Method to perform IV injections on mice using the facial vein

High-mobility group box-1 peptide ameliorates bronchopulmonary dysplasia by suppressing inflammation and fibrosis in a mouse model

BACKGROUND

This study aimed to examine the effect of the HMGB1 peptide on Bronchopulmonary dysplasia (BPD)-related lung injury in a mouse model.

RESULTS

HMGB1 peptide ameliorates lung injury by suppressing the release of inflammatory cytokines and decreasing soluble collagen levels in the lungs. Single-cell RNA sequencing showed that the peptide suppressed the hyperoxia-induced inflammatory signature in macrophages and the fibrotic signature in fibroblasts. These changes in the transcriptome were confirmed using protein assays.

CONCLUSION

Systemic administration of HMGB1 peptide exerts anti-inflammatory and anti-fibrotic effects in a mouse model of BPD. This study provides a foundation for the development of new and effective therapies for BPD.

AAV9 transduction mediated by systemic delivery of vector via retro-orbital injection in newborn, neonatal and juvenile mice

Adeno-associated virus (AAV)-based gene therapy is gaining popularity owing to its excellent safety profile and effective therapeutic outcomes in a number of diseases. Intravenous (IV) injection of AAV into the tail vein, facial vein and retro-orbital (RO) venous sinus have all been useful strategies to infuse the viral vector systemically. However, tail vein injection is technically challenging in juvenile mice, and injection at young ages (≤ postnatal day-(P)21) is essentially impossible. The temporal or facial vein is localized anterior to the ear bud and is markedly visible in the first couple of days postnatally. However, this method is age-dependent and requires a dissecting microscope. Retro-orbital injection (ROI), on the other hand, is suitable for all murine ages, including newborn and older mice, and is relatively less stressful to animals compared to tail vein injection. Although many reports have shown ROI as an effective route of AAV delivery, herein we aim to highlight and summarize the methods and benefits of ROI. To capture the full spectrum of transduction efficiency mediated by ROI, we transduced the editing-dependent reporter mice (Ai9 Cre reporter mice) with the AAV9 vector, which targets a wide range of peripheral tissues with exceptional brain tropism. We also provide a comprehensive description of the ROI technique to facilitate viral vector administration without complications.

Assessment of the Therapeutic Potential of Metallothionein-II Application in Focal Cerebral Ischemia In Vitro and In Vivo

Metallothionein-II (MT-II) is an ubiquitously expressed small-molecular-weight protein and highly induced in various species and tissues upon stress, inflammation, and ischemia. MT-deficiency exacerbates ischemic injury in rodent stroke models in vitro and in vivo. However, there is conflicting data on the potential neuroprotective effect of exogenously applied metallothionein. Thus, we applied MT-II in an in vitro stroke model and intraperitoneally (i.p.) in two in vivo standard models of transient middle cerebral artery occlusion (MCAO) (a ‘stringent’ one [60min MCAO/48h reperfusion] and a ‘mild’ one [30min MCAO/72h reperfusion]), as well as i.v. together with recombinant tissue plasminogen activator (rtPA) to evaluate if exogenous MT-II-application protects against ischemic stroke. Whereas MT-II did not protect against 60min MCAO, there was a significant reduction of direct and indirect infarct volumes and neurological deficit in the MT-II (i.p.) treated animals in the ‘mild’ model at 3d after MCAO. Furthermore, MT-II also improved survival of the mice after MCAO, suppressed TNF-α mRNA induction in ischemic brain tissue, and protected primary neuronal cells against oxygen-glucose-deprivation in vitro. Thus, exogenous application of MT-II protects against ischemic injury in vitro and in vivo. However, long-term studies with different species and larger sampling sizes are required before a clinical use can be envisaged.

IV and IP administration of rhodamine in visualization of WBC-BBB interactions in cerebral vessels

Epi-illuminescence intravital fluorescence microscopy has been employed to study leukocyte-endothelial interactions in a number of brain pathologies. Historically, dyes such as Rhodamine 6G have been injected intravenously. However, intravenous injections can predispose experimental animals to a multitude of complications and requires a high degree of technical skill. Here, we study the efficacy of injecting Rhodamine 6G into the peritoneum (IP) for the purpose of analyzing leukocyte-endothelial interactions through a cranial window during real time intravital microscopy. After examining the number of rolling and adherent leukocytes through a cranial window, we found no advantage to the intravenous injection (IV). Additionally, we tested blood from both routes of injection by flow cytometry to gain a very precise picture of the two methods. The two routes of administration failed to show any difference in the ability to detect cells. The study supports the notion that IP Rhodamine 6G works as efficaciously as IV and should be considered a viable alternative in experimental design for investigations employing intravital microscopy. Facilitated intravital studies will allow for more exploration into cerebral pathologies and allow for more rapid translation from the laboratory to the patient with less chance of experimental error from failed IV access.

