Axonal regeneration in monkey retina present through life

Fort Lauderdale, FL-Regeneration of retinal axons continues throughout life in monkey retinas, but the ability to regenerate is stronger in younger animals. Using in vitro culture models, Solon Thanos, MD, PhD, discussed the molecular mechanisms involved in regeneration of monkey retinal ganglion cell axons in retinal cultures in vitro.

Dr. Thanos and colleagues cultured retinas from newborn and adult monkeys and monitored axonal growth. Experiments were conducted to identify the selected molecules that triggered axonal growth. Dr. Thanos is from the Department of Experimental Ophthalmology, University of Muenster, Munster, Germany.

After placing the retina in culture with laminin, an artificial optic nerve forms. When the axons were again cut, the astrocytes are activated as happens in the optic nerve, and axons and glial cells are regenerated. Testing of various substrates indicated that laminin 1 was essential for axonal growth.

Dr. Thanos also demonstrated that younger retinal tissue, results in growth of more axonal fibers faster, although retinas from a mature monkey showed slower growth of fewer axons.

“There is a huge difference between the newborn monkey retina and the mature monkey retina,” he said.

Another finding was that the proteins that are prominent in the retina of newborn monkeys are less prominent in the retina of mature monkeys.

An important point of this research was that axons continued to regenerate even after being cut a second time. This has clinical implications for humans who might require a second retinal surgery.

“These axons have a huge potential for growth after a second surgery,” Dr. Thanos emphasized. Growth-associated protein-43 was found in both young and mature monkeys, which differs from other species with no expression of GAP-43 in mature retinas.

“The monkey retina re-expresses molecules that are involved in axonal regeneration,” he said.

In association with this, a final experiment indicated that human retinas also express GAP-43 and behave like the monkey retina.

“The challenge now is to determine the contribution of proteins to the degenerative process,” Dr. Thanos said.

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