# Whole Transcriptomic Analysis Identifies Candidate Biomarkers from Saliva of Temporomandibular Joint Osteoarthritis Patients

## TL;DR

This study identifies potential salivary biomarkers for temporomandibular joint osteoarthritis, offering new insights into its disease mechanisms and diagnostic possibilities.

## Contribution

The study proposes four candidate salivary genes as potential biomarkers for TMJOA through transcriptomic analysis and validation.

## Key findings

- RNA sequencing identified 743 overlapping differentially expressed genes between TMJOA patients and controls.
- CRIP1, PPA1, TARS1, and GCLC were validated as elevated in TMJOA patient saliva samples.
- Immune-related, metabolic, and osteoclast-related pathways were highlighted as key in TMJOA pathophysiology.

## Abstract

Temporomandibular joint osteoarthritis (TMJOA) is a degenerative disease characterized by progressive cartilage degeneration and subchondral bone remodeling, resulting in chronic pain and functional impairment. Although conservative treatments such as physical therapy and non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used, their effectiveness is limited due to the poorly understood pathophysiology of TMJOA. Identifying reliable molecular biomarkers is essential to improving early diagnosis and guiding therapeutic development. This proof-of-concept study aims to identify candidate salivary biomarkers for TMJOA using an integrative approach combining clinical validation with in silico analysis. RNA sequencing was performed on saliva samples from TMJOA patients and healthy controls. In parallel, publicly available transcriptomic dataset GSE205389 was analyzed to identify differentially expressed genes (DEGs). DEGs were validated using qRT-PCR. Gene set enrichment analysis (GSEA) and Metascape were used to explore biological pathways associated with TMJOA. Integration of clinical and in silico RNA sequencing datasets identified 2758 and 3548 DEGs, respectively, with 743 overlapping genes. Pathway enrichment analyses highlighted immune-related, metabolic and osteoclast-related pathways. Four genes, CRIP1, PPA1 and TARS1 (statistically significant) and GCLC (non-significant trend), were validated by qRT-PCR in the clinical saliva samples, confirming elevated expression in TMJOA patients. Validation of the in silico dataset showed an upregulation of PTK2B, ABL1, TNF and IL-1B, supporting their relevance as salivary biomarkers in TMJOA. This exploratory study identifies four candidate salivary genes, CRIP1, PPA1, TARS1 and GCLC, as candidate salivary biomarkers for TMJOA, offering insights into disease mechanisms. Larger studies are needed to validate these findings and assess their clinical utility.