Transport and Possible Outcome of Lipofuscin in Mouse Myocardium

Abstract

This study was performed to clarify the transfer and final end of lipofuscin substances that have been formed in cardiomyocytes. The hearts of BALB/c mice were obtained for resin embedding and ultra-thin sectioning. The specimens were observed under a transmission electron microscope, and the images were acquired using an XR401 side-insertion device. Lipofuscin granules are found abundantly in myocardial cells. Cardiomyocytes can excrete lipofuscin granules into the myocardial interstitium using capsule-like protrusions that are formed on the sarcolemma. These granules enter the myocardial interstitium and can be de-aggregated to form membrane-like garbage, which can pass from the myocardial stroma into the lumen of the vessel through its walls. Smaller lipofuscin granules can pass through the walls of the vessels and enter the blood vessel lumen through the capillary endothelial cells. When the extended cytoplasmic end of macrophages and fibroblasts fuse with the endothelial cells, the lipofuscin granules or clumps in the myocardial interstitium are transported to the capillary walls, and then, are released into the lumen of the blood vessel by the endothelial cells. The myocardial tissues of mice may have the ability to eliminate the lipofuscin produced in the cardiomyocytes into the myocardial blood circulation.