The Development, Growth, and Regeneration of the Crystalline Lens: A Review

Abstract

Purpose: This review aims to provide an understanding of the history of research on, the biological processes governing the different forms of, and an overview of more recent work on lens regeneration as they will likely prove vital in bringing the study of lens regeneration into the clinic. Methods: A review of the literature on lens regeneration research was conducted. Results: Lens regeneration is characterized by the regrowth or repair of the lens following the removal of either a portion or of the entire lens. A brief history of research on lens regeneration is provided, from the discovery in early antiquity of the ability of some animals to regenerate lost tissue, to the systematic cataloguing of the mechanisms of lens regeneration in the 19th century, until the more modern unraveling of the genetic and biochemical processes governing lens regeneration. The anatomy and physiology of the lens as well as the mechanisms by which the lens develops inform its regenerative capabilities by determining the processes that must occur in order to regrow a new lens or repair a damaged one. Lens regeneration occurs by one of several species-dependent methods: some amphibians can regrow a new lens after complete removal of the old one while some mammals can only repair a damaged lens. This review provides an overview of the mechanisms controlling the different types of lens regeneration. Conclusion: The development and growth of the intact lens influence the mechanisms that govern lens regeneration. Recent advances in the field have begun to apply concepts of the field in the clinic and have made significant progress towards realizing the goal of using lens regeneration to repair a damaged lens in the clinic.

Application of Collagen I and IV in Bioengineering Transparent Ocular Tissues

“…For example, Gwon and Gruber utilized a biodegradable hyaluronic acid scaffold and found lenses of greater optical clarity and normal fiber arrangement regenerated (117). It is believed these scaffolds provide the necessary mechanical support to the remaining lens capsule and LECs, mimicking the support previously provided by the natural fiber mass (118). Furthermore, this then encourages normal regeneration as opposed to aberrant proliferation and migration of LECs (i.e., PCO also linked to a sudden disruption of contact inhibition) (119,120).…”

“…This can lead to a significant loss of crucial LECs and possible damage to the supporting lens capsule, both of which are essential for LEC-mediated regeneration. Adult lenses also have larger capsules "stretched" from years of continuous lens growth (118). This impacts on the mechanical environment present and makes it unconducive to regeneration.…”

Posterior capsule opacification: What's in the bag?

“…Lens regeneration has been well studied in urodeles, but has become increasingly relevant in mammals (Kumar and Reilly, 2020) with much of our basic understanding of lens fibre cell differentiation formed from developmental biology (Lovicu et al, 2011). A great deal of information can be drawn from developmental systems and translated to the study of human lens fibre cell differentiation in relation to regenerative PCO.…”

Structure of the lens and its associations with the visual quality

“…The growth of crystalline lens can be divided into two stages (figure 3): the formation of lens vesicles and the production of lens fibers. 29 At the 22nd day of the embryo, the neural folds on both sides of the forebrain developed from the neural tube invaginate, forming the optic groove, which continues to form optic vesicle. The distal end of the optic vesicle continues to expand and form a double-layer cup-shaped structure, called the optic cup.…”