Recapitulating porcine cardiac development in vitro: from expanded potential stem cell to embryo culture models

Domestic pigs (Sus scrofa) share many genetic, anatomical, and physiological traits with humans and therefore constitute an excellent preclinical animal model. Fundamental understanding of the cellular and molecular processes governing early porcine cardiogenesis is critical for developing advanced porcine models used for the study of heart diseases and new regenerative therapies. Here, we provide a detailed characterization of porcine cardiogenesis based on fetal porcine hearts at various developmental stages and cardiac cells derived from porcine expanded pluripotent stem cells (pEPSCs), i.e., stem cells having the potential to give rise to both embryonic and extraembryonic tissue. We notably demonstrate for the first time that pEPSCs can differentiate into cardiovascular progenitor cells (CPCs), functional cardiomyocytes (CMs), epicardial cells and epicardial-derived cells (EPDCs) in vitro. Furthermore, we present an enhanced system for whole-embryo culture which allows continuous ex utero development of porcine post-implantation embryos from the cardiac crescent stage (ED14) up to the cardiac looping (ED17) stage. These new techniques provide a versatile platform for studying porcine cardiac development and disease modeling.

Cell cycle defects underlie childhood-onset cardiomyopathy associated with Noonan syndrome

Childhood-onset myocardial hypertrophy and cardiomyopathic changes are associated with significant morbidity and mortality in early life, particularly in patients with Noonan syndrome, a multisystemic genetic disorder caused by autosomal dominant mutations in genes of the Ras-MAPK pathway. Although the cardiomyopathy associated with Noonan syndrome (NS-CM) shares certain cardiac features with the hypertrophic cardiomyopathy caused by mutations in sarcomeric proteins (HCM), such as pathological myocardial remodeling, ventricular dysfunction, and increased risk for malignant arrhythmias, the clinical course of NS-CM significantly differs from HCM. This suggests a distinct pathophysiology that remains to be elucidated. Here, through analysis of sarcomeric myosin conformational states, histopathology, and gene expression in left ventricular myocardial tissue from NS-CM, HCM, and normal hearts complemented with disease modeling in cardiomyocytes differentiated from patient-derived PTPN11 N308S/+ induced pluripotent stem cells, we demonstrate distinct disease phenotypes between NS-CM and HCM and uncover cell cycle defects as a potential driver of NS-CM.

Sequential Defects in Cardiac Lineage Commitment and Maturation Cause Hypoplastic Left Heart Syndrome

BACKGROUND

Complex molecular programs in specific cell lineages govern human heart development. Hypoplastic left heart syndrome (HLHS) is the most common and severe manifestation within the spectrum of left ventricular outflow tract obstruction defects occurring in association with ventricular hypoplasia. The pathogenesis of HLHS is unknown, but hemodynamic disturbances are assumed to play a prominent role.

METHODS

To identify perturbations in gene programs controlling ventricular muscle lineage development in HLHS, we performed whole-exome sequencing of 87 HLHS parent-offspring trios, nuclear transcriptomics of cardiomyocytes from ventricles of 4 patients with HLHS and 15 controls at different stages of heart development, single cell RNA sequencing, and 3D modeling in induced pluripotent stem cells from 3 patients with HLHS and 3 controls.

RESULTS

Gene set enrichment and protein network analyses of damaging de novo mutations and dysregulated genes from ventricles of patients with HLHS suggested alterations in specific gene programs and cellular processes critical during fetal ventricular cardiogenesis, including cell cycle and cardiomyocyte maturation. Single-cell and 3D modeling with induced pluripotent stem cells demonstrated intrinsic defects in the cell cycle/unfolded protein response/autophagy hub resulting in disrupted differentiation of early cardiac progenitor lineages leading to defective cardiomyocyte subtype differentiation/maturation in HLHS. Premature cell cycle exit of ventricular cardiomyocytes from patients with HLHS prevented normal tissue responses to developmental signals for growth, leading to multinucleation/polyploidy, accumulation of DNA damage, and exacerbated apoptosis, all potential drivers of left ventricular hypoplasia in absence of hemodynamic cues.

CONCLUSIONS

Our results highlight that despite genetic heterogeneity in HLHS, many mutations converge on sequential cellular processes primarily driving cardiac myogenesis, suggesting novel therapeutic approaches.

A radiometric study of factors affecting drug output of jet nebulizers

Jet nebulizers show an unreasonable variation in drug output and nebulization rates that leads to clinical and regulatory problems. Current evaluation methods appear inadequate for the purpose. Our objective was to evaluate Technetium-99m radiometry to study nebulizer parameters and the factors influencing it quantitatively. Drug output, output rate and residual mass and the effect of excipient, temperature, surface tension, air-jet speed, and equipment brand and aging were studied. Though nebulization of radiolabeled drugs followed first-order kinetics, the rates were significantly different; the heaviest drug (Tc-99m colloid) and Tc-99m salbutamol had the least nebulization. Nebulization rate for the first minute was invariably higher than the mean rate signifying the concentration effect of the solute. Drug residue was 35-75%. Drug output of different nebulizer chamber and air compressor brands was different to the extent of 270% and 180% respectively. ‘Aging’ of fluid chamber, cold drug fluid and obstruction in air-jet resulted in significant reduction in output, while addition of 2% saline as excipient did not change the output rate. Addition of ethyl alcohol resulted in a maximum of 260% enhancement (with Tc-99m salbutamol), while further reduction in surface tension was counterproductive irrespective of the drug used. We conclude that radiometry can provide valuable parametric information on the performance of different jet nebulizers.

