Innervation of the mitral valve is strikingly depleted with age

Abstract

Previous reports demonstrated that mammalian atrioventricular (AV) valves possess a dense nerve plexus, consisting of nerve subpopulations which differ from each other in densities and patterns of distribution in the valves, and which may have sensory or motor roles in valve function. Although there is extensive evidence that age-related changes occur in autonomic nerves of animals and humans (Daly et al. that these changes contribute to changes in cardiac function (Klausner and Schwartz Clin. Geriat. Med., 1985;1(1):119-114), there is little information about age-related changes in heart valve innervation. In this study, we used acetylcho-linesterase (AChE) histochemistry to localize and compare qualitative and quantitative changes in the innervation of the mitral valves in young adult and aged animals of three species. Young adult and aged guinea pigs, mice, and Wistar and Fischer 344 rats were anesthetized with Nembutal, the hearts removed, and the mitral valves dissected out and processed for AChE localization. Camera lucida drawings of the AChE-positive nerves in representative segments of valve cusps were made directly from slides; these drawings were digitized and subjected to computer-assisted image analysis to obtain quantitative information about nerve plexus density in the valves. All three animal species showed profuse AChE-positive innervation in the mitral valves of young adult animals, and decreases in the density of this innervation in aged animals. The most striking loss of innervation, compared to the young adult, occurred in the mitral valves of aged Fischer 344 rats, in which large regions of the valves appeared virtually devoid of nerves. Further studies are needed to investigate whether and to what extent age-related losses in heart valve innervation affect valvular structure and function.

Genomic expression patterns of mitral valve tissues from dogs with degenerative mitral valve disease

“…In the normal mitral valve, an extensive plexus of nerves innervates the basilar region of the valve nearest the atrioventricular ring, whereas the free leaflet edges are relatively devoid of nerve endings. 45 This pattern is largely maintained in humans with mitral valve prolapse. 46 The exact function of valvular nerve tissue is unknown but may involve mechanoreception, active valve contraction, arrhythmogenesis, or transmission of the hyperadrenergic heart failure state directly to valve tissue.…”

“…46 The exact function of valvular nerve tissue is unknown but may involve mechanoreception, active valve contraction, arrhythmogenesis, or transmission of the hyperadrenergic heart failure state directly to valve tissue. 45,47 Proteolytic enzymes such as MMPs regulate turnover and remodeling of the valvular extracellular matrix. A previous study e reported increased expression of collagenase-type MMPs 1 and 13 in dogs with DMVD.…”

Differentiating the aging of the mitral valve from human and canine myxomatous degeneration

“…29,30 In rats, both sensory and motor type of nerves were markedly diminished in older animals. 31 There was no difference in mitral valve nerve density between young dogs aged 6–12 months and adult dogs aged 5 years, but there was a significant reduction in mitral valve nerve density in dogs above 10 years of age.…”

Neuronal Regulation of Aortic Valve Cusps

“…Nevertheless, from the available data, most studies support an age-related decrease in the density and distribution of nerves in heart valves [5,15]. These changes are seen both in the aortic and mitral valves [5,15]. The ageassociated changes are thought to affect cholinergic AchE nerve fibers more than adrenergic AchE nerve fibers (at least in the atrioventricular valves) [16].…”