Reshaping the Preterm Heart: Shifting Cardiac Renin-Angiotensin System Towards Cardioprotection in Rats Exposed to Neonatal High-Oxygen Stress

Background: Approximately 10% of infants are born preterm. Preterm birth leads to short and long-term changes in cardiac shape and function. By using a rat model of neonatal high-oxygen (80%O2) exposure, mimicking the premature hyperoxic transition to the extrauterine environment, we revealed a major role of the renin-angiotensin system peptide Angio II (angiotensin II) and its receptor AT1 (angiotensin receptor type 1) on neonatal O2-induced cardiomyopathy. Here, we tested whether treatment with either orally active compounds of the peptides Angio-(1–7) or alamandine included in cyclodextrin could prevent postnatal cardiac remodeling and the programming of cardiomyopathy induced by neonatal high-O2 exposure. Methods: Sprague-Dawley pups were exposed to room air or 80% O2 from postnatal day 3 (P3) to P10. Neonatal rats were treated orally from P3 to P10 and assessed at P10 and P28. Left ventricular (LV) shapes were characterized by tridimensional computational atlases of ultrasound images in addition to histomorphometry. Results: At P10, high O2-exposed rats presented a smaller, globular and hypertrophied LV shape versus controls. Treatment with cyclodextrin–Angio-(1–7) significantly improved LV function in the O2-exposed neonatal rats and slightly changed LV shape. Cyclodextrin-alamandine and cyclodextrin–Angio-(1–7) treatments similarly reduced hypertrophy at P10 as well as LV remodeling and dysfunction at P28. Both treatments upregulated cardiac angiotensin-converting enzyme 2 in O2-exposed rats at P10 and P28. Conclusions: Our findings demonstrate LV remodeling changes induced by O2-stress and the potential benefits of treatments targeting the cardioprotective renin-angiotensin system axis, supporting the neonatal period as an important window for interventions aiming at preventing cardiomyopathy in people born preterm.

The protocol was prospectively written Yes The primary and secondary endpoints are specified Yes For primary endpoints, a description is provided as to how the type I error multiplicity issue was addressed (e.g., correction for multiple comparisons was or was not used and why). (Note: correction for multiple comparisons is not necessary if the study was exploratory or hypothesis-generating in nature).

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A description of the control group is provided including whether it matched the treated groups. Yes

Inclusion and Exclusion criteria
Inclusion and exclusion criteria for enrollment into the study were defined and are reported in the manuscript. N/A These criteria were set a priori (before commencing the study). N/A

Randomization
Animals were randomly assigned to the experimental groups. If random assignment was not used, adequate explanation has been provided.

Yes
Type and methods of randomization have been described. Yes Allocation concealment was used. N/A Methods used for allocation concealment have been reported. N/A

Blinding
Blinding procedures with regard to masking of group/treatment assignment from the experimenter were used and are described. The rationale for nonblinding of the experimenter has been provided, if such was not performed.

Yes
Blinding procedures with regard to masking of group assignment during outcome assessment were used and are described. Yes If blinding was not performed, the rationale for nonblinding of the person(s) analyzing outcome has been provided. N/A

Sample size and power calculations
Formal sample size and power calculations were conducted before commencing the study based on a priori determined outcome(s) and treatment effect(s), and the data are reported.

N/A
If formal sample size and power calculation was not conducted, a rationale has been provided. N/A

Data Reporting
Baseline characteristics (species, sex, age, strain, chow, bedding, and source) of animals are reported. Yes The number of animals in each group that were randomized, tested, and excluded and that died is reported. If the experimentation involves repeated measurements, the number of animals assessed at each time point is provided is provided for all experimental groups.

Yes
Baseline data on assessed outcome(s) for all experimental groups are reported. Yes Details on important adverse events and death of animals during the course of the experiment are reported for all experimental groups. Yes Numeric data on outcomes are provided in the text or in a tabular format in the main article or as supplementary tables, in addition to the figures.

Yes
To the extent possible, data are reported as dot plots as opposed to bar graphs, especially for small sample size groups. N/A In the online Supplemental Material, methods are described in sufficient detail to enable full replication of the study. Yes

Statistical methods
The statistical methods used for each data set are described. Yes For each statistical test, the effect size with its standard error and P value is presented. Authors are encouraged to provide 95% confidence intervals for important comparisons.

Yes
Central tendency and dispersion of the data are examined, particularly for small data sets. Yes Nonparametric tests are used for data that are not normally distributed.
Yes Two-sided P values are used. Yes In studies that are not exploratory or hypothesis-generating in nature, corrections for multiple hypotheses testing and multiple comparisons are performed.

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In "negative" studies or null findings, the probability of a type II error is reported. N/A

Experimental details, ethics, and funding statements
Details on experimentation including formulation and dosage of therapeutic agent, site and route of administration, use of anesthesia and analgesia, temperature control during experimentation, and postprocedural monitoring are described.

Yes
Both male and female animals have been used. If not, the reason/justification is provided.