MDPI Acta Medica Okayama 2072-6694 17 9 2025 Impacts of Dental Follicle Cells and Periodontal Ligament Cells on the Bone Invasion of Well-Differentiated Oral Squamous Cell Carcinoma 1559 EN Anqi Chang Department of Oral Pathology and Medicine, Okayama University Kiyofumi Takabatake Department of Oral Pathology and Medicine, Okayama University Tianyan Piao Department of Oral Pathology and Medicine, Okayama University Takuma Arashima Department of Oral Pathology and Medicine, Okayama University Hotaka Kawai Department of Oral Pathology and Medicine, Okayama University Htoo Shwe Eain Department of Oral Pathology and Medicine, Okayama University Yamin Soe Department of Oral Pathology and Medicine, Okayama University Zin Zin Min Department of Oral Pathology and Medicine, Okayama University Keisuke Nakano Department of Oral Pathology and Medicine, Okayama University Hitoshi Nagatsuka Department of Oral Pathology and Medicine, Okayama University Background: Oral squamous cell carcinoma (OSCC) frequently invades the jawbone, leading to diagnostic and therapeutic challenges. While tumor-bone interactions have been studied, the specific roles of dental follicle cells (DFCs) and periodontal ligament cells (PDLCs) in OSCC-associated bone resorption remain unclear. This study aimed to compare the effects of DFCs and PDLCs on OSCC-induced bone invasion and elucidate the underlying mechanisms. Methods: Primary human DFCs and PDLCs were isolated from extracted third molars and characterized by Giemsa and immunofluorescence staining. An in vitro co-culture system and an in vivo xenograft mouse model were established using the HSC-2 OSCC cell line. Tumor invasion and osteoclast activation were assessed by hematoxylin and eosin (HE) and tartrate-resistant acid phosphatase (TRAP) staining. Immunohistochemical analysis was performed to evaluate the expression of receptor activator of NF-kappa B ligand (RANKL) and parathyroid hormone-related peptide (PTHrP). Results: DFCs significantly enhanced OSCC-induced bone resorption by promoting osteoclastogenesis and upregulating RANKL and PTHrP expression. In contrast, PDLCs suppressed RANKL expression and partially modulated PTHrP levels, thereby reducing osteoclast activity. Conclusions: DFCs and PDLCs exert opposite regulatory effects on OSCC-associated bone destruction. These findings underscore the importance of stromal heterogeneity and highlight the therapeutic potential of targeting specific stromal-tumor interactions to mitigate bone-invasive OSCC. No potential conflict of interest relevant to this article was reported.