Collagen Cross-linking Research Articles

Structural Characterization and Hydration Dynamics of Cross-Linked Collagen and Hyaluronic Acid Scaffolds by Nuclear Magnetic Resonance.

Understanding a biomaterial's structural and hydration dynamics is essential for its development and applications in tissue regeneration. In this study, collagen-hyaluronic acid (HA) scaffolds were analyzed utilizing Nuclear Magnetic Resonance (NMR) techniques to elucidate how different cross-linking conditions influence the internal architecture and interaction with solvents in these scaffolds. The scaffolds were fabricated using 3D printing and cross-linked with 1,4-butanediol diglycidyl ether (BDDGE), a process known to impact their mechanical properties. We gained insights into the microstructural organization and hydration behavior within the scaffolds when exposed to water and ethanol by employing proton relaxation and diffusion measurements. To better understand the system's performance, static and dynamic experiments were performed. Our results indicate that the degree of cross-linking affects the scaffold's ability to retain water, with higher cross-linking leading to more rigid structures. This also altered the hydration dynamics mainly due to a difference in the diffusion of water within the scaffold. In addition, the anisotropy of the collagen fibers also decreases with the cross-linking. Ethanol, a less polar solvent, provided a contrasting environment that further revealed the structural dependencies on the cross-linking density. The study's findings contribute to a deeper understanding of how the structure and morphology affect the functionality of collagen-HA scaffolds, offering critical information for optimizing their design for specific biomedical applications, such as soft tissue regeneration. Our experiments show how NMR is a valuable tool to provide information on dynamic processes not only in collagen-HA scaffolds but also in many biocompatible polymeric samples. The outcomes of this research provide a foundation for future work aimed at tailoring scaffold properties to enhance their performance in clinical settings, ultimately advancing the field of tissue engineering.

Socioeconomic and Demographic Disparities in Keratoconus Treatment

ObjectiveTo investigate healthcare disparities associated with keratoconus (KCN) patients receiving treatment (collagen cross-linking (CXL) and keratoplasty), as well as comorbidities associated with KCN. DesignRetrospective clinical cohort study. Subjects3224 patients from the UI-Health database from 2020 to 2024, including 1612 patients with an ICD-10 diagnosis of KCN and 1612 ophthalmology patients as a control group. MethodsMultivariable and univariable logistic regression were performed to evaluate association between sociodemographic traits and rates of CXL and keratoplasty. Sociodemographic traits included age, sex, race/ethnicity, insurance status, and neighborhood social vulnerability. Best corrected visual acuity (BCVA) and manifest cylinder were used as indicators of disease impact. Comorbid disease rates were compared to a 1:1 distance-matched control group. Main Outcome MeasuresOdds ratio of undergoing keratoplasty and CXL, and prevalence of comorbid conditions. ResultsFemales received less keratoplasty than males (OR=0.55, P<0.001). Black individuals received less CXL than White individuals (OR=0.68, P<0.05), as did those with Medicaid (OR=0.27, P<0.0001) or no insurance (OR=0.41, P<0.001) compared to those with commercial insurance. Socially vulnerable neighborhoods received less CXL (OR=0.56, P<0.01) and keratoplasty (OR=0.66, P<0.05). Black females were the most vulnerable, undergoing fewer procedures than White females (OR=0.58, P<0.01) and Black males (OR=0.65, P<0.05). Black and Hispanic/Latin-X individuals presented with more severe disease (P<0.01, P<0.0001). Down Syndrome was more common (P<0.01), and diabetes was less common (P<0.0001) in KCN patients. ConclusionsSignificant sociodemographic disparities exist in the treatment of KCN. While further research is necessary, addressing these disparities is crucial for ensuring equitable access to care.

