Myosin 1f-mediated activation of microglia contributes to the photoreceptor degeneration in a mouse model of retinal detachment

MYO1F in neutrophils is required for the response to immune checkpoint blockade therapy

Tumor-associated neutrophils (TANs) represent a significant barrier to the effectiveness of immune checkpoint blockade (ICB) therapy. A comprehensive understanding of TANs' regulatory mechanisms is therefore essential for predicting ICB efficacy and improving immunotherapy strategies. Our study reveals that MYO1F is selectively downregulated in neutrophils within both human cancers and murine tumor models, showing a negative correlation with ICB response. Mechanistically, MYO1F normally inhibits neutrophil immunosuppression and proliferation by restraining STAT3 activity. However, during tumorigenesis, tumor-derived TGF-β1 disrupts the binding of SPI1 to intron 8 of Myo1f via DNA methylation, thereby suppressing Myo1f transcription. The resultant decrease in MYO1F reprograms neutrophils into an immunosuppressive state through the STAT3-dependent signaling pathways. This immunosuppressive state further contributes to tumor microenvironment (TME) remodeling by inducing CTL exhaustion. These findings establish MYO1F as a critical regulator within TANs, highlighting its significant role in modulating ICB therapy efficacy.

Instrumenting Carotid Sonography Biomarkers and Polygenic Risk Score As a Novel Screening Approach for Retinal Detachment

Purpose

Retinal detachment (RD) is a vision-threatening condition that manifests silently before abrupt disease onset; thus, most of the RD at-risk individuals are left unchecked until the first RD attack.

Methods

To establish an RD risk-informing system for a broader population, we utilized carotid ultrasonography (CUS) biometrics, RD polygenic risk score (PRSRD), and clinical covariates (COVs) to assess RD risk predisposition factors. First, a backpropagation logistic regression model identified RD-associated CUS biomarkers and further incorporated them as a multivariable RD-risk nomogram. Next, a PRSRD model was established with the selected single-nucleotide polymorphisms (SNPs) curated as high functional expression candidates in the retina single-cell RNA datasets. Finally, a three-component RD prediction model (CUS, PRSRD, and COVs) was assembled by logistic cumulative analysis.

Results

Demographic analysis reported hypertension (HTN) status was associated with RD (odds ratio [OR] = 1.601). The CUS regression model revealed that the minimum flow of the right internal carotid artery (ICA-Qmin; OR = 1.04) and the time-averaged maximum velocity of the right common carotid artery (CCA-TAMAX; OR = 1.03) were associated with increased RD risk. Notably, genome-wide association studies (GWAS) identified three significant SNPs (IGFBPL1 rs117248428, OR = 1.63; CELF2 rs56168975, OR = 1.72; and PAX6 rs11825821, OR = 1.61; P < 5.00 × 10-6) that are highly expressed at the RD border of the retinal pigment epithelium and choroid. Finally, the three-component model demonstrated state-of-the-art RD prediction (AUCHTN+ = 0.95, AUCHTN- = 0.93).

Conclusions

Based on instrumenting CUS images and genetic PRSRD, we are proposing a screening method for RD at-risk patients.

Translational Relevance

Results from this study demonstrated the combination of CUS and GWAS as a cost-effective, population-wide screening framework for identifying RD at-risk individuals.

Ameboid Microglia as a Scavenger Role in Phagocytosis of Photoreceptor Outer Segment in an Experimental Retinal Detachment Model

Purpose

Photoreceptor (PR) death is the ultimate cause of irreversible vision loss in retinal detachment (RD). Previous studies have shown that microglia may have a dual role in RD. Nevertheless, the potential protective effects of microglia on PR are largely unknown. We aimed to uncover the phagocytic role of microglia in RD and propose a new concept to regulate PR survival.

Methods

An RD model was conducted by injecting sodium hyaluronate into the subretinal space (SRS) of C57BL/6J wild type mice. Bioinformatics analysis was used to evaluate the highly enriched pathways and terms relating to phagocytosis in human datasets and mouse transcriptomes of RD. The observation of microglial morphology was performed by immunofluorescence through cryosection and flat mount. PLX 3397 was used for microglial ablation. Phagocytosis of the outer segment (OS) by microglia was confirmed by immunofluorescence and hematoxylin and eosin staining. Expression of phagocytic markers in microglia was detected by immunofluorescence of cryosection. The PR survival was measured by TUNEL assay and hematoxylin and eosin staining. The optical coherence tomography (OCT) images through the center of the fovea in twelve patients were obtained to observe the clinic features of IS/OS dynamics after RD.

Results

The results showed that OS went through an accumulation-clearance process after RD. Ameboid microglia accumulated in the SRS and engulfed OS. Upregulation of phagocytic markers was observed in subretinal microglia. Depletion of microglia led to failure of OS clearance and retinal ruffling, which had the same characteristics as outer retinal undulation (ORU) in some patients with RD. PR did not benefit from microglial depletion, as no morphology and thickness recovery of PR was observed in the long term.

Conclusions

These results elucidate that microglial phagocytosis of OS is a critical process after RD. Insufficient phagocytosis leads to the accumulation of OS in the SRS and PR abnormalities. Appropriate regulation of microglial phagocytosis to remove OS may be a new concept to regulate photoreceptor survival.

Role of MYO1F in neutrophil and macrophage recruitment and pro-inflammatory cytokine production in Aspergillus fumigatus keratitis

PURPOSE

Myosin 1f (Myo1f), an unconventional long-tailed class Ⅰ myosin, plays significant roles in immune cell motility and innate antifungal immunity. This study was aimed to assess the expression and role of Myo1f in Aspergillus fumigatus (AF) keratitis.

