Laminin expression in adult and developing retinae: evidence of two novel CNS laminins

The mechanics of the retina: Müller glia role on retinal extracellular matrix and modelling

The retina is a highly heterogeneous tissue, both cell-wise but also regarding its extracellular matrix (ECM). The stiffness of the ECM is pivotal in retinal development and maturation and has also been associated with the onset and/or progression of numerous retinal pathologies, such as glaucoma, proliferative vitreoretinopathy (PVR), age-related macular degeneration (AMD), epiretinal membrane (ERM) formation or uveitis. Nonetheless, much remains unknown about the biomechanical milieu of the retina, and specifically the role that Müller glia play as principal mechanosensors and major producers of ECM constituents. So far, new approaches need to be developed to further the knowledge in the field of retinal mechanobiology for ECM-target applications to arise. In this review, we focus on the involvement of Müller glia in shaping and altering the retinal ECM under both physiological and pathological conditions and look into various biomaterial options to more accurately replicate the impact of matrix stiffness in vitro.

Cell-Penetrating Chaperone Nuc1 for Small- and Large-Molecule Delivery Into Retinal Cells and Tissues

Purpose

There are currently no means available for the efficient delivery of recombinant proteins into retinal cells in vivo. Although cell-penetrating peptides have been somewhat effective in protein delivery to the retina, they generally require conjugation chemistry with the payload, negatively impacting function of the therapeutic protein. In this study, we developed a novel peptide (Nuc1) that acts as a chaperone for delivery of small and large molecules, including steroids, peptides, antibodies, recombinant proteins, and viruses (adeno-associated viruses [AAVs]) across biological membranes in vivo without the need for conjugation.

Methods

Nuc1 peptide was designed based on sequences known to bind heparan sulfate proteoglycans and nucleolin found on the surface of retinal cells. Nuc1 was injected into the vitreous of mice with a variety of molecules and retinas examined for uptake and function of these molecules.

Results

Nuc1 engages the process of macropynocytosis for cell entry. The delivery of functional recombinant X-linked inhibitor of apoptosis protein to photoreceptors via the intravitreal route of injection inhibited retinal apoptosis. Nuc1 was found to enhance the delivery of anti-VEGF antibodies delivered intravitreally or topically in models of age-related macular degeneration (AMD). Nuc1 enhanced delivery of decorin, facilitating significant inhibition of neovascularization and fibrosis in a model of AMD. Finally, Nuc1 was found to enhance penetration of retinal cells and tissues by AAV via both the subretinal and intravitreal routes of injection.

Conclusions

Nuc1 shows promise as a novel approach for the delivery of recombinant proteins into retinal cells in vivo.

Early-Onset Myopia and Retinal Detachment without Typical Microcoria or Severe Proteinuria due to a Novel LAMB2 Variant

PURPOSE

To describe the ocular and renal features, as well as outcomes of retinal detachment repair, in patients with a novel, homozygous laminin β-2 (LAMB2) pathogenic variant.

DESIGN

Single-center retrospective chart review of patients with a homozygous variant, c.619T>C p.(Ser207Pro), in the LAMB2 gene.

SUBJECTS

Eleven patients (22 eyes) from 4 families.

METHODS

Demographic data and ocular findings were recorded. Patients were recalled for a detailed renal evaluation.

MAIN OUTCOME MEASURES

Ocular features, renal features, and outcomes of retinal detachment repair.

RESULTS

The mean age at presentation was 6.0 (range, 1-26) years. None of the study eyes had microcoria, and none of the patients had nephrotic-range proteinuria. The mean refraction and axial length were -7.9 diopters (range, -4.0 to -12.0 diopters) and 25.3 (range, 22.7-27.7) mm, respectively. Eleven eyes (50%) had cataract at presentation. Fifteen eyes had a clear view to the fundus and all showed tessellated myopic fundus, avascular peripheral retina evident clinically or on fluorescein angiography, and rudimentary fovea. Optic disc pallor was observed in 10 eyes (66.7%). Straightened retinal vessels, abnormal vascular emanation (situs inversus) from the optic disc, supernumerary vascular branching at the optic disc, and vascular tortuosity were observed in 10 (66.7%), 2 (13.4%), 2 (13.4%), and 2 (13.4%) eyes, respectively. Discrete areas of punched-out chorioretinal atrophy were observed in 4 (26.7%) eyes. Spectral-domain OCT showed retinal and choroidal thinning in 13 eyes (86.7%), retinoschisis temporal to the fovea in 2 eyes (13.4%), and rudimentary fovea in 15 eyes (100%). Among the 22 eyes, 14 eyes (63.6%) developed rhegmatogenous retinal detachment (RRD), mostly during childhood, of which 5 patients had bilateral RRD. Eight eyes were operated on and 6 (75%) achieved retinal reattachment at the last follow-up. The mean preoperative visual acuity was 20/300 and the mean postoperative visual acuity at the last follow-up was 20/400.

CONCLUSIONS

This study describes a distinct phenotype of LAMB2-related disease with a novel, homozygous LAMB2 variant, and further expands the spectrum of ophthalmic and renal features, and the molecular genetic basis, of LAMB2-related disease. Because the typical microcoria and nephrotic-range proteinuria might be absent, the retinal features can guide the diagnosis.

FINANCIAL DISCLOSURE(S)

The authors have no proprietary or commercial interest in any materials discussed in this article.

A treatment within sight: challenges in the development of stem cell-derived photoreceptor therapies for retinal degenerative diseases

Stem cell therapies can potentially treat various retinal degenerative diseases, including age-related macular degeneration (AMD) and inherited retinal diseases like retinitis pigmentosa. For these diseases, transplanted cells may include stem cell-derived retinal pigmented epithelial (RPE) cells, photoreceptors, or a combination of both. Although stem cell-derived RPE cells have progressed to human clinical trials, therapies using photoreceptors and other retinal cell types are lagging. In this review, we discuss the potential use of human pluripotent stem cell (hPSC)-derived photoreceptors for the treatment of retinal degeneration and highlight the progress and challenges for their efficient production and clinical application in regenerative medicine.

Photoreceptor laminin drives differentiation of human pluripotent stem cells to photoreceptor progenitors that partially restore retina function

Blindness caused by advanced stages of inherited retinal diseases and age-related macular degeneration are characterized by photoreceptor loss. Cell therapy involving replacement with functional photoreceptor-like cells generated from human pluripotent stem cells holds great promise. Here, we generated a human recombinant retina-specific laminin isoform, LN523, and demonstrated the role in promoting the differentiation of human embryonic stem cells into photoreceptor progenitors. This chemically defined and xenogen-free method enables reproducible production of photoreceptor progenitors within 32 days. We observed that the transplantation into rd10 mice were able to protect the host photoreceptor outer nuclear layer (ONL) up to 2 weeks post transplantation as measured by full-field electroretinogram. At 4 weeks post transplantation, the engrafted cells were found to survive, mature, and associate with the host's rod bipolar cells. Visual behavioral assessment using the water maze swimming test demonstrated visual improvement in the cell-transplanted rodents. At 20 weeks post transplantation, the maturing engrafted cells were able to replace the loss of host ONL by extensive association with host bipolar cells and synapses. Post-transplanted rabbit model also provided congruent evidence for synaptic connectivity with the degenerated host retina. The results may pave the way for the development of stem cell-based therapeutics for retina degeneration.

