Research Article Viability, Apoptosis, Proliferation, Activation, and Cytokine Secretion of Human Keratoconus Keratocytes after Cross-Linking Xuefei Song, 1 Tanja Stachon, 1 Jiong Wang, 2 Achim Langenbucher, 3 Berthold Seitz, 1 and Nóra Szentmáry 1 1 Department of Ophthalmology, Saarland University Medical Center, Kirrberger Straße 100, 66424 Homburg, Germany 2 Department of Ophthalmology, he First Ailiated Hospital of Zhengzhou University, Zhengzhou 450052, China 3 Experimental Ophthalmology, Saarland University, 66424 Homburg, Germany Correspondence should be addressed to Xuefei Song; song19850724@gmail.com Received 20 August 2014; Accepted 2 December 2014 Academic Editor: Antoni Camins Copyright © 2015 Xuefei Song et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Purpose. he purpose of this study was to determine the impact of cross-linking (CXL) on viability, apoptosis, proliferation, activation, and cytokine secretion of human keratoconus (KC) keratocytes, in vitro. Methods. Primary KC keratocytes were cultured in DMEM/Ham’s F12 medium supplemented with 10% FCS and underwent UVA illumination (370 nm, 2 J/cm 2 ) during exposure to 0.1% ribolavin and 20% Dextran in PBS. Twenty-four hours ater CXL, viability was assessed using Alamar blue assay; apoptosis using APO-DIRECT Kit; proliferation using ELISA-BrdU kit; and CD34 and alpha-smooth muscle actin (-SMA) expression using low cytometry. Five and 24 hours ater CXL, FGFb, HGF, TGF1, VEGF, KGF, IL-1, IL-6, and IL-8 secretion was measured using enzyme-linked-immunoabsorbent assay (ELISA). Results. Following CXL, cell viability and proliferation decreased ( < 0.05;  = 0.009), the percentage of apoptotic keratocytes increased ( < 0.05) signiicantly, and CD34 and -SMA expression remained unchanged ( > 0.06). Five hours ater CXL, FGFb secretion increased signiicantly ( = 0.037); however no other cytokine secretion difered signiicantly from controls ater 5 or 24 hours ( > 0.12). Conclusions. Cross-linking decreases viability, triggers apoptosis, and inhibits proliferation, without an impact on multipotent hematopoietic stem cell transformation and myoibroblastic transformation of KC keratocytes. CXL triggers FGFb secretion of KC keratocytes transiently (5 hours), normalizing ater 24 hours. 1. Introduction Keratoconus (KC) is the most common primary ectasia, char- acterized by localized corneal thinning leading to protrusion of the thinned cornea. It usually occurs in the second decade of life and afects both genders and all ethnicities [1, 2]. he estimated prevalence in the general population is 54 per 100,000 [3]. In recent years the technique of corneal collagen cross- linking (CXL), which has the ability to stop the progression of corneal ectasia in KC, has been developed [4, 5]. Infectious keratitis is a potentially blinding ocular disease of the cornea. Besides antimicrobial drugs, the use of CXL as photodynamic therapy (PDT) is also considered as potential alternative in the management of infectious keratitis [6– 10]. hus, CXL has also been described as ribolavin-UVA- photodynamic-inactivation (ribolavin-UVA-PDI) [11]. Recent studies have shown that, in normal keratocytes, CXL decreases viability and induces myoibroblastic trans- formation and multipotent haematopoietic stem cell transfor- mation but has no impact on apoptosis of the cells [12, 13]. In the short term, the iatrogenic thinning or swelling efect of the ribolavin solution on the cornea during CXL could also be described, depending on the properties of the ribolavin solution used [14]. However, the impact of CXL on human KC keratocytes has not yet been analyzed. Growth factors and interleukins regulate proliferation, motility, cellular interactions, diferentiation, apoptosis, and Hindawi Publishing Corporation BioMed Research International Volume 2015, Article ID 254237, 11 pages http://dx.doi.org/10.1155/2015/254237