Meteorin-like protein, IL-1β, TNF-α, and IL-10 levels in peri-implant crevicular fluid in peri-implant health and peri-implantitis: a comparative cross-sectional study

Abstract Background: Peri-implantitis is a plaque-associated inflammatory disease that leads to progressive loss of the bone supporting dental implants, yet clinical probing and radiography alone often detect it only after substantial tissue damage has already occurred. Meteorin-like (Metrnl), a recently described immunoregulatory cytokine linked to anti-inflammatory macrophage activity, has been associated with disease severity in periodontitis, but has not previously been examined in the peri-implant crevicular fluid (PICF) compartment. This study aimed to compare PICF Metrnl concentrations between peri-implant health and peri-implantitis and to explore their relationship with local pro- and anti-inflammatory cytokines and clinical parameters. Methods: In this comparative cross-sectional study, 68 participants (34 with peri-implant health and 34 with peri-implantitis; one implant per participant) were assessed according to the 2017 World Workshop case definitions. Clinical parameters (plaque index, bleeding on probing, relative attachment level, and probing depth) were recorded by a single calibrated examiner, and PICF was collected using standardized paper strips. PICF eluate concentrations of Metrnl, IL-1β, TNF-α, and IL-10 were measured using commercially available ELISA kits. Metrnl was expressed in ng/mL, whereas IL-1β, TNF-α, and IL-10 were expressed in pg/mL. Group comparisons used independent-samples or Welch's t-tests and Mann–Whitney U tests as appropriate. Associations with Metrnl were evaluated using Spearman correlations calculated for the whole sample, separately within each diagnostic group, and as group-adjusted partial correlations; ROC analysis was exploratory. Results: PICF Metrnl concentrations were markedly lower in peri-implantitis than in peri-implant health, while IL-1β and TNF-α were higher and IL-10 was lower (all p < 0.001). Strong whole-sample correlations between Metrnl, cytokines, and clinical parameters were largely attributable to separation between the diagnostic groups. Within the peri-implantitis group, positive correlations remained between Metrnl and TNF-α and between Metrnl and bleeding on probing. In this selected sample, Metrnl showed complete separation between the groups in exploratory ROC analysis; this finding should not be interpreted as a validated diagnostic threshold. Conclusions: PICF Metrnl concentrations differed between peri-implant health and peri-implantitis and varied with the local inflammatory profile in this sample. These findings identify Metrnl as a candidate biomarker for further investigation but do not establish diagnostic validity or a causal role. Independent, prospectively recruited cohorts that include intermediate peri-implant conditions are needed before clinical application can be considered.