Modulation of Schlemm's canal endothelial cell stiffness via latrunculin loaded block copolymer micelles

Block copolymer micelles as ocular drug delivery systems

Block copolymer micelles, formed by the self-assembly of amphiphilic polymers, address formulation challenges, such as poor drug solubility and permeability. These micelles offer advantages including a smaller size, easier preparation, sterilization, and superior solubilization, compared with other nanocarriers. Preclinical studies have shown promising results, advancing them toward clinical trials. Their mucoadhesive properties enhance and prolong contact with the ocular surface, and their small size allows deeper penetration through tissues, such as the cornea. Additionally, copolymeric micelles improve the solubility and stability of hydrophobic drugs, sustain drug release, and allow for surface modifications to enhance biocompatibility. Despite these benefits, long-term stability remains a challenge. In this review, we highlight the preclinical performance, structural frameworks, preparation techniques, physicochemical properties, current developments, and prospects of block copolymer micelles as ocular drug delivery systems.

In vitro assessment of varying peptide surface density on the suppression of angiogenesis by micelles displaying αvβ3 blocking peptides

Ligand targeted therapy (LTT) is a precision medicine strategy that can selectively target diseased cells while minimizing off-target effects on healthy cells. Integrin-targeted LTT has been developed recently for angiogenesis-related diseases. However, the clinical success is based on the optimal design of the nanoparticles for inducing receptor clustering within the cell membrane. The current study focused on determining the surface density of Ser-Asp-Val containing anti-integrin heptapeptide on poly (ethylene glycol)-b-poly(propylene sulfide) micelles (MC) required for anti-angiogenic effects on HUVECs. Varying peptide density on PEG-b-PPS/Pep-PA MCs (Pep-PA-Peptide-palmitoleic acid) was used in comparison to a random peptide (SGV) and cRGD (cyclic-Arginine-Glycine-Aspartic acid) construct at 5%-density on MCs. Immunocytochemistry using CD51/CD31 antibody was performed to study the integrin blocking by MCs. In addition, the expression of VWF and PECAM-1, cell migration and tube formation was evaluated in the presence of PEG-b-PPS/Pep-PA MCs. The results show PEG-b-PPS/SDV-PA MCs with 5%-peptide density to achieve significantly higher αvβ3 blocking compared to random peptide as well as cRGD. In addition, αvβ3 blocking via MCs further reduced the expression of vWF and PECAM-1 angiogenesis protein expression in HUVECs. Although a significant level of integrin blocking was observed for 1%-peptide density on MCs, the cell migration and tube formation were not significantly affected. In conclusion, the results of this study demonstrate that the peptide surface density on PEG-b-PPS/Pep-PA MCs has a significant impact in integrin blocking as well as inhibiting angiogenesis during LTT. The outcomes of this study provides insight into the design of ligand targeted nanocarriers for various disease conditions.

Enzyme Nanoreactor for In Vivo Detoxification of Organophosphates

A nanoreactor containing an evolved mutant of Saccharolobus solfataricus phosphotriesterase (L72C/Y97F/Y99F/W263V/I280T) as a catalytic bioscavenger was made for detoxification of organophosphates. This nanoreactor intended for treatment of organophosphate poisoning was studied against paraoxon (POX). Nanoreactors were low polydispersity polymersomes containing a high concentration of enzyme (20 μM). The polyethylene glycol-polypropylene sulfide membrane allowed for penetration of POX and exit of hydrolysis products. In vitro simulations under second order conditions showed that 1 μM enzyme inactivates 5 μM POX in less than 10 s. LD₅₀-shift experiments of POX-challenged mice through intraperitoneal (i.p.) and subcutaneous (s.c.) injections showed that intravenous administration of nanoreactors (1.6 nmol enzyme) protected against 7 × LD₅₀ i.p. in prophylaxis and 3.3 × LD₅₀ i.p. in post-exposure treatment. For mice s.c.-challenged, LD₅₀ shifts were more pronounced: 16.6 × LD₅₀ in prophylaxis and 9.8 × LD₅₀ in post-exposure treatment. Rotarod tests showed that transitory impaired neuromuscular functions of challenged mice were restored the day of experiments. No deterioration was observed in the following days and weeks. The high therapeutic index provided by prophylactic administration of enzyme nanoreactors suggests that no other drugs are needed for protection against acute POX toxicity. For post-exposure treatment, co-administration of classical drugs would certainly have beneficial effects against transient incapacitation.