Fibrillin-1 G234D mutation in the hybrid1 domain causes tight skin associated with dysregulated elastogenesis and increased collagen cross-linking in mice

Fibrillin-1, an extracellular matrix (ECM) protein encoded by the FBN1 gene, serves as a microfibril scaffold crucial for elastic fiber formation and homeostasis in pliable tissue such as the skin. Aside from causing Marfan syndrome, some mutations in FBN1 result in scleroderma, marked by hardened and thicker skin which limits joint mobility. Here, we describe a tight skin phenotype in the Fbn1G234D/G234D mice carrying a corresponding variant of FBN1 in the hybrid1 domain that was identified in a patient with familial aortic dissection. Unlike scleroderma, skin thickness and collagen fiber abundance do not change in the Fbn1G234D/G234D mutant skin. Instead, increased collagen cross-links were observed. In addition, short elastic fibers were sparsely located underneath the panniculus muscle layer, and an abundance of thin, aberrant elastic fibers was increased within the subcutaneous fascia, which may have tightened skin attachment to the underlying skeletal muscle. Structurally, Fbn1G234D/G234D microfibrils have a disrupted shoulder region that shares similarities with hybrid1 deletion mutant microfibrils. We then demonstrate the consequence of fibrillin-1 G234D mutation on dermal fibroblast functions. Mutant primary fibroblasts produce fewer elastic fibers, exhibit slower migration and increased cell stiffness. Moreover, secretome from mutant fibroblasts are marked by enhanced secretion of ECM, ECM-modifying enzymes, proteoglycans and cytokines, which are pro-tissue repair/fibrogenic. The transcriptome of mutant fibroblasts displays an increased expression of myogenic developmental and immune-related genes. Our study proposes that imbalanced ECM homeostasis due to a fibrillin-1 G234Dmutation impacts fibroblast properties with potential ramifications on skin function.

Age-Related ECM Stiffness Mediates TRAIL Activation in Muscle Stem Cell Differentiation.

The stiffening of the extracellular matrix (ECM) with age hinders muscle regeneration by causing intrinsic muscle stem cell (MuSC) dysfunction through a poorly understood mechanism. Here, the study aims to study those age-related molecular changes in the differentiation of MuSCs due to age and/or stiffness. Hence, young and aged MuSCs are seeded onto substrates engineered to mimic a soft and stiff ECM microenvironment to study those molecular changes using single-cell RNA sequencing (scRNA). The trajectory of scRNA data of the MuSCs under four different conditions undergoing differentiation is analyzed as well as the active molecular pathways and transcription factors driving those differentiation fates. Data revealed the presence of a branching point within the trajectory leading to the emergence of an age-related fibroblastic population characterized by activation of the TNF-related apoptosis-inducing ligand (TRAIL) pathway, which is significantly activated in aged cells cultured on stiff substrates. Next, using the collagen cross-linking inhibitor β-aminopropionitrile (BAPN) in vivo, the study elucidates stiffness changes on TRAIL downstream apoptotic targets (caspase 8 and caspase 3) using immunostaining. TRAIL activity is significantly inhibited by BAPN in aged animals, indicating a complex mechanism of age-related declines in muscle function through inflammatory and apoptotic mediators.

Cost-Effectiveness of Corneal Collagen Crosslinking for Progressive Keratoconus: A Brazilian Unified Health System Perspective

Keratoconus is a burden to health systems and patients worldwide. Corneal collagen crosslinking (CXL) treatment has been shown abroad to be cost-effective for treating progressive keratoconus. However, no cost-effectiveness studies have been performed in Brazil. The aim of this study was to assess the cost-effectiveness of corneal collagen crosslinking (CXL) compared with the conventional treatment for progressive keratoconus from the Brazilian Unified Health System (SUS) payer’s perspective. A lifetime microsimulation model was utilized to compare the lifetime costs and quality-adjusted life years for patients undergoing corneal collagen CXL or conventional treatment. Two groups of 5000 18-year-old patients were simulated, with one group receiving corneal CXL at the outset and the control group remaining untreated. The TreeAge Pro Healthcare 2024 software was used for modeling and analysis. Corneal collagen CXL demonstrated superior cost-effectiveness compared to the conventional treatment, with an incremental cost-effectiveness ratio of 58.26 USD/quality-adjusted life years (QALY) gained (95% CI: 58.17–58.36) and a positive incremental net monetary benefit of USD 11,613.82 (95% CI: 11,605.66–11,621.99). CXL significantly reduced the number of required corneal transplants, with a mean of 968.8 (95% CI: 959–978.58) fewer transplants per 10,000 eyes treated. The variable with the most significant impact on the incremental net monetary benefit was the duration of the CXL effect. This study concluded that corneal CXL is a highly cost-effective intervention for progressive keratoconus within the Brazilian SUS. These findings advocate for broader accessibility to this vision-saving treatment within the SUS.