Post-GWAS screening of candidate genes for refractive error in mutant zebrafish models

Genome-wide association studies (GWAS) have dissected numerous genetic factors underlying refractive errors (RE) such as myopia. Despite significant insights into understanding the genetic architecture of RE, few studies have validated and explored the functional role of candidate genes within these loci. To functionally follow-up on GWAS and characterize the potential role of candidate genes on the development of RE, we prioritized nine genes (TJP2, PDE11A, SHISA6, LAMA2, LRRC4C, KCNQ5, GNB3, RBFOX1, and GRIA4) based on biological and statistical evidence; and used CRISPR/cas9 to generate knock-out zebrafish mutants. These mutant fish were screened for abnormalities in axial length by spectral-domain optical coherence tomography and refractive status by eccentric photorefraction at the juvenile (2 months) and adult (4 months) developmental stage. We found a significantly increased axial length and myopic shift in refractive status in three of our studied mutants, indicating a potential involvement of the human orthologs (LAMA2, LRRC4C, and KCNQ5) in myopia development. Further, in-situ hybridization studies showed that all three genes are expressed throughout the zebrafish retina. Our zebrafish models provide evidence of a functional role of these three genes in refractive error development and offer opportunities to elucidate pathways driving the retina-to-sclera signaling cascade that leads to myopia.

Crosstalk between Blood Vessels and Glia during the Central Nervous System Development

The formation of proper blood vessel patterns in the central nervous system (CNS) is crucial to deliver oxygen and nutrient to neurons efficiently. At the same time, neurons must be isolated from the outer blood circulation by a specialized structure, the blood-brain barrier (BBB), to maintain the microenvironment of brain parenchyma for the survival of neurons and proper synaptic transmission. To develop this highly organized structure, glial cells, a major component of the brain, have been reported to play essential roles. In this review, the crosstalk between the macroglia, including astrocytes and oligodendrocytes, and endothelial cells during the development of CNS will be discussed. First, the known roles of astrocytes in neuro-vascular unit and its development, and then, the requirements of astrocytes for BBB development and maintenance are shown. Then, various genetic and cellular studies revealing the roles of astrocytes in the growth of blood vessels by providing a scaffold, including laminins and fibronectin, as well as by secreting trophic factors, including vascular endothelial growth factor (VEGF) and transforming growth factor-β (TGF-β) are introduced. Finally, the interactions between oligodendrocyte progenitors and blood vessels are overviewed. Although these studies revealed the necessity for proper communication between glia and endothelial cells for CNS development, our knowledge about the detailed cellular and molecular mechanisms for them is still limited. The questions to be clarified in the future are also discussed.

The Effect of Intravitreal Ocriplasmin on Hue Discrimination

SIGNIFICANCE

We report 13 patients who received ocriplasmin for symptomatic vitreomacular adhesion. Farnsworth-Munsell 100 (FM 100) hue test total error score (TES) increased from baseline to month 1, before recovering at year 1. Ocriplasmin may alter hue discrimination.

PURPOSE

This study aimed to determine whether intravitreal ocriplasmin affects hue discrimination.

METHODS

Thirteen patients with symptomatic vitreomacular adhesion received intravitreal ocriplasmin 125 μg. Patients underwent full ocular examination, optical coherence tomography, and FM 100 hue test at baseline, 1 week, 1 month, and 1 year.

RESULTS

Mean age was 74.8 years. The median baseline FM 100 TES was similar in the injected and fellow eyes (272 vs. 252, respectively). Median TES in the injected eye increased from 272 to 348 at 1 week (median difference compared with baseline, +52.0; 98.8% confidence interval of difference, -64.0 to 184.0; P = .29), decreased to 324 at 1 month (median difference compared with baseline, -4.0; 98.8% confidence interval of difference, -44.0 to 256.0; P = .40), and decreased to 268 at 1 year (median difference compared with baseline, -108.0; 93.8% confidence interval of difference, -200.0 to 52.0; P = .19). Two patients (15.4%) had anatomic release of vitreomacular adhesion, occurring within 1 month of injection.

CONCLUSIONS

Ocriplasmin may alter hue discrimination, but larger studies are required to provide sufficient power to detect or exclude a statistically significant effect. Longer follow-up is needed to determine the duration of any effect.

Visual functional changes after ocriplasmin injection for vitreomacular traction: A microperimetric analysis

PURPOSE:

The purpose is to evaluate functional changes after ocriplasmin injection to treat vitreomacular traction (VMT) by microperimetry.

MATERIALS AND METHODS:

Prospective interventional study on patients underwent an intravitreal ocriplasmin injection. Optical coherence tomography, best-corrected visual acuity (BCVA) test, and microperimetry were performed at baseline, 1 week, 1 and 3 months. Microperimeter recorded retinal sensitivity (RS) and central retinal sensitivity (CRS) at central 12° and 4°, respectively, and fixation as bivariate contour ellipse area (BCEA) at 68%, 95%, and 99% of fixation points. Functional parameters were analyzed in patients who had (Group A) or not (Group B) VMT release.

RESULTS:

Twenty-one patients including 18 with VMT and 3 with VMT plus macular hole (MH) were treated. Eleven patients achieved VMT resolution including all cases with MH that achieved hole closure. An impairment of BCVA, RS and CRS (P < 0.01; P < 0.001; P = 0.001, respectively) was reported at 1 week followed by a significant improvement (BCVA, P = 0.001; RS, CRS, P = 0.02) at 3 months. The early impairment of visual acuity and sensitivity significantly occurred in Group B (P ≤ 0.01) while their recovery significantly occurred in Group A (P < 0.01). BCEA significantly increased in dimension (68%, P = 0.01; 95%, P = 0.03) at 1 week, subsequently returning to near baseline values over follow-up. Only in Group A, fixation stability significantly improved at 3 months.

CONCLUSION:

Microperimetry confirms an early and reversible functional impairment after ocriplasmin injection regardless VMT resolution. If a greater decrease in function could occur in the eyes without VMT resolution, a better functional recovery could occur in the event of VMT resolution.

Laminin Polymerization and Inherited Disease: Lessons From Genetics

The laminins (LM) are a family of basement membranes glycoproteins with essential structural roles in supporting epithelia, endothelia, nerves and muscle adhesion, and signaling roles in regulating cell migration, proliferation, stem cell maintenance and differentiation. Laminins are obligate heterotrimers comprised of α, β and γ chains that assemble intracellularly. However, extracellularly these heterotrimers then assemble into higher-order networks via interaction between their laminin N-terminal (LN) domains. In vitro protein studies have identified assembly kinetics and the structural motifs involved in binding of adjacent LN domains. The physiological importance of these interactions has been identified through the study of pathogenic point mutations in LN domains that lead to syndromic disorders presenting with phenotypes dependent on which laminin gene is mutated. Genotype-phenotype comparison between knockout and LN domain missense mutations of the same laminin allows inferences to be drawn about the roles of laminin network assembly in terms of tissue function. In this review, we will discuss these comparisons in terms of laminin disorders, and the therapeutic options that understanding these processes have allowed. We will also discuss recent findings of non-laminin mediators of laminin network assembly and their implications in terms of basement membrane structure and function.

