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Background/purpose: Oral lichen planus (OLP) is a chronic inflammatory disorder characterized by basement membrane disruption, which plays a crucial role in its pathogenesis. Matrix metalloproteinases (MMPs), a group of proteolytic enzymes, contribute to the degradation of the basement membrane. The specific MMPs secreted by keratinocytes in OLP lesions and relevant regulatory mechanisms are not fully understood. This study aimed to investigate the involvement of MMPs in OLP pathogenesis, focusing on their expression in keratinocytes and regulatory mechanisms., Materials and Methods: MMP mRNA expression in OLP epithelium was analyzed using RNA sequencing data obtained from the Gene Expression Omnibus (GEO) database. Mucosa samples from 30 OLP patients and 30 healthy controls were collected to observe the expression and regulation of MMPs in keratinocytes. The involvement of the mitogen-activated protein kinase (MAPK) pathway in MMP regulation was studied using HaCaT cells., Results: RNA sequencing analysis revealed upregulation of MMP1 and MMP9 in OLP epithelium. MMP9 expression was predominantly observed in basal keratinocytes of OLP lesions. Elevated levels of phosphorylated c-Jun N-terminal kinase (JNK), a component of the MAPK pathway, were detected in OLP samples and co-localized with MMP9 in keratinocytes. Activation of the JNK pathway in HaCaT cells induced MMP9 expression, implicating JNK signaling in MMP9 regulation., Conclusion: Keratinocytes contribute to OLP pathogenesis by secreting MMP9 through JNK pathway activation. This understanding may provide insights into targeted therapeutic interventions for this chronic recurrent disease., Competing Interests: The authors have no conflicts of interest relevant to this article., (© 2024 Association for Dental Sciences of the Republic of China. Publishing services by Elsevier B.Vé.)