Aging of perennial cells and organ parts according to the programmed aging paradigm

Abstract

If aging is a physiological phenomenon-as maintained by the programmed aging paradigm-it must be caused by specific genetically determined and regulated mechanisms, which must be confirmed by evidence. Within the programmed aging paradigm, a complete proposal starts from the observation that cells, tissues, and organs show continuous turnover: As telomere shortening determines both limits to cell replication and a progressive impairment of cellular functions, a progressive decline in age-related fitness decline (i.e., aging) is a clear consequence. Against this hypothesis, a critic might argue that there are cells (most types of neurons) and organ parts (crystalline core and tooth enamel) that have no turnover and are subject to wear or manifest alterations similar to those of cells with turnover. In this review, it is shown how cell types without turnover appear to be strictly dependent on cells subjected to turnover. The loss or weakening of the functions fulfilled by these cells with turnover, due to telomere shortening and turnover slowing, compromises the vitality of the served cells without turnover. This determines well-known clinical manifestations, which in their early forms are described as distinct diseases (e.g., Alzheimer's disease, Parkinson's disease, age-related macular degeneration, etc.). Moreover, for the two organ parts (crystalline core and tooth enamel) without viable cells or any cell turnover, it is discussed how this is entirely compatible with the programmed aging paradigm.

Perspectives to Modify and Counter Aging in the Frame of Subtelomere–Telomere Theory of Aging

“…The explanation of the aging of tissues/organs with no turnover of major cells was provided by two works [151,152]. A detailed discussion and the necessary references are also provided.…”

“…In contrast, not all neurons are perennial. For example, olfactory receptor cells, a specialized type of neurons, are subject to turnover and age, similar to other cells with turnover [151].…”

Running out of developmental program and selfish anti-aging: a new hypothesis explaining the aging process in primates

“…This concept is the basis for all evolutionary theories of aging. Medawar's critiques of Weismann's adaptive view of aging remain valid in discussions with modern Bprogrammed aging^supporters, who believe aging is beneficial for the species and thus programmed like other developmental processes (Libertini and Ferrara 2016).…”

From cellular senescence towards age-related macular degeneration: the role of telomeres

“…Гипотетический оборот нейронов должен восстанавливать для каждого из них все существовавшие ранее связи, чтобы избежать потери его функций. Это частично объясняет, почему, за единичными исключениями (Zhao С. et al, 2008), у нейронов отсутствует непрерывное обновление, в отличие от других типов клеток [3]. Функционирование фоторецепторов сетчатки, клеток центральной нервной системы и необходимость поддержания их полной функциональной активности на протяжении всей жизни организма хорошо сбалансированы.…”