Seeing stars: Development and function of retinal astrocytes

Throughout the central nervous system, astrocytes adopt precisely ordered spatial arrangements of their somata and arbors, which facilitate their many important functions. Astrocyte pattern formation is particularly important in the retina, where astrocytes serve as a template that dictates the pattern of developing retinal vasculature. Thus, if astrocyte patterning is disturbed, there are severe consequences for retinal angiogenesis and ultimately for vision - as seen in diseases such as retinopathy of prematurity. Here we discuss key steps in development of the retinal astrocyte population. We describe how fundamental developmental forces - their birth, migration, proliferation, and death - sculpt astrocytes into a template that guides angiogenesis. We further address the radical changes in the cellular and molecular composition of the astrocyte network that occur upon completion of angiogenesis, paving the way for their adult functions in support of retinal ganglion cell axons. Understanding development of retinal astrocytes may elucidate pattern formation mechanisms that are deployed broadly by other axon-associated astrocyte populations.

Partially Differentiated Neuroretinal Cells Promote Maturation of the Retinal Pigment Epithelium

Purpose

Many studies have demonstrated the ability of the retinal pigment epithelium (RPE) to foster the maturation of the developing retina. Few studies have examined the reciprocal effects of developing retina on the RPE.

Methods

RPE isolated from human fetal RPE or differentiated from human stem cells was cultured on Transwell filter inserts. Retinal progenitor cells (RPCs) were differentiated from human stem cells and cultured on a planar scaffold composed of gelatin, chondroitin sulfate, hyaluronic acid, and laminin-521. Cultures were analyzed by quantitative RT-PCR, immunofluorescence, immunoblotting, and transepithelial electrical resistance (TER).

Results

RPCs initially differentiated into several retina-like cell types that segregated from one another and formed loosely organized layers or zones. With time, the presumptive photoreceptor and ganglion cell layers persisted, but the intervening zone became dominated by cells that expressed glial markers with no evidence of bipolar cells or interneurons. Co-culture of this underdeveloped retinoid with the RPE resulted in a thickened layer of recoverin-positive cells but did not prevent the loss of interneuron markers in the intervening zone. Although photoreceptor inner and outer segments were not observed, immunoblots revealed that co-culture increased expression of rhodopsin and red/green opsin. Co-culture of the RPE with this underdeveloped retinal culture increased the TER of the RPE and the expression of RPE signature genes.

Conclusions

These studies indicated that an immature neurosensory retina can foster maturation of the RPE; however, the ability of RPE alone to foster maturation of the neurosensory retina is limited.

A laminin-based local regulatory network in the testis that supports spermatogenesis

In adult rat testes, the basement membrane is structurally constituted by laminin and collagen chains that lay adjacent to the blood-testis barrier (BTB). It plays a crucial scaffolding role to support spermatogenesis. On the other hand, laminin-333 comprised of laminin-α3/ß3/γ3 at the apical ES (ectoplasmic specialization, a testis-specific cell-cell adherens junction at the Sertoli cell-step 8-19 spermatid interface) expressed by spermatids serves as a unique cell adhesion protein that forms an adhesion complex with α6ß1-integrin expressed by Sertoli cells to support spermiogenesis. Emerging evidence has shown that biologically active fragments are derived from basement membrane and apical ES laminin chains through proteolytic cleavage mediated by matrix metalloproteinase 9 (MMP9) and MMP2, respectively. Two of these laminin bioactive fragments: one from the basement membrane laminin-α2 chain called LG3/4/5-peptide, and one from the apical ES laminin-γ3 chain known as F5-peptide, are potent regulators that modify cell adhesion function at the Sertoli-spermatid interface (i.e., apical ES) but also at the Sertoli cell-cell interface designated basal ES at the blood-testis barrier (BTB) with contrasting effects. These findings not only highlight the physiological significance of these bioactive peptides that create a local regulatory network to support spermatogenesis, they also open a unique area of research. For instance, it is likely that several other bioactive peptides remain to be identified. These bioactive peptides including their downstream signaling proteins and cascades should be studied collectively in future investigations to elucidate the underlying mechanism(s) by which they coordinate with each other to maintain spermatogenesis. This is the goal of this review.

The extracellular matrix complexity of idiopathic epiretinal membranes and the bilaminar arrangement of the associated internal limiting membrane in the posterior retina

PURPOSE

To study the composition of the internal limiting membrane (ILM) of the retina, the extracellular matrix (ECM) of idiopathic epiretinal membranes (iERMs), and the relationships occurring between the two membranes.

METHODS

Forty-six iERMs, 24 of them associated with the ILM, were collected and included in this study. The investigation has been carried out by immunofluorescence and confocal microscopy on glutaraldehyde- and osmium-fixed epon-embedded samples and on frozen samples. Sections were double or triple labelled with antibodies against vimentin; collagens I, III, IV, α5(IV), and VI; laminin 1 + 2; laminin α2-, α4-, α5-, β1-, β2-, β3-, γ1-, and γ2-chains; entactin; and fibronectin.

RESULTS

iERM thickness was not uniform. Almost 14% of iERMs showed thickenings due to folding of their ECM component under the cell layer. The vitreal side of iERMs was often shorter than the attached ILM. In this case, the ILM resulted folded under the iERM. ILMs contained laminin 111; laminin α2-, α5-, β1-, β2-, and γ1-chains; entactin; collagens I; α5(IV); [α1(IV)]₂α2(IV); and VI. Laminins, entactin, and α5(IV) were gathered on the retinal half of the ILM, whereas collagens [α1(IV)]₂α2(IV) and I were restricted to the vitreal side. Collagen VI was detected on both sides of the ILM. iERMs expressed laminin 111, collagens III, [α1(IV)]₂α2(IV) and VI, entactin, and fibronectin. Entactin co-localized with laminins and collagen IV.

CONCLUSIONS

Analysis of laminins and collagen chain expression indicates that ILM contains laminin 111 (former laminin 1), laminin 521 (former laminin 11), laminin 211 (former laminin 2), collagen [α1(IV)]₂α2(IV), and collagen α3(IV)α4(IV)α5. In contrast, iERMs express only collagen [α1(IV)]₂α2(IV) and laminin 111. In addition, both iERMs and ILMs contain entactin. The presence of three major constituents of the basement membranes co-localized together in iERMs is suggestive for a deranged process of basement membrane formation which fails to assemble properly. In view of the many interactions occurring among its proteins, the ECM of either the iERMs or the ILMs can account for their reciprocal adhesiveness. In addition, the peculiar deposition of the ECM observed in some samples of iERM is suggestive for its involvement in the formation of macular puckers.