Nanoparticle based medicines: approaches for evading and manipulating the mononuclear phagocyte system and potential for clinical translation

For decades, nanomedicines have been reported as a potential means to overcome the limitations of conventional drug delivery systems by reducing side effects, toxicity and the non-ideal pharmacokinetic behaviour typically exhibited by small molecule drugs. However, upon administration many nanoparticles prompt induction of host inflammatory responses due to recognition and uptake by macrophages, eliminating up to 95% of the administered dose. While significant advances in nanoparticle engineering and consequent therapeutic efficacy have been made, it is becoming clear that nanoparticle recognition by the mononuclear phagocyte system (MPS) poses an impassable junction in the current framework of nanoparticle development. Hence, this has negative consequences on the clinical translation of nanotechnology with respect to therapeutic efficacy, systemic toxicity and economic benefit. In order to improve the translation of nanomedicines from bench-to-bedside, there is a requirement to either modify nanomedicines in terms of how they interact with intrinsic processes in the body, or modulate the body to be more accommodating for nanomedicine treatments. Here we provide an overview of the current standard for design elements of nanoparticles, as well as factors to consider when producing nanomedicines that have minimal MPS-nanoparticle interactions; we explore this landscape across the cellular to tissue and organ levels. Further, rather than designing materials to suit the body, a growing research niche involves modulating biological responses to administered nanomaterials. We here discuss how developing strategic methods of MPS 'pre-conditioning' with small molecule or biological drugs, as well as implementing strategic dosing regimens, such as 'decoy' nanoparticles, is essential to increasing nanoparticle therapeutic efficacy. By adopting such a perspective, we hope to highlight the increasing trends in research dedicated to improving nanomedicine translation, and subsequently making a positive clinical impact.

Oxidative Stress, Vascular Endothelium, and the Pathology of Neurodegeneration in Retina

Oxidative stress (OS) is an imbalance between free radicals/ROS and antioxidants, which evokes a biological response and is an important risk factor for diseases, in both the cardiovascular system and central nervous system (CNS). The underlying mechanisms driving pathophysiological complications that arise from OS remain largely unclear. The vascular endothelium is emerging as a primary target of excessive glucocorticoid and catecholamine action. Endothelial dysfunction (ED) has been implicated to play a crucial role in the development of neurodegeneration in the CNS. The retina is known as an extension of the CNS. Stress and endothelium dysfunction are suspected to be interlinked and associated with neurodegenerative diseases in the retina as well. In this narrative review, we explore the role of OS-led ED in the retina by focusing on mechanistic links between OS and ED, ED in the pathophysiology of different retinal neurodegenerative conditions, and how a better understanding of the role of endothelial function could lead to new therapeutic approaches for neurodegenerative diseases in the retina.

Cellular crosstalk regulates the aqueous humor outflow pathway and provides new targets for glaucoma therapies

Primary congenital glaucoma (PCG) is a severe disease characterized by developmental defects in the trabecular meshwork (TM) and Schlemm's canal (SC), comprising the conventional aqueous humor outflow pathway of the eye. Recently, heterozygous loss of function variants in TEK and ANGPT1 or compound variants in TEK/SVEP1 were identified in children with PCG. Moreover, common variants in ANGPT1and SVEP1 have been identified as risk alleles for primary open angle glaucoma (POAG) in GWAS studies. Here, we show tissue-specific deletion of Angpt1 or Svep1 from the TM causes PCG in mice with severe defects in the adjacent SC. Single-cell transcriptomic analysis of normal and glaucomatous Angpt1 deficient eyes allowed us to identify distinct TM and SC cell populations and discover additional TM-SC signaling pathways. Furthermore, confirming the importance of angiopoietin signaling in SC, delivery of a recombinant ANGPT1-mimetic promotes developmental SC expansion in healthy and Angpt1 deficient eyes, blunts intraocular pressure (IOP) elevation and RGC loss in a mouse model of PCG and lowers IOP in healthy adult mice. Our data highlight the central role of ANGPT1-TEK signaling and TM-SC crosstalk in IOP homeostasis and provide new candidates for SC-targeted glaucoma therapy.

