Fibrillar Material Research Articles

Histopathological Analysis of Pseudoexfoliation Material in Ocular Surgeries: Clinical Implications

Background: Pseudoexfoliation syndrome (PEX) is a common age-related ocular condition characterized by the accumulation of a fibrillar, pseudoexfoliative material on the anterior segment of the eye. This study aims to investigate the histopathological characteristics of pseudoexfoliative material within different ocular structures, including the eyelid, conjunctiva, and anterior lens capsule. Methods: A total of 32 anterior lens capsules, 3 eyelid fragments, and 12 conjunctival specimens were obtained from patients clinically diagnosed with PEX during ocular surgeries at the Onioptic Hospital of Ophthalmology. The tissue specimens were subsequently processed using the classical histological technique of paraffin embedding. This process enabled the production of serial sections with a thickness of 4 microns, facilitating the microscopic examination of fine details. The sections were stained with the hematoxylin-eosin (HE) method for the observation of microscopic structures. Results: This study’s findings reveal that PEX material, characterized by its fibrillar and amorphous components, is consistently present across multiple ocular structures, including the anterior lens capsule, eyelid, and conjunctiva. When stained with H&E, the PEX material typically appears as amorphous, eosinophilic deposits. Under higher magnification, these deposits exhibit a fibrillar structure, often appearing as irregular, granular, or filamentous aggregates. Conclusions: The deposit of fibrillar material in the eyelid and conjunctiva, though less commonly emphasized compared to other structures, is a significant finding that sheds light on the systemic nature of the syndrome. The consistent identification of fibrillar eosinophilic deposits across these structures highlights the systemic distribution of PEX material, reinforcing the notion that PEX syndrome is not confined to the anterior segment of the eye.

Focal Adhesion Maturation Responsible for Behavioral Changes in Human Corneal Stromal Fibroblasts on Fibrillar Substrates.

The functioning of the human cornea heavily relies on the maintenance of its extracellular matrix (ECM) mechanical properties. Within this context, corneal stromal fibroblasts (CSFs) are essential, as they are responsible for remodeling the corneal ECM. In this study, we used a decellularized human amniotic membrane (dHAM) and a custom fibrillar collagen film (FCF) to explore the effects of fibrillar materials on human CSFs. Our findings indicate that substrates like FCF can enhance the early development of focal adhesions (FAs), leading to the activation and propagation of mechanotransduction signals. This is primarily achieved through FAK autophosphorylation and YAP1 nuclear translocation pathways. Remarkably, inhibiting FAK autophosphorylation negated the observed changes. Proteome analysis further confirmed the central role of FAs in mechanotransduction propagation in CSFs cultured on FCF. This analysis also highlighted complex signaling pathways, including chromatin epigenetic modifications, in response to fibrillar substrates. Overall, our research highlights the potential pathways through which CSFs undergo behavioral changes when exposed to fibrillar substrates, identifying FAs as essential mechanotransducers.

Secondary growth ovarian follicles of the pigmented sterlet sturgeon Acipenser ruthenus L. 1758 (Acipenseriformes, Chondrostei, Actinopterygii, Osteichthyes) – Microscopic study of oocytes, egg envelope and diversification of follicular cells

The individual ovarian follicle of sturgeons (Acipenseriformes, Acipenseridae) contains an oocyte surrounded by follicular cells (FCs), basal lamina, and thecal cells. The late stages of the secondary growth of follicles (mid- and advanced vitellogenic) are not fully explained in Acipenseriformes. To explore and discuss the ultrastructure of oocytes, FCs, an egg envelope, and explain how micropylar cells differentiate and the canals of a multiple micropyle are formed, the samples of ovaries of the mature sterlet sturgeon Acipenser ruthenus were examined. The oocytes are polarized, the nucleus is located in the animal hemisphere, contains lampbrush chromosomes and multiple nucleoli. In the ooplasm three regions are present: a perinuclear (contains the mitochondria), an endoplasm (contains the lipid droplets and yolk platelets), and a periplasm (contains the cortical granules, melanosomes, endocytotic and exocytotic vesicles). The melanosomes in animal hemisphere form two concentric rings separated by a lighter region between them. The FCs are differentiated into bright and dark cells that are both translationally and secretory active. Diversification of FCs involves repeated and cytoskeleton-dependent change of shape. In the advanced follicles the FCs are diversified into micropylar, the animal and vegetal regions cells, and the cells that delaminated from the epithelium in the animal region. The egg envelope is present in the perioocytic space and consists of three layers: (1) an inner layer or vitelline envelope, (2) a middle layer, and (3) an outer layer. The inner layer consists of four sublayers: (a) a filamentous sublayer composed of filaments released from the oocytes, (b) a trabecular 1 sublayer and (c) a trabecular 2 sublayer named due to the sequence of the deposition, and composed of filaments, fibres and trabecules, (d) a homogeneous sublayer located between the trabecular 1 and trabecular 2 sublayers composed of filaments that adhere to each other closely. The middle layer contains two sublayers: a porous 1 and a porous 2 (composed of granular material) which are released by the oocyte and FCs. The outer layer consists of fibrillar material released by the FCs. The egg envelope is pierced by radial canals formed around the microvilli of the oocyte and the microvilli-like processes of FCs. A micropylar field in the egg envelope that covers the animal pole of the oocyte contains 1 – 4 micropylar canals. Micropylar cells are involved in their formation. The shape of these cells is icicle-like and the cytoplasm is differentiated into two regions (a basal and apical bearing a projection) equipped with different sets of organelles.