Retinal organoids: a window into human retinal development

Retinal development and maturation are orchestrated by a series of interacting signalling networks that drive the morphogenetic transformation of the anterior developing brain. Studies in model organisms continue to elucidate these complex series of events. However, the human retina shows many differences from that of other organisms and the investigation of human eye development now benefits from stem cell-derived organoids. Retinal differentiation methods have progressed from simple 2D adherent cultures to self-organising micro-physiological systems. As models of development, these have collectively offered new insights into the previously unexplored early development of the human retina and informed our knowledge of the key cell fate decisions that govern the specification of light-sensitive photoreceptors. Although the developmental trajectories of other retinal cell types remain more elusive, the collation of omics datasets, combined with advanced culture methodology, will enable modelling of the intricate process of human retinogenesis and retinal disease in vitro.

Summary: Retinal organoid systems derived from human pluripotent stem cells are micro-physiological systems that offer new insights into previously unexplored human retina development.

Secretory proteostasis of the retinal pigmented epithelium: Impairment links to age-related macular degeneration

Secretory proteostasis integrates protein synthesis, processing, folding and trafficking pathways that are essential for efficient cellular secretion. For the retinal pigment epithelium (RPE), secretory proteostasis is of vital importance for the maintenance of the structural and functional integrity of apical (photoreceptors) and basal (Bruch's membrane/choroidal blood supply) sides of the environment it resides in. This integrity is achieved through functions governed by RPE secreted proteins, which include extracellular matrix modelling/remodelling, angiogenesis and immune response modulation. Impaired RPE secretory proteostasis affects not only the extracellular environment, but leads to intracellular protein aggregation and ER-stress with subsequent cell death. Ample recent evidence implicates dysregulated proteostasis as a key factor in the development of age-related macular degeneration (AMD), the leading cause of blindness in the developed world, and research aiming to characterise the roles of various proteins implicated in AMD-associated dysregulated proteostasis unveiled unexpected facets of the mechanisms involved in degenerative pathogenesis. This review analyses cellular processes unveiled by the study of the top 200 transcripts most abundantly expressed by the RPE/choroid in the light of the specialised secretory nature of the RPE. Functional roles of these proteins and the mechanisms of their impaired secretion, due to age and genetic-related causes, are analysed in relation to AMD development. Understanding the importance of RPE secretory proteostasis in relation to maintaining retinal health and how it becomes impaired in disease is of paramount importance for the development and assessment of future therapeutic advancements involving gene and cell therapies.

The Tumor Microenvironment: Focus on Extracellular Matrix

The extracellular matrix (ECM) regulates the development and maintains tissue homeostasis. The ECM is composed of a complex network of molecules presenting distinct biochemical properties to regulate cell growth, survival, motility, and differentiation. Among their components, proteoglycans (PGs) are considered one of the main components of ECM. Its composition, biomechanics, and anisotropy are exquisitely tuned to reflect the physiological state of the tissue. The loss of ECM's homeostasis is seen as one of the hallmarks of cancer and, typically, defines transitional events in tumor progression and metastasis. In this chapter, we discuss the types of proteoglycans and their roles in cancer. It has been observed that the amount of some ECM components is increased, while others are decreased, depending on the type of tumor. However, both conditions corroborate with tumor progression and malignancy. Therefore, ECM components have an increasingly important role in carcinogenesis and this leads us to believe that their understanding may be a key in the discovery of new anti-tumor therapies. In this book, the main ECM components will be discussed in more detail in each chapter.

Dendritic Effects of Injectable Biodegradable Thermogels on Pharmacotherapy of Inflammatory Glaucoma-Associated Degradation of Extracellular Matrix

The development of advanced drug delivery systems with extensively sustained release and multiple functions is highly imperative for effective attenuation of the degradation of ocular extracellular matrix that is associated with inflammatory glaucoma. Here, the generation of amine-terminated polyamidoamine dendrimers in an injectable biodegradable thermogel is demonstrated to be important for achieving prolonged drug release profiles and potent anti-inflammatory effects. Among various generations (Gx, x = 0, 1, 3, 5), third-generation G3 is proved as the most effective material for optimizing the synergistic effects of gelatin and poly(N-isopropylacrylamide) and generating a thermogel with the highest biodegradation resistance, the best drug encapsulation/extended-release performance, and the best ability to reduce the elevated expression of inflammatory molecules. A pharmacotherapy based on intracameral injection of thermogels coloaded with pilocarpine and ascorbic acid results in effective alleviation of progressive glaucoma owing to the anti-inflammatory activity and long-acting drug release (above a therapeutic level of 10 µg mL^-1 over 80 days) of thermogels, which simultaneously suppress inflammation and stimulate regeneration of stromal collagen and retinal laminin. These findings on the dendritic effects of rationally designed injectable biomaterials with potent anti-inflammatory effects and controlled drug release demonstrate great promise of their use for pharmacological treatment of progressive glaucoma.

Development of High-Resolution Three-Dimensional-Printed Extracellular Matrix Scaffolds and Their Compatibility with Pluripotent Stem Cells and Early Retinal Cells

Purpose: Widely used approaches for retinal disease modeling and in vitro therapeutic testing can be augmented by using tissue-engineered scaffolds with a precise 3-dimensional structure. However, the materials currently used for these scaffolds are poorly matched to the biochemical and mechanical properties of the in vivo retina. Here, we create biopolymer-based scaffolds with a structure that is amenable to retinal tissue engineering and modeling. Methods: Optimal two-photon polymerization (TPP) settings, including laser power and scanning speed, are identified for 4 methacrylated biopolymer formulations: collagen, gelatin, hyaluronic acid (HA), and a 50/50 mixture of gelatin/HA, each with methylene blue as a photoinitiator. For select formulations, fabrication accuracy and swelling are determined and biocompatibility is evaluated by using human induced pluripotent stem cells and rat postnatal retinal cells. Results: TPP is feasible for each biopolymer formulation, but it is the most reliable for mixtures containing gelatin and the least reliable for HA alone. The mean size of microscaffold pores is within several microns of the intended value but the overall structure size is several times greater than the modeled volume. The addition of HA to gelatin scaffolds increases cell viability and promotes neuronal phenotype, including Tuj-1 expression and characteristic morphology. Conclusion: We successfully determined a useful range of TPP settings for 4 methacrylated biopolymer formulations. When crosslinked, these extracellular matrix-derived molecules support the growth and attachment of retinal cells. We anticipate that when combined with existing patient-specific approaches, this technique will enable more efficient and accurate retinal disease modeling and therapeutic testing in vitro than current techniques allow.

Pharmacotherapy for Choroidal Neovascularization Due to Uncommon Causes

BACKGROUND

Choroidal neovascularization (CNV) in adults is most commonly associated with neovascular age-related macular degeneration (AMD) and pathologic myopia. Though less common, CNV can also develop from other conditions such as uveitis, central serous chorioretinopathy, angioid streaks, intraocular tumors, hereditary chorioretinal dystrophies, or can be idiopathic in origin. If left untreated, CNV may cause visual loss because of exudation of intraretinal or subretinal fluid, retinal or subretinal hemorrhage, or fibrosis involving the macula. It is well known that one of the main drivers of angiogenesis in CNV development is vascular endothelial growth factor (VEGF) and therefore inhibitors of VEGF might be an effective treatment for CNV.