Detecting protein losing enteropathy by Tc-99m dextran scintigraphy: a novel experience

OBJECTIVE

To evaluate protien using enteropathy by Tc-99m dextran scintigraphy.

METHODS

Methods for detecting protein loss from the intestine revolve around fecal nitrogen excretion, the clearance of alpha-1 antitrypsin in stools and by endoscopic biopsy.

RESULT

The diagnosis of protein-losing enteropathy (PLE) can also be established by a scintigraphic method that is noninvasive, simple and requires no patient preparation or motivation. This diagnostic modality can also delineate the site of protein loss, thereby offering a targeted approach, and if need be, surgery. Radiolabelling of a non-protein, noncolloidal, nonparticulate and biofriendly molecule like dextran with Technetium-99m for imaging enteric protein loss was utilized in imaging eight children with PLE.

CONCLUSION

The results were encouraging. The authors advocate the use of this diagnostic tool in identifying patients with PLE, particularly in the pediatric age group.

Interactions between the nematode parasite of pigs, Ascaris suum, and the earthworm Aporrectodea longa

Pig faeces in which Ascaris suum eggs had been embryonating for 57 days were placed in buckets of soil containing either 30 or no earth-worms (Aporrectodea longa). When present, earthworms consumed the faeces and transported the eggs down into the soil, without inflicting any visible damage on the eggs. In later experiments 10 earthworms from the above experiment were fed to each of ten pigs, and another 40 earthworms were dissected. None of the 10 pigs became infected with A. suum through consumption of earthworms, and none of the dissected earthworms were found to contain A. suum larvae. This experiment indicates that A. longa did not act as a paratenic host for A. suum but shows that earthworms are very efficient in transporting A. suum eggs from faeces deposited on the soil surface into the soil.

Interactions between the nematode parasite of pigs, Ascaris suum, and the earthworm Aporrectodea longa

Pig faeces in which Ascaris suum eggs had been embryonating for 57 days were placed in buckets of soil containing either 30 or no earth-worms (Aporrectodea longa). When present, earthworms consumed the faeces and transported the eggs down into the soil, without inflicting any visible damage on the eggs. In later experiments 10 earthworms from the above experiment were fed to each of ten pigs, and another 40 earthworms were dissected. None of the 10 pigs became infected with A. suum through consumption of earthworms, and none of the dissected earthworms were found to contain A. suum larvae. This experiment indicates that A. longa did not act as a paratenic host for A. suum but shows that earthworms are very efficient in transporting A. suum eggs from faeces deposited on the soil surface into the soil.

Induction of traps by Ostertagia ostertagi larvae, chlamydospore production and growth rate in the nematode-trapping fungus Duddingtonia flagrans

Biological control of parasitic nematodes of domestic animals can be achieved by feeding host animals chlamydospores of the nematode-trapping fungus Duddingtonia flagrans. In the host faeces, D. flagrans develop traps that may catch nematode larvae. In experiments on agar, D. flagrans had a growth rate between 15 and 60 mm/week at temperatures between 20 and 30 degrees C. The presence of nematodes induces the fungus to produce traps. The rate of trap formation in D. flagrans has an optimum at 30 degrees C, producing 700-800 traps/cm2/2 days, when induced by 20 nematodes/cm2 on agar. Approaching 10 and 35 degrees C the ability to produce traps is gradually reduced. The response of chlamydospore production on agar to changes in temperature is the same as that for trap formation. On agar, at 10, 20 and 30 degrees C D. flagrans loses its trap inducibility after 2-3 weeks. During the ageing process, increasing numbers of chlamydospores are produced up to a certain limit. The time for reaching maximum chlamydospore concentration coincided with the time for loss of induction potential. The implications of these results in relation to biological control in faeces are discussed.

Scintigraphic diagnosis of gastrointestinal bleeding with 99Tcm-dextran

Intravenously administered dextran is used clinically as a plasma expander. The aim of this study was to assess the use of 99Tcm-dextran in the diagnosis of gastrointestinal (GI) blood leaks. Twenty-one patients with GI blood loss underwent 99Tcm-dextran scintigraphy, 17 of whom were found to be positive. Pathologic or 99Tcm-RBC (red blood cell) blood pool correlation was possible in 15 cases, while 2 were unconfirmed. No case had a positive 99Tcm-RBC blood pool study and a negative 99Tcm-dextran study. Images obtained with 99Tcm-dextran were generally better than those with 99Tcm-RBC. This agent may have several other advantages over 99Tcm-RBC blood pool and 99Tcm-sulphur colloid scintigraphy for detecting GI blood loss.

Unusual diversity of human rotavirus G and P genotypes in India

Between April and December 1993, we determined P and G genotypes of group A rotavirus strains obtained from children admitted to diarrhea treatment centers in five Indian cities. From a total of 63 rotavirus-positive specimens, we identified 10 different strains with five different G genotypes and four distinct P types by using reverse transcription-PCR. The common worldwide strains G1P8, G2P4, G3P8, and G4P8 were underrepresented among Indian children (33%), whereas strains of P type 6 (G1P6, G2P6, G3P6, G4P6, and G9P6), which primarily infect asymptomatic newborns but are rare in children with diarrhea were common in India (43%). Of these, G9P6, a strain not previously reported to be found in children with diarrhea, was the most prevalent (22%). Eleven percent of the strains were nontypeable, and another 11% of the specimens had mixed infections. Using digoxigenin-labeled, genotype-specific hybridization probes, we confirmed all G9 strains and mixed infections tested and identified three nontypeable strains (one G9 and two P8). The epidemiological significance of G9 rotavirus strains, if confirmed in other settings, may have important implications for vaccine development.