VIP Stabilizes the Cytoskeleton of Schlemm's Canal Endothelia via Reducing Caspase-3 Mediated ZO-1 Endolysosomal Degradation

Objectives

In glaucomatous eyes, the main aqueous humor (AH) outflow pathway is damaged by accumulated oxidative stress arising from the microenvironment, vascular dysregulation, and aging, which results in increased outflow resistance and ocular hypertension. Schlemm's canal (SC) serves as the final filtration barrier of the main AH outflow pathway. The present study is aimed at investigating the possible regulation of vasoactive intestinal peptide (VIP) on the cytoskeleton by stabilizing ZO-1 in SC.

Methods

Model of chronic ocular hypertension (COH) induced by episcleral venous cauterization was treated with topical VIP. The ultrastructure of junctions, ZO-1 levels, and permeability of the SC inner wall to FITC-dextran (70 kDa) were detected in the COH models. The F-actin distribution, F/G-actin ratio, and ZO-1 degradation pathway in human umbilical vein endothelial cells (HUVECs) and HEK 293 cells were investigated.

Results

ZO-1 in the outer wall of the SC was less than that in the inner wall. COH elicited junction disruption, ZO-1 reduction, and increased permeability of the SC inner wall to FITC-dextran in rats. ZO-1 plays an essential role in maintaining the F/G-actin ratio and F-actin distribution. VIP treatment attenuated the downregulation of ZO-1 associated with COH or H₂O₂-induced oxidative damage. In H₂O₂-stimulated HUVECs, the caspase-3 inhibitor prevents ZO-1 disruption. Caspase-3 activation promoted endolysosomal degradation of ZO-1. Furthermore, a decrease in caspase-3 activation and cytoskeleton redistribution was demonstrated in VIP + H₂O₂-treated cells. The knockdown of ZO-1 or the overexpression of caspase-3 blocked the effect of VIP on the cytoskeleton.

Conclusion

This study provides insights into the role of VIP in stabilizing the interaction between the actin cytoskeleton and cell junctions and may provide a promising targeted strategy for glaucoma treatment.

The Combination of Morphology and Surface Chemistry Defines the Immunological Identity of Nanocarriers in Human Blood

Upon exposure to blood, a corona of proteins adsorbs to nanocarrier surfaces to confer a biological identity that interfaces with the immune system. While the nanocarrier surface chemistry has long been the focus of protein corona formation, the influence of nanostructure has remained unclear despite established influences on biodistribution, clearance, and inflammation. Here, combinations of nanocarrier morphology and surface chemistry are engineered to i) achieve compositionally distinct protein coatings in human blood and ii) control protein-mediated interactions with the immune system. A library of nine PEGylated nanocarriers differing in their combination of morphology (spheres, vesicles, and cylinders) and surface chemistry (methoxy, hydroxyl, and phosphate) are synthesized to represent properties of therapeutic and biomimetic delivery vehicles. Analysis by quantitative label-free proteomic techniques reveal that specific surface chemistry and morphology combinations adsorb unique protein signatures from human blood, resulting in differential complement activation and elicitation of distinct proinflammatory cytokine responses. Furthermore, nanocarrier morphology is shown to primarily influence uptake and clearance by human monocytes, macrophages, and dendritic cells. This comprehensive analysis provides mechanistic insights into rational design choices that impact the immunological identity of nanocarriers in human blood, which can be leveraged to engineer drug delivery vehicles for precision medicine and immunotherapy.

