Cellular Senescence in the Development of Cataracts
The ability to selectively destroy senescent cells through the use of senolytic therapies doesn't make greater understanding of the biochemistry of senescent cells irrelevant, but it does mean that we don't have to wait around for that greater understanding to arrive in order for the development of therapies to get started. Destroy the bad cells now, benefit the patients now, and let the ongoing research proceed at its own pace. The open access paper here is an example of that ongoing research, an exploration of the proteins that might be important in cellular senescence in cataracts, a prominent cause of age-related blindness. Regardless of the outcome here, senolytic therapies should be under development to treat cataracts now, not later.
Senescence is a leading cause of age-related cataract (ARC). The current study indicated that the senescence-associated protein, p53, total laminin (LM), LMα4, and transforming growth factor-beta1 (TGF-β1) in the cataractous anterior lens capsules (ALCs) increase with the grades of ARC. In cataractous ALCs, patient age, total LM, LMα4, TGF-β1, were all positively correlated with p53.
In lens epithelial cell senescence models, matrix metalloproteinase-9 (MMP-9) alleviated senescence by decreasing the expression of total LM and LMα4; TGF-β1 induced senescence by increasing the expression of total LM and LMα4. Furthermore, MMP-9 silencing increased p-p38 and LMα4 expression; anti-LMα4 globular domain antibody alleviated senescence by decreasing the expression of p-p38 and LMα4; pharmacological inhibition of p38 MAPK signaling alleviated senescence by decreasing the expression of LMα4. Finally, in cataractous ALCs, positive correlations were found between LMα4 and total LM, as well as between LMα4 and TGF-β1.
Taken together, our results implied that the elevated LMα4, which was possibly caused by the decreased MMP-9, increased TGF-β1 and activated p38 MAPK signaling during senescence, leading to the development of ARC. LMα4 and its regulatory factors show potential as targets for drug development for prevention and treatment of ARC.
Then what causes presbyopia?
here is a quote:
Presbyopia is an age-related process. It is a gradual thickening and loss of flexibility of the natural lens inside your eye.
These age-related changes occur within the proteins in the lens, making the lens harder and less elastic over time. Age-related changes also take place in the muscle fibers surrounding the lens. With less elasticity, it gets difficult for the eyes to focus on close objects.
I would add that the vitreous body also does change and might be contributing too. So crosslinks are a major suspect here. There might be some deterionration in the motor nerves too.