Study of Blood Monocytes as a Predictive Marker of Cystic Fibrosis-related Bone Disease

Hypothesis: Circulating monocytes RANK and MCSF-R expression is predictive of Cystic Fibrosis-related Bone Disease.

Study design: Single-center comparative cross-sectional study Population: Patients with a CFTR channel mutation causing cystic fibrosis consulting the Centre de Ressources et de Compétences de la Mucoviscidose (CRCM) at Reims University Hospital will be recruited. Healthy controls will be recruited from donors at the Etablissement Français du Sang Grand Est, Reims.

Judgment criteria:

• Main judgment criterion: X Expression level of CD115 (MCSF receptor) and CD265 (RANK) evaluated by flow cytometry receptors on the membranes of circulating monocytes.

• Secondary judgment criteria: X Rate of circulating CD115 +, CD265 +, CD115 + / CD265 + monocytes X Number of multinucleated cells with more than 2 nuclei and with an actin ring observed under fluorescence microscopy after osteoclastic differentiation X Surface of dentin resorbed in vitro by osteoclasts during an osteoclastic functionality test on dentin X Serum S1P levels assayed by ELISA technique.

Investigation plan:

Any eligible patient will be offered to participate in the study during the consultation at the CRCM. If the patient agrees to participate in the study, he/she will be included. Participation in the study will not affect its coverage. Participation will lead to the collection of three tubes of whole blood additional to those used as part of usual care, as well as the collection of demographic data (age, sex, height, weight, body mass index), sports practice, clinical images and interpretation, medical history (diabetes, infectious status, bone metabolism disorders, drug treatments followed, psychiatric disorders). Any subsequent donor from the EFS GE collected under the ALC / PIL / DIR / AJR / FO / 606 agreement and presenting characteristics of age +/- 2 years and identical gender will then be included.

Statistical analysis plan:

Qualitative variables will be described in terms of number and percentage. The quantitative distribution variables according to the Normal law will be described in the form of mean +/- standard deviation or in the form of boxplots (median, quartiles, deciles) if a distribution not following the Normal law is observed. ANOVA test, non-parametric Wilcoxon signed-rank test or chi² test will be aplied depending on the application conditions. A value of p <0.05 will be considered statistically significant.