Morphological Characterization of Genetically Altered Murine Hearts Using Scanning Electron Microscopy

In striated muscle, the barbed ends of actin filaments are attached to Z lines. Biochemical and cell biological studies suggest that actin capping protein (CP) mediates this attachment by binding the barbed ends of actin filaments. Previous transgenic studies revealed that defective interaction between CP and actin filaments causes major structural defects in sarcomere organization, leading to cardiac hypertrophy and lethality. To determine the basis of the myofibril defect, we have examined the hearts of transgenic mice using scanning electron microscopy. Murine myocardium, both transgenic and wildtype were removed and fixed in 2% Paraformaldehyde/2% glutaraldehyde. A portion of the left ventricular wall, parallel to the papillary muscle, was further dissected and digested with collagenase (type I and H) to remove the extracellar matrix. The prepared tissue was dehydrated, critical point dried, gold coated and visualized using an JEOL jsm-35cf Scanning Electron Microscope and digital images captured using Scion Image acquisition software. The transgenic hearts were hypertrophied relative to wildtype and showed disorganized myofibrillar architecture