A quick protocol for the preparation of mouse retinal cryosections for immunohistochemistry

A novel function and mechanism of ischemia-induced retinal astrocyte-derived exosomes for RGC apoptosis of ischemic retinopathy

Retinal ischemia is a common clinical event leading to retinal ganglion cell (RGC) death, resulting in irreversible vision loss. In the retina, glia-neuron communication is crucial for multiple functions and homeostasis. Extracellular vesicles, notably exosomes, play a critical role. The functions and mechanisms of retinal astrocyte-secreted exosomes remain unclear. Here, we isolated astrocyte-derived exosomes under hypoxia or normoxia and explored their role in an in vivo retinal ischemia-reperfusion (RIR) model. We found that hypoxia triggered astrocytes to produce a significantly increased number of exosomes, which could be internalized by RGCs in vivo or in vitro. Also, in the RIR model, the hypoxia-induced exosomes ameliorated the RIR injury and suppressed the RGC apoptosis. Furthermore, microRNA sequencing of retinal astrocyte-secreted exosomes revealed different patterns of exosomal miRNAs under hypoxia, particularly enriched with miR-329-5p. We verified that miR-329-5p was specifically bound to mitogen-activated protein kinase 8 mRNA, and subsequent JNK-pathway molecules were downregulated. We anticipated that the miR-329-5p/JNK pathway is a key to suppressing RGC apoptosis and preventing RIR injury. Such findings provided insights into the therapeutic potential of hypoxia-induced astrocyte-secreted exosomes and the miR-329-5p for treating retina ischemic diseases.

Modulation of CXCL10 activity as a therapeutic target of ocular toxoplasmosis in diabetic mice

Ocular toxoplasmosis is likely the most common cause of infectious posterior uveitis worldwide. CXCL10 chemokine has an important role in the maintenance of the T-cell response and the control of Toxoplasma gondii in the eye during chronic infection. Drugs that can modulate the chemokine activity could be effective against the parasite. In this work, CXCL10 local retinal expression was investigated in a diabetic mouse model with ocular toxoplasmosis for the first time. In addition, the efficacy of naphthoquinones and quinolones was compared to spiramycin (SP) in treating the infection and modulating the chemokine expression. Our results revealed that chloroquine (CQ) achieved the best results regarding the reduction of cerebral cyst burden (84.36%), improving the retinal histopathological changes, cellular infiltrates, and vasculitis significantly (P < 0.005), and balancing the strong CXCL10 expression caused by the infection. Buparvaquone-treated mice showed a significant percentage of reduction of brain cysts (76.25%), moderate improvement of histopathology, and mild to moderate CXCL10 expression. While SP showed the least efficacy against the parasite in the eye in the form of mild improvement of histopathological changes and downregulation of retinal chemokine expression with the least reduction rate of cerebral parasitic burden (57%). In conclusion, Optimal control of pathogens probably needs a balanced immune response with an optimum expression of chemokines. So, targeting the modulation of retinal CXCL10 may eventually be beneficial in the management of ocular toxoplasmosis plus its potential to act as a marker for predictive local immunological response during the infection.

A signalling pathway for transcriptional regulation of sleep amount in mice

In mice and humans, sleep quantity is governed by genetic factors and exhibits age-dependent variation^1-3. However, the core molecular pathways and effector mechanisms that regulate sleep duration in mammals remain unclear. Here, we characterize a major signalling pathway for the transcriptional regulation of sleep in mice using adeno-associated virus-mediated somatic genetics analysis⁴. Chimeric knockout of LKB1 kinase-an activator of AMPK-related protein kinase SIK3^5-7-in adult mouse brain markedly reduces the amount and delta power-a measure of sleep depth-of non-rapid eye movement sleep (NREMS). Downstream of the LKB1-SIK3 pathway, gain or loss-of-function of the histone deacetylases HDAC4 and HDAC5 in adult brain neurons causes bidirectional changes of NREMS amount and delta power. Moreover, phosphorylation of HDAC4 and HDAC5 is associated with increased sleep need, and HDAC4 specifically regulates NREMS amount in posterior hypothalamus. Genetic and transcriptomic studies reveal that HDAC4 cooperates with CREB in both transcriptional and sleep regulation. These findings introduce the concept of signalling pathways targeting transcription modulators to regulate daily sleep amount and demonstrate the power of somatic genetics in mouse sleep research.

Experimental study of different dehydration methods in the process of preparing frozen brain sections

This study aimed to provide a recommendable protocol for the preparation of brain cryosections of rats to reduce and avoid ice crystals. We have designed five different dewatering solutions (Scheme 1: dehydrate with 15%, 20%, and 30% sucrose-phosphate-buffered saline solution; Scheme 2: 20% sucrose and 30% sucrose; Scheme 3: 30% sucrose; Scheme 4: 10%, 20%, and 30% sucrose; and Scheme 5: the tissue was dehydrated with 15% and 30% sucrose polyacetate I until it sank to the bottom, followed by placement in 30% sucrose polyacetate II) to minimize the formation of ice crystals. Cryosections from different protocols were stained with Nissl staining and compared with each other by density between cells and the distance of intertissue spaces. The time required for the dehydration process from Scheme 1 to Scheme 5 was 24, 23, 24, 24, and 33 h, respectively. Density between cells gradually decreased from Scheme 1 to Scheme 5, and the distance of intertissue spaces was differentiated and irregular in different schemes according to the images of Nissl staining. We recommend the dewatering method of Scheme 4 (the brain tissues were dehydrated in 10%, 20% and 30% sucrose solution in turn until the tissue samples were completely immersed in the solution and then immersed in the next concentration solution for dehydration).

Ten Approaches That Improve Immunostaining: A Review of the Latest Advances for the Optimization of Immunofluorescence

Immunostaining has emerged as one of the most common and valuable techniques that allow the localization of proteins at a quantitative level within cells and tissues using antibodies coupled to enzymes, fluorochromes, or colloidal nanogold particles. The application of fluorochromes during immunolabeling is referred to as immunofluorescence, a method coupled to widefield or confocal microscopy and extensively applied in basic research and clinical diagnosis. Notwithstanding, there are still disadvantages associated with the application of this technique due to technical challenges in the process, such as sample fixation, permeabilization, antibody incubation times, and fluid exchange, etc. These disadvantages call for continuous updates and improvements to the protocols extensively described in the literature. This review contributes to protocol optimization, outlining 10 current methods for improving sample processing in different stages of immunofluorescence, including a section with further recommendations. Additionally, we have extended our own antibody signal enhancer method, which was reported to significantly increase antibody signals and is useful for cervical cancer detection, to improve the signals of fluorochrome-conjugated staining reagents in fibrous tissues. In summary, this review is a valuable tool for experienced researchers and beginners when planning or troubleshooting the immunofluorescence assay.