Effect of Dentin Bio-Modifiers Grape Seed Extract, Hesperidin on Shear Bond Strength and Microleakage: AScanning Electron Microscopic Assessment.

Investigation of different collagen cross-linking (CCL) agents, grape seed extract (GSE), Hesperidin (Hes), and rose bengal photosensitizer (RBP) on shear bond strength (SBS) and marginal leakage (ML) of composite bonded to carious affected dentin (CAD). Sixty-eight human molars in which carious lesions up to the middle third of the dentin were included. CAD was made flat followed by acid etching. Teeth were allocated randomly into four groups based on the application of CCL agents. Group 1: no CCL agent, Groups 2-4 samples treated with CCL agents. Bonding of adhesive and composite was performed followed by artificial aging. ML assessment was performed using a dye penetration test. SBS was evaluated using a universal testing machine followed by failure mode analysis. Analysis of the resin CAD interface with SEM was performed to identify the resin tag. For group comparisons, one-way ANOVA and post hoc Tukey test were used. The length and number of resin tags in GSE and Hes groups were greater than in the control and RBP. Furthermore, samples treated with GSE presented the highest scores of SBS and lowest ML. The control group presented the lowest bond integrity and highest ML. GSE and Hes positively influenced both SBS and ML.

Granular Nanofiber-Hydrogel Composite-Programmed Regenerative Inflammation and Adipose Tissue Formation.

The interplay between biomaterials and host immune responses critically determines outcomes in tissue restoration. Recent studies suggest that physicochemical properties of materials can dictate pro-regenerative versus pro-fibrotic responses and have begun to define the key immune cell types and signals governing these divergent effects. This emerging understanding enables the engineering of regenerative biomaterials capable of functional restoration in situ. An injectable nanofiber-hydrogel composite (NHC) microparticles are designed and constructed from cross-linked electrospun collagen nanofiber fragments surface-bonded to the hyaluronic acid hydrogel network via covalent conjugation during the cross-linking process. The collagen nanofiber fragments, acting as the structural reinforcement component, increased the overall storage modulus of the NHC to a level comparable to native soft tissues while maintaining a sufficiently high degree of porosity of the hydrogel phase to allow host cell infiltration following subcutaneous injection of the NHC microparticles. More importantly, the NHC promoted macrophage/monocyte infiltration, migration, and spreading, sustained cell recruitment over time, and enhanced the proangiogenic effect and recruitment of PDGFRα+ perivascular progenitor cells, leading to extensive adipose tissue remodeling. This study demonstrates the regenerative potential of the injectable NHC microgels as an off-the-shelf solution for devastating soft tissue losses.

Bmpr1aa modulates the severity of the skeletal phenotype in an fkbp10-deficient Bruck syndrome zebrafish model.

Rare monogenic disorders often exhibit significant phenotypic variability among individuals sharing identical genetic mutations. Bruck syndrome (BS), a prime example, is characterized by bone fragility and congenital contractures, although with a pronounced variability among family members. BS arises from recessive biallelic mutations in FKBP10 or PLOD2. FKBP65, the protein encoded by FKBP10, collaborates with the LH2 enzyme (PLOD2) in type I collagen telopeptide lysine hydroxylation, crucial for collagen cross-linking. To identify potential modifier genes and to investigate the mechanistic role of FKBP10 in BS pathogenesis, we established an fkbp10a knockout zebrafish model. Mass-spectrometry analysis in fkbp10a-/- mutants revealed a generally decreased type I collagen lysyl hydroxylation, paralleled by a wide skeletal variability similar to human patients. Ultrastructural examination of the skeleton in severely affected mutants showed enlarged type I collagen fibrils and disturbed elastin layers. Whole-exome sequencing of 7 mildly and 7 severely affected mutant zebrafish siblings, followed by SNP-based linkage analysis, indicated a linked region on chromosome 13, which segregates with phenotypic severity. Transcriptome analysis identified six differentially expressed genes (DEGs) between mildly and severely affected mutants. The convergence of genes within the linked region and DEGs highlighted bmpr1aa as a potential modifier gene, as its reduced expression correlates with increased skeletal severity. In summary, our study provides deeper insights into the role of FKBP10 in BS pathogenesis. Additionally, we identified a pivotal gene that influences phenotypic severity in a zebrafish model of BS. These findings hold promise for novel treatments in the field of bone diseases.

