Myo/Nog cells are present in the ciliary processes, on the zonule of Zinn and posterior capsule of the lens following cataract surgery

Evaluation of Dose-Response Relationship in Novel Extended Release of Targeted Nucleic Acid Nanocarriers to Treat Secondary Cataracts

Purpose: The present study aimed to determine the dose-response relationship between targeted nanocarriers released from a novel, sustained release formulation and their ability to specifically deplete cells responsible for the development of posterior capsular opacification (PCO) in month-long, dynamic cell cultures. Methods: Injectable, thermosensitive poly(D,L-lactic-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(D,L-lactic-co-glycolic acid) triblock copolymer hydrogels were loaded with either a low or a high dose of doxorubicin-loaded antibody-targeted nanocarriers (G8:3DNA:Dox). Human rhabdomyosarcoma cells, selected for their expression of PCO marker brain-specific angiogenesis inhibitor 1 (BAI1), were kept under dynamic media flow and received either a low or high dose of nanocarriers. Cells were fixed and stained at predetermined time points to evaluate targeted depletion of BAI1+ cells. Results: A lower dose of nanocarriers in hydrogel depleted BAI1+ cells at a slower rate than the higher dose, whereas both reached over 90% BAI1+ cellular nonviability at 28 days. Both treatment groups also significantly lowered the relative abundance of BAI1+ cells in the population compared with the control group. Conclusions: Controlled release of a lower dose of nanocarriers can still achieve therapeutically relevant effects in the prevention of PCO, while avoiding potential secondary effects associated with the administration of a higher dose.

Myo/Nog Cells: The Jekylls and Hydes of the Lens

Herein, we review a unique and versatile lineage composed of Myo/Nog cells that may be beneficial or detrimental depending on their environment and nature of the pathological stimuli they are exposed to. While we will focus on the lens, related Myo/Nog cell behaviors and functions in other tissues are integrated into the narrative of our research that spans over three decades, examines multiple species and progresses from early stages of embryonic development to aging adults. Myo/Nog cells were discovered in the embryonic epiblast by their co-expression of the skeletal muscle-specific transcription factor MyoD, the bone morphogenetic protein inhibitor Noggin and brain-specific angiogenesis inhibitor 1. They were tracked from the epiblast into the developing lens, revealing heterogeneity of cell types within this structure. Depletion of Myo/Nog cells in the epiblast results in eye malformations arising from the absence of Noggin. In the adult lens, Myo/Nog cells are the source of myofibroblasts whose contractions produce wrinkles in the capsule. Eliminating this population within the rabbit lens during cataract surgery reduces posterior capsule opacification to below clinically significant levels. Parallels are drawn between the therapeutic potential of targeting Myo/Nog cells to prevent fibrotic disease in the lens and other ocular tissues.

Research progress of lens zonules

Background

The lens zonule, a circumferential system of fibres connecting the ciliary body to the lens, is responsible for centration of the lens. The structural, functional, and positional abnormalities of the zonular apparatus can lead to the abnormality of the intraocular structure, presenting a significant challenge to cataract surgery.

Main text

The lens zonule is the elaborate system of extracellular fibers, which not only centers the lens in the eye but also plays an important role in accommodation and lens immunity, maintains the shape of the lens, and corrects spherical aberration. The zonules may directly participate in the formation of cataract via the immune mechanism. Abnormal zonular fibers that affect the position and shape of the lens may play an important role in the pathogenesis of angle closure disease and increase the complexity of the surgery. Capsular tension rings and related endocapsular devices are used to provide sufficient capsular bag stabilization and ensure the safety of cataract surgery procedures. Better preoperative and intraoperative evaluation methods for zonules are needed for clinicians.

Conclusions

The microstructure, biomechanical properties, and physiological functions of the lens zonules help us to better understand the pathogenesis of cataract and glaucoma, facilitating the development of safer surgical procedures for cataract. Further studies are needed to carefully analyze the structure-function relationship of the zonular apparatus to explore new treatment strategies for cataract and glaucoma.

Myo/Nog Cells Give Rise to Myofibroblasts During Epiretinal Membrane Formation in a Mouse Model of Proliferative Vitreoretinopathy

Purpose

Myo/Nog cells are the source of myofibroblasts in the lens and synthesize muscle proteins in human epiretinal membranes (ERMs). In the current study, we examined the response of Myo/Nog cells during ERM formation in a mouse model of proliferative vitreoretinopathy (PVR).

