Ageing is defined as the gradual deterioration of functional characteristics which are necessary for survival and the whole process of aging is termed as senescence in biological sense. In recent years, the processes and mechanisms of ageing and age-related diseases have also made progress. The scientific study of old age or the process of ageing is called as the gerontology and the biological aspect of process of aging or gerontology is called Biogerontology which is defined as the subfield of gerontology concerned with the biological aging process, its evolutionary origins, and potential means to intervene in the process. It involves interdisciplinary research on biological aging’s causes, effects and mechanisms. Lifespan is the length of time for which an organism lives and Life expectancy is the average period that a person may expect to live. It is found that genetic factors play roles in determining the longevity both within and between species.
Ageing is a complex biological process with complex mechanisms characterised by functional decline of tissues and organs, deterioration of functional characteristics, reduced adaptability and resistance, all contribute to an increase in the mortality caused by multiple chronic diseases. Ageing is divided into two types namely pathological and physiological ageing.
Pathological Ageing is defined as that type of aging in which people grow old with no significant antemortem cognitive impairment, and some of them may be high functioning. Physiological Ageing can be defined as that type of aging in which organism lead to senescence or the decline in the biological functions and organism’s ability to adapt to metabolic stress. The later one is the common ageing type in the human beings and most of the animals. As the process of ageing continues the susceptibility of the body towards different diseases increases like diabetes, muscle dysfunction, skin diseases etc. Ageing related disorders are really a serious threat to human health and reduce quality of life among elderly people.
CELL TYPES INVOLVED IN AGEING
Stem cells are the cells which have the ability to perpetuate themselves as they are capable of continuous, repeated self-renewal divisions in order to maintain their population. A single stem cell can differentiate into or form different types of mature cell types. Stem cells are basically pluripotent cells characterized as undifferentiated and immature with the ability to self-renew.
Stem cell therapy is widely used in bone regeneration, organ regeneration and especially in cardiovascular regenerative medicine. This is done by regenerating various functional stem cells, with the potential function of regenerating various tissues and organs. Changes in cell cycle and a decline in the self-renewal ability of stem cells are closely related to aging. Decline of self-renewal factors contributes to stem cell aging. Although some changes in their function are intrinsic, more external factors can lead to impairment in their function. Physiological levels of ROS (Reactive oxygen species (ROS) are essential signaling molecules in many biological processes, wherein their level is tightly regulated. Excess ROS may cause apoptosis, premature senescence or unscheduled differentiation of stem cells) could regulate the balance between self-renewal and stem cell differentiation. High ROS levels could lead to DNA damage, shortening of telomeres and onset of premature ageing markers
Vascular Smooth Muscle Cells
According to the evidences it is said that senescent vascular smooth muscle cells have been observed in aging related diseases like diabetes mellitus which indicates that these cells contribute to aging. Aging results in a significant reduction of contractile vascular smooth muscle cells in focal patches along arterioles. Focal loss of contractile VSMCs occurs at a younger age due to the deficiency of senescence related protein which is called as caveolin-1. Age related contractile VSMC loss is not exacerbated by genetic depletion of insulin-like growth factor-1. The patchy loss of contractile VSMCs provides a cellular explanation for previous clinical studies showing focal micro-irregularities in retinal arteriolar responsiveness in healthy aged human subjects and is likely to contribute age-related retinal vascular complications.
Endothelial cells have important functions in paracrine and endocrine actions, such as regulating vascular tension, maintaining blood circulation and neovascularization. Endothelial cells are essential part of the heart and vasculature. Senescence is closely related to endothelial cells. ROS (Reactive Oxygen Species) and inflammation play a role in the apoptosis of endothelial cells. Autophagy and exosomes containing harbor miRNAs which play a very important role in the course of a disease and also participate in the regulation of endothelial functions. Age related diseases are related to endothelial dysfunction and impaired autophagic activity.