Use of Human Pluripotent Stem Cells to Define Initiating Molecular Mechanisms of Cataract for Anti-Cataract Drug Discovery

Generation of Lens Progenitor Cells and Lentoid Bodies from Pluripotent Stem Cells: Novel Tools for Human Lens Development and Ocular Disease Etiology

In vitro differentiation of human pluripotent stem cells (hPSCs) into specialized tissues and organs represents a powerful approach to gain insight into those cellular and molecular mechanisms regulating human development. Although normal embryonic eye development is a complex process, generation of ocular organoids and specific ocular tissues from pluripotent stem cells has provided invaluable insights into the formation of lineage-committed progenitor cell populations, signal transduction pathways, and self-organization principles. This review provides a comprehensive summary of recent advances in generation of adenohypophyseal, olfactory, and lens placodes, lens progenitor cells and three-dimensional (3D) primitive lenses, "lentoid bodies", and "micro-lenses". These cells are produced alone or "community-grown" with other ocular tissues. Lentoid bodies/micro-lenses generated from human patients carrying mutations in crystallin genes demonstrate proof-of-principle that these cells are suitable for mechanistic studies of cataractogenesis. Taken together, current and emerging advanced in vitro differentiation methods pave the road to understand molecular mechanisms of cataract formation caused by the entire spectrum of mutations in DNA-binding regulatory genes, such as PAX6, SOX2, FOXE3, MAF, PITX3, and HSF4, individual crystallins, and other genes such as BFSP1, BFSP2, EPHA2, GJA3, GJA8, LIM2, MIP, and TDRD7 represented in human cataract patients.

Drugs associated with cataract formation represent an unmet need in cataract research

Decreased light transmittance through the ocular lens, termed cataract, is a leading cause of low vision and blindness worldwide. Cataract causes significantly decreased quality of life, particularly in the elderly. Environmental risk factors, including aging, UV exposure, diabetes, smoking and some prescription drugs, are all contributors to cataract formation. In particular, drug-induced cataract represents a poorly-addressed source of cataract. To better understand the potential impact of prescription drugs on cataract, we analyzed publicly-available drug prescriptions data from the Australian Pharmaceutical Benefits Scheme. The data was analyzed for the 5-year period from July 2014 to June 2019. Analyses included the number of prescriptions for each drug, as well as the associated government and total prescription costs. The drugs chosen for analysis belonged to any of four broad categories—those with known, probable, possible or uncertain association with cataract in patients. The analyses revealed high prescription rates and costs for drugs in the Known category (e.g., steroids) and Possible category (e.g., psychotropic drugs). Collectively, these data provide valuable insights into specific prescription drugs that likely contribute to the increasing annual burden of new cataract cases. These data highlight the need—as well as new, stem cell-based opportunities—to elucidate molecular mechanisms of drug-induced cataract formation.

Knowledge, views and experiences of Australian optometrists in relation to ocular stem cell therapies

CLINICAL RELEVANCE

Findings from this study examining Australian optometrists' insights into ocular stem cell (SC) therapies have capacity to inform continuing professional development (CPD) about these interventions.

BACKGROUND

This study investigated Australian optometrists' knowledge, views, experiences, and preferred education sources regarding ocular SC therapies.

METHODS

An online survey was distributed to optometrists via Optometry Australia, Mivision magazine, professional groups, and social media from August 2020 to March 2021. Data were collected on demographics, and SC knowledge, awareness and experience.

RESULTS

Of 81 optometrists who completed the survey, many were metropolitan-based (85%), worked in independent practice (47%), female (56%) and >46 years of age (45%). Approximately one-fifth indicated awareness of ocular SC therapies used in standard practice; one-third had knowledge of SC clinical trials. The most noted SC therapies were for corneal disease in the United States [US] (72%) and Australia (44%). Respondents identified the availability of SC therapies for dry eye disease in Australia and the US (39% and 44% respectively), despite no regulatory-approved treatments for this indication. Clinical trials investigating inherited retinal and corneal diseases in Australia were the most commonly identified (44% and 36%, respectively). Half the respondents felt 'unsure' about the quality of evidence for treating eye conditions using SCs. One-fifth indicated concerns with these therapies; of these, most mentioned efficacy (82%), safety (76%) and/or cost (71%). About one-fifth reported being asked for advice about SCs by patients. Two-thirds felt neutral, uncomfortable, or very uncomfortable providing this advice, due to lack of knowledge or the topic being beyond their expertise. Over half (57%) were unsure if clinical management should change if patients received SC therapies. Respondents were receptive to face-to-face education.

CONCLUSION

Some optometrists responding to this survey were aware of ocular SC therapies and/or clinical trials. CPD programs may assist with maintaining currency in this evolving field.

Lens regeneration: scientific discoveries and clinical possibilities

In the process of exploring new methods for cataract treatment, lens regeneration is an ideal strategy for effectively restoring accommodative vision and avoiding postoperative complications and has great clinical potential. Lens regeneration, which is not a simple repetition of lens development, depends on the complex regulatory network comprising the FGF, BMP/TGF-β, Notch, and Wnt signaling pathways. Current research mainly focuses on in situ and in vitro lens regeneration. On the one hand, the possibility of the autologous stem cell in situ regeneration of functional lenses has been confirmed; on the other hand, both embryonic stem cells and induced pluripotent stem cells have been induced into lentoid bodies in vitro which are similar to the natural lens to a certain extent. This article will briefly summarize the regulatory mechanisms of lens development, describe the recent progress of lens regeneration, explore the key molecular signaling pathways, and, more importantly, discuss the prospects and challenges of their clinical applications to provide reference for clinical transformations.