Roles of thrombospondin-1 and -2 in regulating corneal and iris angiogenesis

Invest Ophthalmol Vis Sci. 2004 Apr;45(4):1117-24. doi: 10.1167/iovs.03-0940.


Purpose: Thrombospondin (TSP)-1 and -2 are important antiangiogenic factors thought to be involved in maintaining corneal avascularity (angiogenic privilege). This study was undertaken to investigate whether deficiencies of these factors altered developmental and inflammation-induced angiogenesis in the cornea and developmental angiogenesis of the iris of mice.

Methods: Expression of TSP-1 and -2 mRNA and protein was assayed in cornea and iris stroma by RT-PCR and Western blot. Corneas and irides of TSP-1(-/-), TSP-2(-/-), and TSP-1,2(-/-) mice aged 2, 3, and 6 months, and wild-type control mice, were analyzed for spontaneous angiogenesis biomicroscopically, histologically, and with CD31 immunohistochemistry. The mouse model of suture-induced, inflammatory corneal neovascularization was used to evaluate the lack of TSP-1,2 and both TSPs on induced-corneal angiogenesis. Seven days after intrastromal placement of three 11-0 sutures, vascularized areas were analyzed morphometrically on CD31-stained corneal flatmounts.

Results: Corneas and irises from normal mouse eyes constitutively expressed TSP-1 and -2 mRNAs and proteins. Corneas of TSP-1(-/-), -2(-/-), and -1,2(-/-) mice displayed no evidence of spontaneous developmental-postnatal angiogenesis, although irises of these mice contained significantly increased iris vessel density compared with wild-type animals (P < 0.01). One week after suturing, corneas of all TSP(-/-) mice had significantly greater corneal angiogenesis than those of control mice (P < 0.05). TSP-1(-/-) had a significantly greater effect on induced corneal neovascularization than did TSP-2(-/-), with the opposite being the case in developmental iris angiogenesis (P < 0.01).

Conclusions: Corneal avascularity during development is redundantly regulated, shown by the fact that lack of the antiangiogenic factors TSP-1 and/or -2 resulted in no spontaneous corneal angiogenesis. By contrast, TSP-1, more than TSP-2, helps to suppress inflammation-induced corneal angiogenesis postnatally, implying that angiogenic privilege in the cornea is actively maintained.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blotting, Western
  • Cornea / metabolism
  • Corneal Neovascularization / metabolism*
  • Corneal Neovascularization / pathology
  • Female
  • Gene Deletion
  • Iris / blood supply*
  • Iris / pathology
  • Male
  • Mice
  • Mice, Knockout
  • Neovascularization, Pathologic / metabolism*
  • Neovascularization, Pathologic / pathology
  • Platelet Endothelial Cell Adhesion Molecule-1 / metabolism
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Thrombospondin 1 / genetics
  • Thrombospondin 1 / physiology*
  • Thrombospondins / genetics
  • Thrombospondins / physiology*


  • Platelet Endothelial Cell Adhesion Molecule-1
  • RNA, Messenger
  • Thrombospondin 1
  • Thrombospondins
  • thrombospondin 2