Methods

PVR was induced by intravitreal injections of gas and ARPE-19 cells. PVR grade was scored by fundus imaging, optical coherence tomography, and histology. Double label immunofluorescence localization was performed to quantify Myo/Nog cells, myofibroblasts, and leukocytes.

Results

Myo/Nog cells, identified by co-labeling with antibodies to brain-specific angiogenesis inhibitor 1 (BAI1) and Noggin, increased throughout the eye with induction of PVR and disease progression. They were present on the inner surface of the retina in grades 1/2 PVR and were the largest subpopulation of cells in grades 3 to 6 ERMs. All α-SMA-positive (+) cells and all but one striated myosin+ cell expressed BAI1 in grades 1 to 6 PVR. Folds and areas of retinal detachment were overlain by Myo/Nog cells containing muscle proteins. Low numbers of CD18, CD68, and CD45+ leukocytes were detected throughout the eye. Small subpopulations of BAI1+ cells expressed leukocyte markers. ARPE-19 cells were found in the vitreous but were rare in ERMs. Pigmented cells lacking Myo/Nog and muscle cell markers were present in ERMs and abundant within the retina by grade 5/6.

Conclusions

Myo/Nog cells differentiate into myofibroblasts that appear to contract and produce retinal folds and detachment. Targeting BAI1 for Myo/Nog cell depletion may be a pharmacological approach to preventing and treating PVR.

Mohawk impedes angiofibrosis by preventing the differentiation of tendon stem/progenitor cells into myofibroblasts

Adult tendons heal via fibrovascular scarring with inferior biomechanical properties. Mohawk (Mkx) emerged as a pivotal actor in tenolineage commitment. However, its precise function in tendinopathy remains poorly understood. This study investigates the cellular and molecular mechanisms underlying Mkx' role in fibrovascular healing. Human samples were collected to test fibrovascular markers. We then performed RNAseq on Mkx-/- mice compared to their wild type littermates to decipher Mkx regulome. We therefore sought to reproduce TSPCs transition to myofibroblasts in-vitro by over-expressing MyoD and followed by phenotypic and experimental cells' characterization using microscopy, qRT-PCR, flow cytometry sorting, presto-blue cell viability assay and immunofluorescence. Two different in vivo models were used to assess the effect of the MyoD-expressing myofibroblasts: transplantation in the dorsal area of immunodeficient mice and in an adult Achilles tendon injury model. To prevent angiofibrosis, we tested the molecule Xav939 and proceeded with histological stainings, q-RT PCR transcriptional quantification of angifibrotic markers, mechanical tests, and immunofluorescence. Tendinopathy samples showed fibrovascular healing with decreased tenolineage phenotype. Transcriptomic analysis of Mkx-/- tendons revealed myofibroblast-associated biological processes. Over-expression of MyoD in WT tendon stem progenitor cells (TSPCs) gave rise to myofibroblasts reprogramming in-vitro and fibrovascular scarring in-vivo. MKX directly binds to MyoD promoter and underlies global regulative processes related to angiogenesis and Wnt signaling pathway. Blocking Wnt signaling with the small molecule Xav393 resulted in higher histological and biomechanical properties. Taken together, our data provide the first in vivo and in-vitro evidence of tendon stem progenitor cells to myofibroblasts transition and show improved tendon healing via angiofibrosis modulation, thus opening potential therapeutic avenues to treat tendinopathy patients.

Sustained Release of Antibody-Conjugated DNA Nanocarriers from a Novel Injectable Hydrogel for Targeted Cell Depletion to Treat Cataract Posterior Capsule Opacification