Surface Engineering of FLT4-Targeted Nanocarriers Enhances Cell-Softening Glaucoma Therapy

Primary open-angle glaucoma is associated with elevated intraocular pressure (IOP) that damages the optic nerve and leads to gradual vision loss. Several agents that reduce the stiffness of pressure-regulating Schlemm's canal (SC) endothelial cells, in the conventional outflow pathway of the eye, lower IOP in glaucoma patients and are approved for clinical use. However, poor drug penetration and uncontrolled biodistribution limit their efficacy and produce local adverse effects. Compared to other ocular endothelia, FLT4/VEGFR3 is expressed at elevated levels by SC endothelial cells and can be exploited for targeted drug delivery. Here, we validate FLT4 receptors as clinically relevant targets on SC cells from glaucomatous human donors and engineer polymeric self-assembled nanocarriers displaying lipid-anchored targeting ligands that optimally engage this receptor. Targeting constructs were synthesized as lipid-PEGx-peptide, differing in the number of PEG spacer units (x), and were embedded in micelles. We present a novel proteolysis assay for quantifying ligand accessibility that we employ to design and optimize our FLT4-targeting strategy for glaucoma nanotherapy. Peptide accessibility to proteases correlated with receptor-mediated targeting enhancements. Increasing the accessibility of FLT4-binding peptides enhanced nanocarrier uptake by SC cells while simultaneously decreasing the uptake by off-target vascular endothelial cells. Using a paired longitudinal IOP study in vivo, we show that this enhanced targeting of SC cells translates to IOP reductions that are sustained for a significantly longer time as compared to controls. Confocal microscopy of murine anterior segment tissue confirmed nanocarrier localization to SC within 1 h after intracameral administration. This work demonstrates that steric effects between surface-displayed ligands and PEG coronas significantly impact the targeting performance of synthetic nanocarriers across multiple biological scales. Minimizing the obstruction of modular targeting ligands by PEG measurably improved the efficacy of glaucoma nanotherapy and is an important consideration for engineering PEGylated nanocarriers for targeted drug delivery.

Just add water: hydratable, morphologically diverse nanocarrier powders for targeted delivery

Two major obstacles that limit the widespread usage of polymeric nanocarriers include the complexity of formulation methods and their stability during storage. To address both of these issues, here we present morphologically complex nanocarriers in a hydratable powder form, which bypasses the need for expensive, harsh, and/or time-consuming nanocarrier fabrication techniques. The powders are composed of carbohydrates and self-assembling polymer amphiphiles having a low glass transition temperature. Hydration requires less than one minute and only involves the addition of aqueous media (water or saline) to rapidly obtain self-assembled micelles, worm-like micelles (i.e. filomicelles), or polymersomes from poly(ethylene glycol)-b-poly(propylene sulfide) (PEG-b-PPS) polymers. The formulated powders are highly stable, achieving hydration into monodisperse nanocarriers following >6 months of storage. Diverse drug cargoes were efficiently encapsulated during hydration, including hydrophobic small molecules for micellar morphologies, as well as individual and concurrent loading of both hydrophobic and hydrophilic molecules for vesicular morphologies. Hydrated polymersomes are shown to load hydrophilic biological macromolecules, and encapsulated enzymes retain bioactivity. Furthermore, we demonstrate that inclusion of lipid-anchored ligands in powder form permits the surface-display of targeting ligands and enhances target cell uptake, thereby extending this technology to targeted drug delivery applications. Our powder-based formulation strategy was extendable to commercially available polymer amphiphiles, including PEG-b-polystyrene and PEG-b-polycaprolactone. The formulated nanotechnologies described herein are highly modular, require minimal preparation, and remain stable in ambient long-term storage (bypassing cold chain requirements), which will enable their use in medicine (human and veterinary), research, and commercial applications from cosmetics to agriculture.