METHODS

The goal of this review is to provide an overview and summary in the use of pharmacotherapy especially anti-VEGF therapy, in the treatment of CNV due to uncommon causes.

RESULTS

Results from uncontrolled case series and controlled clinical trials have reported good efficacy and safety in using anti-VEGF agents including bevacizumab, ranibizumab, aflibercept and ziv-aflibercept in the treatment of CNV due to uncommon causes. Anti-VEGF has also been used in combination with verteporfin PDT and anti-inflammatory agents for treating CNV of various causes.

CONCLUSION

Pharmacotherapy with anti-VEGF agents is an effective treatment option for CNV due to uncommon etiologies.

Early posterior vitreous detachment is associated with LAMA5 dominant mutation

BACKGROUND

Extracellular matrix molecular components, previously linked to multisystem syndromes include collagens, fibrillins and laminins. Recently, we described a novel multisystem syndrome caused by the c.9418G>A p.(V3140M) mutation in the laminin alpha-5 (LAMA5) gene, which affects connective tissues of all organs and apparatus in a three generation family. In the same family, we have also reported a myopic trait, which, however, was linked to the Prolyl 4-hydroxylase subunit alpha-2 (P4HA2) gene. Results of investigation on vitreous changes and their pathogenesis are reported in the present study.

MATERIALS AND METHODS

Nineteen family individuals underwent complete ophthalmic examination including best-corrected visual acuity (BCVA), fundus examination, fundus photography, intraocular pressure measurement, axial length measurement using ocular biometry, Goldmann visual field examination, standard electroretinogram, SD-OCT. Segregation analysis of LAMA5 and P4HA2 mutations was performed in enrolled members.

RESULTS

The vitreous alterations fully segregated with LAMA5 mutation in both young and adult family members. Slight reduction of retinal thickness and peripheral retinal degeneration in only two patients were reported.

CONCLUSIONS

In this work we showed that PVD is a common trait of LAMA5 multisystem syndrome, therefore occurring as an age-unrelated trait. We hypothesize that the p.(V3140M) mutation results in a reduction of retinal inner limiting membrane (ILM) stability, leading to a derangement in the macromolecular structure of the vitreous gel, and PVD. Further investigations will be necessary to elucidate the role of wild type and mutated LAMA5 in the pathogenesis of PVD.

Laminin-dystroglycan signaling regulates retinal arteriogenesis

Proper arteriovenous morphogenesis is crucial for maintaining normal tissue perfusion. However, our understanding of how arterial morphogenesis is regulated in the CNS is incomplete. In this study, we asked whether vascular basement membrane (BM) laminins, specifically the γ3-containing isoforms, regulate retinal arterial morphogenesis. We provide evidence that Laminin-γ3 is deposited at both arterial and venous BMs during arteriogenesis. Vascular BM Laminin-γ3 bound dystroglycan (DG), a laminin receptor preferentially expressed by arterial endothelial cells (ECs) during arteriogenesis. Blockade of laminin-DG binding in vitro led to decreased Delta-like ligand (DLL)-4 expression in ECs. Moreover, genetic deletion of the Laminin-γ3- and EC-specific deletion of DG led to similar defects in retinal arteriogenesis, including reduced Dll4 expression, hyperbranching and reduced smooth muscle coverage. These results implicate a newly identified Laminin-γ3-DG signaling cascade that regulates arterial Dll4/Notch signaling to specify and stabilize retinal arteries.-Biswas, S., Watters, J., Bachay, G., Varshney, S., Hunter, D. D., Hu, H., Brunken, W. J. Laminin-dystroglycan signaling regulates retinal arteriogenesis.

Laminin γ3 plays an important role in retinal lamination, photoreceptor organisation and ganglion cell differentiation

Laminins are heterotrimeric glycoproteins of the extracellular matrix. Eleven different laminin chains have been identified in vertebrates. They are ubiquitously expressed in the human body, with a distinct tissue distribution. Laminin expression in neural retina and their functional role during human retinogenesis is still unknown. This study investigated the laminin expression in human developing and adult retina, showing laminin α1, α5, β1, β2 and γ1 to be predominantly expressed in Bruch's membrane and the inner limiting membrane. Laminin-332 and laminin γ3 expression were mainly observed in the neural retina during retinal histogenesis. These expression patterns were largely conserved in pluripotent stem cell-derived retinal organoids. Blocking of laminin γ3 function in retinal organoids resulted in the disruption of laminar organisation and synapse formation, the loss of photoreceptor organisation and retinal ganglion cells. Our data demonstrate a unique temporal and spatial expression for laminins and reveal a novel role for laminin γ3 during human retinogenesis.

Collective adhesion and displacement of retinal progenitor cells upon extracellular matrix substrates of transplantable biomaterials

Strategies to replace retinal photoreceptors lost to damage or disease rely upon the migration of replacement cells transplanted into sub-retinal spaces. A significant obstacle to the advancement of cell transplantation for retinal repair is the limited migration of transplanted cells into host retina. In this work, we examine the adhesion and displacement responses of retinal progenitor cells on extracellular matrix substrates found in retina as well as widely used in the design and preparation of transplantable scaffolds. The data illustrate that retinal progenitor cells exhibit unique adhesive and displacement dynamics in response to poly-l-lysine, fibronectin, laminin, hyaluronic acid, and Matrigel. These findings suggest that transplantable biomaterials can be designed to improve cell integration by incorporating extracellular matrix substrates that affect the migratory behaviors of replacement cells.

Knockdown of Laminin gamma-3 (Lamc3) impairs motoneuron guidance in the zebrafish embryo

Background: Previous work in the zebrafish embryo has shown that laminin γ-3 ( lamc3) is enriched in endothelial cells marked by expression of fli1a, but the role of Lamc3 has been unknown. Methods: We use antisense morpholino oligonucleotides, and CRISPR/Cas9 mutagenesis of F0 embryos, to create zebrafish embryos in which lamc3 expression is compromised. Transgenic imaging, immunofluorescence, and in situ hybridisation reveal that Lamc3 loss-of-function affects the development of muscle pioneers, endothelial cells, and motoneurons. Results:  Lamc3 is enriched in endothelial cells during zebrafish development, but it is also expressed by other tissues. Depletion of Lamc3 by use of antisense morpholino oligonucleotides perturbs formation of the parachordal chain and subsequently the thoracic duct, but Lamc3 is not required for sprouting of the cardinal vein. F0 embryos in which lamc3 expression is perturbed by a CRISPR/Cas9 approach also fail to form a parachordal chain, but we were unable to establish a stable lamc3 null line. Lamc3 is dispensable for muscle pioneer specification and for the expression of netrin-1a in these cells. Lamc3 knockdown causes netrin-1a up-regulation in the neural tube and there is increased Netrin-1 protein throughout the trunk of the embryo. Axonal guidance of rostral primary motoneurons is defective in Lamc3 knockdown embryos. Conclusions: We suggest that knockdown of Lamc3 perturbs migration of rostral primary motoneurons at the level of the horizontal myoseptum, indicating that laminin γ3 plays a role in motoneuron guidance.

