title: Influence of extracellular matrix components on the expression of integrins and regeneration of adult retinal ganglion cells.
abstract: OBJECTIVE
  Retinal ganglion cells (RGCs) are exposed to injury in a variety of optic nerve diseases including glaucoma. However, not all cells respond in the same way to damage and the capacity of individual RGCs to survive or regenerate is variable. In order to elucidate factors that may be important for RGC survival and regeneration we have focussed on the extracellular matrix (ECM) and RGC integrin expression. Our specific questions were: (1) Do adult RGCs express particular sets of integrins in vitro and in vivo? (2) Can the nature of the ECM influence the expression of different integrins? (3) Can the nature of the ECM affect the survival of the cells and the length or branching complexity of their neurites?
  
  
  METHODS
  Primary RGC cultures from adult rat retina were placed on glass coverslips treated with different substrates: Poly-L-Lysine (PL), or PL plus laminin (L), collagen I (CI), collagen IV (CIV) or fibronectin (F). After 10 days in culture, we performed double immunostaining with an antibody against βIII-Tubulin to identify the RGCs, and antibodies against the integrin subunits: αV, α1, α3, α5, β1 or β3. The number of adhering and surviving cells, the number and length of the neurites and the expression of the integrin subunits on the different substrates were analysed.
  
  
  RESULTS
  PL and L were associated with the greatest survival of RGCs while CI provided the least favourable conditions. The type of substrate affected the number and length of neurites. L stimulated the longest growth. We found at least three different types of RGCs in terms of their capacity to regenerate and extend neurites. The different combinations of integrins expressed by the cells growing on different substrata suggest that RGCs expressed predominantly α1β1 or α3β1 on L, α1β1 on CI and CIV, and α5β3 on F. The activity of the integrins was demonstrated by the phosphorylation of focal adhesion kinase (FAK).
  
  
  CONCLUSIONS
  Adult rat RGCs can survive and grow in the presence of different ECM tested. Further studies should be done to elucidate the different molecular characteristics of the RGCs subtypes in order to understand the possible different sensitivity of different RGCs to damage in diseases like glaucoma in which not all RGCs die at the same time.
authors.affiliation: Dept. of Cell Biology and Histology, University of the Basque Country, UPV/EHU, Leioa, Vizcaya, Spain; John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Elena
authors.initials: E
authors.lastname: Vecino
authors.affiliation: John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Janosch P
authors.initials: JP
authors.lastname: Heller
authors.affiliation: Dept. of Cell Biology and Histology, University of the Basque Country, UPV/EHU, Leioa, Vizcaya, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Veiga-Crespo
authors.affiliation: John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom; Welcome Trust-MRC Cambridge Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Keith R
authors.initials: KR
authors.lastname: Martin
authors.affiliation: John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom.
authors.forename: James W
authors.initials: JW
authors.lastname: Fawcett
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000502:physiology; D005109:Extracellular Matrix / Q000378:metabolism*; D005260:Female; D007150:Immunohistochemistry; D039423:Integrin alpha1 / Q000378:metabolism; D039482:Integrin alpha5 / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism; D039661:Integrin beta3 / Q000378:metabolism; D016023:Integrins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000378:metabolism*
chemical_list: D039423:Integrin alpha1; D039482:Integrin alpha5; D019012:Integrin beta1; D039661:Integrin beta3; D016023:Integrins