Enhancing subcutaneous injection and target tissue accumulation of nanoparticles via co-administration with macropinocytosis inhibitory nanoparticles (MiNP)

A significant barrier to the application of nanoparticles for precision medicine is the mononuclear phagocyte system (MPS), a diverse population of phagocytic cells primarily located within the liver, spleen and lymph nodes. The majority of nanoparticles are indiscriminately cleared by the MPS via macropinocytosis before reaching their intended targets, resulting in side effects and decreased efficacy. Here, we demonstrate that the biodistribution and desired tissue accumulation of targeted nanoparticles can be significantly enhanced by co-injection with polymeric micelles containing the actin depolymerizing agent latrunculin A. These macropinocytosis inhibitory nanoparticles (MiNP) were found to selectively inhibit non-specific uptake of a second "effector" nanoparticle in vitro without impeding receptor-mediated endocytosis. In tumor bearing mice, co-injection with MiNP in a single multi-nanoparticle formulation significantly increased the accumulation of folate-receptor targeted nanoparticles within tumors. Furthermore, subcutaneous co-administration with MiNP allowed effector nanoparticles to achieve serum levels that rivaled a standard intravenous injection. This effect was only observed if the effector nanoparticles were injected within 24 h following MiNP administration, indicating a temporary avoidance of MPS cells. Co-injection with MiNP therefore allows reversible evasion of the MPS for targeted nanoparticles and presents a previously unexplored method of modulating and improving nanoparticle biodistribution following subcutaneous administration.

Normal and glaucomatous outflow regulation

Glaucoma remains only partially understood, particularly at the level of intraocular pressure (IOP) regulation. Trabecular meshwork (TM) and Schlemm's canal inner wall endothelium (SCE) are key to IOP regulation and their characteristics and behavior are the focus of much investigation. This is becoming more apparent with time. We and others have studied the TM and SCE's extracellular matrix (ECM) extensively and unraveled much about its functions and role in regulating aqueous outflow. Ongoing ECM turnover is required to maintain IOP regulation and several TM ECM manipulations modulate outflow facility. We have established clearly that the outflow pathway senses sustained pressure deviations and responds by adjusting the outflow resistance correctively to keep IOP within an appropriately narrow range which will not normally damage the optic nerve. The glaucomatous outflow pathway has in many cases lost this IOP homeostatic response, apparently due at least in part, to loss of TM cells. Depletion of TM cells eliminates the IOP homeostatic response, while restoration of TM cells restores it. Aqueous outflow is not homogeneous, but rather segmental with regions of high, intermediate and low flow. In general, glaucomatous eyes have more low flow regions than normal eyes. There are distinctive molecular differences between high and low flow regions, and during the response to an IOP homeostatic pressure challenge, additional changes in segmental molecular composition occur. In conjunction with these changes, the biomechanical properties of the juxtacanalicular (JCT) segmental regions are different, with low flow regions being stiffer than high flow regions. The JCT ECM of glaucomatous eyes is around 20 times stiffer than in normal eyes. The aqueous humor outflow resistance has been studied extensively, but neither the exact molecular components that comprise the resistance nor their exact location have been established. Our hypothetical model, based on considerable available data, posits that the continuous SCE basal lamina, which lies between 125 and 500 nm beneath the SCE basal surface, is the primary source of normal resistance. On the surface of JCT cells, small and highly controlled focal degradation of its components by podosome- or invadopodia-like structures, PILS, occurs in response to pressure-induced mechanical stretching. Sub-micron sized basement membrane discontinuities develop in the SCE basement membrane and these discontinuities allow passage of aqueous humor to and through SCE giant vacuoles and pores. JCT cells then relocate versican with its highly charged glycosaminoglycan side chains into the discontinuities and by manipulation of their orientation and concentration, the JCT and perhaps the SCE cells regulate the amount of fluid passage. Testing this outflow resistance hypothesis is ongoing in our lab and has the potential to advance our understanding of IOP regulation and of glaucoma.

Surface chemistry-mediated modulation of adsorbed albumin folding state specifies nanocarrier clearance by distinct macrophage subsets

Controlling nanocarrier interactions with the immune system requires a thorough understanding of the surface properties that modulate protein adsorption in biological fluids, since the resulting protein corona redefines cellular interactions with nanocarrier surfaces. Albumin is initially one of the dominant proteins to adsorb to nanocarrier surfaces, a process that is considered benign or beneficial by minimizing opsonization or inflammation. Here, we demonstrate the surface chemistry of a model nanocarrier can be engineered to stabilize or denature the three-dimensional conformation of adsorbed albumin, which respectively promotes evasion or non-specific clearance in vivo. Interestingly, certain common chemistries that have long been considered to convey stealth properties denature albumin to promote nanocarrier recognition by macrophage class A1 scavenger receptors, providing a means for their eventual removal from systemic circulation. We establish that the surface chemistry of nanocarriers can be specified to modulate adsorbed albumin structure and thereby tune clearance by macrophage scavenger receptors.

