What Is Aging
Cellular aging refers to the progressive decline that cells undergo over time; this is an inevitable process of life. At the cellular level, aging involves reduced synthesis of cellular structural proteins, enzyme proteins and receptor proteins, as well as a decline in the ability to take up nutrients and repair chromosomal damage.This manifests as deformation of cells and nuclei, distortion or vesiculation of mitochondria and the Golgi apparatus, cytoplasmic pigmentation, reduced cell volume, leading to decreased organ weight, interstitial hyperplasia and sclerosis, reduced functional metabolism, and insufficient reserve function.Under the microscope, aged cells may show vacuoles internally (possibly apoptotic bodies), and black dots may also appear, mostly distributed along the cell periphery, with some also visible in the central interior, though fewer than around the periphery.
Main microscopic features of aged cells under the microscope:
1, vacuoles (possibly apoptotic bodies) may appear inside the cell, and black dots may also occur, mostly distributed along the cell periphery with some in the central interior, though fewer than around the periphery.
2, aged cells undergo morphological changes: the three-dimensional appearance gradually disappears and cells become flattened; the spacing between cells decreases or they merge together; cells are no longer spindle-shaped but take on various irregular shapes.
3, refractility decreases, and under the microscope cells appear "thinner"; in transfection experiments, cell mortality is higher. However, the medium does not turn yellow rapidly and remains clear.
4, cell adherence weakens and some cells begin to float in the medium.
5, aged cells secrete more surface material, and the cell surface becomes increasingly less clean.
6, the number of dividing cells decreases markedly and the proliferation rate drops significantly.
7, cells begin to undergo keratinization and differentiation.
Causes of Aging
1, Oxidative stress: oxidative pressure caused by intrinsic or extrinsic factors accelerates cell aging.
2, Telomere shortening: telomeres are protective structures at the ends of chromosomes; their shortening limits the number of cell divisions, thereby triggering cell aging.
3, Reduced autophagy: autophagy is part of the cell's internal cleanup and repair mechanism; reduced function leads to cell aging.
4, Insufficient nutrients: inadequate nutrients in the medium also cause cell aging.
5, Excessive passaging: during in vitro culture, too many passages or prolonged culture also cause cell aging.
How to Prevent Cell Aging
1, Do not wait until cells are overgrown before passaging. Excessive density degrades cell condition and causes contact inhibition. Generally, cells can be passaged at about 80-90% confluence.
2, Do not over-digest cells. Trypsin digestion causes a certain degree of cell surface damage. Pay close attention to the trypsin brand and volume used; most cells use 0.25 trypsin containing EDTA; for this digestion solution, t25 flasks, 1ml; incubate in the incubator for 1min, then take it out and check cell detachment under the microscope.
3, Most importantly, use high-quality serum and medium: stem cells are very sensitive to endotoxin in the medium. In addition to the endotoxin in the basal medium, pay attention to the endotoxin in the serum. If the endotoxin level in serum is ≥3EU/ml or above, stem cells easily age or die, leaving cells in a "sub-healthy" state, which affects experiments. Many users review the batch's test report in advance before trialing a serum, in order to decide whether it is worth trialing.
4, When starting to culture and passage cells, pay particular attention to cryopreserving cells so that a seed bank is maintained, which effectively avoids cell damage.