The Human Cornea: Unravelling Its Structural, Chemical and Biochemical Complexities.

The cornea, the transparent part of the anterior eye, is vital for light refraction and vision. This review examines the intricate chemical and biochemical interactions essential for maintaining corneal transparency and highlights significant advancements in corneal biology. The cornea comprises five layers: the epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium, each contributing uniquely to its structure and function. The epithelium, maintained by limbal stem cells, serves as a barrier and interacts with the tear film to maintain ocular surface health. The stroma, abundant in organized collagen fibrils and regulated by proteoglycans, is crucial for corneal clarity and biomechanical integrity, while the endothelium regulates corneal hydration and nutrition. Recent imaging advances have improved visualization of these molecular structures, enhancing our understanding of collagen organization and cross-linking. Proteoglycans such as decorin and lumican regulate collagen spacing and hydration, directly influencing corneal clarity. Biochemical processes within the cornea involve signaling molecules, growth factors, and cytokines, which are essential for wound healing, inflammation, and injury response. Despite progress, questions remain regarding corneal wound healing mechanisms, the impact of oxidative stress, and the roles of microRNAs. This review synthesizes recent discoveries to advance our understanding of corneal physiology and biochemical functions.

Long-duration type 1 diabetes is associated with deficient cortical bone mechanical behavior and altered matrix composition in human femoral bone.

Type 1 diabetes (T1D) is associated with an increased risk of hip fracture beyond what can be explained by reduced bone mineral density, possibly due to changes in bone material from accumulation of advanced glycation end products (AGEs) and altered matrix composition, though data from human cortical bone in T1D are limited. The objective of this study was to evaluate cortical bone material behavior in T1D by examining specimens from cadaveric femora from older adults with long-duration T1D (≥50years; n= 20) and age- and sex-matched non-diabetic controls (n= 14). Cortical bone was assessed by mechanical testing (4-point bending, cyclic reference point indentation, impact microindentation), AGE quantification (total fluorescent AGEs, pentosidine, carboxymethyl-lysine (CML)), and matrix composition via Raman spectroscopy. Cortical bone from older adults with T1D had diminished post-yield toughness to fracture (-30%, P=.036), elevated levels of AGEs (pentosidine, +17%, P=.039), lower mineral crystallinity (-1.4%, P=.010), greater proline hydroxylation (+1.9%, P=.009), and reduced glycosaminoglycan (GAG) content (-1.3%, P<.03) compared to non-diabetics. In multiple regression models to predict cortical bone toughness, cortical tissue mineral density (Ct.TMD), CML, and Raman spectroscopic measures of enzymatic collagen crosslinks and GAG content remained highly significant predictors of toughness, while diabetic status was no longer significant (adjusted R2> 0.60, P<.001). Thus, impairment of cortical bone to absorb energy following long-duration T1D is well explained by AGE accumulation and modifications to the bone matrix. These results provide novel insight into the pathogenesis of skeletal fragility in individuals with T1D.

Collagen crosslinking-induced corneal morphological changes: a three-dimensional light sheet Microscopy-based evaluation

Stiffness-related eye diseases such as keratoconus require comprehensive visualization of the complex morphological matrix changes. The aim of this study was to use three-dimensional (3D) light sheet fluorescence microscopy (LSFM) to analyze unlabeled corneal tissue samples, qualitatively visualizing changes in corneal stiffness. Isolated porcine corneal tissue samples were treated with either NaCl or 0.1% glutaraldehyde (GTA) prior to clearing with benzyl alcohol/benzyl benzoate (BABB) and subsequently scanned with LSFM. After analysis of the LSFM data sets, the samples were embedded in paraffin to validate the results by conventional planar microscopy. In the unlabeled corneal tissue samples the 2D/3D morphology of the entire tissue volume was identified by specific autofluorescence signals. An enhancement of collagen crosslinking was induced by applying GTA to the corneal tissue. Subsequent LSFM scans showed specific morphological changes due to altered autofluorescence signals of the corneal stroma, which were confirmed by conventional histology. Therefore, LSFM analysis of corneal tissue samples allowed label-free 3D autofluorescence assessment of the corneal morphology in its anatomical context. It provides the technical basis for the examination of the pathologically altered cornea and facilitates ophthalmologic examinations of corneal diseases based on the altered tissue stiffness.

