Compressive strength of elderly vertebrae is reduced by disc degeneration and additional flexion

Computer tomography (CT)-based finite element (FE) models assess vertebral strength better than dual energy X-ray absorptiometry. Osteoporotic vertebrae are usually loaded via degenerated intervertebral discs (IVD) and potentially at higher risk under forward bending, but the influences of the IVD and loading conditions are generally overlooked. Accordingly, magnetic resonance imaging was performed on 14 lumbar discs to generate FE models for the healthiest and most degenerated specimens. Compression, torsion, bending, flexion and extension conducted experimentally were used to calibrate both models. They were combined with CT-based FE models of 12 lumbar vertebral bodies to evaluate the effect of disc degeneration compared to a loading via endplates embedded in a stiff resin, the usual experimental paradigm. Compression and lifting were simulated, load and damage pattern were evaluated at failure. Adding flexion to the compression (lifting) and higher disc degeneration reduces the failure load (8–14%, 5–7%) and increases damage in the vertebrae. Under both loading scenarios, decreasing the disc height slightly increases the failure load; embedding and degenerated IVD provides respectively the highest and lowest failure load. Embedded vertebrae are more brittle, but failure loads induced via IVDs correlate highly with vertebral strength. In conclusion, osteoporotic vertebrae with degenerated IVDs are consistently weaker—especially under lifting, but clinical assessment of their strength is possible via FE analysis without extensive disc modelling, by extrapolating measures from the embedded situation.

Retinal layer measurements after successful macula-off retinal detachment repair using optical coherence tomography

PURPOSE Optical coherence tomography (OCT) was used to analyze the thickness of various retinal layers of patients following successful macula-off retinal detachment (RD) repair. METHODS Optical coherence tomography scans of patients after successful macula-off RD repair were reanalyzed with a subsegmentation algorithm to measure various retinal layers. Regression analysis was performed to correlate time after surgery with changes in layer thickness. In addition, patients were divided in two groups. Group 1 had a follow-up period after surgery of up to 7 weeks (range, 21-49 days). In group 2, the follow-up period was >8 weeks (range, 60-438 days). Findings were compared to a group of age-matched healthy controls. RESULTS Correlation analysis showed a significant positive correlation between inner nuclear-outer plexiform layer (INL-OPL) thickness and time after surgery (P=0.0212; r2=0.1551). Similar results were found for the ellipsoid zone-retinal pigment epithelium complex (EZ-RPE) thickness (P=0.005; r2=0.2215). Ganglion cell-inner plexiform layer thickness (GCL-IPL) was negatively correlated with time after surgery (P=0.0064; r2=0.2101). For group comparison, the retinal nerve fiber layer in both groups was thicker compared to controls. The GCL-IPL showed significant thinning in group 2. The outer nuclear layer was significantly thinner in groups 1 and 2 compared to controls. The EZ-RPE complex was significantly thinner in groups 1 and 2 compared to controls. In addition, values in group 1 were significantly thinner than in group 2. CONCLUSIONS Optical coherence tomography retinal layer thickness measurements after successful macular-off RD repair revealed time-dependent thickness changes. Inner nuclear-outer plexiform layer thickness and EZ-RPE thickness was positively correlated with time after surgery. Ganglion cell-inner plexiform layer thickness was negatively correlated with time after surgery.

Quality control for retinal OCT in multiple sclerosis: validation of the OSCAR-IB criteria.

BACKGROUND Retinal optical coherence tomography (OCT) permits quantification of retinal layer atrophy relevant to assessment of neurodegeneration in multiple sclerosis (MS). Measurement artefacts may limit the use of OCT to MS research. OBJECTIVE An expert task force convened with the aim to provide guidance on the use of validated quality control (QC) criteria for the use of OCT in MS research and clinical trials. METHODS A prospective multi-centre (n = 13) study. Peripapillary ring scan QC rating of an OCT training set (n = 50) was followed by a test set (n = 50). Inter-rater agreement was calculated using kappa statistics. Results were discussed at a round table after the assessment had taken place. RESULTS The inter-rater QC agreement was substantial (kappa = 0.7). Disagreement was found highest for judging signal strength (kappa = 0.40). Future steps to resolve these issues were discussed. CONCLUSION Substantial agreement for QC assessment was achieved with aid of the OSCAR-IB criteria. The task force has developed a website for free online training and QC certification. The criteria may prove useful for future research and trials in MS using OCT as a secondary outcome measure in a multi-centre setting.

Retinal differentiation of human bone marrow-derived stem cells by co-culture with retinal pigment epithelium in vitro.