Purpose: To compare a novel, sustained release formulation and a bolus injection of a targeted nanocarrier for the ability to specifically deplete cells responsible for the development of posterior capsule opacification (PCO) in week-long, dynamic cell cultures. Methods: A novel, injectable, thermosensitive poly(D,L-lactic-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(D,L-lactic-co-glycolic acid) (PLGA-PEG-PLGA) triblock copolymer hydrogel was engineered for the sustained release of targeted, nucleic acid nanocarriers loaded with cytotoxic doxorubicin (G8:3DNA:Dox). Human rhabdomyosarcoma (RD) cells were used due to their expression of brain-specific angiogenesis inhibitor 1 (BAI1), a specific marker for the myofibroblasts responsible for PCO. Under constant media flow, nanocarriers were injected into cell cultures as either a bolus or within the hydrogel. Cells were fixed and stained every other day for 7 days to compare targeted depletion of BAI1⁺ cells. Results: The formulation transitions to a gel at physiological temperatures, is optically clear, noncytotoxic, and can release G8:3DNA:Dox nanocarriers for up to 4 weeks. In RD cell cultures, G8:3DNA:Dox nanocarriers specifically eliminated BAI1⁺ cells. The bolus nanocarrier dose showed significantly reduced cell depletion overtime, while the sustained release of nanocarriers showed increased cell depletion over time. By day 7, <2% of BAI1⁺ cells were depleted by the bolus injection and 74.2% BAI1⁺ cells were targeted by the sustained release of nanocarriers. Conclusions: The sustained release of nanocarriers from the hydrogel allows for improved therapeutic delivery in a dynamic system. This method can offer a more effective and efficient method of prophylactically treating PCO after cataract surgery.

Acute Response and Neuroprotective Role of Myo/Nog Cells Assessed in a Rat Model of Focal Brain Injury

Focal brain injury in the form of a needlestick (NS) results in cell death and induces a self-protective response flanking the lesion. Myo/Nog cells are identified by their expression of bone morphogenetic protein inhibitor Noggin, brain-specific angiogenesis inhibitor 1 (BAI1) and the skeletal muscle specific transcription factor MyoD. Myo/Nog cells limit cell death in two forms of retinopathy. In this study, we examined the acute response of Myo/Nog cells to a NS lesion that extended from the rat posterior parietal cortex to the hippocampus. Myo/Nog cells were identified with antibodies to Noggin and BAI1. These cells were the primary source of both molecules in the uninjured and injured brain. One day after the NS, the normally small population of Myo/Nog cells expanded approximately eightfold within a 1 mm area surrounding the lesion. Myo/Nog cells were reduced by approximately 50% along the lesion with an injection of the BAI1 monoclonal antibody and complement. The number of dying cells, identified by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), was unchanged at this early time point in response to the decrease in Myo/Nog cells. However, increasing the number of Myo/Nog cells within the lesion by injecting BAI1-positive (+) cells isolated from the brains of other animals, significantly reduced cell death and increased the number of NeuN+ neurons compared to brains injected with phosphate buffered saline or exogenous BAI1-negative cells. These findings demonstrate that Myo/Nog cells rapidly react to injury within the brain and increasing their number within the lesion is neuroprotective.

Mutation of the TRPM3 cation channel underlies progressive cataract development and lens calcification associated with pro-fibrotic and immune cell responses

Transient-receptor-potential cation channel, subfamily M, member 3 (TRPM3) serves as a polymodal calcium sensor in diverse mammalian cell-types. Mutation of the human TRPM3 gene (TRPM3) has been linked with inherited forms of early-onset cataract with or without other eye abnormalities. Here, we have characterized the ocular phenotypes of germline "knock-in" mice that harbor a human cataract-associated isoleucine-to-methionine mutation (p.I65M) in TRPM3 (Trpm3-mutant) compared with germline "knock-out" mice that functionally lack TRPM3 (Trpm3-null). Despite strong expression of Trpm3 in lens epithelial cells, neither heterozygous (Trpm3^+/- ) nor homozygous (Trpm3^-/- ) Trpm3-null mice developed cataract; however, the latter exhibited a mild impairment of lens growth. In contrast, homozygous Trpm3-M/M mutants developed severe, progressive, anterior pyramid-like cataract with microphthalmia, whereas heterozygous Trpm3-I/M and hemizygous Trpm3-M/- mutants developed anterior pyramidal cataract with delayed onset and progression-consistent with a semi-dominant lens phenotype. Histochemical staining revealed abnormal accumulation of calcium phosphate-like deposits and collagen fibrils in Trpm3-mutant lenses and immunoblotting detected increased αII-spectrin cleavage products consistent with calpain hyper-activation. Immunofluorescent confocal microscopy of Trpm3-M/M mutant lenses revealed fiber cell membrane degeneration that was accompanied by accumulation of alpha-smooth muscle actin positive (α-SMA+ve) myofibroblast-like cells and macrosialin positive (CD68+ve) macrophage-like cells. Collectively, our mouse model data support an ocular disease association for TRPM3 in humans and suggest that (1) Trpm3 deficiency impaired lens growth but not lens transparency and (2) Trpm3 dysfunction resulted in progressive lens degeneration and calcification coupled with pro-fibrotic (α-SMA+ve) and immune (CD68+ve) cell responses.

