C57BL/6 mice are widely used in experimental studies. However, there are several substrains, which could have important implications on the results of the study and its interpretation. To date, there is no studies demonstrating direct comparison of the pulmonary vascular remodeling and RV function response to chronic hypoxic exposure in C57BL/6J and C57Bl/6N substrains.
Pulmonary hypertension (PH) was induced in C57BL/6 mice by 3 weeks of exposure to 10% oxygen. Pulmonary vascular remodeling and RV function were evaluated by histology and echocardiography respectively.
Baseline echocardiographic evaluation of the RV function revealed that C57BL/6N mice have significantly lower left ventricular ejection fraction (EF) and cardiac output (CO) in comparison with C57Bl/6J animals. However, upon hypoxia, both substrains developed similar degree of RV hypertrophy. Although, CO, tricuspid annular plane systolic excursion (TAPSE) were decreased and RV internal diameter, myocardial performance index (MPI) were increased upon hypoxic exposure in both substrains, indicating impaired RV function, there were no difference between C57BL/6J and C57Bl/6N mice in cardiac response to chronic hypoxia.
In conclusion, variation in substrains might have remarkable influence on the nature and severity of the response to chronic hypoxia.