METHODS

Myo1f expression in the corneas of mice afflicted with AF keratitis and in AF keratitis-related cells was assessed using protein mass spectrometry, quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and immunofluorescence. Myo1f expression following pre-treatment with inhibitors of dendritic cell-associated C-type lectin-1 (Dectin-1), Toll-like receptor 4 (TLR-4), and lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) was also examined. In AF keratitis mouse models, Myo1f small interfering RNA (siRNA) was administered via subconjunctival injection to observe disease progression, inflammatory cell recruitment, and protein production using slit lamp examination, immunofluorescence, hematoxylin-eosin (HE) staining, and western blotting.

RESULTS

Myo1f expression was upregulated in both AF keratitis mouse models and AF keratitis-related cells. Dectin-1, TLR-4, and LOX-1 were found to be essential for the production of Myo1f in response to the infection with AF. In mice with AF keratitis, knockdown of Myo1f reduced disease severity, decreased the recruitment of neutrophils alongside macrophages to inflammatory areas, suppressed the myeloid differentiation factor 88 (MyD88)/ nuclear factor-kappaB (NF-κB) signaling pathway, and decreased the production of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, along with IL-6. Additionally, Myo1f was associated with apoptosis and pyroptosis in mice with AF keratitis.

CONCLUSIONS

These findings demonstrated that Myo1f contributed to the recruitment of neutrophils and macrophages, the production of pro-inflammatory cytokines, and was associated with apoptosis and pyroptosis during AF keratitis.

Qualitative evaluations of reactive microglial heterogeneity in cultured porcine retina

A late stage of several retinal disorders is retinal detachment, a complication that results in rapid photoreceptor degeneration and synaptic damage. The porcine retina is a favorable in vitro model for studies of the degenerative processes that follow retinal detachment. Photoreceptor degeneration and synaptic injuries develop rapidly in the cultured porcine retina and correlate with resident microglial cell transition into a reactive phenotype. In this in vitro study, we used retinas cultured for five days and analyzed reactive CD11b and Iba1 immunoreactive microglia that localized close to/within the synaptic outer plexiform layer (OPL) and in the outer nuclear layer (ONL). A subpopulation of the CD11b and Iba1immunoreactive microglia also expressed CD68 immunoreactivity on lysosomal membranes or as a diffuse cytoplasmic stain. Some CD68 immunoreactive microglia were juxtaposed to L/M-opsin immunoreactive cone photoreceptors in the ONL. CD11b and Iba immunoelectron microscopy further suggests the presence of a dark microglial phenotype in the degenerating cultured porcine retina. For immunoelectron microscopy, nickel-enhanced diaminobenzidine (DAB) staining resulted in clearly distinguished reaction products in the cytosol of dark microglia.

Caspase-1 Inhibition Ameliorates Photoreceptor Damage Following Retinal Detachment by Inhibiting Microglial Pyroptosis

Retinal detachment (RD) is a sight-threatening condition that occurs in several retinal diseases. Microglia that reside in retina are activated after RD and play a role in the death of photoreceptor cells. The involvement of microglial pyroptosis in the early pathological process of RD is still unclear. VX-765, an inhibitor of caspase-1, may exert neuroprotective effects by targeting microglial pyroptosis in nervous system disease; however, whether it plays a role in RD is uncertain. This study detected and localized pyroptosis to specific cells by immunofluorescence co-staining and flow cytometry in rat RD models. The majority of gasdermin D N-terminal (GSDMD-N)-positive cells exhibited IBA1-positive or P2RY12-positive microglia in the early stage of RD, indicating the pyroptosis of microglia. Administration of VX-765 shifted the microglia phenotype from M1 to M2, inhibited microglial migration toward the outer nuclear layer (ONL) post-RD, and most importantly, inhibited microglial pyroptosis. The thickness of ONL increased with VX-765 administration, and the photoreceptors were more structured and orderly under hematoxylin and eosin staining and transmission electron microscopy, revealing the protective effects of VX-765 on photoreceptors. Overall, this study demonstrated that inflammation induced by pyroptosis of microglia is the early pathological process of RD. VX-765 may serve as a candidate therapeutic approach for the treatment of RD by targeting microglia.

Microglia in Cultured Porcine Retina: Qualitative Immunohistochemical Analyses of Reactive Microglia in the Outer Retina

A late stage of several retinal disorders is retinal detachment, a complication that results in rapid photoreceptor degeneration and synaptic damages. Experimental retinal detachment in vivo is an invasive and complicated method performed on anesthetized animals. As retinal detachment may result in visual impairment and blindness, research is of fundamental importance for understanding degenerative processes. Both morphological and ethical issues make the porcine retina a favorable organotypic model for studies of the degenerative processes that follow retinal detachment. In the cultured retina, photoreceptor degeneration and synaptic injuries develop rapidly and correlate with resident microglial cells' transition into a reactive phenotype. In this immunohistochemical study, we have begun to analyze the transition of subsets of reactive microglia which are known to localize close to the outer plexiform layer (OPL) in degenerating in vivo and in vitro retina. Biomarkers for reactive microglia included P2Ry12, CD63 and CD68 and the general microglial markers were CD11b, Iba1 and isolectin B₄ (IB₄). The reactive microglia markers labeled microglia subpopulations, suggesting that protective or harmful reactive microglia may be present simultaneously in the injured retina. Our findings support the usage of porcine retina cultures for studies of photoreceptor injuries related to retinal detachment.