Corneal Nerves Regenerate and Function After Injury and DHA Plus PEDF Treatment
[frame src="/wp-content/uploads/images/FOL4.12_Figure2.JPG" alt="" width="164" height="134" align="right"]Some nerve cells have the ability to grow and repair themselves after they have been injured. Encouraging nerves to regenerate and function after damage is a topic of vigorous research and progress. Nervous system and spinal cord injuries affect over 90,000 people in the U.S. every year and recovery from central nervous system (brain and spinal cord) injury is limited. Nerve regeneration happens more readily in the peripheral nerves than in the central nervous system, although emerging research suggests that some central nervous system repair may occur under the right circumstances. [frame src="/wp-content/uploads/images/FOL4.12_Callout15.png" alt="" width="179" height="178" align="left"]In this report, researchers at Louisiana State University, USA, studied the ability of the sensory nerves in the cornea to regenerate after injury. The cornea is the transparent covering of the eye and is rich in sensory nerve fibers (Illustration). These nerves are damaged in certain types of surgery, such as LASIK, performed to reshape the cornea and sharpen vision. Usually, these nerves do not regenerate after injury. Damage to the corneal nerves reduces sensitivity, blinking and tear secretion. These changes may lead to dry eye syndrome and reduced corneal sensitivity. Experimental studies in animals with corneal nerve damage have shown that when DHA, a long-chain omega-3 fatty acid found mainly in seafood, and a growth factor called PEDF are applied to the eye after surgery, corneal nerves regenerate almost fully. In this study, the investigators evaluated corneal nerve regeneration after injury and to what extent the regenerated nerves were functional. To do that, they assessed the treated eyes with a fine probe to elicit a blink response. If no blinking was observed, the cornea was considered insensitive. As in their previous work, the researchers observed extensive corneal nerve regeneration in the injured eyes treated with DHA and PEDF growth factor. Nerve regeneration was similar to that in the uninjured eyes. In the sensory evaluation, the investigators found that for the first 4 weeks after surgery, corneal sensitivity was low, about a quarter of the control eyes. However, by week 6, sensitivity was nearly 70% of the control eyes and at 8 weeks, sensitivity was similar to that in the control eyes. [frame src="/wp-content/uploads/images/FOL4.12_Callout16.png" alt="" width="177" height="174" align="right"]Additional evaluation of how well the regenerated nerves functioned showed that a topical injury to the surface of the cornea healed just as quickly in the corneas with regenerated nerves treated with DHA and PEDF as in the control corneas. After 72 hours, corneas from the treated regenerated group had healed virtually completely, similar to the control corneas. These fascinating and insightful studies have demonstrated the powerful effect of DHA and PEDF on the regeneration of corneal nerves after surgical injury. Moreover, the regenerated nerves functioned as well as uninjured corneal nerves. These studies have clear and practical implications for eye care immediately following corneal surgical procedures, such as LASIK surgery. They have the potential to prevent the undesirable side effects of such surgery that occurs in untreated eyes, namely, dry eye syndrome and reduced corneal nerve sensitivity. Next, perhaps, corneal nerve regeneration will be demonstrated in humans.