Assessment of Ocriplasmin Effects on the Vitreoretinal Compartment in Porcine and Human Model Systems

Ocriplasmin (Jetrea®) is a recombinant protease used to treat vitreomacular traction. To gain insight into vitreoretinal observations reported after ocriplasmin treatment, we have developed an in vivo porcine ocriplasmin-induced posterior vitreous detachment (PVD) model in which we investigated vitreoretinal tissues by optical coherence tomography, histology, and cytokine profiling. Eight weeks postinjection, ocriplasmin yielded PVD in 82% of eyes. Subretinal fluid (85%) and vitreous hyperreflective spots (45%) were resolved by week 3. Histological analysis of extracellular matrix (ECM) proteins such as laminin, fibronectin, and collagen IV indicated no retinal ocriplasmin-induced ECM distribution changes. Retinal morphology was unaffected in all eyes. Cytokine profiles of ocriplasmin-treated eyes were not different from vehicle. In cell-based electrical resistance assays, blood-retinal barrier permeability was altered by ocriplasmin concentrations of 6 μg/mL and higher, with all effects being nontoxic, cell-type specific, and reversible. Ocriplasmin was actively taken up by RPE and Müller cells, and our data suggest both lysosomal and transcellular clearance routes for ocriplasmin. In conclusion, transient hyperreflective spots and fluid in a porcine ocriplasmin-induced PVD model did not correlate with retinal ECM rearrangement nor inflammation. Reversible in vitro effects on blood-retinal barrier permeability provide grounds for a hypothesis on the mechanisms behind transient subretinal fluid observed in ocriplasmin-treated patients.

CNS synapses are stabilized trans-synaptically by laminins and laminin-interacting proteins

The retina expresses several laminins in the outer plexiform layer (OPL), where they may provide an extracellular scaffold for synapse stabilization. Mice with a targeted deletion of the laminin β2 gene (Lamb2) exhibit retinal disruptions: photoreceptor synapses in the OPL are disorganized and the retinal physiological response is attenuated. We hypothesize that laminins are required for proper trans-synaptic alignment. To test this, we compared the distribution, expression, association and modification of several pre- and post-synaptic elements in wild-type and Lamb2-null retinae. A potential laminin receptor, integrin α3, is at the presynaptic side of the wild-type OPL. Another potential laminin receptor, dystroglycan, is at the post-synaptic side of the wild-type OPL. Integrin α3 and dystroglycan can be co-immunoprecipitated with the laminin β2 chain, demonstrating that they may bind laminins. In the absence of the laminin β2 chain, the expression of many pre-synaptic components (bassoon, kinesin, among others) is relatively undisturbed although their spatial organization and anchoring to the membrane is disrupted. In contrast, in the Lamb2-null, β-dystroglycan (β-DG) expression is altered, co-localization of β-DG with dystrophin and the glutamate receptor mGluR6 is disrupted, and the post-synaptic bipolar cell components mGluR6 and GPR179 become dissociated, suggesting that laminins mediate scaffolding of post-synaptic components. In addition, although pikachurin remains associated with β-DG, pikachurin is no longer closely associated with mGluR6 or α-DG in the Lamb2-null. These data suggest that laminins act as links among pre- and post-synaptic laminin receptors and α-DG and pikachurin in the synaptic space to maintain proper trans-synaptic alignment.

Novel Insights into the Pathogenesis of Monogenic Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidneys and urinary tract (CAKUT) comprise a large spectrum of congenital malformations ranging from severe manifestations, such as renal agenesis, to potentially milder conditions, such as vesicoureteral reflux. CAKUT causes approximately 40% of ESRD that manifests within the first three decades of life. Several lines of evidence indicate that CAKUT is often caused by recessive or dominant mutations in single (monogenic) genes. To date, approximately 40 monogenic genes are known to cause CAKUT if mutated, explaining 5%-20% of patients. However, hundreds of different monogenic CAKUT genes probably exist. The discovery of novel CAKUT-causing genes remains challenging because of this pronounced heterogeneity, variable expressivity, and incomplete penetrance. We here give an overview of known genetic causes for human CAKUT and shed light on distinct renal morphogenetic pathways that were identified as relevant for CAKUT in mice and humans.

WIDESPREAD MACULAR NEUROSENSORY DETACHMENT AFTER OCRIPLASMIN INTRAVITREAL INJECTION

PURPOSE

To present the case of a patient with vitreomacular traction who experienced immediate severe acute complications after ocriplasmin intravitreal injection.

METHODS

Case report.

RESULTS

A 61-year-old woman with vitreomacular traction underwent ocriplasmin treatment. Within 24 hours after injection, she noticed severe reduction in visual acuity. Spectral domain optical coherence tomography revealed release of vitreous traction, together with widespread subretinal fluid and decreased reflectivity in the outer retina. Ten weeks after treatment, visual acuity improved, although below pretreatment levels, with partial reduction in subretinal fluid.

CONCLUSION

Intravitreal ocriplasmin can produce acute visual acuity changes with widespread subretinal fluid and outer retinal ellipsoid zone hyporeflectivity on spectral domain optical coherence tomography. The overall acute and long-term safety profile of ocriplasmin remains unknown.

PERSISTENT RETINAL CHANGES AFTER INTRAVITREAL OCRIPLASMIN

BACKGROUND/PURPOSE

Postmarket analysis helps identify potentially important side effects not discovered during clinical trials. Ocriplasmin is a recently approved medication administered by intravitreal injection for the treatment of symptomatic vitreomacular adhesion and macular hole. Overall, clinical trials of ocriplasmin have shown a relatively high safety profile. However, recently, a series of case reports have highlighted acute vision loss associated with abnormal findings on spectral domain optical coherence tomography and electroretinography.

METHODS/RESULTS

A 70-year-old man developed multiple discrete pockets of macular subretinal fluid 10 weeks after intravitreal ocriplasmin injection, with minimal resolution of fluid over 11 months. Electroretinographic findings demonstrated persistent rod photoreceptor sensitivity loss at 14 months after injection.

CONCLUSION

This is the first report of persistent electroretinographic and optical coherence tomographic abnormalities after ocriplasmin injection. Electroretinography abnormalities were noted in a small percentage of patients during ocriplasmin clinical trials and in a recent series of case reports and postmarket survey analysis. The authors propose that cleavage of fibronectin and laminin causes disruption of the interphotoreceptor matrix, leading to the ellipsoid layer attenuation and resultant electroretinographic sensitivity loss and subretinal fluid described on spectral domain optical coherence tomography. Persistent changes over 14 months in this patient indicate that ocriplasmin may have the potential to cause permanent retinal damage.

Autoimmunity against laminins

Laminins are ubiquitous constituents of the basement membranes with major architectural and functional role as supported by the fact that absence or mutations of laminins lead to either lethal or severely impairing phenotypes. Besides genetic defects, laminins are involved in a wide range of human diseases including cancer, infections, and inflammatory diseases, as well as autoimmune disorders. A growing body of evidence implicates several laminin chains as autoantigens in blistering skin diseases, collagenoses, vasculitis, or post-infectious autoimmunity. The current paper reviews the existing knowledge on autoimmunity against laminins referring to both experimental and clinical data, and on therapeutic implications of anti-laminin antibodies. Further investigation of relevant laminin epitopes in pathogenic autoimmunity would facilitate the development of appropriate diagnostic tools for thorough characterization of patients' antibody specificities and should decisively contribute to designing more specific therapeutic interventions.

