Retinoic acid treatment abrogates elastase-induced pulmonary emphysema in rats

Pulmonary emphysema is a common disease(1) in which destruction of the lung's gas-exchange structures (alveoli)(2) leads to inadequate oxygenation(3), disability(4) and frequently death(1); lung transplantation provides its only remediation. Because treatment of normal rats with all-trans-retinoic acid increases the number of alveoli(5), we tested whether a similar effect would occur in rats with emphysema. Elastase was instilled into rat lungs, producing changes characteristic of human(2) and experimental(6) emphysema: increased lung volume reflecting a loss of lung elastic recoil, larger but fewer alveoli and diminished volume-corrected alveolar surface area due to destruction of alveolar walls. Treatment with all-trans-retinoic acid reversed these changes providing nonsurgical remediation of emphysema and suggesting the possibility of a similar effect in humans.