Purchase this article with an account.
Joo Youn Oh, Gavin Roddy, Hosoon Choi, Ryang Hwa Lee, Robert H. Rosa, Jr., Darwin J. Prockop; Defining a Therapeutic Window for Sterile Injuries of Cornea. The Anti-inflammatory Protein (TSG-6) Inhibits the Severe Second Phase of Inflammation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1122.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
We previously observed (Oh et al., Stem Cells, 2008; Oh et al., PNAS, 2010) that a sterile injury to the cornea can be rescued with the anti-inflammatory protein (TSG-6) that is secreted by adult stem/progenitor cells (MSCs). Here we sought to define how administration of TSG-6 within 4 hr after injury limits the excessive inflammatory reaction in the cornea.
We injured the cornea of rats by exposure to 100 % alcohol (30 sec) followed by scraping of the epithelium and limbus. We then used microarrays to detect candidate genes that might trigger the two distinct phases of the inflammatory response: the initial invasion of a small number of neutrophils in the first 4 hr (Phase I) and the massive invasion of neutrophils that peaks at about 24 hr (Phase II). The roles of the candidate genes were evaluated by experiments that included intracorneal injections of the proteins they encoded, experiments with cultures of corneal cells, and experiments with transgenic mice.
Genes up-regulated in Phase I included secretoneurin, a chemotactic and angiogenic neuropeptide, and the small heat shock protein HSPB4, a member of a family of chaperone proteins. Injection of secretoneurin into corneas of rats elicited the Phase I inflammatory response but not the Phase II. Injection of HSPB4 elicited Phase II. However, HSPB4 had no effect after resident macrophages were depleted with clodronate. In cultures, secretoneurin had no effect on secretion of pro-inflammatory cytokines by keratocytes or macrophages. In contrast, necrotic extracts of cornea activated keratocytes to increase synthesis and secretion of HSPB4. The HSPB4 then activated the NF-ΚB signaling pathway via TLR2 in macrophages to secrete the pro-inflammatory cytokines. TSG-6 attenuated NF-ΚB signaling in a CD44-dependent manner in cultures of macrophages. TSG-6 also decreased the Phase II response in wild-type mice with sterile injuries of the cornea but not in transgenic mice lacking the CD44 receptor.
After sterile injury to the cornea, the anti-inflammatory protein TSG-6 attenuates NF-ΚB signaling in resident macrophages and thereby limits the severe Phase II inflammatory response. Because the Phase II response begins about 4 hr after the injury, there is a well-defined therapeutic window for acute corneal injuries with TSG-6.
This PDF is available to Subscribers Only