Plasma collagen neoepitopes are associated with multiorgan disease in the ACCESS and GRADS sarcoidosis cohorts

IntroductionThe pathogenesis of sarcoidosis involves tissue remodelling mediated by the accumulation of abnormal extracellular matrix, which is partly the result of an imbalance in collagen synthesis, cross-linking and degradation. During...

Epi-off riboflavin with vitamin E TPGS (Ribocross®) cross-linking: one-year outcome.

To assess the short and mid-term outcomes of epithelium-off (epi-off) corneal collagen cross-linking using Riboflavin with Vitamin E TPGS (Epi-off Ribocross® CXL) for progressive keratoconus (KC). Retrospective, single-center non-comparative interventional study. Patients with progressive keratoconus who underwent CXL using (Epi-off Ribocross® CXL) from May 2021 to May 2022 who completed at least 12months of follow-up in Humanitas Clinical and Research Center, Rozzano, Milan, Italy. Corrected distance visual acuity with spectable (CDVA), tomographic parameters (Belin ABCD) and topographic parameters were evaluated at baseline and at last follow up. Twenty eyes of twenty patients fulfilled inclusion criteria. CDVA remained stable at last follow up (0.88 ± 0.19 from 0.83 ± 0.21, p = 0.45) with a significant reduction in cylinder (1.97 ± 1.69 from 2.78 ± 2.19, p = 0.03). Kmax significantly improved from 53.18D ± 6.32 to 50.96 ± 5.3D (p = 0.005). At the last follow up, no case of progression was noted. Epi-off Ribocross® CXL proved to be a safe treatment for progressive KC, with a stabilization of all cases at the one year follow up. Further studies are needed to confirm long-term stability.

Accelerated versus conventional corneal collagen cross-linking for keratoconus: A meta-analysis of randomized controlled trials.

To systematically compare the effectiveness of conventional corneal collagen cross-linking (CCXL) protocols and accelerated corneal collagen cross-linking (ACXL) protocols in cases with progressive keratoconus. The Cochrane library, EMBASE, MEDLINE, PubMed, and Web of Science databases were searched for randomized controlled trials (RCTs). Outcomes were clinical results and changes in corneal properties. Standardized mean differences (SMD) and 95% confidence interval (CI) were used to estimate the clinical consequences. All outcomes were distributed by different follow-up durations (6 months, 12 months, and > 12 months). We also compared maximum keratometry (Kmax) and best spectacle-corrected visual acuity (BCVA) in subgroups, which were categorized by the discrepant impregnation time period of riboflavin. We included 14 RCTs that met the eligibility criteria in this meta-analysis. At the last follow-up, CCXL was superior in postoperative change in demarcation line (SMD: -1.573; 95% CI: -2.897 to -0.248) and in Kmax (SMD:0.302; 95% CI: 0.071 to 0.533), whereas ACXL provided a significantly lower reduction in central corneal thickness (SMD: 0.498; 95% CI: 0.125 to 0.871). No differences in the changes in uncorrected visual acuity, BCVA, manifest refraction spherical equivalent, corneal biomechanical properties, and the endothelial cell density were found among both groups. CCXL was superior to ACXL in greater corneal flattening and deeper demarcation line, while ACXL seemed to cause less reduction in CCT and allow for earlier UDVA stability. To clearly define the comparative safety and clinical consequences of the different regimens of CXL, more RCTs are required.

Corneal Collagen Cross-linking (CXL) Only vs CXL Combined with INTACS: 12-month Follow-up Data

Corneal Collagen Cross-linking (CXL) Only vs CXL Combined with INTACS: 12-month Follow-up Data

Abstract 4112931: The Nature of Collagen Cross-links Differs in Reversibly and Irreversibly Infarcted Myocardium

