III-nitride m-plane violet narrow ridge edge-emitting laser diodes with sidewall passivation using atomic layer deposition.

A novel deep-ridge laser structure with atomic-layer deposition (ALD) sidewall passivation was proposed that enhances the optical characteristics of 8-µm ridge width III-nitride violet lasers on freestanding m-plane GaN substrates. The internal loss was determined using the variable stripe length method, where the laser structure with ALD sidewall passivation showed lower internal loss compared to the conventional shallow-ridge laser design. ALD sidewall passivation plays a critical role in device improvements; compared to the lasers without ALD sidewall passivation, the lasers with ALD sidewall passivation yield improved optoelectrical performance and longer lifetime under continuous-wave operation at high current density. This work demonstrates the importance of ALD sidewall passivation to laser performance, which enables high energy efficiency.

CHARMM-GUI Membrane Builder for Lipid Droplet Modeling and Simulation.

Lipid droplets (LDs) are organelles that are necessary for eukaryotic and prokaryotic metabolism and energy storage. They have a unique structure consisting of a spherical phospholipid monolayer encasing neutral lipids such as triacylglycerol (TAG). LDs have garnered increased interest for their implications in disease and for drug delivery applications. Consequently, there is an increased need for tools to study their structure, composition, and dynamics in biological contexts. In this work, we utilize CHARMM-GUI Membrane Builder to simulate and analyze LDs with and without a plant LD protein, oleosin. The results show that Membrane Builder can generate biologically relevant all-atom LD systems with relatively short equilibration times using a new TAG library having optimized headgroup parameters. TAG molecules originally inserted into a lipid bilayer aggregate in the membrane center, forming a TAG-only core flanked by two monolayers. The TAG-only core thickness stably grows with increasing TAG mole fraction. A 70 % TAG system has a core that is thick enough to house oleosin without its interactions with the distal leaflet or disruption of its secondary structure. We hope that Membrane Builder can aid in the future study of LD systems, including their structure and dynamics with and without proteins.

ERK3 and DGKζ interact to modulate cell motility in lung cancer cells.

Extracellular signal-regulated kinase 3 (ERK3) promotes cell migration and tumor metastasis in multiple cancer types, including lung cancer. The extracellular-regulated kinase 3 protein has a unique structure. In addition to the N-terminal kinase domain, ERK3 includes a central conserved in extracellular-regulated kinase 3 and ERK4 (C34) domain and an extended C-terminus. However, relatively little is known regarding the role(s) of the C34 domain. A yeast two-hybrid assay using extracellular-regulated kinase 3 as bait identified diacylglycerol kinase ζ (DGKζ) as a binding partner. DGKζ was shown to promote migration and invasion in some cancer cell types, but its role in lung cancer cells is yet to be described. The interaction of extracellular-regulated kinase 3 and DGKζ was confirmed by co-immunoprecipitation and in vitro binding assays, consistent with their co-localization at the periphery of lung cancer cells. The C34 domain of ERK3 was sufficient for binding to DGKζ, while extracellular-regulated kinase 3 bound to the N-terminal and C1 domains of DGKζ. Surprisingly, in contrast to extracellular-regulated kinase 3, DGKζ suppresses lung cancer cell migration, suggesting DGKζ might inhibit ERK3-mediated cell motility. Indeed, co-overexpression of exogenous DGKζ and extracellular-regulated kinase 3 completely blocked the ability of ERK3 to promote cell migration, but DGKζ did not affect the migration of cells with stable ERK3 knockdown. Furthermore, DGKζ had little effect on cell migration induced by overexpression of an ERK3 mutant missing the C34 domain, suggesting DGKζ requires this domain to prevent ERK3-mediated increase in cell migration. In summary, this study has identified DGKζ as a new binding partner and negative regulator of extracellular-regulated kinase 3 in controlling lung cancer cell migration.

Molecular Condensate in a Membrane: A Tugging Game between Hydrophobicity and Polarity with Its Biological Significance.

Lipid self-organization and lipid-water interfaces have been an increasingly important topic positioned at the crossroads of physical chemistry and biology. Some neutral lipids can partition into the biomembrane and play an important biological role. In this study, we have used all-atom molecular dynamics simulations to dissect the partition, aggregation, flip-flop, and modulation of neutral lipids including (i) menaquinone/menaquinol, (ii) ubiquinone/ubiquinol, and (iii) triacylglycerol. The partitioning of these molecules is driven by the balancing force between headgroup hydrophilicity and acyl chain hydrophobicity as well as the lipid shapes. We then discuss the emerging questions in this area, share our own perspectives, and mention the development of the CHARMM-GUI membrane modeling platform, which enables further computational investigations into those questions.

