K14, p63, and Ki67 expression was higher in epithelial cells expanded on the LAM. K12 was negative in the basal epithelium on the LAM, while there was strong immunoreaction in the epithelium on the DAM. Furthermore, the epithelial cells on the LAM could be easily separated as an intact cell sheet and successfully used to reconstruct the ocular surface in the LSCD rabbit model, while the cells on the DAM could not generate intact cell sheets.
Currently they are utilizing the culture system combining air-exposure, low oxygen, and the LAM culture system to generate tissue engineered corneal epithelium for a clinical trial, which shows promising outcome in the treatment of LSCD. Jeffrey L Goldberg, Professor and Chair of Ophthalmology at Stanford University, presented an update on the progress in using stem cells for glaucoma treatment. Retinal ganglion cells RGCs, Figure 2 degenerate in glaucoma and other optic neuropathies, and are not replaced in humans or other adult mammals.
Cell therapies are being explored for two components of glaucoma [ 25 , 26 , 27 ]. First, trabecular meshwork cells either expanded from primary tissues or derived from stem cell populations, are being studied for repopulating the collagen beams in the trabecular meshwork. Refreshing the cellular content in the trabecular meshwork is currently hypothesized by many to be a strong and perhaps durable approach to lowering intraocular pressure [ 28 ]. Second, stem cells are being studied actively to treat the RGC degeneration in glaucoma and in other optic neuropathies [ 29 ].
Early in degenerative disease, stem cells could be used to provide neurotrophic survival and growth signals and thereby counteract the degenerative process [ 26 ].
This would provide a neuroprotective effect and slow the course of vision loss and perhaps even restore some vision. Many stem cell populations have been demonstrated to secrete a variety of neurotrophic factors that could independently or coordinately promote RGC survival and growth of retinal ganglion cells. Late in glaucoma or other optic nerve degenerations, however, a significant number of RGCs will have already died. Neurotrophic or neuroprotection approaches will be less useful at such later stages, but cell replacement therapies will be very promising for vision restoration [ 25 , 30 ].
Choose your preferred view mode
Here, the challenge is scientifically much greater: In collaboration with his collaborator Ken Muller at the University of Miami, and led by his graduate student Praseeda Venugopalan, his team began by asking whether RGCs can be transplanted and integrate into the mature retina [ 32 , 33 ].
They used a normal, uninjured rat recipient to investigate whether transplanted RGCs can integrate into the mature retina, by transplanting GFP-labeled donor RGCs in vivo by intravitreal injection. Goldberg presented data demonstrating that transplanted RGCs acquired morphologic features of endogenous ones, with axons growing towards the optic nerve head of the host retina and dendrites extending into their target zones in the inner plexiform layer.
Goldberg also shared data from electrophysiological recordings from transplanted RGCs, which demonstrated their electrical excitability. These data presented a promising approach to developing cell replacement strategies in diseased retinas with degenerating RGCs [ 26 ]. The retina is the visual information sensing, primary processing and projecting neural tissue in the eye. Similar to other parts of the nervous system in our body, all the retinal neurons are generated during development, and the adult human retina shows little regeneration activity [ 34 ].
On the other hand, the retina is vulnerable to a variety of insults ranging from physical assaults, genetic defects to aging, resulting in the degeneration of retinal neurons. However, studies in the past decade indicate that mammalian retinas still possess cells that retain regeneration potential [ 35 , 36 ]. Exploring regeneration potential of mammalian retinas may provide alternative donor cell sources for cell replacement therapy for retinal degeneration diseases, and may even lead to endogenous repair strategies [ 37 ]. In the chick embryo, RPE cells can be efficiently converted to photoreceptor-like cells in the subretinal space by ectopically expressing the neurogenic gene neurogenin1 Ngn1 or Ngn3 [ 38 ].
Similarly, forced expression of Ngn1 or Ngn3 can also successfully transform RPE cells into photoreceptor-like cells in the mouse eye [ 39 ]. Two main challenges remain for using RPE trans-differentiation into functional photoreceptor cells: In the future, it will be important to identify critical growth factors and intrinsic factors for promoting the generation of functional photoreceptors in the degenerative adult retina.
She pointed out that many clues to the cellular and molecular features of retinal regeneration come from studies in lower vertebrates, especially teleost fishes. The retina in fish continuously grows throughout lifetime, and can recover all types of retinal cells after injury, exhibiting tremendous regeneration ability [ 49 ]. The regeneration ability of the fish retina relies on two populations of retinal stem cells RSCs: Using versatile genetic and experimental tools developed by the zebrafish research community, a number of important intrinsic factors and extrinsic signals that govern the regeneration processes in zebrafish retinas have been discovered, which is providing interesting directions to explore to unlock the regeneration potential in the mammalian retina [ 54 , 55 , 56 , 57 , 58 , 59 ].
