Negative impact of rAAV2 mediated expression of SOCS3 on the regeneration of adult retinal ganglion cell axons

Mol Cell Neurosci. 2011 Feb;46(2):507-15. doi: 10.1016/j.mcn.2010.12.003. Epub 2010 Dec 9.

Abstract

Intravitreal injections of recombinant ciliary neurotrophic factor (rCNTF) protect adult rat retinal ganglion cells (RGCs) after injury and stimulate regeneration, an effect enhanced by co-injection with a cAMP analogue (CPT-cAMP). This effect is partly mediated by PKA and associated signaling pathways, but CPT-cAMP also moderates upregulation of suppressor of cytokine signaling (SOCS) pathways after rCNTF injection, which will also enhance the responsiveness of RGCs to this and perhaps other cytokines. We now report that intravitreal injections of CPT-cAMP do not potentiate RGC axonal regeneration when CNTF is expressed via an adeno-associated viral vector (rAAV2), and concomitantly we show that increases in retinal SOCS mRNA expression are less when CNTF is delivered using the vector. We also directly tested the impact of elevated SOCS3 expression on the survival and regeneration of injured adult RGCs by injecting a bicistronic rAAV2-SOCS3-GFP vector into the vitreous of eyes in rats with a peripheral nerve graft sutured onto the cut optic nerve. Overexpression of SOCS3 resulted in an overall reduction in axonal regrowth and almost complete regeneration failure of RGCs transduced with the rAAV2-SOCS3-GFP vector. Furthermore, rAAV2-mediated expression of SOCS3 abolished the normally neurotrophic effects elicited by intravitreal rCNTF injections. In summary, CNTF delivery to the retina using viral vectors may be more effective than bolus rCNTF injections because the gene therapy approach has a less pronounced effect on neuron-intrinsic SOCS repressor pathways. Our new gain of function data using rAAV2-SOCS3-GFP demonstrate the negative impact of enhanced SOCS3 expression on the regenerative potential of mature CNS neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / genetics
  • Animals
  • Axons / metabolism*
  • Ciliary Neurotrophic Factor / administration & dosage*
  • Ciliary Neurotrophic Factor / genetics
  • Ciliary Neurotrophic Factor / metabolism
  • Cyclic AMP / administration & dosage
  • Cyclic AMP / analogs & derivatives
  • Female
  • Gene Expression
  • Genetic Therapy / methods*
  • Genetic Vectors / genetics
  • Immunohistochemistry
  • Intravitreal Injections
  • Microscopy, Confocal
  • Nerve Regeneration / drug effects
  • Nerve Regeneration / physiology*
  • Neuroprotective Agents / administration & dosage
  • Optic Nerve Injuries / physiopathology
  • Optic Nerve Injuries / therapy
  • Polymerase Chain Reaction
  • RNA, Messenger / analysis
  • Rats
  • Rats, Wistar
  • Recombinant Proteins / administration & dosage
  • Retinal Ganglion Cells / drug effects
  • Retinal Ganglion Cells / metabolism*
  • Suppressor of Cytokine Signaling 3 Protein
  • Suppressor of Cytokine Signaling Proteins / drug effects
  • Suppressor of Cytokine Signaling Proteins / metabolism*
  • Transduction, Genetic

Substances

  • Ciliary Neurotrophic Factor
  • Neuroprotective Agents
  • RNA, Messenger
  • Recombinant Proteins
  • Socs2 protein, rat
  • Socs3 protein, rat
  • Suppressor of Cytokine Signaling 3 Protein
  • Suppressor of Cytokine Signaling Proteins
  • Cyclic AMP