Comparative Molecular Dynamics Simulation Studies of Realistic Eukaryotic, Prokaryotic, and Archaeal Membranes.

We present a comparative all-atom molecular dynamics simulation study of 18 biomembrane systems with lipid compositions corresponding to eukaryotic, bacterial, and archaebacterial membranes together with three single-component lipid bilayers. A total of 105 lipid types used in this study include diverse sterols and glycerol-based lipids with acyl chains of various lengths, unsaturation degrees, and branched or cyclic moieties. Our comparative analysis provides deeper insight into the influences of sterols and lipid unsaturation on the structural and mechanical properties of these biomembranes, including water permeation into the membrane hydrocarbon core. For sterol-containing membranes, sterol fraction is correlated with the membrane thickness, the area compressibility modulus, and lipid order but anticorrelated with the area per lipid and sterol tilt angles. Similarly, for all 18 biomembranes, lipid order is correlated with the membrane thickness and area compressibility modulus. Sterols and lipid unsaturation produce opposite effects on membrane thickness, but only sterols influence water permeation into the membrane. All membrane systems are accessible for public use in CHARMM-GUI Archive. They can be used as templates to expedite future modeling of realistic cell membranes with transmembrane and peripheral membrane proteins to study their structure, dynamics, molecular interactions, and function in a nativelike membrane environment.

Glycemic Control and Aspirin Resistance in Patients Taking Low-Dose Aspirin for Pre-eclampsia Prevention.

OBJECTIVES: To assess the association between aspirin and glycemic control in diabetic, pregnant patients, and the risk for aspirin resistance in those with poor glycemic control across gestation taking low-dose aspirin (LDA) for pre-eclampsia (PEC) prevention. STUDY DESIGN: We performed a secondary analysis of samples collected during the Maternal-Fetal Medicine Units trial of LDA for PEC prevention. A subset of insulin-controlled diabetic patient samples on placebo or 60 mg aspirin daily were evaluated. Glycosylated hemoglobin was measured at randomization, mid-second trimester, and third trimester time points. Thromboxane B2 (TXB2) measurements were previously assessed as part of the original study. Primary outcome was the effect of LDA on glycosylated hemoglobin levels compared with placebo across gestation. RESULTS: Levels of glycosylated hemoglobin increased across gestation in the placebo group (2,067.7 [interquartile range, IQR: 1,624.6-2,713.5 µg/mL] vs. 2,461.9 [1,767.0-3,209.9 µg/mL] vs. 3,244.3 [2,691.5-4,187.0 µg/mL]; p < 0.01) compared with no difference in levels of glycosylated hemoglobin across gestation in the LDA group (2,186.4 [IQR: 1,462.3-3,097.7 µg/mL] vs. 2,337.1 [1,327.7-5,932.6 µg/mL] vs. 2,532.9 [1,804.9-5,511.8 µg/mL]; p = 0.78). Higher levels of glycosylated hemoglobin were associated with increased TXB2 levels prior to randomization (r = 0.67, p < 0.05). Incomplete TXB2 was higher in pregnancies with increasing levels of glycosylated hemoglobin compared with those with decreasing levels of glycosylated hemoglobin across gestation (69.2 vs. 18.1%, p = 0.02). CONCLUSION: LDA exposure may be beneficial to glycemic control in this patient population. Additionally, poor glycemic control is associated with a higher level of TXB2 in diabetic pregnant patients on LDA. Higher doses of aspirin may be required in these patients to prevent development of PEC. KEY POINTS: · Low-dose aspirin may improve glycemic control.. · Poor glycemic control increases risk for aspirin resistance.. · Higher doses of aspirin may be required for pre-eclampsia prevention..

Maternal and fetal outcomes in pregnant women with pulmonary hypertension: The impact of left heart disease.

