Assessment of vascular regeneration in the CNS using the mouse retina

Identification and validation of lactate metabolism-related genes in oxygen-induced retinopathy

Retinopathy of Prematurity (ROP) is a multifactorial disease characterized by abnormal retinal vascular growth in premature infants, which is one of the leading causes of childhood blindness. Lactic acid metabolism may play an imperative role in the development of ROP, but there are still few relevant studies. Our team use a dataset GSE158799 contained 284 genes in 3 P17_OIR mice and 3 P30_OIR mice to identify 41 potentially differentially expressed lactate metabolism-related genes (LMRGs) related to ROP. Then through bioinformatics analysis, we strive to reveal the interaction, the enriched pathways and the immune cell infiltration among these LMRGs, and predict their functions and internal mechanisms. These DEGs may regulate lactate metabolism, leading to the changes of metabolism and immunity, thereby inducing the development of ROP. Our results will expand our understanding of the intrinsic mechanism of ROP and may be helpful for the directions for treatment of ROP in the future.

Effect of human very low-density lipoproteins on cardiotrophin-like cytokine factor 1 (CLCF1) activity

The cytokines CLCF1 and CNTF are ligands for the CNTF receptor and the apolipoprotein E (ApoE) receptor sortilin. Both share structural similarities with the N-terminal domain of ApoE, known to bind CNTF. We therefore evaluated whether ApoE or ApoE-containing lipoproteins interact with CLCF1 and regulate its activity. We observed that CLCF1 forms complexes with the three major isoforms of ApoE in co-immunoprecipitation and proximity assays. FPLC analysis of mouse and human sera mixed with CLCF1 revealed that CLCF1 co-purifies with plasma lipoproteins. Studies with sera from ApoE^-/- mice indicate that ApoE is not required for CLCF1-lipoprotein interactions. VLDL- and LDL-CLCF1 binding was confirmed using proximity and ligand blots assays. CLCF1-induced STAT3 phosphorylation was significantly reduced when the cytokine was complexed with VLDL. Physiological relevance of our findings was asserted in a mouse model of oxygen-induced retinopathy, where the beneficial anti-angiogenic properties of CLCF1 were abrogated when co-administrated with VLDL, indicating, that CLCF1 binds purified lipoproteins or lipoproteins in physiological fluids such as serum and behave as a "lipocytokine". Albeit it is clear that lipoproteins modulate CLCF1 activity, it remains to be determined whether lipoprotein binding directly contributes to its neurotrophic function and its roles in metabolic regulation.

Retinal microvascular network alterations: potential biomarkers of cerebrovascular and neural diseases

Increasing evidence suggests that the conditions of retinal microvessels are indicators to a variety of cerebrovascular, neurodegenerative, psychiatric, and developmental diseases. Thus noninvasive visualization of the human retinal microcirculation offers an exceptional opportunity for the investigation of not only the retinal but also cerebral microvasculature. In this review, we show how the conditions of the retinal microvessels could be used to assess the conditions of brain microvessels because the microvascular network of the retina and brain share, in many aspects, standard features in development, morphology, function, and pathophysiology. Recent techniques and imaging modalities, such as optical coherence tomography (OCT), allow more precise visualization of various layers of the retina and its microcirculation, providing a "microscope" to brain microvessels. We also review the potential role of retinal microvessels in the risk identification of cerebrovascular and neurodegenerative diseases. The association between vision problems and cerebrovascular and neurodegenerative diseases, as well as the possible role of retinal microvascular imaging biomarkers in cerebrovascular and neurodegenerative screening, their potentials, and limitations, are also discussed.

In Vivo Angiography Quantifies Oxygen-Induced Retinopathy Vascular Recovery

Purpose

Retinopathy of prematurity (ROP) is a potentially blinding vasoproliferative disease. There is no standardized way to quantify plus disease (tortuous and dilated retinal vessels) or characterize abnormal recovery during ROP monitoring. This study objectively studies vascular features in live mice during development using noninvasive retinal imaging.

Methods

Using fluorescein angiography (FA), retinal vascular features were quantified in live mice with oxygen induced retinopathy (OIR). A total of 105 wild-type mice were exposed to 77% oxygen from postnatal day 7 (P7) till P12 (OIR mice). Also, 105 age-matched pups were raised in room air (RA mice). In vivo FA was performed at early (P16 to P20), mid (P23 to P27), late (P30 to P34), and mature (P47) phases of retinal vascular development. Retinal vascular area, retinal vein width, and retinal artery tortuosity were quantified.

Results

Retinal artery tortuosity was higher in OIR than RA mice at early (p < 0.0001), mid (p < 0.0001), late (p < 0.0001), and mature (p < 0.0001) phases. Retinal vascular area in OIR mice increased from early to mid-phase (p < 0.0001), but remained unchanged from mid to late (p = 0.23), and from late to mature phase (p = 0.98). Retinal vein width was larger in OIR mice compared to RA mice during early phase only. Arteries in OIR mice were more tortuous from early to mid-phase (p < 0.0001), but tortuosity remained stable from mid through mature phase. RA mice had an increase in retinal vascular area from early to late phase, but maintained uniform retinal vein width and retinal artery tortuosity in all phases.

Conclusions

In vivo FA distinguished arterial and venous features, similar to plus disease, and revealed aberrant recovery of OIR mice (arterial tortuosity, reduced capillary density, and absent neovascular buds) that persisted into adulthood. Retinal artery tortuosity may be a reliable, objective marker of severity of ROP. Infants with abnormal retinal vascular recovery may need extended monitoring.

Neuropilin-1 mediates myeloid cell chemoattraction and influences retinal neuroimmune crosstalk

Immunological activity in the CNS is largely dependent on an innate immune response and is heightened in diseases, such as diabetic retinopathy, multiple sclerosis, amyotrophic lateral sclerosis, and Alzheimer's disease. The molecular dynamics governing immune cell recruitment to sites of injury and disease in the CNS during sterile inflammation remain poorly defined. Here, we identified a subset of mononuclear phagocytes (MPs) that responds to local chemotactic cues that are conserved among central neurons, vessels, and immune cells. Patients suffering from late-stage proliferative diabetic retinopathy (PDR) had elevated vitreous semaphorin 3A (SEMA3A). Using a murine model, we found that SEMA3A acts as a potent attractant for neuropilin-1-positive (NRP-1-positive) MPs. These proangiogenic MPs were selectively recruited to sites of pathological neovascularization in response to locally produced SEMA3A as well as VEGF. NRP-1-positive MPs were essential for disease progression, as NRP-1-deficient MPs failed to enter the retina in a murine model of oxygen-induced retinopathy (OIR), a proxy for PDR. OIR mice with NRP-1-deficient MPs exhibited decreased vascular degeneration and diminished pathological preretinal neovascularization. Intravitreal administration of a NRP-1-derived trap effectively mimicked the therapeutic benefits observed in mice lacking NRP-1-expressing MPs. Our findings indicate that NRP-1 is an obligate receptor for MP chemotaxis, bridging neural ischemia to an innate immune response in neovascular retinal disease.