Severe tissue defects in the oral and maxillofacial region are commonly caused by tumor resection and trauma and can impair physiological function and aesthetics in patients. Applying a soft-tissue free flap transfer may avoid exposing important blood vessels and nerves and restore basic anatomical structures and facial features. However, the outcomes of soft-tissue free flap transfer have tended to be unsatisfactory because of the exquisite anatomical structure and complicated functions of the oral and maxillofacial region. Therefore, it is clinically important to choose a proper reconstructive method based on specific tissue defects and to optimize the processes involved in the designing and harvesting of soft-tissue free flaps. In this review, we summarize the application of soft-tissue free flaps in oral and maxillofacial defects and strategies for optimizing the quality of tissue reconstruction.

Oral squamous cell carcinoma (OSCC) is a common head and neck malignancy. Approximately 50% to 60% of patients with OSCC are diagnosed at a locally advanced stage (clinical staging Ⅲ-Ⅳa). Even with systemic and sequential treatment primarily based on surgery, the 5-year overall survival rate remains below 50%, and patients often suffer from postoperative functional impairments such as difficulties with speaking and swallowing. Programmed death receptor-1 (PD-1) inhibitors are increasingly used in the neoadjuvant treatment of locally advanced OSCC and have shown encouraging efficacy. However, clinical practice still faces key challenges, including the definition of indications, optimization of combination regimens, and standards for efficacy evaluation. Based on the latest research advances worldwide and the clinical experience of the expert group, this expert consensus systematically evaluates the application of PD-1 inhibitors in the neoadjuvant treatment of locally advanced OSCC, covering combination strategies, treatment cycles and surgical timing, efficacy assessment, use of biomarkers, management of special populations and immune related adverse events, principles for immunotherapy rechallenge, and function preservation strategies. After multiple rounds of panel discussion and through anonymous voting using the Delphi method, the following consensus statements have been formulated: 1) Neoadjuvant therapy with PD-1 inhibitors can be used preoperatively in patients with locally advanced OSCC. The preferred regimen is a PD-1 inhibitor combined with platinum based chemotherapy, administered for 2-3 cycles. 2) During the efficacy evaluation of neoadjuvant therapy, radiographic assessment should follow the dual criteria of Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 and immune RECIST (iRECIST). After surgery, systematic pathological evaluation of both the primary lesion and regional lymph nodes is required. For combination chemotherapy regimens, PD-L1 expression and combined positive score need not be used as mandatory inclusion or exclusion criteria. 3) For special populations such as the elderly (≥ 70 years), individuals with stable HⅣ viral load, and carriers of chronic HBV/HCV, PD-1 inhibitors may be used cautiously under the guidance of a multidisciplinary team (MDT), with close monitoring for adverse events. 4) For patients with a poor response to neoadjuvant therapy, continuation of the original treatment regimen is not recommended; the subsequent treatment plan should be adjusted promptly after MDT assessment. Organ transplant recipients and patients with active autoimmune diseases are not recommended to receive neoadjuvant PD-1 inhibitor therapy due to the high risk of immune related activation. Rechallenge is generally not advised for patients who have experienced high risk immune related adverse events such as immune mediated myocarditis, neurotoxicity, or pneumonitis. 5) For patients with a good pathological response, individualized de-escalation surgery and function preservation strategies can be explored. This consensus aims to promote the standardized, safe, and precise application of neoadjuvant PD-1 inhibitor strategies in the management of locally advanced OSCC patients.

The homeostasis of the oral microbiome is essential for maintaining host health, and its disruption can contribute to the development of both oral and systemic diseases. The oral microbiome influences the initiation and progression of oral squamous cell carcinoma (OSCC) through multiple mechanisms. ① Oral microbes can directly act on epithelial cells, inducing cell-cycle dysregulation, DNA damage, and epigenetic reprogramming, thereby promoting cell proliferation and epithelial-mesenchymal transition (EMT). For example, Fusobacterium nucleatum binds to E-cadherin via its adhesin FadA, activating the β-catenin pathway and directly driving tumor-cell proliferation and EMT, while Porphyromonas gingivalis reprograms lipid synthesis to enhance the stemness of OSCC cells. ② Oral microbes and their metabolites reshape the tumor immune-suppressive microenvironment by altering the density, composition, and function of infiltrating immune cells. Periodontal pathogens induce a chronic inflammatory state in the oral cavity and activate signaling cascades such as MAPK/ERK and NF-κB, thereby indirectly accelerating OSCC progression. ③ Bacteria and viruses in the oral cavity exhibit synergistic interactions. Bacterial biofilms and proteases facilitate viral activation and infection, and microbial metabolites such as butyrate can enhance histone acetylation to promote the lytic reactivation of latent viruses. ④ At the ecological level, the depletion of commensals and expansion of anaerobic pathogens disrupt the metabolic network of the community, and complex interspecies interactions collectively shape a pro-carcinogenic niche that drives OSCC progression on multiple fronts. Future studies should integrate multi-omics analyses with longitudinal clinical cohorts to explore functional causal networks of key microbial communities and develop individualized targeted intervention strategies for microecology.

Oral potentially malignant disorders (OPMDs) are precursors of oral squamous cell carcinoma (OSCC). Deregulated cellular energy metabolism is a critical hallmark of cancer cells. Peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC1α) plays vital role in mitochondrial energy metabolism. However, the molecular mechanism of PGC1α on OPMDs progression is less unclear. Therefore, we investigated the effects of knockdown PGC1α on human dysplastic oral keratinocytes (DOKs) comprehensively, including cell proliferation, cell cycle, apoptosis, xenograft tumor, mitochondrial DNA (mtDNA), mitochondrial electron transport chain complexes (ETC), reactive oxygen species (ROS), oxygen consumption rate (OCR), extracellular acidification rate (ECAR), and glucose uptake. We found that knockdown PGC1α significantly inhibited the proliferation of DOKs in vitro and tumor growth in vivo, induced S-phase arrest, and suppressed PI3K/Akt signaling pathway without affecting cell apoptosis. Mechanistically, downregulated of PGC1α decreased mtDNA, ETC, and OCR, while enhancing ROS, glucose uptake, ECAR, and glycolysis by regulating lactate dehydrogenase A (LDHA). Moreover, SR18292 (an inhibitor of PGC1α) induced oxidative phosphorylation dysfunction of DOKs and declined DOK xenograft tumor progression. Thus, our work suggests that PGC1α plays a crucial role in cell proliferation by reprograming energy metabolism and interfering with energy metabolism, acting as a potential therapeutic target for OPMDs.