Expression of Concern.

"MiRNA-218 regulates osteoclast differentiation and inflammation response in periodontitis rats through MMP9", Cell. Microbiol. 2019;21:e12979, by Jie Guo, Xuemin Zeng, Jie Miao, Chunpeng Liu, Fulan Wei, Dongxu Liu, Zhong Zheng, Kang Ting, Chunling Wang, and Yi Liu. The Editors of Cellular Microbiology and the publisher John Wiley & Sons agree to publish an Expression of Concern regarding the above article, published online in Cellular Microbiology on November 16, 2018, in Wiley Online Library (https://onlinelibrary.wiley.com/doi/full/10.1111/cmi.12979). In September 2019, the journal was contacted regarding concerns about the data presented in Figures 6 and 7 because of high level of similarities in the graphs presented in these figures. The different bars in the graphs show identical height. The standard deviation bars are also of identical length. Although one graph expresses the number of TRAP-positive cells (Figure 6b) and the other graphs express the relative mRNA expression of different osteoclast-related genes (Figure 6c-g), all graphs are identical. The bars in the graphs in Figure 7 that represent 5 different osteoclast genes show the same height. Figures 6 and 7 show identical mRNA expression for a series of different genes: V-ATPase, NFATc1, CTSK, DC-STAMP and TRAP. In December 2019, the journal requested the authors to provide the raw data of the experiments presented in the article and for explanations of the similarities. The authors responded that the similarities were due to unintentional errors and provided Excel spread sheets containing processed data in March 2020. The data provided in the Excel sheets that were sent by the authors were analyzed and it was concluded that the calculations as shown in the Excel sheets are correct. However, the concerns raised regarding similarities in the heights of bars representing different parameters and narrow range of standard deviations presented in Figures 6-7 remained. The authors disagree with the concerns raised. In addition, the editors were concerned by manipulations of western blot images to represent single bands instead of doublets for COL1 in Figures 5 and 8 and for MMP9 in Figures 3A and C, 4C, 5A and D, and 8A. The first issue concerning COL1 bands has been addressed and corrected during the peer-review process. The latter has been clarified after publication and following a request from the editors for the raw data of all figures in the article. In the published article, western blots of MMP-9 in Figures 3A and C, 4C, 5A and D, and 8A show active-MMP-9 only and do not include pro-MMP-9 bands that were present in the original western blot experiments. The authors explained that on the original blots that were provided during the peer-review process, MMP-9 show doublets that represent pro-MMP-9 and active-MMP-9. As no significant difference was found for pro-MMP-9, the authors only presented single bands for active-MMP-9 in the publication version. The authors' institution, Shandong University, did not respond to a request from the Publisher and the Editor-in-Chief to investigate whether the data arose from the originally reported experiments, are unmodified, and are suitable for publication. As a result, the journal is issuing this expression of concern to readers.