Bioengineered self-assembled nanofibrils for high-affinity SARS-CoV-2 capture and neutralization

The recent coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spurred intense research efforts to develop new materials with antiviral activity. In this study, we genetically engineered amyloid-based nanofibrils for capturing and neutralizing SARS-CoV-2. Building upon the amyloid properties of a short Sup35 yeast prion sequence, we fused it to SARS-CoV-2 receptor-binding domain (RBD) capturing proteins, LCB1 and LCB3. By tuning the reaction conditions, we achieved the spontaneous self-assembly of the Sup35-LCB1 fusion protein into a highly homogeneous and well-dispersed amyloid-like fibrillar material. These nanofibrils exhibited high affinity for the SARS-CoV-2 RBD, effectively inhibiting its interaction with the angiotensin-converting enzyme 2 (ACE2) receptor, the primary entry point for the virus into host cells. We further demonstrate that this functional nanomaterial entraps and neutralizes SARS-CoV-2 virus-like particles (VLPs), with a potency comparable to that of therapeutic antibodies. As a proof of concept, we successfully fabricated patterned surfaces that selectively capture SARS-CoV-2 RBD protein on wet environments. Collectively, these findings suggest that these protein-only nanofibrils hold promise as disinfecting coatings endowed with selective SARS-CoV-2 neutralizing properties to combat viral spread or in the development of sensitive viral sampling and diagnostic tools.

Lack of evidence for GWAS signals of exfoliation glaucoma working via monogenic loss-of-function mutation in the nearest gene.

Exfoliation syndrome (XFS) is a systemic disease of elastin-rich tissues involving a deposition of fibrillar exfoliative material (XFM) in the anterior chamber of the eye, which can promote glaucoma. The purpose of this study was to create mice with CRISPR/Cas9-induced variations in candidate genes identified from human genome-wide association studies (GWAS) and screen them for indices of XFS. Variants predicted to be deleterious were sought in the Agpat1, Cacna1a, Loxl1, Pomp, Rbms3, Sema6a, and Tlcd5 genes of C57BL/6J mice using CRISPR/Cas9-based gene editing. Strains were phenotyped by slit-lamp, SD-OCT imaging, and fundus exams at 1-5 mos of age. Smaller cohorts of 12-mos-old mice were also studied. Deleterious variants were identified in six targets; Pomp was recalcitrant to targeting. Multiple alleles of some targets were isolated, yielding 12 strains. Across all genotypes and ages, 277 mice were assessed by 902 slit-lamp exams, 928 SD-OCT exams, and 358 fundus exams. Homozygosity for Agpat1 or Cacna1a mutations led to early lethality; homozygosity for Loxl1 mutations led to pelvic organ prolapse, preventing aging. Loxl1 homozygotes exhibited a conjunctival phenotype of potential relevance to XFS. Multiple other genotype-specific phenotypes were variously identified. XFM was not observed in any mice. This study did not detect XFM in any of the strains. This may have been due to species-specific differences, background dependence, or insufficient aging. Alternatively, it is possible that the current candidates, selected based on proximity to GWAS signals, are not effectors acting via monogenic loss-of-function mechanisms.

Synthetic Colonic Mucus Enables the Development of Modular Microbiome Organoids.