The retinal cell lines established by this approach express typical RPC markers, actively proliferate and give rise to all types of retinal neurons and glia cells under appropriate culture conditions. When transplanted, these in vitro expanded retinal cells partially restore visual response to photoreceptor degenerated mice [ 64 ].
- Ein Sommer in London (German Edition).
Recent advances in cell fate reprogramming studies show that forced expression of key factors can reprogram terminally differentiated somatic cells not only to pluoripotent stem cells, but also to various types of tissue-specific stem cells [ 65 , 66 , 67 , 68 ]. All three donor stem-cell types, after transplantation into the subretinal space, demonstrated promising therapeutic effects in terms of protection of retinal structure and function in RCS rats. MSCs could differentiate into retinal cells and replaced some of the injured host cells.
ASDCs appear to function primarily through paracrine effects. Xu reported that the glia enriched rESC-RPC1 obtained through early and longer adherent culture only increased the b-wave amplitude at four weeks, while longer suspension cultured cells gave rise to what appeared to be more neuronal differentiation in the rESC-RPC2 cultures which significantly improved visual function in the transplanted RCS rats [ 70 ]. Hibernation is a trait that some animals have evolved to cope with harsh winter environments.
By lowering their metabolic rate and utilizing lipid fuels accumulated during the summer and fall, mammals such as ground squirrels seal themselves underground and survive the cold winter with little food and water intake. This is an amazing biological feat, as hibernators have to alternate between two vastly different metabolic states multiple times. Studying hibernation can help us not only to understand this fascinating biological phenomenon, but also to provide invaluable information about mechanisms of metabolic regulation that are critical for adapting to metabolic challenges.
Such challenges are frequently brought upon in diseases and pathological conditions. In many non-hibernating animals, neurons cannot cope with a body temperature substantially lower than their euthermic level. To further study the unique features of ground squirrel retinal cells and of other neurons in response to cold temperatures during hibernation, Li and his team have worked to develop a cell culture system that can easily be subjected to pharmacological and genetic manipulations.
With this goal in mind, they generated several lines of ground squirrel iPSCs derived from postnatal cortical neural precursor cells and developed a system for studying intrinsic hibernating features of ground squirrel retinal cells by further differentiating these precursor cells into eyecups. In addition, positive results for teratoma formation further confirmed the pluripotency of the cells in vivo. Finally, karyotyping experiments suggested that the cell lines are genetically stable.
Human iPSC-derived neurons, on the other hand, could not withstand low temperature culturing for as little as 10—12 h. Experimental studies in the last three decades have clearly established that the behavior of glial cells is far from passive, and that they are at least as complex as neurons with regard to their membrane properties. In addition, glial cells are of importance in signal processing, cellular metabolism, nervous system development, and the pathophysiology of neurological diseases.
Read more Read less. Perspectives in Vision Research Paperback: Springer; Softcover reprint of the original 1st ed. Be the first to review this item Would you like to tell us about a lower price? Related Video Shorts 0 Upload your video. Try the Kindle edition and experience these great reading features: Customer reviews There are no customer reviews yet.
Share your thoughts with other customers. Write a customer review. Amazon Giveaway allows you to run promotional giveaways in order to create buzz, reward your audience, and attract new followers and customers. Learn more about Amazon Giveaway. The Development of the Red Pulp in the Spleen. Biochemistry of Characterised Neurons. Tissue Engineering in Regenerative Medicine. Some Current Concepts of Synaptic Organization. Dynamics of Degeneration and Growth in Neurons. Skin Cancer and UV Radiation. The Foundations of Human and Animal Emotions.
Clinical Neurophysiology in Disorders of Consciousness. The Cerebral Perivascular Cells. Commentaries in the Neurosciences. Glycoscience and Microbial Adhesion.
The Retinal Muller Cell: Structure & Function (Perspectives by Vijay Sarthy
Central Functions of the Ghrelin Receptor. Functional Organization of Vertebrate Plasma Membrane. The Neuroscience of Hallucinations. Medical Advancements in Aging and Regenerative Technologies. A Tutorial Study Guide. Progenitor Cell Therapy for Neurological Injury.
Encephalopathy and Nitrogen Metabolism in Liver Failure. Sport and the Brain: Bioengineering Aspects in the Design of Gas Exchangers. Clinical Pharmacology of Cerebral Ischemia. Regenerative Medicine - from Protocol to Patient. History of Exercise Physiology. Engineering of Stem Cells. Foundations of Regenerative Medicine.