VIP Induces Changes in the F-/G-Actin Ratio of Schlemm's Canal Endothelium via LRRK2 Transcriptional Regulation

Purpose

A previous study reported that vasoactive intestinal peptide (VIP) can regulate the cytoskeleton of Schlemm's canal (SC) endothelium and expand the SC lumen in a rat glaucoma model. In this study, we aimed to investigate the molecular mechanism of VIP on cytoskeleton regulation.

Methods

During in vivo experiments in rats, leucine-rich repeat kinase 2 (LRRK2) expression and the ratio of F-actin to G-actin (F-/G-actin) surrounding SC were examined by immunofluorescence after the application of VIP. For in vitro experiments in human umbilical vein endothelial cells, both quantitative PCR (qPCR) and western blotting were performed to evaluate Sp1 and LRRK2 expression after the application of VIP (and Sp1/LRRK2 inhibitor). In addition, the F-/G-actin ratio was examined by both immunofluorescence and western blotting after the application of VIP (and LRRK2 inhibitor).

Results

VIP induced increases in the expression of LRRK2 both in vivo and in vitro and the nuclear translocation of Sp1 in vitro. The application of Sp1 inhibitor abolished the increase in LRRK2 expression induced by VIP in vitro. In addition, VIP changed the F-/G-actin ratio, and this effect was abolished by the LRRK2 inhibitor both in vivo and in vitro.

Conclusions

VIP increased the expression of LRRK2, and this regulation was due to the nuclear translocation of Sp1. VIP further changed the F-/G-actin ratio and regulated the balance between the stabilization and destabilization of the F-actin architecture. This study elucidates a novel mechanism by which VIP regulates the actin cytoskeleton of SC endothelium via the Sp1–LRRK2 pathway, suggesting a potential novel treatment strategy for glaucoma.

Targeted Delivery of Cell Softening Micelles to Schlemm's Canal Endothelial Cells for Treatment of Glaucoma

Increased stiffness of the Schlemm's canal (SC) endothelium in the aqueous humor outflow pathways has been associated with elevated intraocular pressure (IOP) in glaucoma. Novel treatments that relax this endothelium, such as actin depolymerizers and rho kinase inhibitors, are in development. Unfortunately, these treatments have undesirable off-target effects and a lower than desired potency. To address these issues, a targeted PEG-b-PPS micelle loaded with actin depolymerizer latrunculin A (tLatA-MC) is developed. Targeting of SC cells is achieved by modifying the micelle surface with a high affinity peptide that binds the VEGFR3/FLT4 receptor, a lymphatic lineage marker found to be highly expressed by SC cells relative to other ocular cells. During in vitro optimization, increasing the peptide surface density increased micellar uptake in SC cells while unexpectedly decreasing uptake by human umbilical vein endothelial cells (HUVEC). The functional efficacy of tLatA-MC, as measured by decreased SC cell stiffness compared to non-targeted micelles (ntLatA-MC) or targeted blank micelles (tBL-MC), is verified using atomic force microscopy. tLatA-MC reduced IOP in an in vivo mouse model by 30-50%. The results validate the use of a cell-softening nanotherapy to selectively modulate stiffness of SC cells for therapeutic reduction of IOP and treatment of glaucoma.

Prodrugs and nanomicelles to overcome ocular barriers for drug penetration

INTRODUCTION

Ocular barriers hinder drug delivery and reduce drug bioavailability. This article focuses on enhancing drug absorption across the corneal and conjunctival epithelium. Both, transporter targeted prodrug formulations and nanomicellar strategy is proven to enhance the drug permeation of therapeutic agents across various ocular barriers. These strategies can increase aqueous drug solubility and stability of many hydrophobic drugs for topical ophthalmic formulations.

