Robin Ali, PhD, FMedSci
Dr. Ali’s research on stem cells focuses on establishing photoreceptor transplantation as a strategy for restoring vision in patients who have lost these cells due to retinal disease. These can include patients with inherited retinal dystrophies as well as those with age-related macular degeneration. Photoreceptors are the light-sensing neurons in the eye, and there are many challenges to developing a successful transplantation strategy, including isolating enough cells for transplantation, ensuring the cells migrate to the correct location in the retina, ensuring that they establish the proper connections with neighboring neurons, and long-term cell survival. Over the past decade Dr. Ali’s lab has made significant contributions toward establishing effective techniques for photoreceptor transplantation, showing that photoreceptor transplantation can restore vision in a degenerated mouse retina, optimizing methods for deriving and isolating photoreceptors from stem cell cultures, and determining the mechanisms by which transplanted photoreceptors restore vision. His current work is focused on continuing to establish the potential of photoreceptors derived from stem cells for transplantation and vision restoration, with the ultimate goal of developing a cellular therapy that can be tested in clinical trials.
Alon Kahana, MD, PhD
Extraocular Muscle Regeneration
Binocular vision in humans requires coordinated movement of both eyes, controlled by 6 EOMs per eye. In children, development of binocular vision in general and stereopsis (binocular depth perception) in particular requires properly coordinated eye movement. Poorly coordinated eye movement, i.e., strabismus, can result in amblyopia (neurologic vision loss) and/or permanent loss of stereopsis. In adults, strabismus can result in diplopia (double vision), leading to loss of visual function, as well as in social stigma and isolation. Strabismic conditions are very common, with a pediatric prevalence of approximately 3%, with a total prevalence of 2-5%. While the majority of ophthalmic disorders have benefitted tremendously from advances in molecular genetics and cell biology, treatment of strabismic conditions still relies on occlusion, prisms and surgery, with high rates of failure and potential complications that can result in loss of visual function. The transformative goal of this project is to cure strabismus and preserve vision through regenerative approaches, with further applications to a multitude of skeletal muscle disorders.
Coordinated eye movement requires intact neurologic control and functional EOMs. Disease and fibrosis (e.g. thyroid eye disease, trauma) can cause irreversible muscle damage. In addition, cranial nerve disorders can secondarily lead to atrophy or contracture of EOMs. Unfortunately, a damaged or maldeveloped muscle will result in poor function, irrespective of neurologic input. While mammalian muscles have a very limited capacity to regenerate de novo, there is experimental evidence of limited EOM repair following injury in mammals . Hence, there is potential for therapeutic EOM repair, but we need a better mechanistic understanding of how to trigger and control it.
In order to address the limitations in the field, our laboratory has developed a novel model of EOM injury and regeneration that takes advantage of the genetic accessibility and regenerative capacity of adult zebrafish. Importantly, we have discovered that adult zebrafish EOMs regeneration begins with reprogramming of “post-mitotic” myocytes – multinucleated, syncytial – into dedifferentiated myoblasts capable of robust proliferation to restore the cell number required to regenerate lost tissue. The discovery of myocyte dedifferentiation has been controversial. However, vertebrate cell reprogramming and dedifferentiation is also well studied in adult zebrafish retina, bone, cartilage, heart, and liver, providing excellent models for developing a mechanistic understanding of the reprogramming process. Since myocyte differentiation and biology are extremely well-conserved across species, there is every reason to believe that studying dedifferentiation in zebrafish will enhance our understanding of the potential for dedifferentiation and regeneration in human muscle. Specifically, we hypothesize that mammalian myocytes have gained, through evolution, molecular repressor pathways to prevent myocyte dedifferentiation in order to reduce the risk of dysregulated reprogramming resulting in malignant transformation. It follows that a mechanistic understanding of dedifferentiation would identify molecular activators and repressors that could be utilized to develop novel therapies. The discovery of induced pluripotent stem (iPS) cell reprogramming through the activation of just 4 transcription factors (TFs) – MYC, KLF4, SOX2 and OCT4 – lends significant credibility to the notion that mammalian cell reprogramming is possible once the basic biology is understood.
Our investigations, now published, have revealed that adult zebrafish EOM myocytes reprogram into dedifferentiated myoblasts capable of reentering the cell cycle by 20 hours post injury (hpi). The reprogramming process involves both transcriptional and cytoplasmic events, including FGF-dependent induction of autophagy to disassemble the sarcomeres and the excess nuclei in the multinucleated starting cells. The lab has now turned its attention to understanding the transcriptional and epigenetic processes that underlie myocyte reprogramming.