The goal of this study was to assess the in vitro differentiation capacity of human bone marrow-derived stem cells (hBMSCs) along retinal lineages. Mononuclear cells (MNC) were isolated from bone marrow (BM) and mobilized peripheral blood (mPB) using Ficoll-Paque density gradient centrifugation, and were sorted by magnetic-activated cell sorting (MACS) for specific stem cell subsets (CD34(+)CD38(+)/CD34(+)CD38(-)). These cells were then co-cultured on human retinal pigment epithelial cells (hRPE) for 7 days. The expression of stem cell, neural and retina-specific markers was examined by immunostaining, and the gene expression profiles were assessed after FACS separation of the co-cultured hBMSCs by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Furthermore, in vitro functionality of the differentiated cells was analyzed by quantifying phagocytosis of CY5-labeled photoreceptor outer segments (POS). After 7 days of co-culture, hBMSCs adopted an elongated epithelial-like morphology and expressed RPE-specific markers, such as RPE65 and bestrophin. In addition, these differentiated cells were able to phagocytose OS, one of the main characteristics of native RPE cells. Our data demonstrated that human CD34(+)CD38(-) hBMSC may differentiate towards an RPE-like cell type in vitro and could become a new type of autologous donor cell for regenerative therapy in retinal degenerative diseases.

Organ Culture Bioreactors - Platforms to Study Human Intervertebral Disc Degeneration and Regenerative Therapy.

In recent decades the application of bioreactors has revolutionized the concept of culturing tissues and organs that require mechanical loading. In intervertebral disc (IVD) research, collaborative efforts of biomedical engineering, biology and mechatronics have led to the innovation of new loading devices that can maintain viable IVD organ explants from large animals and human cadavers in precisely defined nutritional and mechanical environments over extended culture periods. Particularly in spine and IVD research, these organ culture models offer appealing alternatives, as large bipedal animal models with naturally occurring IVD degeneration and a genetic background similar to the human condition do not exist. Latest research has demonstrated important concepts including the potential of homing of mesenchymal stem cells to nutritionally or mechanically stressed IVDs, and the regenerative potential of "smart" biomaterials for nucleus pulposus or annulus fibrosus repair. In this review, we summarize the current knowledge about cell therapy, injection of cytokines and short peptides to rescue the degenerating IVD. We further stress that most bioreactor systems simplify the real in vivo conditions providing a useful proof of concept. Limitations are that certain aspects of the immune host response and pain assessments cannot be addressed with ex vivo systems. Coccygeal animal disc models are commonly used because of their availability and similarity to human IVDs. Although in vitro loading environments are not identical to the human in vivo situation, 3D ex vivo organ culture models of large animal coccygeal and human lumbar IVDs should be seen as valid alternatives for screening and feasibility testing to augment existing small animal, large animal, and human clinical trial experiments.

Unified detection and tracking of instruments during retinal microsurgery

Methods for tracking an object have generally fallen into two groups: tracking by detection and tracking through local optimization. The advantage of detection-based tracking is its ability to deal with target appearance and disappearance, but it does not naturally take advantage of target motion continuity during detection. The advantage of local optimization is efficiency and accuracy, but it requires additional algorithms to initialize tracking when the target is lost. To bridge these two approaches, we propose a framework for unified detection and tracking as a time-series Bayesian estimation problem. The basis of our approach is to treat both detection and tracking as a sequential entropy minimization problem, where the goal is to determine the parameters describing a target in each frame. To do this we integrate the Active Testing (AT) paradigm with Bayesian filtering, and this results in a framework capable of both detecting and tracking robustly in situations where the target object enters and leaves the field of view regularly. We demonstrate our approach on a retinal tool tracking problem and show through extensive experiments that our method provides an efficient and robust tracking solution.

Vision-based Proximity Detection in Retinal Surgery

In retinal surgery, surgeons face difficulties such as indirect visualization of surgical targets, physiological tremor, and lack of tactile feedback, which increase the risk of retinal damage caused by incorrect surgical gestures. In this context, intraocular proximity sensing has the potential to overcome current technical limitations and increase surgical safety. In this paper, we present a system for detecting unintentional collisions between surgical tools and the retina using the visual feedback provided by the opthalmic stereo microscope. Using stereo images, proximity between surgical tools and the retinal surface can be detected when their relative stereo disparity is small. For this purpose, we developed a system comprised of two modules. The first is a module for tracking the surgical tool position on both stereo images. The second is a disparity tracking module for estimating a stereo disparity map of the retinal surface. Both modules were specially tailored for coping with the challenging visualization conditions in retinal surgery. The potential clinical value of the proposed method is demonstrated by extensive testing using a silicon phantom eye and recorded rabbit in vivo data.

Fluorescence lifetime imaging in retinal artery occlusion.

