Retinal ganglion cell neuroprotection in animal models of glaucoma
Glaucoma is a consequence of an increased intra-ocular pressure which causes retinal ganglion cells (the cells connecting the retina to the brain and forming the optic nerve) to degenerate, leading to a loss of vision over time. The molecular mechanisms triggering neuronal death are unknown. Evidence in the literature showed that the inhibition of a specific type of receptor (the Eph-tyrosine kinase receptor A4 -EphA4) expressed on the membranes of neurons and glial cells enhances neuronal regeneration in spinal cord and optic nerve injury models, decreases axonal pathology in MS and is the only disease-modifier gene identified so far in ALS, suggesting that EphA4 is a detrimental factor for neuron survival/regeneration.
Is the connectivity rearranged in the superior colliculus during retinal cell degeneration? Does the visual system adapt to counterbalance the loss of retinal neurons? Could the inhibition of EphA4 signaling in retinal ganglion cells protect them from degeneration in animal models of glaucoma?
We will induce elevated intra-ocular pressure in an animal model devoid of EphA4 (EphA4KO mouse) and in animal model (wild-type mouse) treated with antagonistic peptides/small molecules interfering with EphA4 signaling. We will analyze retinal ganglion cell degeneration and visual network integrity in the superior colliculus using specific cellular/molecular markers and neural tracing coupled to brain imaging in these models. We will also check the relevance of the mechanosensors mentioned above (project 1) in the progression of glaucoma as these receptors might sense increased intra-ocular pressure and trigger neuronal degeneration.
An innovative technology to support retinal cells survival and regeneration – 3D silk fibers/mats bio-printing
Despite many years of intense research, there are no available treatments to cure eye diseases such as glaucoma or age-related macular degeneration. One cause is the complexity of the molecular pathways involved. In the meantime, one approach could consist of protecting the surviving neuronal cells or hampering the progression of the disease. Previous work in our lab showed that engineered silk fibers containing biological nutrients (also called biofunctionalized silk fibers) support retinal neuron survival and regrowth. However, generating these silk fibers is challenging, therefore an efficient and reliable technology must be developed to engineer reproducible and large amount of such fibers.
Could 3D bio-printing generate reliable and large amounts of biofunctionalized silk fibers/mats? Can these 3D-printed biofunctionalized fibers/mats when in contact with retinal neurons protect them from degeneration or support their regeneration?
In collaboration with RegenHU, a company leader in the field of 3D bioprinting, we will optimize current 3D bio-printing technologies, particularly electrospinning, to standardize the engineering of the biofunctionalized silk fibers/mats. Next, we will test different combination of nutrients that will be included in the silk fibers/mats and study their mechanism of action. Retinal neurons from different animal models of eye diseases will be cultured on these fibers/mats. Their survival and regrowth will be analyzed using cellular and molecular markers. The dynamic of neuronal survival and regrowth will be studied using real-time microscopy. The main objective is to find the optimal nutrients mix/concentration, by combining growth promoting factors and inhibitors of detrimental factors, leading to the most efficient survival and regrowth. A long-term goal is to engineer implantable silk material (fibers or mats) for in vivo stimulation of retinal neuron survival/regeneration.
Discoveries and Innovation:
Wittmer CR, Claudepierre T, Reber M, Wiedemann P, Garlick JA, Kaplan D and Egles C. (2011) Multifunctionalized electrospun silk fibers promote axon regeneration in central nervous system. Adv. Funct. Mater. 21, 4232-4242.