Antenatal Endotoxin Impairs Lung Mechanics and Increases Sensitivity to Ventilator-Induced Lung Injury in Newborn Rat Pups.

Perinatal inflammation due to chorioamnionitis and ventilator-induced lung injury (VILI) at birth is independent risk factors for the development of bronchopulmonary dysplasia (BPD). We have previously shown that antenatal endotoxin (ETX) causes abnormal lung structure and function in 2-week-old rats, but whether ETX impairs lung mechanics at birth and increases risk for VILI is unknown. Fetal rats were exposed to 10 µg endotoxin or saline via intra-amniotic injection. At birth (D0) or 7 days (D7), rats received 90 min of lung protective ventilation [PROTECT group; tidal volume (Vt) = 6 ml/kg with positive end expiratory pressure (PEEP) = 2 cmH2O]; P20 ventilation [plateau pressure (Pplat) = 20 cmH2O, PEEP = 0]; or P24 ventilation (Pplat = 24 cmH2O, PEEP = 0, only applied to D7). Prior to prolonged ventilation at D0, endotoxin-exposed rats had decreased compliance and inspiratory capacity (IC) compared to controls. At D7, endotoxin was associated with reduced compliance. High-pressure ventilation (P20 and P24) tended to increase IC and compliance in all saline-treated groups. Ventilation at D0 with P20 increased IC and compliance when applied to saline-treated but not endotoxin-exposed pups. At D7, P24 ventilation of endotoxin-exposed pups increased elastance, bronchoalveolar lavage protein content, and IL-1b and TEN-C mRNA expression in comparison to the saline group. In summary, antenatal endotoxin exposure alters lung mechanics at birth and 1 week of life and increases susceptibility to VILI as observed in lung mechanics, alveolocapillary barrier injury, and inflammatory mRNA expression. We speculate that antenatal inflammation primes the lung for a more marked VILI response, suggesting an adverse synergistic effect of antenatal and postnatal exposures.

Breast Cancer Cells Transition from Mesenchymal to Amoeboid Migration in Tunable Three-Dimensional Silk-Collagen Hydrogels.

Invading cancer cells adapt their migration phenotype in response to mechanical and biochemical cues from the extracellular matrix. For instance, mesenchymal migration is associated with strong cell-matrix adhesions and an elongated morphology, while amoeboid migration is associated with minimal cell-matrix adhesions and a rounded morphology. However, it remains challenging to elucidate the role of matrix mechan-ics and biochemistry, since these are both dependent on ECM protein concentration. Here, we demonstrate a composite silk fibroin and collagen I hydrogel where stiffness and microstructure can be systematically tuned over a wide range. Using an overlay assay geometry, we show that the invasion of metastatic breast cancer cells exhibits a biphasic dependence on silk fibroin concentration at fixed collagen I concentration, first increasing as the hydrogel stiffness increases, then decreasing as the pore size of silk fibroin decreases. Indeed, mesenchymal morphology exhibits a similar biphasic depen-dence on silk fibroin concentration, while amoeboid morphologies were favored when cell-matrix adhesions were less effective. We used exogenous biochemical treatment to perturb cells towards increased contractility and a mesenchymal morphology, as well as to disrupt cytoskeletal function and promote an amoeboid morphology. Overall, we envision that this tunable biomaterial platform in a 96-well plate format will be widely applicable to screen cancer cell migration against combinations of designer biomaterials and targeted inhibitors.