Factors Affecting Posterior Capsule Opacification in the Development of Intraocular Lens Materials

Posterior capsule opacification (PCO) is the most common complication arising from the corrective surgery used to treat cataract patients. PCO arises when lens epithelial cells (LEC) residing in the capsular bag post-surgery undergo hyper-proliferation and transdifferentiation into myofibroblasts, migrating from the posterior capsule over the visual axis of the newly implanted intraocular lens (IOL). The developmental pathways underlying PCO are yet to be fully understood and the current literature is contradictory regarding the impact of the recognised risk factors of PCO. The aim of this review is firstly to collate the known biochemical pathways that lead to PCO development, providing an up-to-date chronological overview from surgery to established PCO formation. Secondly, the risk factors of PCO are evaluated, focussing on the impact of IOLs’ properties. Finally, the latest experimental model designs used in PCO research are discussed to demonstrate the ongoing development of clinical PCO models, the efficacy of newly developed IOL technology, and potential therapeutic interventions. This review will contribute to current PCO literature by presenting an updated overview of the known developmental pathways of PCO, an evaluation of the impact of the risk factors underlying its development, and the latest experimental models used to investigate PCO. Furthermore, the review should provide developmental routes for research into the investigation of potential therapeutic interventions and improvements in IOL design in the aid of preventing PCO for new and existing patients.

Myo/Nog cells are nonprofessional phagocytes

Myo/Nog cells were discovered in the chick embryo epiblast. Their expression of MyoD reflects a commitment to the skeletal muscle lineage and capacity to differentiate into myofibroblasts. Release of Noggin by Myo/Nog cells is essential for normal morphogenesis. Myo/Nog cells rapidly respond to wounding in the skin and eyes. In this report, we present evidence suggesting that Myo/Nog cells phagocytose tattoo ink in tissue sections of human skin and engulf cell corpses in cultures of anterior human lens tissue and magnetic beads injected into the anterior chamber of mice in vivo. Myo/Nog cells are distinct from macrophages in the skin and eyes indicated by the absence of labeling with an antibody to ionized calcium binding adaptor molecule 1. In addition to their primary roles as regulators of BMP signaling and progenitors of myofibroblasts, Myo/Nog cells behave as nonprofessional phagocytes defined as cells whose primary functions are unrelated to phagocytosis but are capable of engulfment.

Brain-specific angiogenesis inhibitor 1 is expressed in the Myo/Nog cell lineage

The Myo/Nog cell lineage was discovered in the chick embryo and is also present in adult mammalian tissues. The cells are named for their expression of mRNA for the skeletal muscle specific transcription factor MyoD and bone morphogenetic protein inhibitor Noggin. A third marker for Myo/Nog cells is the cell surface molecule recognized by the G8 monoclonal antibody (mAb). G8 has been used to detect, track, isolate and kill Myo/Nog cells. In this study, we screened a membrane proteome array for the target of the G8 mAb. The array consisted of >5,000 molecules, each synthesized in their native confirmation with appropriate post-translational modifications in a single clone of HEK-293T cells. G8 mAb binding to the clone expressing brain-specific angiogenesis inhibitor 1 (BAI1) was detected by flow cytometry, re-verified by sequencing and validated by transfection with the plasmid construct for BAI1. Further validation of the G8 target was provided by enzyme-linked immunosorbent assay. The G8 epitope was identified by screening a high-throughput, site directed mutagenesis library designed to cover 95–100% of the 954 amino acids of the extracellular domain of the BAI1 protein. The G8 mAb binds within the third thrombospondin repeat of the extracellular domain of human BAI1. Immunofluorescence localization experiments revealed that G8 and a commercially available BAI1 mAb co-localize to the subpopulation of Myo/Nog cells in the skin, eyes and brain. Expression of the multi-functional BAI1 protein in Myo/Nog cells introduces new possibilities for the roles of Myo/Nog cells in normal and diseased tissues.

