Background: Cardiac dysfunction in AL amyloidosis is thought to be partly related to the direct impact of AL LCs on cardiomyocyte function, with the degree of dysfunction at diagnosis as a major determinant of clinical outcomes. Nonetheless, mechanisms underlying LC-induced myocardial toxicity remain unclear.

Methods: We identified gene expression changes correlating with human cardiac cell exposure to cardiomyopathy-associated AL LCs. We then confirmed these findings in a clinical dataset focusing on clinical parameters associated with pathways dysregulated at the gene expression level.

Results: Upon exposure to cardiomyopathy-associated AL LCs, cardiac cells exhibited gene expression changes related to myocardial contractile function and inflammation, leading us to hypothesise that there could be clinically detectable changes in global longitudinal strain (GLS) on echocardiogram and serum inflammatory markers in patients. Thus, we identified 29 patients with normal interventricular septum diameter (IVSd) but abnormal cardiac biomarkers, suggestive of LC-induced cardiac dysfunction. These patients display early cardiac biomarker staging, abnormal GLS, and significantly reduced serum inflammatory markers compared to patients with clinically evident amyloid fibril deposition.

Conclusion: Collectively, our findings highlight early molecular and functional signatures of cardiac AL amyloidosis, with potential impact for developing improved patient biomarkers and novel therapeutics.

Keywords: AL amyloidosis; cardiac dysfunction; induced pluripotent stem cell-derived cardiomyocytes; light chain-induced cardiotoxicity; transcriptomics.