Distinct Molecular Signature of Earlobe Keloids: Integrated Transcriptomic Analysis of Extracellualr Matrix,...

Keloids are fibroproliferative scars that extend beyond the original wound margins and may cause pain, pruritus, and substantial psychosocial distress. Earlobe keloids are common, clinically distinctive lesions with high recurrence rates; however, the molecular mechanisms underlying their development remain incompletely characterized. Existing transcriptomic studies have largely focused on extracellular matrix genes, with limited integration of metabolism-related pathways.

To characterize the integrated transcriptomic profile of earlobe keloids compared with site-matched normotrophic scars, allowing the characterization of a site-specific molecular profile, focusing on collagen and extracellular matrix, metalloproteinases, and metabolism-related genes, and to validate selected targets at the mRNA and protein levels.

In this primary analytical case-control study, tissue samples were obtained from 11 earlobe keloids and 10 normotrophic earlobe scars in adults aged 18-50 years. After histopathological confirmation, total RNA was extracted and analyzed using next-generation RNA sequencing on the Ion S5 platform. Differentially expressed genes were identified using an absolute fold change ≥ 2 and a false discovery rate (FDR)-adjusted p value < 0.05, as calculated in Ion Reporter. Panels of collagen and extracellular matrix genes, metalloproteinase-related genes, and metabolism-related genes were selected for validation by quantitative real-time polymerase chain reaction, with ACTB and GAPDH as housekeeping genes. Relative expression was calculated using the 2^-ΔΔCt method. ADAM12 protein levels were quantified in tissue lysates using enzyme-linked immunosorbent assay. Statistical significance was set at p < 0.05.

RNA sequencing identified 20,809 genes across all samples, of which 664 were differentially expressed between keloid and normotrophic scar tissue. Earlobe keloids showed marked upregulation of collagen and extracellular matrix genes, including FN1, COL1A1, COL1A2, COL3A1, COL5A1, COL5A2, SPARC, LOX, and LOXL2, indicating reinforced matrix deposition and crosslinking. Metalloproteinase genes, such as ADAM12, MMP2, MMP11, MMP13, ADAMTS2, and ADAMTS12, together with TIMP1, were also overexpressed. Quantitative real-time PCR showed high concordance with transcriptomic fold changes, and ADAM12 protein was significantly increased in keloid tissue compared with normotrophic scars (p < 0.001). Metabolism-related genes, CPXM1, GALNT5, CHST6, and NOX4, were overexpressed, whereas ACADM, LEPR, APOC1, THRSP, and AWAT2 were downregulated, suggesting altered glycosylation, oxidative stress, and disturbed lipid metabolism in earlobe keloids.

Earlobe keloids display a site-specific molecular profile characterized by coordinated dysregulation of collagen, metalloproteinases, and metabolism-related genes. The convergence of extracellular matrix accumulation, protease-antiprotease imbalance, and metabolic reprogramming supports the concept of keloids as metabolically active fibrotic tumors and identifies targets, such as ADAM12 and NOX4, for future translational studies. These findings reinforce the concept of anatomical site-dependent keloid biology and support targeted therapeutic approaches.

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