RGMa Mediates Reactive Astrogliosis and Glial Scar Formation Through TGFβ1/Smad2/3 Signaling After Stroke

Cell Death Differ. 2018 Aug;25(8):1503-1516. doi: 10.1038/s41418-018-0058-y. Epub 2018 Feb 2.

Abstract

In response to stroke, astrocytes become reactive astrogliosis and are a major component of a glial scar. This results in the formation of both a physical and chemical (production of chondroitin sulfate proteoglycans) barrier, which prevent neurite regeneration that, in turn, interferes with functional recovery. However, the mechanisms of reactive astrogliosis and glial scar formation are poorly understood. In this work, we hypothesized that repulsive guidance molecule a (RGMa) regulate reactive astrogliosis and glial scar formation. We first found that RGMa was strongly expressed by reactive astrocytes in the glial scar in a rat model of middle cerebral artery occlusion/reperfusion. Genetic or pharmacologic inhibition of RGMa in vivo resulted in a strong reduction of reactive astrogliosis and glial scarring as well as in a pronounced improvement in functional recovery. Furthermore, we showed that transforming growth factor β1 (TGFβ1) stimulated RGMa expression through TGFβ1 receptor activin-like kinase 5 (ALK5) in primary cultured astrocytes. Knockdown of RGMa abrogated key steps of reactive astrogliosis and glial scar formation induced by TGFβ1, including cellular hypertrophy, glial fibrillary acidic protein upregulation, cell migration, and CSPGs secretion. Finally, we demonstrated that RGMa co-immunoprecipitated with ALK5 and Smad2/3. TGFβ1-induced ALK5-Smad2/3 interaction and subsequent phosphorylation of Smad2/3 were impaired by RGMa knockdown. Taken together, we identified that after stroke, RGMa promotes reactive astrogliosis and glial scar formation by forming a complex with ALK5 and Smad2/3 to promote ALK5-Smad2/3 interaction to facilitate TGFβ1/Smad2/3 signaling, thereby inhibiting neurological functional recovery. RGMa may be a new therapeutic target for stroke.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Astrocytes / cytology
  • Astrocytes / drug effects
  • Astrocytes / metabolism
  • Cells, Cultured
  • Cicatrix / pathology
  • Disease Models, Animal
  • Fibronectin Type III Domain / genetics
  • GPI-Linked Proteins
  • Male
  • Membrane Proteins / antagonists & inhibitors
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Nerve Tissue Proteins / antagonists & inhibitors
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Neuroglia / pathology*
  • Phosphorylation
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Transforming Growth Factor-beta Type I / metabolism
  • Signal Transduction / drug effects*
  • Smad2 Protein / metabolism
  • Smad3 Protein / metabolism
  • Stroke / metabolism
  • Stroke / pathology*
  • Transforming Growth Factor beta1 / pharmacology*

Substances

  • GPI-Linked Proteins
  • Membrane Proteins
  • Nerve Tissue Proteins
  • RGMA protein, rat
  • RNA, Small Interfering
  • Smad2 Protein
  • Smad3 Protein
  • Transforming Growth Factor beta1
  • Receptor, Transforming Growth Factor-beta Type I
  • Tgfbr1 protein, rat