PURPOSE Fluorescence lifetime imaging ophthalmoscopy is a technique to measure decay times of endogenous retinal fluorophores. The purpose of this study was to investigate fluorescence lifetimes in eyes with central and branch retinal artery occlusion. METHODS Twenty-four patients with central or branch retinal artery occlusion were included in this study. The contralateral unaffected fellow eye was used as control. Measurements were performed using a fluorescence lifetime imaging ophthalmoscope based on a HRA Spectralis system. Fluorescence excitation wavelength was 473 nm, and mean lifetimes were measured in a short (498-560 nm) and in a long (560-720 nm) spectral channel. Fluorescence lifetimes in the area of retinal artery occlusion were measured and compared to corresponding areas in contralateral unaffected eyes. Additionally, findings were correlated to optical coherence tomography measurements. RESULTS Retinal lifetime images of 24 patients with retinal artery occlusion were analyzed. Mean retinal fluorescence lifetimes were prolonged by 50% in the short and 20% in the long spectral channel in ischemic retinal areas up to 3 days after retinal artery occlusion compared to the contralateral unaffected eyes. In the postacute disease stage there was no difference between the lifetimes of affected areas and unaffected fellow eyes. CONCLUSIONS Retinal artery occlusion leads to significantly longer fluorescence lifetimes of the retina in the acute phase and may serve as a useful indicator for acute ischemic retinal damage.

TREAT-AND-EXTEND REGIMENS WITH ANTI-VEGF AGENTS IN RETINAL DISEASES: A Literature Review and Consensus Recommendations

PURPOSE A review of treat-and-extend regimens (TERs) with intravitreal anti-vascular endothelial growth factor agents in retinal diseases. METHODS There is a lack of consensus on the definition and optimal application of TER in clinical practice. This article describes the supporting evidence and subsequent development of a generic algorithm for TER dosing with anti-vascular endothelial growth factor agents, considering factors such as criteria for extension. RESULTS A TER algorithm was developed; TER is defined as an individualized proactive dosing regimen usually initiated by monthly injections until a maximal clinical response is observed (frequently determined by optical coherence tomography), followed by increasing intervals between injections (and evaluations) depending on disease activity. The TER regimen has emerged as an effective approach to tailoring the dosing regimen and for reducing treatment burden (visits and injections) compared with fixed monthly dosing or monthly visits with optical coherence tomography-guided regimens (as-needed or pro re nata). It is also considered a suitable approach in many retinal diseases managed with intravitreal anti-vascular endothelial growth factor therapy, given that all eyes differ in the need for repeat injections. CONCLUSION It is hoped that this practical review and TER algorithm will be of benefit to health care professionals interested in the management of retinal diseases.

Retinal Cell Death Caused by Sodium Iodate Involves Multiple Caspase-Dependent and Caspase-Independent Cell-Death Pathways

Herein, we have investigated retinal cell-death pathways in response to the retina toxin sodium iodate (NaIO3) both in vivo and in vitro. C57/BL6 mice were treated with a single intravenous injection of NaIO3 (35 mg/kg). Morphological changes in the retina post NaIO3 injection in comparison to untreated controls were assessed using electron microscopy. Cell death was determined by TdT-mediated dUTP-biotin nick end labeling (TUNEL) staining. The activation of caspases and calpain was measured using immunohistochemistry. Additionally, cytotoxicity and apoptosis in retinal pigment epithelial (RPE) cells, primary retinal cells, and the cone photoreceptor (PRC) cell line 661W were assessed in vitro after NaIO3 treatment using the ApoToxGlo™ assay. The 7-AAD/Annexin-V staining was performed and necrostatin (Nec-1) was administered to the NaIO3-treated cells to confirm the results. In vivo, degenerating RPE cells displayed a rounded shape and retracted microvilli, whereas PRCs featured apoptotic nuclei. Caspase and calpain activity was significantly upregulated in retinal sections and protein samples from NaIO3-treated animals. In vitro, NaIO3 induced necrosis in RPE cells and apoptosis in PRCs. Furthermore, Nec-1 significantly decreased NaIO3-induced RPE cell death, but had no rescue effect on treated PRCs. In summary, several different cell-death pathways are activated in retinal cells as a result of NaIO3.

Multiple programmed cell death pathways are involved in N-methyl-N-nitrosourea-induced photoreceptor degeneration.

