Mesenchymal stromal cell therapy for chronic lung diseases: experimental and clinical evidence.

INTRODUCTION: Cell therapy has emerged as an alternative option for chronic lung diseases with the highest rates of morbidity and mortality rates worldwide. AREAS COVERED: This review addresses the definition of mesenchymal stromal cells (MSCs), their properties, mechanisms of action, as well as preclinical and clinical studies that have used cell therapy in chronic lung diseases such as asthma, chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, pulmonary arterial hypertension, and silicosis. Ongoing clinical trials are also presented. EXPERT OPINION: Experimental evidence has shown that MSCs have immunomodulatory and regenerative properties that could rescue impaired lung function and histoarchitecture. Their beneficial effects have been mainly associated with their ability to communicate with target cells through the secretion of soluble mediators and extracellular vesicles or even through transfer of organelles (e.g. mitochondria). MSC-derived conditioned medium, extracellular vesicles and mitochondria induce beneficial effects in selected scenarios. The initial results in clinical trials were modest compared with the experimental results, therefore researchers were encouraged to move from bedside back to bench to develop new strategies able to potentiate the effects of MSCs.