In the coculture of HGFs and U937, upregulated EMMPRIN expression in U937, which may be triggered by HGFs, can enhance MMP-2 expression in HGFs. Crosstalk between HGFs and U937 involving MMP-2 from HGFs was proposed; EMMPRIN from U937 may play a particular role.

Background: Cluster of differentiation 147 (CD147) is a multifunctional glycoprotein that functions as an inducer of matrix metalloproteinase (MMP) expression in fibroblasts. Synergistically enhanced MMP-2 expression was recently observed in the coculture of human gingival fibroblasts (HGFs) and U937 human monocytic cells; however, the responsible mechanisms have not yet been fully established. The aim of this study was to evaluate the release of soluble CD147 in HGFs after coculturing with U937 cells and its functional effect on the enhancement of MMP-2 expression in HGFs.Methods: Enzyme-linked immunosorbent assay was used to determine the amount of CD147 protein in media, whereas real-time polymerase chain reaction was performed to evaluate the mRNA levels of CD147 and MMP-2 in HGFs and U937 cells.The enzyme activities of MMP-2 released from cells were examined by zymography. Transwell coculturing and conditioned media treatments were selected to rule out the effect of direct contact of HGFs and U937 cells. Results:The protein and mRNA expression of CD147 in HGFs were enhanced after transwell coculturing with U937 cells and exposure to U937-conditioned medium. MMP-2 enzyme activities in HGFs were also significantly increased by the coculturing methods. Administration of exogenous CD147 enhanced MMP-2 expression in HGFs, whereas treatment with cyclosporine-A, which inhibited CD147 expression, reduced U937-enhanced MMP-2 expression in HGFs. Conclusions: CD147 can interact with fibroblasts to stimulate the expression ofMMPs associated with periodontal extracellular matrix degradation. This study has demonstrated that CD147 released from fibroblasts might play a role in monocyteenhanced MMP-2 expression in HGFs. K E Y W O R D Santigens, CD147, fibroblasts, matrix metalloproteinase 2, monocytes, U937 cells J Periodontol. 2020;91:651-660.

Objective This in vitro study aimed to evaluate the expression of cyclophilin A (CyPA) in U937 monocytic cells after coculturing with the human gingival fibroblasts (HGFs) and the effect of CyPA on the augmentation of MMP‐2 expression in the coculture environment. Background Leukocyte infiltration in gingival connective tissue is one of the major findings in the lesions of inflammatory periodontal diseases. A crosstalk between the resident gingival fibroblasts and the recruited inflammatory cells that promote the expression of matrix metalloproteinases (MMPs) was proposed based on recent findings, whereas the cluster of differentiation 147 (CD147)‐CyPA pathway was suggested to be involved with the crosstalk. Material and Methods CyPA was released into media, in the independent or transwell coculture of HGF and U937 cells, as determined by enzyme‐linked immunosorbent assay, whereas intracellular mRNA expressions for CyPA and MMP‐2 were examined by quantitative real‐time polymerase chain reaction, in the transwell coculture or conditional medium models. Zymography was conducted to analyze the activities of pro‐MMP‐2/MMP‐2 released into the media. Results (a) A significantly increased CyPA protein level was observed in the transwell coculture media compared with that in the independent culture. (b) The transwell coculture‐enhanced mRNA expression for CyPA was noticed in U937 cells but not in HGFs. After adding with HGF‐conditioned medium, the mRNA enhancement in U937 cells occurred in a dose‐dependent manner. (c) Although the MMP‐2 activities significantly increased after transwell coculturing, the MMP‐2 mRNA enhancement was observed only in HGFs. (d) Exogenous CyPA could enhance MMP‐2 activities in HGFs in a dose‐dependent manner. However, the CyPA antagonist reduced the MMP‐2 activities in the transwell cocultures. (e) Moreover, the CyPA‐enhanced MMP‐2 activity in HGF was decreased significantly by the pathway inhibitor for c‐Jun amino‐terminal kinase (JNK). Conclusion Based on the present findings, we suggest that gingival fibroblasts could enhance the CyPA release from U937 cells, via the JNK pathway, resulting in MMP‐2 enhancement in fibroblasts. The finding shed light on a new mechanism of cellular interaction involving MMP‐2 and CyPA, in two cells.