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Ting Su, Xueting Chen, Xulin Liao, Zheng Wan, Yunpeng Li, Winston W Y Kao, Wei Li, Yongxiong Chen, Zuguo Liu; Identification of the function of keratocan positive keratocytes. Invest. Ophthalmol. Vis. Sci. 2018;59(9):534.
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© ARVO (1962-2015); The Authors (2016-present)
Keratocytes (KCs) were previously reported to be homogenous and quiescent cells whose specific marker was keratocan (Kera). They formed an interconnected cellular network with one another through dendritic processes in corneal stroma and could migrate and be transition into myofibroblasts upon injury to cornea and induce scar formation during the wound healing. This study aimed to identify the exact function of Kera positive (+) KCs.
A mouse strain (Kera-mTmG cKO) exhibiting green fluorescence specifically in Kera + cells and a mouse strain (Kera-TGFβr2 cKO) whose TGFβr2 was deficient in Kera+ cells were established by conditional knockout methods using the Cre/loxP recombination system. The morphology and distribution of the Kera+ KCs were observed via corneal whole-mounts and paraffin sections of normal and alkali-burned corneas. The cell proliferation was determined by EDU detection. The transition of KCs was examined via the immunofluorescence (IF) staining with antibody to α-SMA and quantitative (q) RT-PCR. The extracellular matrix (ECM) genes expression of TGFβr2-Kera cKO and wild type (WT) mice were determined via qRT-PCR and /or Western blot analysis. Corneal neovascularization (CNV) was observed under a slit lamp microscope and evaluated via HE staining and IF staining with antibody to endothelial cell marker Endomucin.
Not all KCs were Kera-expressing cells with GFP in corneas. These Kera+ KCs arranged sparsely and unevenly in the stroma, and had no long dendritic processes, yet seldom connected with each other. They neither proliferate and migrate into the sites of tissue injury, nor expressed α-SMA and took part in closing the wound with the exception of the lengthened dendritic processes during corneal healing after alkali burn.The eye appearance and corneal histology of Kera-TGFβr2 cKO mice appeared indistinguishable from WT mice, except a bit thinner central corneal stroma and lower expression level of collagen type 1,3,4,6,8,12 and the proteoglycans such as biglycan, osteoglycin, decorin, lumican and Kera. After alkali burn, Kera-TGFβr2 cKO mice showed more abundant newly ingrowth corneal blood vessels but hadn’t corneal stroma thickening compared with WT mice.
The Kera+ KCs were not involved in closing corneal wound, but could promote CNV by decreased ECM synthesis.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Whole-mounts of normal and alkali-burned Kera-mTmG cKO mice cornea
Kera-TGFβr2 cKO mice exhibited exacerbated CNV
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