title: In vivo characterization of astrocyte precursor cells (APCs) and astrocytes in developing rat retinae: differentiation, proliferation, and apoptosis.
abstract: OBJECTIVE
  To characterize the timing of differentiation, antigenic expression, morphology, proliferative potential, and apoptosis during astrocyte differentiation in the rat retina in vivo.
  
  
  METHODS
  Whole mounts of rat retinae from embryonic day (E) 13 to postnatal day (P) 21 and adults were examined utilizing combinations of Pax2, GFAP, vimentin, S100, and GS lectin. These markers were also combined with BrdU and TUNEL to identify proliferation and apoptosis of cells of the astrocytic lineage.
  
  
  RESULTS
  Three distinct stages of astrocytic differentiation were identified: (i) Pax2+/vimentin+/GFAP(-) astrocyte precursor cell (APC), (ii) Pax2+/vimentin+/GFAP+ immature perinatal astrocytes, and (iii) Pax2+/vimentin(-)/GFAP+ mature perinatal astrocytes. An earlier transient site of astrocyte generation was detected from E13 to E15 at the ventricular surface, but unlike the majority of retinal astrocytes that migrate into the retina starting at E15-E16, this ventricular source of retinal astrocytes were restricted to a small rim surrounding the optic nerve head. APCs and perinatal astrocytes were highly proliferative and migratory. Significant numbers of perinatal astrocytes were lost because of apoptosis, which was matched closely to the retraction of excess capillary segments during postnatal maturation of the retinal vasculature.
  
  
  CONCLUSIONS
  This study provides evidence of a second site of astrocyte generation at the ventricular zone early in embryonic development of the mammalian retinae. APCs are present from E16 to E20 only during perinatal development and are a highly migratory and proliferative cell. As the retina is considered a part of the central nervous system (CNS), this is the first in vivo characterization of cells of the astrocytic lineage in mammalian CNS development.
authors.affiliation: Department of Anatomy, University of Sydney, Sydney, New South Wales, Australia. tailoi@anatomy.usyd.edu.au
authors.forename: Tailoi
authors.initials: T
authors.lastname: Chan-Ling
authors.forename: Yi
authors.initials: Y
authors.lastname: Chu
authors.forename: Louise
authors.initials: L
authors.lastname: Baxter
authors.forename: Michael
authors.initials: M
authors.lastname: Weible Ii
authors.forename: Suzanne
authors.initials: S
authors.lastname: Hughes
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000502:physiology*; D001253:Astrocytes / Q000166:cytology* / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D005260:Female; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology* / Q000196:embryology / Q000254:growth & development; D013234:Stem Cells / Q000166:cytology* / Q000502:physiology