ImportanceSARS-CoV-2 infection directly causes severe acute respiratory illness, leading to systemic tissue hypoxia and ischemia including the heart. Myocardial cytopathy associated with hypoxic response has been largely overlooked in COVID-19 patients. Additionally, histology analysis and cardiac function of COVID-19 cases are often reported separately, rendering an incomplete understanding of COVID-19 cardiac symptoms. ObjectiveTo examine the relationship between myocardial cellular responses to hypoxic stress versus cardiac functional alterations within the same COVID-19 patients. Design, Setting, and ParticipantsCellular hypoxia Inducible Factor 1 alpha (HIF1) expression was analyzed by immunohistochemistry using post-mortem COVID-19 heart and lung tissues with known cardiac echocardiography records from a total of 8 patients. Clinical echocardiography data were obtained from Mount Sinai Heart between March to December, 2020. All gender and age groups were considered as long as cardiac involvement meets the preserved (EF > 50%) or moderate to severe (EF < 45%) criteria with confirmed SARS-CoV-2 infection. Cell-type specific subcellular localization of HIF1 expression and nuclear stability was examined by immunohistochemistry and transmission electronic microscopy (TEM). Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was used to quantify apoptosis. Main Outcomes and MeasuresNo planned outcomes of this study as this is a retrospective analysis based on post-mortem specimens exclusively. ResultsCardiac HIF1 expression was found to be significantly higher in patients with preserved EF levels than it was in the low EF group. In the preserved EF group, HIF1 is protective against apoptosis predominantly in endothelial cells and cardiac fibroblasts. In the low EF group, HIF1 protects cardiomyocyte nuclear integrity as evident by its nuclear accumulation with nuclear envelope preservation. Conclusions and RelevanceThis study establishes a direct link of cardiac cellular responses to hypoxic stress with matching functional and histological data, serving as one of the first studies to bridge previous stand-alone clinical data and cellular data. The protective role of HIF1 in hearts may help predict cardiac involvement in not only COVID-19 patients, but also decipher the underlying mechanisms in other forms of viral cardiomyopathy. KEY POINTSO_ST_ABSQuestionC_ST_ABSAre hypoxic signaling pathways associated with cardiac functional alterations in COVID-19 patients? FindingsCardiac HIF1 expression of COVID-19 patients with EF>50% or EF<45% was analyzed and quantified. Increased cardiac HIF1+ cells were found in patients with higher EF. HIF1+ endothelial cells are resistant to apoptosis, and HIF1+ cardiomyocytes are able to retain nuclear envelope under hypoxic stress. MeaningHIF1 is cardioprotective in hearts of COVID-19 patients.
HIF1alpha cardioprotection in COVID-19 patients