The human colon is home to trillions of microorganisms that modulate gastrointestinal physiology. Our understanding of how this gut ecosystem impacts human health, although evolving, has been slowed by the lack of accessible tools suitable to studying complex host-mucus-microbe interactions. Here, we report a synthetic gel-like material capable of recapitulating the varied structural, mechanical, and biochemical profiles of native human colonic mucus to develop compositionally simple microbiome screening platforms with utility in microbiology and drug discovery. The viscous fibrillar material is realized through templated assembly of a fluorine-rich amino acid at liquid-liquid interphases. The fluorine-assisted mucus surrogate (FAMS) can be decorated with mucins to serve as a habitat for microbial colonization and integrated with human colorectal cells to generate artificial mucosae, referred to as a microbiome organoid. Notably, FAMS are made with inexpensive and commercially available materials, and can be generated using simple protocols and standard laboratory hardware. As a result, this platform can be broadly incorporated into various laboratory settings to advance probiotic research and inform in vivo approaches. If implemented into high throughput screening approaches, FAMS may represent a valuable tool to study compound metabolism and gut permeability, with an exemplary demonstration of this utility presented here.

Cardiac Amyloidosis: Approach to Diagnosis

Amyloid is an amorphous, fibrillar material formed from various abnormally folded proteins that deposits locally or systemically. Over 95% of cases have been attributed to light chain deposition (AL) or transthyretin deposition (ATTR) amyloidosis. The basic investigations in the evaluation of cardiac amyloidosis include the electrocardiogram, echocardiography and cardiac biomarkers. Echocardiography in a patient with cardiac amyloidosis shows biatrial enlargement, biventricular hypertrophy, diastolic dysfunction, interatrial septal thickening, valvular thickening, a glistening appearance of the interventricular septum, and pericardial effusion. Magnetic resonance imaging can help distinguish amyloidosis from other causes of infiltrative/restrictive cardiomyopathy, from example, sarcoidosis, hemochromatosis, and Fabry disease based on characteristic enhancement patterns in these diseases. The latest Expert Consensus recommends that serum/urine immunofixation electrophoresis along with a serum free light chain assay must be done in all the cases of suspected cardiac amyloidosis. If the light chain assays are positive, we proceed with tissue diagnosis for confirmation of AL amyloidosis. If the screening assays are negative for monoclonal gammopathy, the next step is to obtain cardiac scintigraphy. If the nuclear scan is negative, but the index of suspicion remains high, an endomyocardial biopsy can be done. Once amyloid is demonstrated in histopathologic specimens, it must be typed to distinguish between AL and ATTR. The ideal method for this is tandem mass spectrometry, although this may not be widely available. It has a sensitivity of 88% and specificity of 96% higher than other techniques 23. In resource-poor settings, immunohistochemistry or immunoelectron microscopy can allow this distinction, although with lesser sensitivity.

The Complications of Cataract Surgery in Patients with Pseudoexfoliation

Abstract The senile cataract represents the blurring of the crystalline lens after the age of 65. It occurs due to metabolic changes in the crystalline lens which occur over the years. The only effective way to treat cataract is the surgical one. Pseudoexfoliation is an age related systemic disorder. PEX represents the accumulation fibrillar material in the extracellular matrix of the tissue. The most known ocular manifestation of the PEX are the collection at iris pupillary margin and anterior lens capsule. This accumulation is associated with many intraoperative and postoperative complications in patients scheduled for cataract surgery. The aim of the study was to investigate the prevalence of the surgical complications during phacoemulsfication in patients with PEX. The study included 91 patients scheduled for cataract surgery divided into two groups (PEX group 46, control group 45 patients). Poor intraoperative midryasis, zonular dehiscence, postoperative corneal edema, anterior chamber inflammation, elevated intraocular pressure and tear film instability had particularly higher rate of occurring in PEX group comparing to the control group (p<0.001). The highest mean value of intraocular pressure was observed in PEX group on the first postoperative day 25.6 ± 1.1 mmHg, while the best corrected visual acuity was measured in control group 0.71 ± 1.2 one month after phacoemulsification. Cataract surgery in patients with PEX carries great risk, but with adequate preoperative planning, the awareness of the potential complications, can provide safe and routine phacoemulification in these patients.

Using elemental staining and mapping techniques for simultaneous visualization of biological structures in the nucleus by multichannel electron microscopy.