AREAS COVERED

The article discusses various ocular barriers, ocular influx, and efflux transporters. It elaborates various prodrug strategies used for enhancing drug absorption. Along with this, the article also describes nanomicellar formulation, its characteristic and advantages, and applications in for anterior and posterior segment drug delivery.

EXPERT OPINION

Prodrugs and nanomicellar formulations provide an effective strategy for improving drug absorption and drug bioavailability across various ocular barriers. It will be exciting to see the efficacy of nanomicelles for treating back of the eye disorders after their topical application. This is considered as a holy grail of ocular drug delivery due to the dynamic and static ocular barriers, restricting posterior entry of topically applied drug formulations.

High Density Display of an Anti-Angiogenic Peptide on Micelle Surfaces Enhances Their Inhibition of αvβ3 Integrin-Mediated Neovascularization In Vitro

Diabetic retinopathy (DR), Retinopathy of Pre-maturity (ROP), and Age-related Macular Degeneration (AMD) are multifactorial manifestations associated with abnormal growth of blood vessels in the retina. These three diseases account for 5% of the total blindness and vision impairment in the US alone. The current treatment options involve heavily invasive techniques such as frequent intravitreal administration of anti-VEGF (vascular endothelial growth factor) antibodies, which pose serious risks of endophthalmitis, retinal detachment and a multitude of adverse effects stemming from the diverse physiological processes that involve VEGF. To overcome these limitations, this current study utilizes a micellar delivery vehicle (MC) decorated with an anti-angiogenic peptide (aANGP) that inhibits αvβ3 mediated neovascularization using primary endothelial cells (HUVEC). Stable incorporation of the peptide into the micelles (aANGP-MCs) for high valency surface display was achieved with a lipidated peptide construct. After 24 h of treatment, aANGP-MCs showed significantly higher inhibition of proliferation and migration compared to free from aANGP peptide. A tube formation assay clearly demonstrated a dose-dependent angiogenic inhibitory effect of aANGP-MCs with a maximum inhibition at 4 μg/mL, a 1000-fold lower concentration than that required for free from aANGP to display a biological effect. These results demonstrate valency-dependent enhancement in the therapeutic efficacy of a bioactive peptide following conjugation to nanoparticle surfaces and present a possible treatment alternative to anti-VEGF antibody therapy with decreased side effects and more versatile options for controlled delivery.

A bioengineering approach to Schlemm's canal-like stem cell differentiation for in vitro glaucoma drug screening

Human Schlemm's canal (HSC) cells are critical for understanding outflow physiology and glaucoma etiology. However, primary donor cells frequently used in research are difficult to isolate. HSC cells exhibit both vascular and lymphatic markers. Human adipose-derived stem cells (ADSCs) represent a potential source of HSC due to their capacity to differentiate into both vascular and lymphatic endothelial cells, via VEGF-A and VEGF-C. Shear stress plays a critical role in maintaining HSC integrity, function, and PROX1 expression. Additionally, the human trabecular meshwork (HTM) microenvironment could provide cues for HSC-like differentiation. We hypothesize that subjecting ADSCs to VEGF-A or VEGF-C, shear stress, and co-culture with HTM cells could provide biological, mechanical, and cellular cues necessary for HSC-like differentiation. To test this hypothesis, effects of VEGF-A, VEGF-C, and shear stress on ADSC differentiation were examined and compared to primary HSC cells in terms of cell morphology, and HSC marker expression using qPCR, immunoblotting, and immunocytochemistry analysis. Furthermore, the effect of co-culture with HTM cells on porous scaffolds on ADSC differentiation was studied. Treatment with VEGF-C under shear stress is effective in differentiating ADSCs into PROX1-expressing HSC-like cells. Co-culture with HTM cells on porous scaffolds leads to HTM/ADSC-derived HSC-like constructs that regulate through-flow and respond as expected to dexamethasone. STATEMENT OF SIGNIFICANCE: We successfully generated human Schlemm's canal (HSC) like cells from adipocyte-derived stem cells induced by biochemical and biomechanical cues as well as bioengineered human trabecular meshwork (HTM) on micropatterned, porous SU8 scaffolds. These stem cell-derived HSC-like cells co-cultured with HTM cells on SU8 scaffolds can regulate through-flow, and in particular, are responsive to steroid treatment as expected. These findings show that ADSC-derived HSC-like cells have the potential to recreate the ocular outflow pathway for in vitro glaucoma drug screening. To the best of our knowledge, it is the very first time to demonstrate derivation of Schlemm's canal-like cells from stem cells. It provides an important alternative source to primary Schlemm's canal cells that are very difficult to be isolated and cultured from human donors.

