In this issue of the Korean Journal of Anesthesiology, an experimental study on the effect of hPMSC-derived exosomes on lung injury in a murine model of aspiration pneumonia is presented [6]. In this study, a gastric content-mimic, adjusted to pH 1.6 with HCl, was administered via oropharyngeal instillation to cause lung injury due to aspiration pneumonia. To investigate the effect of hPMSC-derived exosomes, these vesicles were intratracheally administered at 2- and 26-h post-aspiration. Thoracic micro-computed tomography was performed to confirm the development of acute lung injury. Additionally, respiratory function parameters (inspiratory volume, expiratory volume, dynamic compliance, and resistance) were measured, and the protein composition and abundance in the lung tissues from the aspiration pneumonia groups were analyzed using liquid chromatography-tandem mass spectrometry. The study demonstrated that intratracheal administration of hPMSC-derived exosomes alleviated the acute lung injury caused by aspiration pneumonia in mice. Moreover, the study clarified that the therapeutic effects were likely due to the attenuation of inflammation, oxidative stress, and apoptosis, in which the small, non-coding RNA molecule (a microRNA) hsa-let-7i-5p played key roles.

In humans, hsa-let-7i-5p plays a crucial role in post-transcriptional gene regulation by binding to messenger RNAs (mRNAs) to either degrade them or to block protein production. This impacts cell functions, such as proliferation, differentiation, and development, which are associated with disease conditions, such as cancer and inflammation.

Aspiration pneumonia, which is caused by inhalation of gastric contents into the lower airways, is a serious condition with high mortality rates, particularly in older patients. This condition can cause acute lung function decline, respiratory failure, bacterial infection, airway obstruction, and chemical pneumonitis [6]. Patients with aspiration pneumonia are often encountered in the operating room or intensive care unit. Treatment of aspiration pneumonia involves antibiotics, suctioning, bronchoscopy, and mechanical ventilation. However, aspiration pneumonia may be discovered late, and current therapies remain inadequate [7].

Various types of stem cells are being clinically tested [8]. Although some beneficial effects of stem cell treatment have been reported, their effectiveness has not yet been proven sufficiently to support application in clinical treatment. The disadvantages of stem cell treatment include biological risks, such as immune rejection, tumor formation, infection, and graft-versus-host disease, particularly in transplant patients. Other disadvantages include high cost, limited accessibility, ethical concerns, uncertain long-term outcomes, lack of insurance coverage, and unexpected complications.

The finding of the beneficial effects of hPMSC-derived exosomes on aspiration pneumonia-related lung injury suggests a new stem cell treatment-related approach that may in future help patients with aspiration pneumonia-related lung injury.