From the analysis of pharmacologic vitreolysis to the comprehension of ocriplasmin safety

INTRODUCTION

Pharmacologic vitreolysis is a strategy used to treat anomalous posterior vitreous detachment, by weakening vitreoretinal adhesion with an intravitreal drug. Pharmacologic vitreolysis facilitates surgery, and abnormalities of the vitreoretinal interface including vitreomacular traction (VMT) and early stage macular hole (MH) could be resolved. Ocriplasmin is a recombinant protease, active against fibronectin and laminin, which are important components of the vitreoretinal interface. Ocriplasmin has been approved for symptomatic treatment of VMT and MH with visible traction, and it functions by dissolving the proteins that link the vitreous to the macula, thereby creating a complete posterior vitreous detachment (PVD).

AREAS COVERED

This paper reviews the current knowledge and status of investigations regarding the use of ocriplasmin for pharmacologic vitreolysis and its safety.

EXPERT OPINION

Ocriplasmin is a non-specific enzyme; therefore, it dissolves vitreal proteins as well as possibly proteins associated with visual function in the retina, choroid, and lens. Ocular adverse events (OAEs) of ocriplasmin include transient visual loss, intraocular inflammation, vitreous floaters, lens opacification, zonular instability of the lens, and intraocular hemorrhage. The prevalence of the OAEs is very low; however, on rare occasions, they can result in widespread retinal dysfunction. Research into the acute and long-term safety of ocriplasmin is required.

Structural Study of Cell Attachment Peptide Derived from Laminin by Molecular Dynamics Simulation

Peptides with cell attachment activity are beneficial component of biomaterials for tissue engineering. Conformational structure is one of the important factors for the biological activities. The EF1 peptide (DYATLQLQEGRLHFMFDLG) derived from laminin promotes cell spreading and cell attachment activity mediated by α2β1 integrin. Although the sequence of the EF2 peptide (DFATVQLRNGFPYFSYDLG) is homologous sequence to that of EF1, EF2 does not promote cell attachment activity. To determine whether there are structural differences between EF1 and EF2, we performed replica exchange molecular dynamics (REMD) simulations and conventional molecular dynamics (MD) simulations. We found that EF1 and EF2 had β-sheet structure as a secondary structure around the global minimum. However, EF2 had variety of structures around the global minimum compared with EF1 and has easily escaped from the bottom of free energy. The structural fluctuation of the EF1 is smaller than that of the EF2. The structural variation of EF2 is related to these differences in the structural fluctuation and the number of the hydrogen bonds (H-bonds). From the analysis of H-bonds in the β-sheet, the number of H-bonds in EF1 is larger than that in EF2 in the time scale of the conventional MD simulation, suggesting that the formation of H-bonds is related to the differences in the structural fluctuation between EF1 and EF2. From the analysis of other non-covalent interactions in the amino acid sequences of EF1 and EF2, EF1 has three pairs of residues with hydrophobic interaction, and EF2 has two pairs. These results indicate that several non-covalent interactions are important for structural stabilization. Consequently, the structure of EF1 is stabilized by H-bonds and pairs of hydrophobic amino acids in the terminals. Hence, we propose that non-covalent interactions around N-terminal and C-terminal of the peptides are crucial for maintaining the β-sheet structure of the peptides.

Cystic cerebellar dysplasia and biallelic LAMA1 mutations: a lamininopathy associated with tics, obsessive compulsive traits and myopia due to cell adhesion and migration defects

BACKGROUND

Laminins are heterotrimeric complexes, consisting of α, β and γ subunits that form a major component of basement membranes and extracellular matrix. Laminin complexes have different, but often overlapping, distributions and functions.

METHODS

Under our clinical protocol, NCT00068224, we have performed extensive clinical and neuropsychiatric phenotyping, neuroimaging and molecular analysis in patients with laminin α1 (LAMA1)-associated lamininopathy. We investigated the consequence of mutations in LAMA1 using patient-derived fibroblasts and neuronal cells derived from neuronal stem cells.

RESULTS

In this paper we describe individuals with biallelic mutations in LAMA1, all of whom had the cerebellar dysplasia, myopia and retinal dystrophy, in addition to obsessive compulsive traits, tics and anxiety. Patient-derived fibroblasts have impaired adhesion, reduced migration, abnormal morphology and increased apoptosis due to impaired activation of Cdc42, a member of the Rho family of GTPases that is involved in cytoskeletal dynamics. LAMA1 knockdown in human neuronal cells also showed abnormal morphology and filopodia formation, supporting the importance of LAMA1 in neuronal migration, and marking these cells potentially useful tools for disease modelling and therapeutic target discovery.

CONCLUSION

This paper broadens the phenotypes associated with LAMA1 mutations. We demonstrate that LAMA1 deficiency can lead to alteration in cytoskeletal dynamics, which may invariably lead to alteration in dendrite growth and axonal formation. Estimation of disease prevalence based on population studies in LAMA1 reveals a prevalence of 1-20 in 1 000 000.

TRIAL REGISTRATION NUMBER

NCT00068224.

Tangential migration of glutamatergic neurons and cortical patterning during development: Lessons from Cajal-Retzius cells

Tangential migration is a mode of cell movement, which in the developing cerebral cortex, is defined by displacement parallel to the ventricular surface and orthogonal to the radial glial fibers. This mode of long-range migration is a strategy by which distinct neuronal classes generated from spatially and molecularly distinct origins can integrate to form appropriate neural circuits within the cortical plate. While it was previously believed that only GABAergic cortical interneurons migrate tangentially from their origins in the subpallial ganglionic eminences to integrate in the cortical plate, it is now known that transient populations of glutamatergic neurons also adopt this mode of migration. These include Cajal-Retzius cells (CRs), subplate neurons (SPs), and cortical plate transient neurons (CPTs), which have crucial roles in orchestrating the radial and tangential development of the embryonic cerebral cortex in a noncell-autonomous manner. While CRs have been extensively studied, it is only in the last decade that the molecular mechanisms governing their tangential migration have begun to be elucidated. To date, the mechanisms of SPs and CPTs tangential migration remain unknown. We therefore review the known signaling pathways, which regulate parameters of CRs migration including their motility, contact-redistribution and adhesion to the pial surface, and discuss this in the context of how CR migration may regulate their signaling activity in a spatial and temporal manner. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 847-881, 2016.

