Parthenogenetic Stem Cell-Derived Human Cornea Models for In-Vitro Toxicity Testing
In the United States, over 65,000 people suffer from work-related eye injuries and illnesses each year. Another 125,000 Americans each year suffer eye injuries from household products. Worldwide, over 10 million people suffer from loss of sight because the cornea, the eye's transparent outer shell, becomes cloudy or opaque through injury or disease. Because eye disease and eye injury affect so many people, there is a need for human corneal tissue that can be transplanted into patients or used for safety testing.
Currently, there is not enough corneal tissue of high enough quality to meet these needs. Some patients receive transplanted corneas from human cadavers, but the supply of transplant-quality corneas is inadequate. Some safety testing is done using cornea-like tissues derived from cells taken from adult donors, but these tissue models do not adequately mimic the microscopic structure of the human cornea. Safety testing is also done on animals, but this practice is controversial and these animal models are also a poor match for the human cornea.
Our main goal is to use human stem cells to provide cornea-like tissue that can be used as a tool to improve the safety testing of chemicals and consumer products, and as a model system for researchers to study eye injuries. Ultimately, this cornea model may also be developed into a source of new, healthy corneal tissue to replace damaged corneas in human patients.
Our corneal tissue model, which we call a corneal orb, is a liquid-filled globe with an outer shell of tissue similar to the cornea. We derive these corneal orbs from human parthenogenetic stem cells (hpSC). These hpSC are derived from unfertilized eggs, so that no human embryo is destroyed in producing them. They therefore avoid the ethical dilemmas surrounding research on human embryonic stem cells.
Our research has shown that these hpSC can develop naturally into corneal orbs that have the same types of cells, arranged in approximately the same structures, as those found in the human cornea. The corneal orbs also have optical qualities similar to those of the human cornea.
However, to supply corneal tissue for transplantation or safety testing, we need to control the process of transforming hpSC into corneal tissue, so that we can produce larger numbers of corneal orbs with more consistent size and properties. This program is designed to make that next crucial step. As described in the full proposal, our main strategy for achieving this goal is to identify the right mix of certain proteins, called growth factors, which must be present in the culture medium to guide the development of corneal tissue. We also propose to manipulate the physical environment of the developing cell cultures in ways that may improve the strength and size of the corneal orbs. By these methods, we hope to meet the need for corneal tissue for transplantation and safety testing.
Large economic and health benefits will accrue to California through the completion of a living stem-cell-based model of the human eye (the cornea) as a research tool to study eye injury. It will provide a safer environment for California consumers and workers through more accurate eye safety testing of chemical and consumer products. It will provide a laboratory model for researchers to study healing of the eye for clinical research. World-wide demand for such a product will provide manufacturing and employment opportunities for Californians and added income to California. Finally, this model will give tangible validation to the public of the benefits that proposition 71 is bringing to California.
There is a world-wide demand for a product that models the human eye for safety testing of chemicals and consumer products. Damage to the cornea is estimated to affect over 10 million people worldwide and household products are involved in 125,000 eye injuries in the USA each year. In June of 2007 The European Union started its “REACH” regulation (Registration, Evaluation and Authorization of Chemicals) requiring approximately 3.9 million test animals be used to assess the safety of chemicals (18% for eye irritation) at a cost of over 1.5 billion EURO (data published by the European Commission, Institute for Health and Consumer Protection, Nov., 2004). Current models use living animals and are regarded by scientists as being flawed and by the public as cruel. Even with these flaws, alternative tests are not effective substitutes for them. In the beginning of 2008, top officials from the U.S. National Institutes of Health (NIH) and Environmental Protection Agency (EPA) announced a five-year deal promising to share technology, information and other resources that will improve the toxicity testing of chemical compounds using current technologies rather than lab animals. This effort is designed to expand the use of human cells for testing and represents the "birth of a new approach to a crucial problem in public health."
Laboratory models of living human cornea will provide a valuable tool for California researchers to study corneal damage and will bypass the current and projected shortages of acceptable human adult corneal tissue for research due to the increased use of laser vision corrective surgery, the increased longevity of the general population, and the increase in incidence of transmissible diseases.
Intellectual property is likely to be generated through this work, resulting in increased valuation for California research organizations involved. This will generate further growth and investment and result in increased employment for Californians and added tax revenue.