Background: Pulmonary hypertension (PH) due to left heart disease (World Health Organization (WHO) Group 2 PH) is the largest PH subgroup, however most reports of PH in pregnancy focus on patients with pulmonary arterial hypertension (WHO Group 1 PH). We evaluated pregnancy outcomes across WHO PH subgroups. Methods: We performed a retrospective single center cohort study of maternal and fetal outcomes in pregnant women with PH (2004-2018). Results: We analyzed outcomes of 70 pregnancies in 70 women with PH (30 ± 6 years-old), classified as WHO Group 1 PH (12 (17%)), Group 2 PH (45 (64%)), Group 3 PH (4 (6%)) and Group 5 PH (9 (13%)). Although no peripartum death occurred, 3 (4.3%) women with WHO Group 2 PH had late mortality (7 ± 4 months post- partum). Additionally, 33 major adverse cardiac events occurred in 26 (37%) women, preterm birth occurred in 32 (49%), and post-partum hemorrhage in 10 (14%), such that only 24 (37%) women completed a viable pregnancy free of an adverse cardiac, obstetric or fetal/neonatal event. Major adverse cardiac events were predominantly due to heart failure (24 (73%)), occurring only in WHO Groups 1 and 2 PH (3 (25%) women vs. 17 (38%), p = 0.07), and significantly associated with pre-eclampsia, left ventricular ejection fraction ≤45%, maternal diabetes, and systemic hypertension. Conclusions: WHO Group 2 PH carries similar risk for maternal cardiovascular events when compared to women with WHO Group 1 PH. Further studies evaluating maternal risk in this cohort are needed.

Decline in Sars-CoV-2 antibodies over 6-month follow-up in obstetrical healthcare workers.

PROBLEM: Limited data exists on the temporal trend of the Sars-CoV-2 immunologic response and duration of protection following natural infection. We sought to investigate the presence and duration of Sars-CoV-2 serum antibodies in obstetrical healthcare workers (HCW) on serial assessments over a 6-month period, and to assess rates of vaccine acceptance and reported vaccine side effects among this cohort. METHOD OF STUDY: A prospective cohort study of a convenience sample of obstetrical HCWs at a tertiary hospital. Serum Sars-CoV-2 antibodies for Immunoglobulin G (IgG) and Immunoglobulin M (IgM) were measured longitudinally at four intervals: baseline, 4 weeks, 12 weeks, and 6 months. Participants completed voluntary surveys on COVID19 testing, high-risk exposures, vaccine acceptance, and vaccine side effects. RESULTS: One hundred twenty-six of 150 (84%) HCWs who volunteered for participation completed all four blood draws. Prevalence of seropositive HCWs based on positive Sars-CoV-2 IgG antibodies increased from 2% at baseline to 31% at 12 weeks but declined to 21% by 6 months. Forty-two percent (19/43) of the participants considered seropositive for Sars-CoV-2 IgG antibodies at any of the initial three blood draws converted to seronegative status at the 6-month follow-up. Eighty-seven percent (72/83) of participants who responded to a follow-up survey were willing to accept the COVID19 vaccine. Rates of acceptance did not differ by participant antibody status. Those that experienced symptoms with the first injection were more likely to have positive Sars-CoV-2 IgG antibodies (36.8% vs. 9.6%, p = .01). CONCLUSION: Sars-CoV-2 IgG antibodies wane over time and may not provide prolonged and robust immune protection. This underscores the importance of vaccination and continued research in this area while the COVID19 pandemic continues.

Correlation of echocardiographic probability of pulmonary hypertension with maternal outcomes in pregnant women with elevated right ventricular systolic pressure.

INTRODUCTION: The use of echocardiography to evaluate the probability for pulmonary hypertension (PH) in pregnant women has not been reported or correlated with outcomes. We hypothesized that in women with elevated right ventricular systolic pressure (RVSP) on echocardiography first identified during pregnancy, those with low probability for PH would have fewer major adverse cardiac events (MACE). METHODS: We performed a retrospective cohort study of pregnant women with RVSP >35 mm Hg on echocardiogram first identified during pregnancy. Women were classified as intermediate-high probability for PH (HP) or low probability for PH (LP) based on simplified European Society of Cardiology echocardiographic criteria. Maternal cardiac, obstetric, and fetal outcomes were assessed. RESULTS: A total of 77 women met inclusion criteria (mean age 30 ± 5 years), with 45 (58%) classified as HP and 32 (42%) as LP. There were 21 (27%) women who experienced MACE, more commonly in the HP cohort (HP 18 (40%) women vs. LP 3 (9%) women, P = .01). The echocardiographic criteria for intermediate-high probability of PH identified women at risk for MACE with 85% sensitivity and 52% specificity. The negative predictive value for MACE in women meeting low echocardiographic probability for PH criteria was 91%. CONCLUSIONS: In women with elevated RVSP on echocardiography first identified during pregnancy, those with low echocardiographic PH probability are at significantly lower risk for MACE during pregnancy, though the risk is not eliminated. This may be useful to risk stratify pregnant women with suspected PH, guiding tertiary care referral and invasive catheterization.