New concepts in basement membrane biology

Basement membranes (BMs) are thin sheets of extracellular matrix that outline epithelia, muscle fibers, blood vessels and peripheral nerves. The current view of BM structure and functions is based mainly on transmission electron microscopy imaging, in vitro protein binding assays, and phenotype analysis of human patients, mutant mice and invertebrata. Recently, MS-based protein analysis, biomechanical testing and cell adhesion assays with in vivo derived BMs have led to new and unexpected insights. Proteomic analysis combined with ultrastructural studies showed that many BMs undergo compositional and structural changes with advancing age. Atomic force microscopy measurements in combination with phenotype analysis have revealed an altered mechanical stiffness that correlates with specific BM pathologies in mutant mice and human patients. Atomic force microscopy-based height measurements strongly suggest that BMs are more than two-fold thicker than previously estimated, providing greater freedom for modelling the large protein polymers within BMs. In addition, data gathered using BMs extracted from mutant mice showed that laminin has a crucial role in BM stability. Finally, recent evidence demonstrate that BMs are bi-functionally organized, leading to the proposition that BM-sidedness contributes to the alternating epithelial and stromal tissue arrangements that are found in all metazoan species. We propose that BMs are ancient structures with tissue-organizing functions and were essential in the evolution of metazoan species.

Molecular Basis of Laminin-Integrin Interactions

Laminins are composed of three polypeptide chains, designated as α, β, and γ. The C-terminal region of laminin heterotrimers, containing coiled-coil regions, short tails, and laminin globular (LG) domains, is necessary and sufficient for binding to integrins, which are the major laminin receptor class. Laminin recognition by integrins critically requires the α chain LG domains and a glutamic acid residue of the γ chain at the third position from the C-terminus. Furthermore, the C-terminal region of the β chain contains a short amino acid sequence that modulates laminin affinity for integrins. Thus, all three of the laminin chains act cooperatively to facilitate integrin binding. Mammals possess 5 α (α1-5), 3 β (β1-3), and 3 γ (γ1-3) chains, combinations of which give rise to 16 distinct laminin isoforms. Each isoform is expressed in a tissue-specific and developmental stage-specific manner, exerting its functions through binding of integrins. In this review, we detail the current knowledge surrounding the molecular basis and physiological relevance of specific interactions between laminins and integrins, and describe the mechanisms underlying laminin action through integrins.

Reversible vision loss and outer retinal abnormalities after intravitreal ocriplasmin injection

PURPOSE

Ocriplasmin is a truncated form of the human serine protease plasmin, which was recently approved for the nonsurgical treatment of symptomatic vitreomacular adhesions. According to its FDA label, approximately 8% of subjects experienced acute transient vision loss during the first week after injection with no alternative explanation for the change. This report focuses on a recent case of recovered vision loss over a 3-month period after the injection.

METHODS

A comprehensive ophthalmic examination was performed before the injection, during the day of the injection, and at 2 days, 2 weeks, 1 month, and 4 months after the injection. This examination included a full ophthalmic workup and imaging with spectral domain optical coherence tomography. A case of a 55-year-old woman who experienced acute severe vision loss 2 days after the treatment with ocriplasmin was reported.

RESULTS

Distinct alterations, as seen with spectral domain optical coherence tomography, were observed in the ellipsoid zone of photoreceptors. These changes together with patient's visual acuity gradually recovered over a 3-month period after the injection.

CONCLUSION

Further investigation may be warranted to fully elucidate the precise molecular mechanisms involved in patients with unexplained vision loss after ocriplasmin injection.

Glia-neuron interactions in the mammalian retina

The mammalian retina provides an excellent opportunity to study glia-neuron interactions and the interactions of glia with blood vessels. Three main types of glial cells are found in the mammalian retina that serve to maintain retinal homeostasis: astrocytes, Müller cells and resident microglia. Müller cells, astrocytes and microglia not only provide structural support but they are also involved in metabolism, the phagocytosis of neuronal debris, the release of certain transmitters and trophic factors and K(+) uptake. Astrocytes are mostly located in the nerve fibre layer and they accompany the blood vessels in the inner nuclear layer. Indeed, like Müller cells, astrocytic processes cover the blood vessels forming the retinal blood barrier and they fulfil a significant role in ion homeostasis. Among other activities, microglia can be stimulated to fulfil a macrophage function, as well as to interact with other glial cells and neurons by secreting growth factors. This review summarizes the main functional relationships between retinal glial cells and neurons, presenting a general picture of the retina recently modified based on experimental observations. The preferential involvement of the distinct glia cells in terms of the activity in the retina is discussed, for example, while Müller cells may serve as progenitors of retinal neurons, astrocytes and microglia are responsible for synaptic pruning. Since different types of glia participate together in certain activities in the retina, it is imperative to explore the order of redundancy and to explore the heterogeneity among these cells. Recent studies revealed the association of glia cell heterogeneity with specific functions. Finally, the neuroprotective effects of glia on photoreceptors and ganglion cells under normal and adverse conditions will also be explored.

Epidermal Basement Membrane in Health and Disease

Skin, as the organ protecting the individual from environmental aggressions, constantly meets external insults and is dependent on mechanical toughness for its preserved function. Accordingly, the epidermal basement membrane (BM) zone has adapted to enforce tissue integrity. It harbors anchoring structures created through unique organization of common BM components and expression of proteins exclusive to the epidermal BM zone. Evidence for the importance of its correct assembly and the nonredundancy of its components for skin integrity is apparent from the multiple skin blistering disorders caused by mutations in genes coding for proteins associated with the epidermal BM and from autoimmune disorders in which autoantibodies target these molecules. However, it has become clear that these proteins not only provide mechanical support but are also critically involved in tissue homeostasis, repair, and regeneration. In this chapter, we provide an overview of the unique organization and components of the epidermal BM. A special focus will be given to its function during regeneration, and in inherited and acquired diseases.

Optimized Culture System to Induce Neurite Outgrowth From Retinal Ganglion Cells in Three-Dimensional Retinal Aggregates Differentiated From Mouse and Human Embryonic Stem Cells

PURPOSE

To establish a practical research tool for studying the pathogenesis of retinal ganglion cell (RGC) diseases, we optimized culture procedures to induce neurite outgrowth from three-dimensional self-organizing optic vesicles (3D-retinas) differentiated in vitro from mouse and human embryonic stem cells (ESCs).

MATERIALS AND METHODS

The developing 3D-retinas isolated at various time points were placed on Matrigel-coated plates and cultured in media on the basis of the 3D-retinal culture or the retinal organotypic culture protocol. The number, length, and morphology of the neurites in each culture condition were compared.

RESULTS

First, we confirmed that Venus-positive cells were double-labeled with a RGC marker, Brn3a, in the 3D-retina differentiated from Fstl4::Venus mouse ESCs, indicating specific RGC-subtype differentiation. Second, Venus-positive neurites grown from these RGC subsets were positive for beta-III tubulin and SMI312 by immunohistochemistry. Enhanced neurite outgrowth was observed in the B27-supplemented Neurobasal-A medium on Matrigel-coated plates from the optic vesicles isolated after 14 days of differentiation from mouse ESCs. For the differentiated RGCs from human ESCs, we obtained neurite extension of >4 mm by modifying Matrigel coating and the culture medium from the mouse RGC culture.

CONCLUSION

We successfully optimized the culture conditions to enhance lengthy and high-frequency neurite outgrowth in mouse and human models. The procedure would be useful for not only developmental studies of RGCs, including maintenance and projection, but also clinical, pathological, and pharmacological studies of human RGC diseases.