Transmission electron microscopy (TEM) has been essential in defining the structural organization of the cell due to its ability to image cell structures at molecular resolution. However, the absence of colour has made it very difficult to compare the distributions and relationships of two or more types of biomolecules simultaneously if they lack clear morphological distinctions. Furthermore, single-channel information limits functional analysis, particularly in the nucleoplasm, where fibrillar material could be chromatin, ribonucleic acid or protein. Where specific stains exist to discriminate among these molecules, they cannot be combined because conventional TEM is a single-channel technology. A potential path around this barrier is through electron spectroscopic imaging (ESI). ESI can map the distributions of chemical elements within an ultrathin section. Here, we present methods to stain specific molecules with elements that ESI can visualize to enable multichannel electron microscopy.

A molecular basis for tetramer destabilization and aggregation of transthyretin Ala97Ser.

Transthyretin (TTR)-related amyloidosis (ATTR) is a syndrome of diseases characterized by the extracellular deposition of fibrillar materials containing TTR variants. Ala97Ser (A97S) is the major mutation reported in Taiwanese ATTR patients. Here, we combine atomic resolution structural information together with the biochemical data to demonstrate that substitution of polar Ser for a small hydrophobic side chain of Ala at residue 97 of TTR largely influences the local packing density of the FG-loop, thus leading to the conformational instability of native tetramer, the increased monomeric species, and thus the enhanced amyloidogenicity of apo-A97S. Based on calorimetric studies, the tetramer destabilization of A97S can be substantially altered by interacting with native stabilizers via similarly energetic patterns compared to that of wild-type (WT) TTR; however, stabilizer binding partially rearranges the networks of hydrogen bonding in TTR variants while FG-loops of tetrameric A97S still remain relatively flexible. Moreover, TTR in complexed with holo-retinol binding protein 4 is slightly influenced by the structural and dynamic changes of FG-loop caused by A97S substitution with an approximately five-fold difference in binding affinity. Collectively, our findings suggest that the amyloidogenic A97S mutation destabilizes TTR by increasing the flexibility of the FG-loop in the monomer, thus modulating the rate of amyloid fibrillization.

Prevalence of Exfoliative Syndrome in Patients Scheduled for Cataract Surgery: A Review of 110 Cases

Background: Capsular pseudoexfoliation syndrome (CEP) is an age-related systemic disorder of unknown etiology defined by the abnormal production and deposition of pseudoexfoliative fibrillar material both in the anterior segment and in several extraocular tissues [1, 2]. CEP is associated with the development of glaucoma, cataract and zonular instability. It is also responsible for specific surgical complications. Hence the interest to evaluate the prevalence of exfoliative syndrome in patients scheduled for cataract surgery and to shed light on its clinical and surgical particularities. Patients and methods: This is a retrospective, descriptive study involving 110 patients, admitted for cataract surgery, in the adult ophthalmology department, Hospital 20 August in Casablanca, from January 1, 2021 to January 2022. Patients underwent extraction by phacoemulsification or manual extraction with placement of an intraocular implant. Results: This study included 110 patients. The mean age was 66.67 years with a slight predominance of the female gender at 56% versus 44%. The percentage of PEC increases with age. Mean intraocular pressure was significantly higher in eyes with PES than in those without PES. The presence of PES increases the risk of intraoperative and postoperative complications, regardless of the surgical technique, regarding zonular rupture and vitreous exit. Conclusion: The exfoliative syndrome remains a frequent pathology in elderly subjects with cataracts, whose prevalence increases significantly over the age of 60. Its presence constitutes an important risk factor for primary open-angle glaucoma and increases the risk of intraoperative complications during cataract surgery, regardless of the technique used. The key points in surgery are the surgeon's experience and good dilatation.

Wide-field Stokes polarimetric microscopy for second harmonic generation imaging.

We employ wide-field second harmonic generation (SHG) microscopy together with nonlinear Stokes polarimetry for quick ultrastructural investigation of large sample areas (700 μm × 700 μm) in thin histology sections. The Stokes vector components for SHG are obtained from the polarimetric measurements with incident and outgoing linear and circular polarization states. The Stokes components are used to construct the images of polarimetric parameters and deduce the maps of ultrastructural parameters of achiral and chiral nonlinear susceptibility tensor components ratios and cylindrical axis orientation in fibrillar materials. The large area imaging was employed for lung tumor margin investigations. The imaging shows reduced SHG intensity, increased achiral susceptibility ratio values, and preferential orientation of collagen strands along the boarder of tumor margin. The wide-field Stokes polarimetric SHG microscopy opens a possibility of quick large area imaging of ultrastructural parameters of tissue collagen, which can be used for nonlinear histopathology investigations.