Background: Persistent scarring after myocardial infarction (MI) is a major driver of heart failure in mammals. However, unlike mammals, zebrafish exhibit a remarkable ability to resorb scar, which consists predominantly of collagen in both species. Aims: We aimed here to develop a toolbox of techniques to characterize the nature of collagen in infarcted mammalian and zebrafish hearts. Specifically, we aimed to characterize the early and late cross-links that form in collagen and determine whether differences in these cross-links exist in zebrafish and mammals. Methods: To characterize the initial oxidation and cross-linking of collagen we developed a novel fluorescent probe (TMR-O) that binds to lysine aldehydes on collagen and inform on the degree of collagen cross-linking. Additionally, we used high performance liquid chromatography (HPLC) to quantify degradation-resistant mature collagen cross-links, such as pyridinoline (Pyd), and its precursor, hydroxylysine. Results: TMR-O imaging revealed similar overall CCL levels in both zebrafish and mouse infarcts. However, the irreversible cross-link pyridinoline (Pyd) was abundant in mouse infarcts but completely absent in zebrafish (p&lt;0.0001). High Pyd levels in mice were accompanied by a dynamic increase in lysine hydoxylation (&gt;200%), which was not observed in zebrafish (&lt;10%). Conclusions: While collagen in mammalian and zebrafish infarcts may appear histologically similar, marked biochemical differences exist. Mature degradation-resistant collagen cross-links, such as Pyd form, in murine but not zebrafish infarcts and likely explains why zebrafish can resorb myocardial scar. Targeting Pyd formation in mammals could pave the way for novel therapeutic strategies to promote scar resolution and improve cardiac function after MI.

Sequential irradiation does not improve fatigue crack propagation resistance of human cortical bone at 15 kGy

Sequential irradiation has been advocated for mitigating the reduction in fatigue properties of tendon compared to a single dose. However, to our knowledge, its capability of mitigating fatigue losses in bone is unknown. Recently, we reported that sequential irradiation did not mitigate losses in high-cycle S-N fatigue life of cortical bone at 15 kGy; however, it is unclear if sequential irradiation provides a benefit to fatigue crack propagation resistance. Our previous study also showed that radiation-induced collagen chain fragmentation and crosslinking increased from 0 to 15 kGy, suggesting that both likely contribute to the reduction in high-cycle S-N fatigue life within this dose range. Our objectives were: 1) to evaluate the fatigue crack propagation resistance of cortical bone and the effect of radiation on fracture plane damage zone thickness (DZT) at the crack tip in the dose range of 0–15 kGy, and 2) to evaluate whether sequential irradiation at 15 kGy mitigates the loss of fatigue crack propagation resistance of cortical bone compared to a single irradiation dose. Compact tension specimens from four male donor femoral pairs (ages 21–61 years old) were divided into 5 treatment groups (0 kGy, 5 kGy, 10 kGy, 15 kGy, and a 15 kGy sequential irradiation dose of 5 kGy sequentially irradiated with 10 kGy) and subjected to fatigue crack propagation testing (n = 3–4 specimens per group) where fatigue crack growth rate da/dN and cyclic stress intensity factor ΔK were determined. Following testing, specimens were bulk stained in basic fuchsin, embedded in poly(methylmethacrylate), sectioned, and mounted on acrylic slides to evaluate fracture plane DZT at known crack lengths. Sections were then imaged with a fluorescence microscope, and fracture plane DZT was measured using ImageJ (n = 3–4 specimens per group) and analyzed as a function of ΔK. We observed a decrease in fatigue crack propagation resistance at 15 kGy compared to doses of 10 kGy or lower (p ≤ 0.013). Fracture plane DZT decreased overall with increasing radiation dose from 0 to 15 kGy. Sequential irradiation offered no improvement in fatigue crack propagation resistance (p = 0.98). Radiation-induced collagen chain fragmentation and crosslinking in this dose range likely contribute to a decrease in energy dissipation capability with increasing radiation dose. Other alternative radiation sterilization methods besides sequential irradiation may be warranted to mitigate radiation-induced tissue damage and extend the functional lifetime of structural cortical bone allografts.

Incidence and Outcomes of Infectious Keratitis After Corneal Collagen Cross-Linking Over 10 years From a Tertiary Care Center in South India.