PURPOSE: To identify programmed cell death (PCD) pathways involved in N-methyl-N-nitrosourea (MNU)-induced photoreceptor (PR) degeneration. METHODS: Adult C57BL/6 mice received a single MNU i.p. injection (60 mg/kg bodyweight), and were observed over a period of 7 days. Degeneration was visualized by H&E overview staining and electron microscopy. PR cell death was measured by quantifying TUNEL-positive cells in the outer nuclear layer (ONL). Activity measurements of key PCD enzymes (calpain, caspases) were used to identify the involved cell death pathways. Furthermore, the expression level of C/EBP homologous protein (CHOP) and glucose-regulated protein 78 (GRP78), key players in endoplasmic reticulum (ER) stress-induced apoptosis, was analyzed using quantitative real-time PCR. RESULTS: A decrease in ONL thickness and the appearance of apoptotic PR nuclei could be detected beginning 3 days post-injection (PI). This was accompanied by an increase of TUNEL-positive cells. Significant upregulation of activated caspases (3, 9, 12) was found at different time periods after MNU injection. Additionally, several other players of nonconventional PCD pathways were also upregulated. Consequently, calpain activity increased in the ONL, with a maximum on day 7 PI and an upregulation of CHOP and GRP78 expression beginning on day 1 PI was found. CONCLUSIONS: The data indicate that regular apoptosis is the major cause of MNU-induced PR cell death. However, alternative PCD pathways, including ER stress and calpain activation, are also involved. Knowledge about the mechanisms involved in this mouse model of PR degeneration could facilitate the design of putative combinatory therapeutic approaches.

Randomized Trial to Evaluate Tandosporine in Geographic Atrophy Secondary to Age-Related Macular Degeneration: the GATE Study.

PURPOSE To determine the safety and efficacy of AL-8309B (tandospirone) in the management of patients with geographic atrophy (GA) secondary to age-related macular degeneration (AMD) and obtain standardized data on GA lesion growth progression. DESIGN Prospective, controlled, double-masked, randomized, multicenter phase 3 clinical trial. METHODS Setting: 48 clinical sites. PATIENTS Patients with GA associated with AMD were enrolled. All patients were followed for a minimum of 30 months, and up to 36 months. Intervention Procedures: Patients were randomized (1:1:1) to receive AL-8309B ophthalmic solution 1.0%, 1.75%, or vehicle, administered as a twice-daily topical ocular drop. MAIN OUTCOME MEASURES The primary efficacy endpoint was mean annualized lesion enlargement from baseline as assessed with fundus autofluorescence (FAF) imaging. RESULTS A total of 768 eyes of 768 patients were enrolled and treated with AL-8309B 1.0% (N=250), AL-8309B 1.75% (N=258), or vehicle (N= 260). An increase in mean lesion size was observed in both the AL-8309B and vehicle treatment groups, and growth rates were similar in all treatment groups. Annualized lesion growth rates were 1.73, 1.76 and 1.71 mm(2) for AL-8309B 1.0%, AL-8309B 1.75%, and vehicle, respectively. CONCLUSIONS AL-8309B 1.0% and 1.75% did not affect lesion growth in eyes with GA secondary to AMD. There were no clinically relevant safety issues identified for AL-8309B. The large natural history dataset from this study is a valuable repository for future comparisons.

Scheduled versus Pro Re Nata Dosing in the VIEW Trials

PURPOSE To analyze visual acuity (VA) outcomes before and after preplanned treatment regimen change in the VIEW studies at week 52 (W52). DESIGN Multiple post hoc analyses for retrospectively defined subgroups in 2 multicenter, multinational, double-masked trials. PARTICIPANTS Two thousand four hundred fifty-seven neovascular age-related macular degeneration (AMD) patients. METHODS Patients were randomized to treatment with 0.5 mg ranibizumab given monthly, a 0.5-mg or 2-mg intravitreal aflibercept injection given monthly, or 2 mg intravitreal aflibercept given every other month, after 3 initial monthly doses, up to W52. From W52 through W96, patients received their original dosing assignment using a capped pro re nata (PRN) regimen, with defined retreatment criteria based on VA and morphologic signs of disease activity and mandatory dosing at least every 12 weeks. MAIN OUTCOME MEASURES Best-corrected VA (BCVA) and optical coherence tomography assessments were mandatory at all visits from baseline to W96. Outcomes were changes in BCVA and central retinal thickness. Outcomes were evaluated in all patients who completed 2 years of the VIEW studies using the last observation carried forward method for missing data at interim visits. RESULTS After W52, approximately 20% of patients lost 5 Early Treatment Diabetic Retinopathy Study (ETDRS) letters or more across all treatment arms with PRN treatment. Patients who met the retreatment criterion of loss of 5 ETDRS letters or more in the first quarter of the PRN dosing phase did not recover; mean final VA loss across the 4 study arms was -4.4 to -5.8 letters. Outcomes of these patients up to W52 were indistinguishable from those of the overall population. There were no differences between groups in serious ocular adverse events or Anti-Platelet Trialists' Collaboration arterial thromboembolic events through W96. CONCLUSIONS These analyses suggest that there are subgroups of patients for whom VA outcomes in the second year of the VIEW studies were less stable than in the first year and for whom W52 seems to be an important inflection point. Although alternate reasons specific to the nature of the underlying AMD cannot be fully excluded, the switch in treatment regimen at W52 is a plausible explanation.