A simple method for the formalin fixation of lungs in toxicological pathology studies

Reduced SARS-CoV-2 disease outcomes in Syrian hamsters receiving immune sera: Quantitative image analysis in pathologic assessments

There is a need to standardize pathologic endpoints in animal models of SARS-CoV-2 infection to help benchmark study quality, improve cross-institutional comparison of data, and assess therapeutic efficacy so that potential drugs and vaccines for SARS-CoV-2 can rapidly advance. The Syrian hamster model is a tractable small animal model for COVID-19 that models clinical disease in humans. Using the hamster model, the authors used traditional pathologic assessment with quantitative image analysis to assess disease outcomes in hamsters administered polyclonal immune sera from previously challenged rhesus macaques. The authors then used quantitative image analysis to assess pathologic endpoints across studies performed at different institutions using different tissue processing protocols. The authors detail pathological features of SARS-CoV-2 infection longitudinally and use immunohistochemistry to quantify myeloid cells and T lymphocyte infiltrates during SARS-CoV-2 infection. High-dose immune sera protected hamsters from weight loss and diminished viral replication in tissues and reduced lung lesions. Cumulative pathology scoring correlated with weight loss and was robust in distinguishing IgG efficacy. In formalin-infused lungs, quantitative measurement of percent area affected also correlated with weight loss but was less robust in non-formalin-infused lungs. Longitudinal immunohistochemical assessment of interstitial macrophage infiltrates showed that peak infiltration corresponded to weight loss, yet quantitative assessment of macrophage, neutrophil, and CD3+ T lymphocyte numbers did not distinguish IgG treatment effects. Here, the authors show that quantitative image analysis was a useful adjunct tool for assessing SARS-CoV-2 treatment outcomes in the hamster model.

Mg2+ -mediated autophagy-dependent polarization of macrophages mediates the osteogenesis of bone marrow stromal stem cells by interfering with macrophage-derived exosomes containing miR-381

Magnesium ion (Mg²⁺ ) has received increased attention due to the roles it plays in promoting osteogenesis and preventing inflammation. This study was designed to investigate the mechanism by which Mg²⁺ influences the osteoblastic differentiation of bone marrow stromal stem cells (BMSCs). The polarization of Mø (macrophages) was measured after treatment with Mg²⁺ . Meanwhile, autophagy in Mø was measured by detecting LC3B expression. Mø-derived exosomes were isolated and cocultured with BMSCs; after which, osteogenic differentiation was evaluated by Alizarin Red staining and detection of alkaline phosphatase (ALP). Our results showed that Mg²⁺ could induce autophagy in macrophages and modulate the M1/M2 polarization of macrophages. Mg²⁺ -mediated macrophages could facilitate the osteogenic differentiation of BMSCs by regulating autophagy, and this facilitation by Mg²⁺ -mediated macrophages was closely related to macrophage-derived exosomes, and especially exosomes containing miR-381. However, miR-381 in macrophages did not influence autophagy or the polarization of Mg²⁺ -mediated macrophages. Furthermore, macrophage-derived exosomes containing miR-381 mainly determined the osteogenic differentiation of BMSCs. Mg²⁺ -mediated macrophages were shown to promote the osteogenic differentiation of BMSCs via autophagy through reducing miR-381 in macrophage-derived exosomes. In conclusion, our results suggest Mg²⁺ -mediated macrophage-derived exosomes containing miR-381 as novel vehicles for promoting the osteogenic differentiation of BMSCs.

Efficacy and safety testing of a COVID-19 era emergency ventilator in a healthy rabbit lung model

Background

The COVID-19 pandemic revealed a substantial and unmet need for low-cost, easily accessible mechanical ventilation strategies for use in medical resource-challenged areas. Internationally, several groups developed non-conventional COVID-19 era emergency ventilator strategies as a stopgap measure when conventional ventilators were unavailable. Here, we compared our FALCON emergency ventilator in a rabbit model and compared its safety and functionality to conventional mechanical ventilation.

Methods

New Zealand white rabbits (n = 5) received mechanical ventilation from both the FALCON and a conventional mechanical ventilator (Engström Carestation™) for 1 h each. Airflow and pressure, blood O₂ saturation, end tidal CO₂, and arterial blood gas measurements were measured. Additionally, gross and histological lung samples were compared to spontaneously breathing rabbits (n = 3) to assess signs of ventilator induced lung injury.

Results

All rabbits were successfully ventilated with the FALCON. At identical ventilator settings, tidal volumes, pressures, and respiratory rates were similar between both ventilators, but the inspiratory to expiratory ratio was lower using the FALCON. End tidal CO₂ was significantly higher on the FALCON, and arterial blood gas measurements demonstrated lower arterial partial pressure of O₂ at 30 min and higher arterial partial pressure of CO₂ at 30 and 60 min using the FALCON. However, when ventilated at higher respiratory rates, we observed a stepwise decrease in end tidal CO₂. Poincaré plot analysis demonstrated small but significant increases in short-term and long-term variation of peak inspiratory pressure generation from the FALCON. Wet to dry lung weight and lung injury scoring between the mechanically ventilated and spontaneously breathing rabbits were similar.

Conclusions

Although conventional ventilators are always preferable outside of emergency use, the FALCON ventilator safely and effectively ventilated healthy rabbits without lung injury. Emergency ventilation using accessible and inexpensive strategies like the FALCON may be useful for communities with low access to medical resources and as a backup form of emergency ventilation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42490-022-00059-x.

Nose-to-brain delivery of levetiracetam after intranasal administration to mice

Despite being one of the most commonly prescribed antiepileptic drugs, levetiracetam is marketed in oral and intravenous dosage forms, which are associated to drug-drug interactions and drug-resistant epilepsy (DRE). The purpose of the present study was to assess the potential of the intranasal route to deliver levetiracetam into the brain, due to the particular anatomical features of the nasal cavity. After development and characterization of the drug formulation, a thermoreversible gel loaded with levetiracetam was administered to CD-1 male mice by intranasal route and its pharmacokinetics compared to those observed after intravenous administration. Similar plasma pharmacokinetic profiles were obtained and the intranasal absolute bioavailability was 107.44%, underscoring that a high drug fraction was systemically absorbed. In brain tissue, maximum drug concentrations were 4.48 and 4.02 μg/g (intranasal vs intravenous) and the mean cerebral concentrations were significantly higher after intranasal administration. The percentage of drug targeting efficiency was 182.35% while direct transport percentage was 46.38%, suggesting that almost 50% of levetiracetam undergoes direct nose-to-brain delivery. Complementarily, an in vivo intranasal repeated dose toxicity study was performed and no relevant histopathological alterations were observed. The herein proposed non-invasive and safe intranasal administration route allowed a direct nose-to-brain delivery of levetiracetam and is a promising strategy for the treatment of DRE.