A murine model of hypertonic saline as a treatment for acute spinal cord injury: effects on autonomic outcome

Object

Spinal cord injury (SCI) continues to be a problem without a definitive cure. Research based on improved understanding of the immunological aspects of SCI has revealed targets for treating and ameliorating the extent of secondary injury. Hypertonic saline (HTS), a substance both easy to create and to transport, has been investigated as an immunologically active material that can be used in a clinically relevant interval after injury. In this pilot study, HTS was investigated in a murine model for its abilities to ameliorate secondary injury after a severe spinal cord contusion.

Methods

Female C57Bl/6 mice with severe T8–10 contusion injuries were used as the model subjects. A group of 41 mice were studied in a blinded fashion. Mice received treatments with HTS (HTS, 7.5%) or normal saline solution (NSS, 0.9%) at 2 discreet time points (3 and 24 hours after injury.) A separate group of 9 untreated animals were also used as controls. Animals were assessed for autonomic outcome (bladder function). In a group of 33 mice, histological assessment (cellular infiltration) was also measured.

Results

Bladder function was found to be improved significantly in those treated with HTS compared with those who received NSS and also at later treatment times (24 hours) than at earlier treatment times (3 hours). Decreased cellular infiltration in each group correlated with bladder recovery.

Conclusions

The increased effectiveness of later administration time of the more osmotically active and immunomodulatory substance (HTS) suggests that interaction with events occurring around 24 hours after injury is critical. These events may be related to the invasion of leukocytes peaking at 8–24 hours postinjury and/or the peak benefit time of subject rehydration.

Deficiency of PAR4 attenuates cerebral ischemia/reperfusion injury in mice

Stroke is the third leading cause of death in the USA. Antithrombotic therapy targeting platelet activation is one of the treatments for ischemic stroke. Here we investigate the role of one of the thrombin receptors, protease-activated receptor 4 (PAR4), in a mouse transient middle cerebral artery occlusion (MCAO) model. After a 60 min MCAO and 23 h reperfusion, leukocyte and platelet rolling and adhesion on cerebral venules, blood-brain barrier (BBB) permeability, and cerebral edema were compared in PAR4-deficient mice and wild-type mice. Cerebral infarction volume and neuronal death were also measured. PAR4-/- mice had more than an 80% reduction of infarct volume and significantly improved neurologic and motor function compared with wild-type mice after MCAO. Furthermore, deficiency of PAR4 significantly inhibits the rolling and adhesion of both platelets and leukocytes after MCAO. BBB disruption and cerebral edema were also attenuated in PAR4-/- mice compared with wild-type animals. The results of this investigation indicate that deficiency of PAR4 protects mice from cerebral ischemia/reperfusion (I/R) injury, partially through inhibition of platelet activation and attenuation of microvascular inflammation.

CB2 receptor activation attenuates microcirculatory dysfunction during cerebral ischemic/reperfusion injury

Previous studies from our laboratory indicated that selective cannabinoid CB(2) agonists were able to attenuate cerebral ischemia/reperfusion (I/R) injury. The goal of current study is to further test whether this attenuation involves cerebral microcirculatory function during I/R injury. Middle cerebral artery occlusion with reperfusion (MCAO/R) was performed in male mice. A selective CB(2) agonist was administered at different dosages and different times. Cerebral infarction volume, neurological function and cerebral microcirculatory function (leukocyte/endothelial interactions, cell adhesion molecule expression and blood-brain barrier disruption) were examined in vivo and in vitro. CB(2) knockout mice were subjected to MCAO/R following same procedures. Administration of the CB(2) agonist at middle dosage exerted optimal effects in reducing cerebral infarction and improving neurological function compared with other dosage groups and control group. Treatment with the CB(2) agonist at the optimal dose was still effective when given 3 h after MCAO. Transient ischemia significantly increased leukocyte/endothelial interactions, adhesion molecules expression and blood-brain barrier disruption which were all attenuated by pre-treatment with a CB(2) agonist. CB(2) knockout mice showed larger cerebral infarction and worse neurological function compared to wide type. In conclusion, CB(2) activation contributed to protecting the brain through the attenuation of cerebral microcirculatory dysfunction during cerebral I/R injury.