The purpose of this study was to report the incidence and outcomes of infectious keratitis after corneal collagen cross-linking (CXL) over 10 years in South India. Patients who underwent CXL for progressive keratoconus between January 2011 and December 2020 and those with infectious keratitis were identified from an electronic database system. The clinical and microbiological profiles of those affected were extracted from the case files and included in the analysis, whereas viral keratitis was excluded. Eleven eyes with post-CXL infectious keratitis were identified, with 3842 CXL procedures (0.21%) occurring in-house, while 3 were referred from outside. The mean age of the patients was 21.8 ± 7.8 years, and 7 (64%) were male. Six eyes (54%) had conventional isotonic CXL, whereas 5 had hypotonic CXL when pachymetry was <400 μm. Six eyes (54%) presented with hypopyon at a median of 3 days after CXL. Culture of the corneal scrapings grew methicillin-sensitive Staphylococcus aureus in 4 patients, methicillin-sensitive Staphylococcus epidermidis in 2, Aspergillus fumigatus in 1, Aspergillus flavus in 1, Haemophilus parainfluenzae in 1, and no organisms in 2 patients. Almost all the isolates were resistant to ciprofloxacin and other fluoroquinolones. The majority of eyes responded well to intensive topical antibiotics guided by antibiograms and regained 6/18 vision (median). Therapeutic keratoplasty was needed in 2 eyes while cyanoacrylate glue was needed in another 2 eyes. Post-CXL infections are rare, most frequently caused by antibiotic-resistant commensals, and resemble the clinical spectrum and outcomes of non-CXL-related infectious keratitis in most cases.

Sociodemographic Predictors of Keratoconus (Severity, Treatment, and Progression) in a Tertiary Center in New York City.

To identify sociodemographic factors as predictors of keratoconus severity, progression, disease outcomes, and appropriate management in a tertiary care ophthalmology institute in the New York City metropolitan area. This is a retrospective chart review. Patients with keratoconus presenting at a tertiary eye institute in an urban setting seen between 2015 and 2022 were included. Sociodemographic data including age, sex, race, ethnicity, income derived from zip code, insurance coverage, and preferred language were recorded. These sociodemographic factors were analyzed as possible predictors of keratoconus severity at presentation (Amsler-Krumeich grades III and IV): patients presenting with acute hydrops, patients receiving corneal cross-linking or corneal transplant, patients showing 1 or more diopters of increase of Kmax during their follow-up, and patients having longer time between the provider's recommendation of corneal cross-linking and the time of the procedure. The retrospective review included 634 patients with a clinical diagnosis of keratoconus. Factors associated with severe keratoconus at presentation in the multivariate analysis were non-White (P < 0.001), lowest income (Q1) (P = 0.018), Q2 income (P = 0.012), and having Medicaid/Medicare coverage (P = 0.021). Medicaid/Medicare coverage was the only factor associated with acute hydrops (P < 0.001), and younger age was the only factor associated with disease progression (P < 0.001). Younger patients and patients with commercial insurance coverage were more likely to receive corneal collagen cross-linking (P < 0.001 and P < 0.001, respectively), whereas patients with Medicaid/Medicare coverage, lowest income, and non-White race were more likely to receive corneal transplantation (P = 0.012, P = 0.062, and P = 0.028, respectively). Medicaid/Medicare was the only factor associated with delay in receiving corneal collagen cross-linking (P = 0.013). Our study demonstrates that there are sociodemographic predictors of keratoconus disease severity, progression, and the type and the time of treatment the patients received. This confirms eye health disparities among patients with keratoconus.

Family-based whole-exome sequencing implicates a variant in lysyl oxidase like 4 in atypical femur fractures.

Atypical femur fractures (AFFs) are rare adverse events associated with bisphosphonate use, having unclear pathophysiology. AFFs also cluster in families and have occurred in patients with monogenetic bone diseases sometimes without bisphosphonate use, suggesting an underlying genetic susceptibility. Our aim was to identify a genetic cause for AFF in a Caucasian family with seven members affected by osteoporosis, including three siblings with bisphosphonate-associated AFFs. Using whole-exome sequencing, we identified a rare pathogenic variant c.G1063A (p.Gly355Ser) in lysyl oxidase like 4 (LOXL4) among 64 heterozygous rare, protein-altering variants shared by the three siblings with AFFs. The same variant was also found in a fourth sibling with a low-trauma femur fracture above the knee, not fulfilling all the ASBMR criteria of AFF and in one of 73 unrelated European AFF patients. LOXL4 is involved in collagen cross-linking and may be relevant for microcrack formation and bone repair mechanisms. Preliminary functional analysis showed that skin fibroblast-derived osteoblasts from the unrelated patient with the LOXL4 variant expressed less collagen type I and elastin, while osteogenic differentiation and mineralization were enhanced compared with two controls. In conclusion, this LOXL4 variant may underlie AFF susceptibility possibly due to abnormal collagen metabolism leading to increased formation of microdamage or compromised healing of microcracks in the femur.