Lung transplantation is the only therapeutic alternative for more and more patients with respiratory diseases in their most advanced stages.

The most limiting factor to achieve long term survival si chronic lung allograft dysfunction, a multifactorial disease without an effective treatment.

The immunomodulatory capacity of mesenchymal stem cells enables them to be a potential therapeutic agent for this condition.

The objective of this study is to assess the safety of endobronchial administration of allogeneic MSCs in patients with chroniclung allograft dysfunction.

Inclusion Criteria:

Patients should have signed written informed consent. Adult patients ≥18 years of age at the time of enrolment Patients recipients of a uni or bipulmonary transplant An established diagnosis of BOS ≧ 0p (FEV1≤90% and / or FEF 25-75% ≤ of the baseline value with no other justifying cause) in the last 6 months.

Exclusion Criteria:

• History of lobar transplantation History of heart-lung transplantation Active infection at the time of inclusion. Active Acute Rejection not treated at the time of inclusion. Oncological history (except cutaneous basal cell or carcinoma in situ) Systemic autoimmune diseases. Active HIV / HBV / HCV infection (confirmed by serology or PCR) Proximal airway stenosis Pregnancy Performance status 3 or 4 (confined to bed or chair for more than 50% of waking hours, able only to perform some self-care activities) Estimated survival less than 3 months. Known hypersensitivity to components used in the production of allogeneic MSCs. Any circumstance that, in the opinion of the investigator, compromises the patient's ability to participate in the clinical trial.