PKCα-mediated phosphorylation of the diacylglycerol kinase ζ MARCKS domain switches cell migration modes by regulating interactions with Rac1 and RhoA.

Cells can switch between Rac1 (lamellipodia-based) and RhoA (blebbing-based) migration modes, but the molecular mechanisms regulating this shift are not fully understood. Diacylglycerol kinase ζ (DGKζ), which phosphorylates diacylglycerol to yield phosphatidic acid, forms independent complexes with Rac1 and RhoA, selectively dissociating each from their common inhibitor RhoGDI. DGKζ catalytic activity is required for Rac1 dissociation but is dispensable for RhoA dissociation; instead, DGKζ stimulates RhoA release via a kinase-independent scaffolding mechanism. The molecular determinants that mediate the selective targeting of DGKζ to Rac1 or RhoA signaling complexes are unknown. Here, we show that protein kinase Cα (PKCα)-mediated phosphorylation of the DGKζ MARCKS domain increased DGKζ association with RhoA and decreased its interaction with Rac1. The same modification also enhanced DGKζ interaction with the scaffold protein syntrophin. Expression of a phosphomimetic DGKζ mutant stimulated membrane blebbing in mouse embryonic fibroblasts and C2C12 myoblasts, which was augmented by inhibition of endogenous Rac1. DGKζ expression in differentiated C2 myotubes, which have low endogenous Rac1 levels, also induced substantial membrane blebbing via the RhoA-ROCK pathway. These events were independent of DGKζ catalytic activity, but dependent upon a functional C-terminal PDZ-binding motif. Rescue of RhoA activity in DGKζ-null cells also required the PDZ-binding motif, suggesting that syntrophin interaction is necessary for optimal RhoA activation. Collectively, our results define a switch-like mechanism whereby DGKζ phosphorylation by PKCα plays a role in the interconversion between Rac1 and RhoA signaling pathways that underlie different cellular migration modes.

Addition of vaginal isosorbide mononitrate for labor induction in pregnancies complicated by hypertensive diseases of pregnancy: a randomized controlled trial.

BACKGROUND: Pregnancies complicated by hypertensive disease of pregnancy often require labor induction. Rates of cesarean delivery range from 15% to 60% in this population. Nitric oxide deficiency has been shown to underlay the pathophysiology of preeclampsia, and nitric oxide promotes cervical ripening. OBJECTIVE: We hypothesized that addition of vaginal isosorbide mononitrate for labor induction could decrease the rate of cesarean delivery in pregnancies with hypertensive disease of pregnancy. STUDY DESIGN: This study was a double-blind, placebo-controlled, randomized trial of patients with singleton pregnancy at ≥24 weeks' gestation undergoing labor induction for hypertensive diseases of pregnancy between November 2017 and February 2020. Participants were eligible if their Bishop score was <6 and if their cervical dilation was ≤2 cm. In addition, participants received up to 3 doses of 40 mg isosorbide mononitrate in addition to misoprostol for labor induction. Labor management was per healthcare provider preference. The primary outcome was rate of cesarean delivery. Secondary outcomes included the length of labor and frequency of intrapartum adverse events, including the use of intrapartum antihypertensive agents. RESULTS: 89 women were randomized to the isosorbide mononitrate group, and 87 women were randomized to the placebo group. Cesarean delivery rates were similar in both groups (32.6% vs 25.3%; relative risk, 1.29; 95% confidence interval, 0.81-2.06; P=.39). Maternal headache was increased in patients exposed to isosorbide mononitrate (42.7% vs 31%; relative risk, 1.52; 95% confidence interval, 1.04-2.23; P=.04). Clinical chorioamnionitis was increased in the placebo group (0% vs 8%; P=.02). Secondary outcomes were similar between groups. CONCLUSION: The addition of vaginal isosorbide mononitrate for labor induction in pregnancies complicated by hypertensive disease of pregnancy did not result in fewer cesarean deliveries.

Meconium-stained amniotic fluid and the risk of postcesarean surgical site infection.

OBJECTIVE: To investigate the association between meconium-stained amniotic fluid (MSAF) and postcesarean surgical site infections. METHODS: This was a secondary analysis of the Maternal-Fetal Medicine Units Network (MFMU) Cesarean Registry. Women with a singleton pregnancy attempting labor or induction of labor, who ultimately had a cesarean delivery, were included in the study. Pregnancies complicated by MSAF (n = 4262) and those who did not have MSAF (n = 13,850) were compared. The primary outcome was the incidence of SSI. RESULTS: A total of 18,112 patients were included in the study. 4262 (38%) had meconium-stained amniotic fluid. After accounting for potential confounders in a multivariable logistic regression, meconium-stained amniotic fluid was associated with an increased risk of postoperative surgical site infection (odds ratio 1.16, 95% CI 1.03-1.30). CONCLUSIONS: Meconium-stained amniotic fluid may be associated with an increased risk of postoperative surgical site infection.