Light Chain Amyloidosis–Induced Autophagy Is Mediated by the Foxo3a/Beclin-1 Pathway in Cardiomyocytes

Cardiac amyloidosis is a disease in which the extracellular space of the heart is deposited with and infiltrated by amyloid fibrillar material, and light chain (LC) amyloidosis (AL) is the most serious form of the disease. AL is caused by the overproduction and aggregation of monoclonal immunoglobulin LCs produced by bone marrow plasma cells. Studies have shown that the initial response at a subcellular level to the toxicity of AL is lysosomal dysfunction with impaired autophagy, elevated reactive oxygen species, cellular dysfunction, and cellular death. Therefore, we speculate that the multiple myeloma complicated by cardiac amyloidosis is due to the deposition of λ LC fibrils in cardiomyocytes, leading to dysregulation of autophagy and cell death. We constructed BACN1 siRNA or FOXO3A siRNA and transfected them into H9c2 cells. We detected changes in oxidative stress- and autophagy-related markers. Our results show that monoclonal immunoglobulin λ LCs can form amyloid aggregates, which are cytotoxic to cardiomyocytes. λ LC fibrils deposit on the cell surface, causing oxidative stress and excessive autophagy by increasing Beclin-1 expression and the LC3 II/LC3 I ratio and decreasing p62 expression, ultimately inducing cell death. Beclin-1 knockdown reversed the increase in the LC3 II/LC3 I ratio and the decrease in p62 induced by LC fibrils, while suppressing overactivated autophagy and oxidative stress. Furthermore, LCs reduce the expression of p-Foxo3a (Ser253) (inactive) and promote Foxo3a translocation into the nucleus to perform transcriptional activity, which induces autophagy-related gene overexpression. Silencing Foxo3a can suppress excessive autophagy induced by LC fibrils and protect cells from death. In summary, the results showed that the cytotoxicity of amyloid fibrils formed by λ LCs on cardiomyocytes is triggered by excessive autophagy and is mediated through the Foxo3a/Beclin-1 pathway.

Clinical profile and surgical outcome of patients with pseudo-exfoliation syndrome undergoing cataract surgery - A retrospective study

Pseudoexfoliation (PXF) syndrome is an age-related process of unknown etiology characterized by the deposition of distinctive fibrillar material in the anterior segment of the eye. The material is commonly deposited in the anterior chamber, angle of the eye, iris, trabecular meshwork, anterior capsule of the lens, and also the cornea. It is associated with open and narrow angle glaucoma, the formation of cataracts and the corneal endothelial decompensation.PXF deposition in the lens zonules leads to disintegration of the lens zonules resulting in lens subluxation and dislocation. PXF deposition on the iris causes poor pupillary dilatation. Both zonular dehiscence and poor pupillary dilatation pose a great challenge to the cataract surgeon during surgery. Intra operatively, the chances of lens subluxation / dislocation, posterior capsular rupture, vitreous loss is high in the presence of pseudoexfoliation. In the immediate post-operative period, intra ocular pressure spikes, increased and prolonged iritis and corneal decompensation can affect the visual outcome of the surgery. This study will retrospectively analyze the clinical profile of the patients with pseudoexfoliation and to evaluate the occurrence of intra and immediate post-op complications of cataract surgery. In this way, the surgeon can plan his/her surgical technique to help avoid complications during cataract surgery and be prepared to manage the potential intraoperative and postoperative complications that can occur in pseudoexfoliation eyes.

Towards preventing exfoliation glaucoma by targeting and removing fibrillar aggregates associated with exfoliation syndrome

