In Australia 7% of all neonates require assisted ventilation due to respiratory difficulties. Mechanical ventilation can cause lung injury and inflammation, leading to chronic lung disease. A therapy that can modulate the pulmonary inflammatory response could therefore prevent chronic lung disease. Human amnion epithelial cells (hAECs) are stem cells isolated from term placentae, with the capacity to modulate the immune system. We hypothesised that ventilation-induced lung injury and inflammation in preterm lambs would be prevented by hAECs.
Lambs were delivered at 126 days of gestation (term is 147 days). Vehicle (ventilation; n=5) or 90x106 hAECs (ventilation+hAECs; n=6) were injected intratracheally and intravenously within 5 min of delivery. Lambs were ventilated for 2 hours to induce injury. A cohort of unventilated control (UVC; n=5) lambs was also assessed. Leukocytes from blood, spleen and bronchoalveolar lavage fluid (BALF) were collected at post-mortem for phenotypic analysis and measurement of T-cell proliferation. Relative mRNA expression was used to assess lung inflammation and injury. Plasma cytokine levels were assessed by ELISA.
BALF expression of CD21 and CD44 was greater in ventilation (p=0.031 and p=0.004, respectively) compared to both UVC and ventilation+hAECs groups. Proliferative responses of T-cells were not different. The relative mRNA expression of cytokines IL-1 (p<0.001), IL-6 (p=0.009) and IL-8 (p=0.007) and injury-associated genes CYR61 (p=0.005) and EGR1 (p=0.005) were increased in ventilation and ventilation+hAEC groups compared to UVC. IL-10 plasma cytokine levels were increased in ventilation compared to UVC (p<0.001) and ventilation+hAECs groups (p=0.003), but TNF-α and IL-6 were not different.
Ventilation induces an inflammatory response within the lung, demonstrated by B cell (CD21) and memory cell activation (CD44) and increases in expression of inflammatory cytokine genes (IL-1, IL-6 and IL-8). The inflammatory response is associated with injury as indicated by the expression of early-response genes (CYR61 and EGR1). Administration of hAECs prevents the initial local inflammatory response, but may not prevent early injury, in response to mechanical ventilation.