_IN) for tocolysis and steroids (Mat_S) for fetal maturation. Coincidentally, ELGANs may receive Neo_IN or Neo_HC within the first week of life. There are limited data on the effect of combined exposures to maternal and neonatal medications. We hypothesized that proximity exposure to these medications may increase the risk of SIP. STUDY DESIGN: We reviewed the medical records of ELGANs from June 2014 to December 2019 at a single level III neonatal intensive care unit. We compared antenatal and postnatal indomethacin and steroid use between neonates with and without SIP. For analysis, chi-square, Student's t-test, Fisher's exact test, and Mann-Whitney U tests were used. RESULTS: Among 417 ELGANs, SIP was diagnosed in 23, predominantly in neonates < 26 weeks' GA (n = 21/126, 16.7%). Risk factors analysis focused on this GA cohort in which SIP was most prevalent. Mat_IN administration within 2 days of delivery increased SIP risk (odds ratio: 3; 95% confidence interval: 1.25-7.94; p = 0.036). Neo_HC was not independently associated with SIP (p = 0.38). A higher proportion of SIP group had close temporal exposure of Mat_IN and Neo_HC compared with the non-SIP group, though not statistically significant (14 vs. 7%, p = 0.24). CONCLUSION: Peripartum Mat_IN was associated with increased risk for SIP in this small study sample. Larger studies are needed to further delineate SIP risk from the interaction of peripartum maternal medication with early postnatal therapies and disease pathophysiology. KEY POINTS: · Perinatal indomethacin is associated with SIP in preterm infants born at less than 26 weeks.. · Temporal proximity of prenatal/postnatal medication exposure matters.. · Indomethacin and Hydrocortisone the risks, benefits, and timing related to SIP..