Extended Release of Doxorubicin-Loaded 3DNA Nanocarriers from In-Situ Forming, Self-Assembled Hydrogels

Purpose: Cataracts are the leading cause of blindness worldwide, resulting in over 30 million surgeries each year. These cases are expected to double within the next 10 years. About 25% of all patients develop secondary cataracts or posterior capsule opacification (PCO) postsurgery. PCO is a vision impairment disorder that develops from myofibroblasts migration and contraction that deforms the capsule surrounding the lens. Currently, Nd:YAG laser therapy is used to treat PCO; however, laser is not available worldwide and adverse side effects may arise. Thus, there is a considerable unmet need for more efficacious and convenient preventive treatments for PCO. Our work focuses on engineering an innovative, prophylactic sustained release platform for DNA-based nanocarriers to further reduce the incidence of PCO. Methods: Novel, optically clear, self-assembled poly(d,l-lactic-co-glycolic acid)-b-poly(ethylene glycol) (PLGA-PEG) triblock copolymer hydrogels were used for the sustained release of the DNA-based nanocarriers (3DNA_®) loaded with cytotoxic doxorubicin (DOX) and targeted with a monoclonal antibody called G8 (3DNA:DOX:G8), which is specific to cells responsible for PCO. Results: The 29 (w/v)% polymer hydrogels with the 3DNA nanocarriers presented over 80% of light transmittance, soft mechanical properties (<350 Pa), and sustained release for 1 month. Conclusions: In this work, we show for the first time that the hydrophobic PLGA-PEG-PLGA hydrogels can be used as platforms for sustained delivery of nucleic acid-based nanocarriers. This work demonstrates that polymeric formulations can be used for the extended delivery of ocular therapeutics and other macromolecules to treat a variety of ocular conditions.

Myo/Nog cells expressing muscle proteins are present in preretinal membranes from patients with proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is a complication of rhegmatogenous retinal detachment and ocular trauma. The disease is characterized by development of membranes that may apply traction to the retina and cause redetachment. Membrane contractions are attributed to myofibroblasts arising from retinal pigment epithelial cells, glia and fibroblasts. The progenitors of myofibrobasts in the lens are Myo/Nog cells that express the skeletal muscle transcription factor MyoD and bone morphogenetic protein inhibitor Noggin. The retina and choroid also contain Myo/Nog cells that respond to stress. We examined preretinal PVR membranes from three ocular trauma patients with retinal detachment for Myo/Nog cells and their expression of muscle proteins. Myo/Nog cells were identified by co-localization of antibodies to the G8 antigen and Noggin. Greater than 80% of all cells in sections from two of three patients expressed both G8 and Noggin. Myo/Nog cells lacked pigment. Alpha smooth muscle actin (α-SMA) and striated myosin II heavy chain were present in the majority of Myo/Nog cells in these two patients. Differentiation of Myo/Nog cells was paralleled by low levels of MyoD. Membrane sections from the third patient consisted mostly of connective tissue with very few cells. A small subpopulation in these sections expressed both G8 and Noggin, and muscle proteins were detected in only a minority of G8-positive (+) cells. In all three patients, greater than 99% of cells with MyoD, α-SMA and striated muscle myosin co-expressed G8. These findings suggest that contractile myofibroblasts in PVR membranes may be derived from differentiating Myo/Nog cells.

Acquired Resilience: An Evolved System of Tissue Protection in Mammals

This review brings together observations on the stress-induced regulation of resilience mechanisms in body tissues. It is argued that the stresses that induce tissue resilience in mammals arise from everyday sources: sunlight, food, lack of food, hypoxia and physical stresses. At low levels, these stresses induce an organised protective response in probably all tissues; and, at some higher level, cause tissue destruction. This pattern of response to stress is well known to toxicologists, who have termed it hormesis. The phenotypes of resilience are diverse and reports of stress-induced resilience are to be found in journals of neuroscience, sports medicine, cancer, healthy ageing, dementia, parkinsonism, ophthalmology and more. This diversity makes the proposing of a general concept of induced resilience a significant task, which this review attempts. We suggest that a system of stress-induced tissue resilience has evolved to enhance the survival of animals. By analogy with acquired immunity, we term this system 'acquired resilience'. Evidence is reviewed that acquired resilience, like acquired immunity, fades with age. This fading is, we suggest, a major component of ageing. Understanding of acquired resilience may, we argue, open pathways for the maintenance of good health in the later decades of human life.