Celastrol-loaded PEG-b-PPS nanocarriers as an anti-inflammatory treatment for atherosclerosis

In this work, the hydrophobic small molecule NF-κB inhibitor celastrol was loaded into poly(ethylene glycol)-b-poly(propylene sulfide) (PEG-b-PPS) micelles. PEG-b-PPS micelles demonstrated high loading efficiency, low polydispersity, and no morphological changes upon loading with celastrol. Encapsulation of celastrol within these nanocarriers significantly reduced cytotoxicity compared to free celastrol, while simultaneously expanding the lower concentration range for effective inhibition of NF-κB signaling by nearly 50 000-fold. Furthermore, celastrol-loaded micelles successfully reduced TNF-α secretion after LPS stimulation of RAW 264.7 cells and reduced the number of neutrophils and inflammatory monocytes within atherosclerotic plaques of ldlr-/- mice. This reduction in inflammatory cells was matched by a reduction in plaque area, suggesting that celastrol-loaded nanocarriers may serve as an anti-inflammatory treatment for atherosclerosis.

Topical application of polymeric nanomicelles in ophthalmology: a review on research efforts for the noninvasive delivery of ocular therapeutics

INTRODUCTION

Polymeric micelles represent nowadays an interesting formulative approach for ocular drug delivery, as they act as solubility enhancers of poorly soluble drugs and promote drug transport across cornea and sclera. In particular, in the last 5 years polymeric nanomicelles have been increasingly investigated to overcome some of the important challenges of the topical treatment of ocular diseases.

AREAS COVERED

The aim of this review was to gather up-to-date information on the different roles that polymeric micelles (commonly in the nanosize scale) can play in ocular delivery. Thus, after a general description of ocular barriers and micelles features, the attention is focused on those properties that are relevant for ophthalmic application. Finally, their efficacy in improving the ocular delivery of different classes of therapeutics (anti-inflammatory, immunosuppressant, antiglaucoma, antifungal, and antiviral drugs) are reported.

EXPERT OPINION

Although still a few, in vivo experiments have clearly demonstrated the capability of polymeric nanomicelles to overcome a variety of hurdles associated to ocular therapy, notably increasing drug bioavailability. However, there are still some very important issues to be solved, such as tolerability and stability; additionally, the role of micelles in drug uptake by the ocular tissues and their potential for the treatment of posterior eye diseases still need to be clarified/verified.

Where No Hand Has Gone Before: Probing Mechanobiology at the Cellular Level

Physical forces and other mechanical stimuli are fundamental regulators of cell behavior and function. Cells are also biomechanically competent: they generate forces to migrate, contract, remodel, and sense their environment. As the knowledge of the mechanisms of mechanobiology increases, the need to resolve and probe increasingly small scales calls for novel technologies to mechanically manipulate cells, examine forces exerted by cells, and characterize cellular biomechanics. Here, we review novel methods to quantify cellular force generation, measure cell mechanical properties, and exert localized piconewton and nanonewton forces on cells, receptors, and proteins. The combination of these technologies will provide further insight on the effect of mechanical stimuli on cells and the mechanisms that convert these stimuli into biochemical and biomechanical activity.

YAP and TAZ, the conductors that orchestrate eye development, homeostasis, and disease

Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are transcriptional coactivators established as a nexus in numerous signaling pathways, notably in Hippo signaling. Previous research revealed multifarious function of YAP and TAZ in oncology and cardiovasology. Recently, the focus has been laid on their pivotal role in eye morphogenesis and homeostasis. In this review, we synthesize advances of YAP and TAZ function during eye development in different model organisms, introduce their function in different ocular tissues and eye diseases, and highlight the potential for therapeutic interventions.