Project Summary: Acute Cardiac Injuries (ACIs) occur in up to 20-25% of hospitalized COVID-19 patients and
are associated with increased risks of morbidity and mortality. COVID-19 has been shown to induce immune
system “overfiring” and “misfiring”, resulting in supraphysiological inflammation. Such cytokine storms have been
shown to lead to organ damage through both direct cytokine insults and indirect mechanisms (e.g., recruitment
of proinflammatory immune cells into organs). Myocarditis (e.g., monocyte infiltration) is a common complication
in COVID-19 ACI hearts. However, the impacts of the infiltrated monocytes on COVID-19 ACI hearts remain
under-defined. As previous studies have been limited to either clinical samples (e.g., peripheral blood,
autopsy/biopsy tissues) or in vitro 2D co-culture experiments, these studies yield limited functional insights. 3D
organotypic models provide a powerful platform to study the functional interactions between hearts and
immune cells in circulation. To develop an organotypic model of human hearts for disease modeling, we
developed 3D human cardiac organoids composed of human pluripotent stem cell-derived cardiomyocytes
(hPSC-CMs), human cardiac fibroblasts, endothelial cells, and stromal cells. Our preliminary data showed the
Interleukin (IL)-1b treated organoids recapitulated key features of transcriptome, structure, and function of
COVID-19 ACI hearts. As IL-1b is not a COVID-19 specific stimulus, these results laid the foundation to use
serum from COVID-19 ACI patients to recapitulate the COVID-19 cytokine insults to the hearts. In addition, the
exclusion of immune cells in the organoids has limited the full recapitulation of hyperinflammation in COVID-19
ACI hearts. The goal of this proposal is to leverage the serum and peripheral blood mononuclear cells (PMBCs)
harvested from COVID-19 ACI patients to 1) simulate the effects of COVID-19 cytokine insults on human hearts,
2) develop the first in vitro COVID-19 myocarditis organoid model to simulate immune cell infiltration to
COVID-19 ACI hearts and assess the infiltrated COVID-19 monocytes. The central hypothesis of this proposal
is that infiltrated COVID-19 immune cells (e.g., monocytes) exacerbate the hyperinflammation of COVID-19 ACI
hearts. This proposal is innovative in that it will, for the first time, develop an organotypic model of myocarditis
to simulate immune cell infiltration into myocardium. Accordingly, we will pursue the following 2 Aims: 1)
Determine the effects of COVID-19 ACI serum on human cardiac organoids, and 2) Determine the ability of
COVID-19 ACI serum treated organoids to recruit immune cells from COVID-19 ACI patients. The proposed
studies will lead to follow-up R01 applications focusing on the effects and mechanisms of the infiltrated
monocytes in COVID-19 ACI hearts. In addition, the 3D organotypic model of myocarditis can be used for
mechanistic studies of the effects of immunomodulatory drugs on hearts.