Exfoliation syndrome presents as an accumulation of insoluble fibrillar aggregates that commonly correlates with age and causes ocular complications, most notably open-angle glaucoma. Despite advances in understanding the pathogenesis and risk factors associated with exfoliation syndrome, there has been no significant progress in curative pharmacotherapy of this disease. It is thought that the ability to target the fibrillar aggregates associated with exfoliation may offer a new therapeutic approach, facilitating their direct removal from affected tissues. Phage display techniques yielded two peptides (LPSYNLHPHVPP, IPLLNPGSMQLS) that could differentiate between exfoliative and non-affected regions of the human lens capsule. These peptides were conjugated to magnetic particles using click chemistry to investigate their ability in targeting and removing exfoliation materials from the anterior human lens capsule. The behavior of the fibrillar materials upon binding to these magnetic particles was assessed using magnetic pins and rotating magnetic fields of various strengths. Ex vivo studies showed that the magnetic particle-peptide conjugates could generate enough mechanical force to remove large aggregates of exfoliation materials from the lens capsule when exposed to a low-frequency rotating magnetic field (5000 G, 20 Hz). Biocompatibility of targeting peptides with and without conjugated magnetic particles was confirmed using MTT cell toxicity assay, live/dead cell viability assay, and DNA fragmentation studies on primary cultured human trabecular meshwork cells. This is a novel, minimally invasive, therapeutic approach for the treatment of exfoliation glaucoma via the targeting and removal of exfoliation materials that could be applied to all tissues within the anterior segment of the eye.

Quantitative analysis of circulating levels of vimentin, clusterin and fibulin-5 in patients with pseudoexfoliation syndrome and glaucoma

Pseudoexfoliation (PEX) is a multifactorial age-related disease involving deposition of extracellular fibrillar material on anterior ocular tissues. If left untreated, the early stage of deposition termed as pseudoexfoliation syndrome (PEXS) may lead to the advanced stage of pseudoexfoliation glaucoma (PEXG) characterised by increased intraocular pressure, damage to the optic nerve and subsequent irreversible blindness. The etiology of PEX is complex and identification of novel factors associated with the disease is needed. This study aimed to identify the involvement of vimentin in pseudoexfoliation pathology and assess the levels of vimentin, clusterin and fibulin-5 in the circulating fluids of PEX patients compared to controls. Eighty-seven participants (35 controls, 35 PEXS and 17 PEXG) were enrolled for this case-control study. The expression of vimentin in lens capsules of patients and age-sex matched controls was assayed by qRT-PCR, western blotting and immunohistochemistry. Aqueous humor (AH) vimentin levels and plasma levels of vimentin, clusterin and fibulin-5 were assayed through ELISA. Increased vimentin was observed in the lens capsule of patients compared to controls at mRNA and protein levels. Compared to control (11.5 ± 1.4 ng/ml [±SEM]), the AH vimentin concentrations were significantly higher (ANOVA p = 0.01) in PEXS (16.4 ± 1.8 ng/ml) and PEXG (20.1 ± 2.5 ng/ml). Compared to controls (372.2 ± 15.1 ng/ml), plasma vimentin levels were significantly higher (ANOVA, p < 0.001) in PEXS (449.9 ± 15.7 ng/ml) and PEXG (535.5 ± 25.0 ng/ml). The plasma and aqueous humor levels of vimentin showed a positive correlation of 0.31. The plasma levels of clusterin were 298.9 ± 19.0 μg/ml, 367.8 ± 25.6 μg/ml and 272.9 ± 16.8 μg/ml in controls, PEXS and PEXG, respectively and were significantly higher in PEXS (p = 0.03) compared to control. Plasma fibulin-5 levels were 149 ± 32.2 pg/ml, 187.6 ± 32.3 pg/ml and 203.8 ± 27.3 pg/ml in controls, PEXS and PEXG, respectively and there was no significant difference in its levels between the groups (ANOVA p = 0.49). In conclusion, vimentin is upregulated in PEX affected eyes. Increased vimentin levels in plasma and AH differentiate PEXS and PEXG from controls.

Robust polymer foams from 2-hydroxyethyl cellulose: Fabrication, stability, and chemical functionalization

We describe the fabrication of polymer foams from aqueous solutions of 2-hydroxyethyl cellulose (HEC), using freezing-induced phase-separation and solvent removal methods. Freezing aqueous solutions of HEC produced 3D polymer networks by a mechanism involving polymer exclusion from ice crystals and concentration at grain boundaries. This phase-separation is viewed as a kinetically controlled process, with properties of the resultant foams reliant on the processing temperatures and other conditions employed. Specifically, HEC foams were obtained by removal of the ice phase either by lyophilization or solvent exchange techniques. The morphology and pore characteristics of the resultant foams were visualized by scanning electron microscopy (SEM), which showed fibrillar and flake-like polymer material embedded in an open-cell porous structure. Foam density and stiffness increased as a function of the initial HEC concentration employed, while the mechanical integrity of the resultant foams was improved by crosslinking with poly(acrylic acid) (PAA) or maleic anhydride (MA). Such crosslinking successfully enabled liquid water sorption into the foams without loss of structural integrity, thus providing opportunities for further incorporation of chemical moieties. Dynamic vapor sorption (DVS) was employed to assess water uptake into the HEC foams, which was generally greater for foams produced by lyophilization, and in all cases exceeded that achieved by conventional, commercially available cellulose foams.

