Can Fish Cure Human Blindness?

Globally, approximately 300 to 400 million people suffer from visual impairment and blindness due to a myriad of causes; this includes diabetes, macular degeneration and infections of various parts of the eyes. In addition, the prevalence of vision impairment is said to be on the rise amongst the aging human population. However, a multitude of ocular diseases are left inadequately controlled and treated due to lack of information of the relevant effective therapies and the pathogenesis. As a result, scientists have delved into the world of organ regeneration, via organisms such as the zebrafish, in an attempt to find a cure for human blindness.

Zebrafish are freshwater fish that have been recognised as the ideal models for this research, mainly due to their infamous regenerative properties and their genetic similarity to humans - they share 70% of humans’ genetic code. Furthermore, zebrafish are able to completely regenerate their retina due to a cell called Müller Glia (MG). According to a Vanderbilt professor of biological sciences, Dr James Patton, “when that cell [MG cell in the fish eye] is damaged, it will activate and then regenerate. So, the fish will go from blind to about 2.5 weeks later, total regain of eyesight”. Likewise, when the retina of a zebrafish is damaged, triggering the regeneration process, the MG cells begin to dedifferentiate into neuronal precursor cells, which then proliferate, before continuing on to differentiate into replacement retinal neurons for specific damaged cells. Although incapable of regeneration like the zebrafish, human eyes also possess the same adult stem cell, Müller Glia, and hence, scientists are attempting to activate this cell, possibly by suppressing specific microRNA, in order to regulate the cell to behave in humans, in the same way it does in zebrafish. For example, Dr Patton and his colleagues found that “when levels of the neurotransmitter GABA decrease, neural stem cells activate”.

However, an array of challenges also surface when scientists utilise such model organisms for human medicine development. For example, the small size of the zebrafish makes it difficult to visualise and diagnose the animals’ skeleton. Additionally, even with sufficient research on the MG cell’s mechanisms, human testing cannot take place before smaller mammals, such as mice, are tested on. Moreover, it was found that high levels of GABA in the retina caused the Müller Glia to remain inactive and hence, inhibit the regeneration process. This contradicts the human body as GABA is present in high concentrations within some retinal neurons. Thus, lowering these concentrations in an attempt to stimulate regeneration, could cause a range of other concerns, such as chronic stress, anxiety and depression.

Similarly, ethical issues also arise when animals are employed for scientific research. This is due to the fact that animals could be considered autonomous and therefore have moral rights, impeding them from being tested on. Conversely, “The Kantian View” - an ethical theory developed by German philosopher, Immanuel Kent - denies moral value to animals as they lack reason. The apparent divide over the use of animals in science is a long-standing debate which plays a vital role in the conduction of such research.

Ultimately, if this research is successful, curing human blindness using zebrafish will not only aid in relieving the $139 million economic burden for eye disorders and vision loss, it will simultaneously and substantially improve the quality of life for millions globally.

Article written by:

Heba Bangash 12C