Outcomes of Isolated Fetal Ventriculomegaly That Resolve In Utero.

OBJECTIVE: Isolated fetal ventriculomegaly is often an incidental finding on antenatal ultrasound. It is benign in up to 90% of cases, although it can be associated with genetic, structural, and neurocognitive disorders. The literature suggests that over 40% of isolated mild ventriculomegaly will resolve in utero, but it is unclear if resolution decreases the associated risks.The aim of this study is to compare the fetal and neonatal genetic outcomes of ventriculomegaly that persists or resolves on subsequent ultrasound. STUDY DESIGN: This is a retrospective cohort study of women diagnosed with isolated ventriculomegaly via fetal ultrasound at a tertiary referral center between 2011 and 2019. Patients were excluded if other structural anomalies were identified on ultrasound. RESULTS: A total of 49 patients were included in the study, 19 in the resolved ventriculomegaly group and 30 in the persistent ventriculomegaly group. Women in the resolved ventriculomegaly group were more likely to be diagnosed earlier (24 vs. 28 weeks, p = 0.007). Additionally, they were more likely to have mild ventriculomegaly (63 vs. 84%, p = 0.15), and less likely to have structural neurological abnormalities diagnosed on postnatal imaging (5 vs. 17%, p = 0.384), although these were not statistically significant. Aneuploidy risk for resolved compared with persistent ventriculomegaly was similar (5 vs. 7%, p = 0.999). CONCLUSION: This study suggests that resolution of isolated ventriculomegaly in utero may not eliminate the risk of genetic or chromosomal abnormalities in this population and may warrant inclusion as part of the counselling of these at-risk patients. Larger prospective studies are needed to confirm these findings. KEY POINTS: · Ventriculomegaly is known to be associated with genetic and chromosomal abnormalities.. · Resolution of the ventriculomegaly in utero may not eliminate those risks.. · Patients with resolved ventriculomegaly should be offered aneuploidy screening or testing..

Fetal renal artery impedance in pregnancies affected by preeclampsia.

Background Preeclampsia (PE) is a pregnancy-specific vascular endothelial disorder characterized by multi-organ system involvement. This includes the maternal kidneys, with changes such as continuous vasospasm of renal arteries and reduced renal blood flow. However, it is unclear whether similar renal vascular changes are seen in the fetus. This study sought to compare renal artery impedance in fetuses of women with and without PE. Methods This was a prospective Doppler assessment study of the fetal renal artery impedance in 48 singleton fetuses. The group with PE consisted of 24 appropriately grown fetuses in pregnancy complicated by both mild and severe PE and a control group of 24 uncomplicated pregnancies. Doppler studies included renal artery systolic/diastolic (S/D) ratio, pulsatility index (PI), resistance index (RI), and identification of end-diastolic blood flow. Results Fetuses of mothers with PE were more likely to have a lower renal artery Doppler S/D ratio (7.85 [6.4-10.2] vs. 10.8 [7.75-22.5], P = 0.03) and lower RI (0.875 [0.842-0.898] vs. 0.905 [0.872-0.957], P = 0.03). However, there was no statistically significant difference in PI. There was also no difference in the incidence of absent end-diastolic flow. Conclusion This study suggests that PE results in changes in blood flow to the renal arteries of the fetus. This may be associated with long-term adverse health effects later in adulthood.

Contractions: Traditional concepts and their role in modern obstetrics.

Contractions are produced through a complex interplay of hormonal, mechanical, and electrical factors. In labor, contractions are measured using the Montevideo unit. Clinical considerations in labor wherein contraction assessment becomes paramount include the care of women whose labor is complicated by abnormal progress or tachysystole. In an era of obstetrics in which the high cesarean rate is a major issue of concern, there remain many questions as to how to best incorporate contraction monitoring into practice in order to optimize care. Technological advancement has led to the development on new modalities that can be used to study contraction physiology, and there may be an opportunity in the future to apply these methods for use in the clinical setting. This article also makes a case for the need to reevaluate the current measures of uterine contractile activity and the definition of contraction adequacy using updated definitions of normal labor progress.

