Impacts of Dental Follicle Cells and Periodontal Ligament Cells on the Bone Invasion of Well-Differentiated Oral Squamous Cell Carcinoma

<b>Background:</b> 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. <b>Methods:</b> 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-κB ligand (RANKL) and parathyroid hormone-related peptide (PTHrP). <b>Results:</b> 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. <b>Conclusions:</b> 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.