Eyeing a cure for retinal blindness

Scientists have successfully grown stem cells isolated from cadaveric human eyes in the lab. Hema Vijay explains that one day, a patient’s own stem cells from the eye could be used as a source of donor cells to cure retinal blindness.

It is a huge step forward in the challenging path leading up to the development of an autologous (from one’s own body) stem cell transplantation cure for so-called ‘irreversible’ blindness arising from retinal degenerative diseases such as retinitis pigmentosa, cone dystrophy, diabetic retinopathy, retinal detachment, retinopathy of prematurity (Leber congenital amaurosis), age related macular degenerations, and glaucoma. 

For the last several years, Srilatha Jasty, Priyadharashni Srinivasan, Gunisha Pasricha, Nivedita Chatterjee and Dr Krishnakumar Subramanian of the Chennai-based Sankara Nethralaya Radheshyam Kanoi Stem cell Laboratory, Kamalanayan Bajaj Research Institute, and Vision Research Foundation have been working under a grant from the Stem Cell Task Force, Department of Biotechnology, to grow retinal cells in the lab. To put things in perspective, the retina is the light-sensitive tissue at the back of the inner eye, which receives the various colours of the light rays and transmits as electrical impulses to the brain, resulting in vision. When the retina is affected, vision is consequently affected, and can be restored only when the retinal cells are restored.

Autologous advantage

This team of scientists has successfully grown in the lab, stem cells isolated from cadaveric human eyes. The scientists have also demonstrated that the cells thus grown maintain their self-renewal properties and also have the ability to differentiate along various retinal cell lines. 

What this indicates is that one day, the patient’s own stem cells from the eye could be roped in as a source of donor cells to cure retinal blindness. The research has been published in the prestigious Stem Cell Reviews and Reports journal. 

This research holds hope for millions of Indians who suffer from loss of vision because of retinal degeneration or damage. Moreover, doctors note that retinal ailments such as diabetic retinopathy, degeneration and detachment are on the rise.

“What holds promise is the fact that stem cells isolated from the adult tissues have the properties of self-renewal and the potential to produce large numbers of retinal neurons in the lab. 

Their path of differentiation along retinal lines is also assured, unlike stem cell lines from other organ sources,” says the principal investigator Dr Krishnakumar Subramanian, Vision Research Foundation, Sankara Nethralaya. Adds Dr Vikas Khetan, consultant oncologist, Medical Research Foundation, Sankara Nethralaya, “Since the stem cells could one day be isolated from the patient’s own eye, they would also not cause rejection reactions, and eliminate the need for immune suppression.” 

World over, scientists are pinning their hope on stem cells in reversing retinal blindness, and various kinds of research have been taken up from how retina of rats could be created in the lab from its own stem cells to using embryonic stem cells to improve the sight of almost-blind persons. 

The value of this research lies in opening a way to culture retinal cells from the human cell line itself, which eliminates a host of concerns. 

Growing retina in the lab

The target was to derive retinal cells. But since the retina is the inner most layer at the posterior segment and so would turn out to be an inaccessible source for stem cell isolation practically, this team decided to isolate pigment cells from the iris (circular structure in the eye) and ciliary body (circumferential tissue around the eye ball). The iris and ciliary stem cells were isolated from cadaveric (donated) eyes, after the donated cornea was transplanted into corneal-blind patients. 

The team cultured the isolated cells in a petri dish, adding growth factors. “We found that the isolated cells produced more cells and also generated neurosphere (NS) containing progenitor retinal cells,” shares Dr Krishnakumar. It is from the progenitor retinal cells that the actual retinal cells of different types are derived. The team then proceeded to evaluate the growth characteristics of the cell lines produced. 

The cultured cells were induced to differentiate using mitogens, and the differentiated cells were analysed by various methods that included RT-PCR, immune-cyto-chemistry, calcium imaging studies and microarray studies. In differentiation conditions, these cells express various specific markers, indicating their differentiation along varied retinal lines.
 Meanwhile, the investigation of the functional differentiation of cells were done by Ca+imaging studies, and it revealed the differentiated cell lines had properties consistent with their retinal cell types that differentiate normally within the body.