Mesenchymal stem cells significantly improved treatment effects of Linezolid on severe pneumonia in a rabbit model

The present study aimed to investigate whether co-administration of mesenchymal stromal cells (MSC) and linezolid (LZD) into a rabbit model of methicillin-resistant Staphylococcus aureus (MRSA)-infected pneumonia would bring a synergistic therapeutic effect. Human umbilical cord-derived MSCs (hUMSCs) were isolated and characterized. A rabbit model of pneumonia was constructed by delivering 1 × 10 10 CFU MRSA via a bronchoscope into the basal segment of lower lobe of right lung. Through analyzing vital sign, pulmonary auscultation, SpO 2 , chest imaging, bronchoscopic manifestations, pathology, neutrophil percentage, and inflammatory factors, we verified that a rabbit model of MRSA-induced pneumonia was successfully constructed. Individual treatment with LZD (50 mg/kg for two times/day) resulted in improvement of body weight, chest imaging, bronchoscopic manifestations, histological parameters, and IL-10 concentration in plasma ( P< 0.01), decreasing pulmonary auscultation, and reduction of IL-8, IL-6, CRP, and TNF-α concentrations in plasma ( P< 0.01) compared with the pneumonia model group at 48 and 168 h. Compared with LZD group, co-administration of hUMSCs (1 × 10 6 /kg for two times at 6 and 72 h after MRSA instillation) and LZD further increased the body weight ( P< 0.05). The changes we observed from chest imaging, bronchoscopic manifestations and pathology revealed that co-administration of hUMSCs and LZD reduced lung inflammation more significantly than that of LZD group. The plasma levels of IL-8, IL-6, CRP, and TNF-α in combined group decreased dramatically compared with the LZD group ( P< 0.05). In conclusion, hUMSCs administration significantly improved therapeutic effects of LZD on pneumonia resulted from MRSA infection in a rabbit model.