Background: The fibrosing form of lung injury had bad progressive course and lethal outcome.
Aim of the work: This study throws light on the possible protective and/or therapeutic consequence of mesenchymal stem cell therapy in lung fibrosis induced by amiodarone in albino rat. In addition to study the possible recovery of damaged lung after amiodarone withdrawal.  Material & Methods: Forty five adult male albino rats were divided into five equal groups. Group I (control); group II (amiodarone) received amiodarone 30 mg/kg orally for 6 days /week for 6 weeks, group III (withdrawal); group IV (early stem cell) mesenchymal stem cell was administrated after 1st dose of amiodarone therapy ; group VI (late stem cell) mesenchymal stem cell was administrated immediately after amiodarone suspension . Lung samples were processed and examined using histological and immunohistochemical techniques and the obtained data was subjected to statistical analysis.
Results: Amiodarone treated group displayed obstructed bronchioles, collapsed alveoli, inflammatory cell infiltration ,thickened interalveolar septa and pulmonary vessels wall. Increased collagen fibers deposition between alveoli and around blood vessels in addition to highly expressed caspase-3. Group III (withdrawal) recorded only mild improvement. Group IV (early stem cell therapy ) showed advanced improvement of pulmonary alveolar architecture, on other side group V (late stem cell therapy)revealed moderate improvement of lung injury.
Conclusion: The majority of amiodarone lung toxicity manifestations and lung fibrosis were regressed by bone marrow derived mesenchymal stem cell (BMSCs) therapy and the best result obtained when stem cell initiated early in the development of pathogenesis.