Intrauterine Pressure Catheter Use Is Associated with an Increased Risk of Postcesarean Surgical Site Infections.

OBJECTIVE: This study aimed to determine if intrapartum placement of an intrauterine pressure catheter (IUPC) is associated with an increased rate of surgical site infections in women undergoing a cesarean delivery. STUDY DESIGN: This was a secondary analysis of the prospective observational Maternal-Fetal Medicine Units Network Vaginal Birth after Cesarean Registry. We compared patients with and without IUPC use. A multivariable logistic regression was performed to evaluate for an association between IUPC use and postcesarean surgical site infections. RESULTS: The study included 16,887 women: 7,441 with IUPC use and 9,446 without IUPC use. After adjustment for potential cofounders, IUPC use was associated with an increased risk of postcesarean infections compared with those without IUPC use (adjusted odds ratio: 1.28; 95% confidence interval: 1.10-1.50; p = 0.002). CONCLUSION: IUPC use is associated with an increased risk of postcesarean surgical site infections. This supports the judicious use of IUPC for limited clinical indications and provides a potential area of focus for reduction in postcesarean infections.

A new worm infiltrating the human cornea: A report of three cases.

PURPOSE: To characterize a new species of parasitic nematode that triggers uveitis. OBSERVATIONS: Three previously healthy, relatively young people each contracted a corneal stromal nematode that, upon surgical removal and examination, did not match any known nematodes. Clinical ocular findings included corneal opacification, visible corneal worms, conjunctival injection, and uveitis. CONCLUSIONS AND IMPORTANCE: The three cases presented here represent a previously undescribed parasitic infection of the cornea by an unidentified nematode. These findings may represent a previously unrecognized zoonotic infection from wildlife sources and potentially a newly documented nematode requiring description. Future clinical findings regarding this newly described nematode are needed to further develop our understanding of the disease.

Regulation of Macropinocytosis by Diacylglycerol Kinase ζ.

Macropinosomes arise from the closure of plasma membrane ruffles to bring about the non-selective uptake of nutrients and solutes into cells. The morphological changes underlying ruffle formation and macropinosome biogenesis are driven by actin cytoskeleton rearrangements under the control of the Rho GTPase Rac1. We showed previously that Rac1 is activated by diacylglycerol kinase ζ (DGKζ), which phosphorylates diacylglycerol to yield phosphatidic acid. Here, we show DGKζ is required for optimal macropinocytosis induced by growth factor stimulation of mouse embryonic fibroblasts. Time-lapse imaging of live cells and quantitative analysis revealed DGKζ was associated with membrane ruffles and nascent macropinosomes. Macropinocytosis was attenuated in DGKζ-null cells, as determined by live imaging and vaccinia virus uptake experiments. Moreover, macropinosomes that did form in DGKζ-null cells were smaller than those found in wild type cells. Rescue of this defect required DGKζ catalytic activity, consistent with it also being required for Rac1 activation. A constitutively membrane bound DGKζ mutant substantially increased the size of macropinosomes and potentiated the effect of a constitutively active Rac1 mutant on macropinocytosis. Collectively, our results suggest DGKζ functions in concert with Rac1 to regulate macropinocytosis.

Centroacinar Cells Are Progenitors That Contribute to Endocrine Pancreas Regeneration.

Diabetes is associated with a paucity of insulin-producing ß-cells. With the goal of finding therapeutic routes to treat diabetes, we aim to find molecular and cellular mechanisms involved in ß-cell neogenesis and regeneration. To facilitate discovery of such mechanisms, we use a vertebrate organism where pancreatic cells readily regenerate. The larval zebrafish pancreas contains Notch-responsive progenitors that during development give rise to adult ductal, endocrine, and centroacinar cells (CACs). Adult CACs are also Notch responsive and are morphologically similar to their larval predecessors. To test our hypothesis that adult CACs are also progenitors, we took two complementary approaches: 1) We established the transcriptome for adult CACs. Using gene ontology, transgenic lines, and in situ hybridization, we found that the CAC transcriptome is enriched for progenitor markers. 2) Using lineage tracing, we demonstrated that CACs do form new endocrine cells after ß-cell ablation or partial pancreatectomy. We concluded that CACs and their larval predecessors are the same cell type and represent an opportune model to study both ß-cell neogenesis and ß-cell regeneration. Furthermore, we show that in cftr loss-of-function mutants, there is a deficiency of larval CACs, providing a possible explanation for pancreatic complications associated with cystic fibrosis.