Macrophages, GM-CSF and MARS Proteinosis (MacroMARS)

Study of Macrophage Function and of the GM-CSF Signaling Pathway in Alveolar Proteinosis by Mutations of the MARS Gene

Mutations in the MARS gene encoding methionyl-tRNA synthetase are responsible for a genetic form of alveolar proteinosis (PAP), but the pathophysiological mechanisms of the respiratory phenotype are not known.

The main hypothesis is that the PAP phenotype in these patients is secondary to a defective clearance of the surfactant by the alveolar macrophages.

The main objective of the study is to study the clearance capacity of lipoproteinaceous material by macrophages of patients with MARS related PAP. This will be investigate in cultured macrophages derived from peripheral blood monocytes of patients (patients with MARS related PAP) and controls (patients without MARS related PAP).

Study Overview

• Status: Completed
• Conditions: Genetic Mutation; Pulmonary Alveolar Proteinosis (PAP); MARS
• Intervention / Treatment: Biological: Blood collection; Biological: Bronchoalveolar lavage fluid collection

Detailed Description

Pulmonary alveolar proteinosis (PAP) is a rare respiratory disease characterized by the accumulation of lipoproteinaceous material within the pulmonary alveoli, resulting in the majority of cases from a defective clearance of the surfactant by intra-alveolar macrophages.

Mutations in the MARS gene encoding methionyl-tRNA synthetase are responsible for a genetic form of alveolar proteinosis, but the pathophysiological mechanisms leading to mutations in the respiratory phenotype are not known.

The main hypothesis is that the alveolar proteinosis phenotype in these patients is secondary to a defective clearance of the surfactant by the alveolar macrophages.

The main objective of the study is to study the clearance capacity of lipoproteinaceous material by macrophages of patients with MARS related PAP. This will be investigate in cultured macrophages derived from peripheral blood monocytes of patients (patients with MARS related PAP) and controls (patients without MARS related PAP).

The subjects and the controls will be included during a hospitalization during which a blood sample and a bronchoscopy with broncoalveolar lavage must be performed as part of their care.

• Study Type: Observational
• Enrollment (Actual): 20

Contacts and Locations

Study Locations

• France
  • Paris, France, 75015
    • Hôpital Necker-Enfants Malades

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: No older than 13 years (Child)
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Minor patients with alveolar proteinosis by mutations of the MARS gene and minor patients without alveolar proteinosis, hospitalized for their care at Necker Enfants Malades hospital and for whom a blood sample and a bronchoscopy with bronchoalveolar lavage must be performed for their care.

Description

Inclusion Criteria:

• Minors from 0 to 17 years hospitalized for their care at Necker Enfants Malades hospital and for whom a blood sample and a bronchoscopy with bronchoalveolar lavage must be performed as part of their care
• Information and consent of the holders of parental authority and the patient

Exclusion Criteria:

- Refusal of holders of parental authority or patient

Study Plan

How is the study designed?

Design Details

• Observational Models: Case-Control
• Time Perspectives: Prospective

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Patients; Minor patients with alveolar proteinosis by mutations of the MARS gene.	Biological: Blood collection; 2 to 5 ml; Biological: Bronchoalveolar lavage fluid collection; 5 to 25 ml
Controls; Minors patients without alveolar proteinosis.	Biological: Blood collection; 2 to 5 ml; Biological: Bronchoalveolar lavage fluid collection; 5 to 25 ml

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Measurement of the clearance	Measurement of the clearance of abnormal lipo-proteinaceous material (from patients) at 48h of culture by cultured macrophages derived from peripheral blood monocytes from patients and controls. Microscopic examination of cell samples prepared on slide after cytospin and stained with oil red'O.	Day 0

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Measurement of the clearance after supplementation with methionine	Measurement of the clearance of abnormal lipo-proteinaceous material (from patients) at 48h culture with methionine supplementation in culture medium by cultured macrophages derived from peripheral blood monocytes from patients and controls. Microscopic examination of cell samples prepared on slide after cytospin and stained with oil red'O.	Day 0
Cellular phenotyping and study of the GM-CSF pathway	Description : Study the impact of mutations on the cell phenotype and the GM-CSF signalling pathway. (i) CD11b and CD49d cell immunostaining which are surface markers of healthy alveolar macrophages ; (ii) measurement of the level of intracellular phosphorylation of STAT5 by flow cytometry; and (iii) measurement of the level of expression of the SPI1, PPARγ and ABCG1 genes by quantitative PCR. These measurements will be performed in cultured macrophages derived from peripheral blood monocytes of patients and controls, but also in alveolar macrophages directly isolated from the BAL fluid of patients and controls. All these measurements will be performed in response to incubation with GM-CSF.	Day 0

Collaborators and Investigators

• Sponsor: Assistance Publique - Hôpitaux de Paris
• Collaborators: URC-CIC Paris Descartes Necker Cochin
• Investigators: Principal Investigator: Alice HADCHOUEL, Assistance Publique - Hôpitaux de Paris

Study record dates

Study Major Dates

• Study Start (Actual): June 7, 2021
• Primary Completion (Actual): November 6, 2021
• Study Completion (Actual): November 6, 2021

Study Registration Dates

• First Submitted: March 19, 2021
• First Submitted That Met QC Criteria: March 19, 2021
• First Posted (Actual): March 23, 2021

Study Record Updates

• Last Update Posted (Actual): April 3, 2026
• Last Update Submitted That Met QC Criteria: March 30, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Pulmonary alveolar proteinosis (PAP); Mutations in the MARS gene; Methionyl-tRNA synthetase; Surfactant clearance; Alveolar macrophages
• Additional Relevant MeSH Terms: Respiratory Tract Diseases; Lung Diseases; Pulmonary Alveolar Proteinosis; Investigative Techniques; Specimen Handling; Clinical Laboratory Techniques; Diagnostic Techniques and Procedures; Diagnosis; Punctures; Surgical Procedures, Operative; Blood Specimen Collection
• Other Study ID Numbers: APHP201476; 2020-A02750-39 (Other Identifier: IDRCB number)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No