The
collagen skeleton in the myocardium of 37 non-human primates (Macaca fascicularis) was studied by scanning electron microscopy. Twenty-one hypertensive animals had "pressure-overload" myocardial
hypertrophy of 4 to 80 weeks duration induced by unilateral perinephric
cellophane insertion and 16 were normotensive controls. The purpose of the study was to examine possible remodeling of the
collagen matrix of the hypertrophied pressure overloaded M. fascicularis myocardium. An extensive
collagen matrix was demonstrated in nonoperated macaques, consisting of a weave which sequestered groups of myocytes and which was joined to the epimysium by long
collagen tendons, and of numerous intermyocyte and myocyte to capillary struts. In addition, strands of
collagen were seen crossing interfascicular planes. This
collagen skeleton was studied at three periods of
perinephritis-induced
hypertension with
hypertrophy: at 4 weeks (evolutionary); at 32 weeks with mild to moderate
hypertension (early compensatory); and at 80 weeks with moderately severe
hypertension (late compensatory). These sequential studies revealed that the matrix was remodeled. At 4 weeks there was slight thickening and increase in density of the weave. At 32 weeks, in addition to changes in the weave, the
collagen strands became thick and pillar-like and the tendons increased in numbers and thickness, and at 80 weeks some myocytes became encased in
collagen. The geometrical arrangement of the normal
collagen matrix of the myocardium is similar to series and parallel elastic elements with respect to myocytes, and, accordingly, it may be responsible for the mechanical properties of the myocardium during diastole and systole. The structural alterations in the
collagen skeleton which we observed in
hypertrophy may play a significant role in deleteriously affecting ventricular function of the pressure-overloaded myocardium.