Stress-controlled shear flow alignment of collagen type I hydrogel systems

Disease research and drug screening platforms require in vitro model systems with cellular cues resembling those of natural tissues. Fibrillar alignment, occurring naturally in extracellular matrices, is one of the crucial attributes in tissue development. Obtaining fiber alignment in 3D, in vitro remains an important challenge due to non-linear material characteristics. Here, we report a cell-compatible, shear stress-based method allowing to obtain 3D homogeneously aligned fibrillar collagen hydrogels. Controlling the shear-stress during gelation results in low strain rates, with negligible effects on the viability of embedded SH-SY5Y cells. Our approach offers reproducibility and tunability through a paradigm shift: The shear-stress initiation moment, being the critical optimization parameter in the process, is related to the modulus of the developing gel, whereas state of the art methods often rely on a predefined time to initiate the alignment procedure. After curing, the induced 3D alignment is maintained after the release of stress, with a linear relation between the total acquired strain and the fiber alignment. This method is generally applicable to 3D fibrillar materials and stress/pressure-controlled setups, making it a valuable addition to the fast-growing field of tissue engineering. Statement of significanceControlling fiber alignment in vitro 3D hydrogels is crucial for developing physiologically relevant model systems. However, it remains challenging due to the non-linear material characteristics of fibrillar hydrogels, limiting the scalability and repeatability.Our approach tackles these challenges by utilizing a stress-controlled rheometer allowing us to monitor structural changes in situ and determine the optimal moment for applying a shear-stress inducing alignment. By careful parameter control, we infer the relationship between time, induced strain, alignment and biocompatibility.This tunable and reproducible method is both scalable and generally applicable to any fibrillar hydrogel, therefore, we believe it is useful for research investigating the link between matrix anisotropy and cell behavior in 3D systems, organ-on-chip technologies and drug research.

The role of the pseudoexfoliative syndrome as a transitional entity to glaucoma

The balance between the secretion of aqueous humor by the ciliary body and its drainage through 2 independent pathways, the trabecular meshwork and the uveoscleral outflow pathway; and this will determine the intraocular pressure, which is considered the determining factor for glaucoma. Glaucoma is an entity of great clinical importance, being the second cause of blindness worldwide. There are different explanations for the pathophysiology of the disease, as well as immunological and vascular factors that lead to an increase in intraocular pressure, causing all these factors to trigger the development of glaucoma. Pseudoexfoliation syndrome can be defined as a systemic pathology that is generated by the deposition of extracellular fibrillar material in different tissues, and which, depending on the affected person, can cause different subsequent entities. Glaucoma progression and its sequelae may be more related to higher intraocular pressures than to other mechanisms. Various studies relate oxidative stress to glaucomatous progression. As the composition of the material causing pseudoexfoliation is further studied, its influence on the eye can be better understood.

A Study of Difficulties and Complications Encountered in Patients with Pseudoexfoliation Syndrome Undergoing Manual Small Incision Cataract Surgery (MSICS)

Pseudoexfoliation syndrome (PEX) is a systemic age-related disorder that is characterised by abnormal production of fibrillar extracellular matrix material and it's deposition in tissues of the eye and other systemic tissues. They are classically seen as deposits on the anterior lens capsule as dandruff-like white powdery residue. The material deposits in all anterior segment structures including iris, pupillary margins, ciliary body, corneal endothelium, zonules and anterior capsule of lens. In the eye, these deposits cause deviancy from normal structure and function, resulting in poor pupil dilatation, zonular weakness, changes in corneal endothelium, secondary glaucoma and nuclear cataract formation. These changes caused in the eye due to Pseudoexfoliation Syndrome can be a challenge for a surgeon doing routine cataract extraction and intraocular lens implantation in such patients, as these manifestations of PEX can prove to be obstacles during the surgery and cause post operative complications. The surgeon also has to keep in mind associated secondary glaucoma during management of such a case. Thus visual outcome could be compromised.