Comparative transcriptional profiling of the limbal epithelial crypt demonstrates its putative stem cell niche characteristics

<p>Abstract</p> <p>Background</p> <p>The Limbal epithelial crypt (LEC) is a solid cord of cells, approximately 120 microns long. It arises from the undersurface of interpalisade rete ridges of the limbal palisades of Vogt and extends deeper into the limbal stroma parallel or perpendicular to the palisade. There are up to 6 or 7 such LEC, variably distributed along the limbus in each human eye.</p> <p>Morphological and immunohistochemical studies on the limbal epithelial crypt (LEC) have demonstrated the presence of limbal stem cells in this region. The purpose of this microarray study was to characterise the transcriptional profile of the LEC and compare with other ocular surface epithelial regions to support our hypothesis that LEC preferentially harbours stem cells (SC).</p> <p>Results</p> <p>LEC was found to be enriched for SC related Gene Ontology (GO) terms including those identified in quiescent adult SC, however similar to cornea, limbus had significant GO terms related to proliferating SC, transient amplifying cells (TAC) and differentiated cells (DC). LEC and limbus were metabolically dormant with low protein synthesis and downregulated cell cycling. Cornea had upregulated genes for cell cycling and self renewal such as <it>FZD7, BTG1, CCNG</it>, and <it>STAT3 </it>which were identified from other SC populations. Upregulated gene expression for growth factors, cytokines, WNT, Notch, TGF-Beta pathways involved in cell proliferation and differentiation were noted in cornea. LEC had highest number of expressed sequence tags (ESTs), downregulated and unknown genes, compared to other regions. Genes expressed in LEC such as <it>CDH1, SERPINF1, LEF1, FRZB1</it>, <it>KRT19, SOD2, EGR1 </it>are known to be involved in SC maintenance. Genes of interest, in LEC belonging to the category of cell adhesion molecules, WNT and Notch signalling pathway were validated with real-time PCR and immunofluorescence.</p> <p>Conclusions</p> <p>Our transcriptional profiling study identifies the LEC as a preferential site for limbal SC with some characteristics suggesting that it could function as a 'SC niche' supporting quiescent SC. It also strengthens the evidence for the presence of "transient cells" in the corneal epithelium. These cells are immediate progeny of SC with self-renewal capacity and could be responsible for maintaining epithelial turn over in normal healthy conditions of the ocular surface (OS). The limbus has mixed population of differentiated and undifferentiated cells.</p

Effect of surgical experience and spine subspecialty on the reliability of the {AO} Spine Upper Cervical Injury Classification System

OBJECTIVE The objective of this paper was to determine the interobserver reliability and intraobserver reproducibility of the AO Spine Upper Cervical Injury Classification System based on surgeon experience (&lt; 5 years, 5–10 years, 10–20 years, and &gt; 20 years) and surgical subspecialty (orthopedic spine surgery, neurosurgery, and "other" surgery). METHODS A total of 11,601 assessments of upper cervical spine injuries were evaluated based on the AO Spine Upper Cervical Injury Classification System. Reliability and reproducibility scores were obtained twice, with a 3-week time interval. Descriptive statistics were utilized to examine the percentage of accurately classified injuries, and Pearson’s chi-square or Fisher’s exact test was used to screen for potentially relevant differences between study participants. Kappa coefficients (κ) determined the interobserver reliability and intraobserver reproducibility. RESULTS The intraobserver reproducibility was substantial for surgeon experience level (&lt; 5 years: 0.74 vs 5–10 years: 0.69 vs 10–20 years: 0.69 vs &gt; 20 years: 0.70) and surgical subspecialty (orthopedic spine: 0.71 vs neurosurgery: 0.69 vs other: 0.68). Furthermore, the interobserver reliability was substantial for all surgical experience groups on assessment 1 (&lt; 5 years: 0.67 vs 5–10 years: 0.62 vs 10–20 years: 0.61 vs &gt; 20 years: 0.62), and only surgeons with &gt; 20 years of experience did not have substantial reliability on assessment 2 (&lt; 5 years: 0.62 vs 5–10 years: 0.61 vs 10–20 years: 0.61 vs &gt; 20 years: 0.59). Orthopedic spine surgeons and neurosurgeons had substantial intraobserver reproducibility on both assessment 1 (0.64 vs 0.63) and assessment 2 (0.62 vs 0.63), while other surgeons had moderate reliability on assessment 1 (0.43) and fair reliability on assessment 2 (0.36). CONCLUSIONS The international reliability and reproducibility scores for the AO Spine Upper Cervical Injury Classification System demonstrated substantial intraobserver reproducibility and interobserver reliability regardless of surgical experience and spine subspecialty. These results support the global application of this classification system

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

Morphological characteristics of the limbal epithelial crypt

Aim: In 2005 we reported the discovery of a novel anatomical structure at the limbus, which we termed the limbal epithelial crypt (LEC). The purpose of this study was to further evaluate the distribution, immunophenotypical, and ultra structural characteristics of the LEC as a putative niche of stem cells.Methods: Sequential histological sections of human corneo-scleral limbal rims were examined for the presence and distribution of the LEC. Immunophenotypical characterisation of the LEC cells using a panel of antibodies of interest was undertaken. Transmission electron microscopy of the LEC was used to examine the ultra structural and morphometric features of cells within the LEC and adjacent limbus.Results: A total of 74 LECs were identified in eight corneo-scleral rims. These varied in number, size and distribution within rims. Cells within the crypt demonstrated the following phenotype: CK3−/CK19+/CD 34−/Vimentin+/p63+/Connexin 43+/MIB1 (Ki67)−. Presence of Cx43 was also demonstrated in the rete pegs adjacent to the LEC. Basal cells of the LEC were significantly smaller than basal cells found in adjacent rete pegs and also smaller than suprabasal limbal and central corneal epithelial cells (

The Global Spine Care Initiative: methodology, contributors, and disclosures.

PURPOSE: The purpose of this report is to describe the Global Spine Care Initiative (GSCI) contributors, disclosures, and methods for reporting transparency on the development of the recommendations. METHODS: World Spine Care convened the GSCI to develop an evidence-based, practical, and sustainable healthcare model for spinal care. The initiative aims to improve the management, prevention, and public health for spine-related disorders worldwide; thus, global representation was essential. A series of meetings established the initiative\u27s mission and goals. Electronic surveys collected contributorship and demographic information, and experiences with spinal conditions to better understand perceptions and potential biases that were contributing to the model of care. RESULTS: Sixty-eight clinicians and scientists participated in the deliberations and are authors of one or more of the GSCI articles. Of these experts, 57 reported providing spine care in 34 countries, (i.e., low-, middle-, and high-income countries, as well as underserved communities in high-income countries.) The majority reported personally experiencing or having a close family member with one or more spinal concerns including: spine-related trauma or injury, spinal problems that required emergency or surgical intervention, spinal pain referred from non-spine sources, spinal deformity, spinal pathology or disease, neurological problems, and/or mild, moderate, or severe back or neck pain. There were no substantial reported conflicts of interest. CONCLUSION: The GSCI participants have broad professional experience and wide international distribution with no discipline dominating the deliberations. The GSCI believes this set of papers has the potential to inform and improve spine care globally. These slides can be retrieved under Electronic Supplementary Material

The Global Spine Care Initiative: model of care and implementation.

PURPOSE: Spine-related disorders are a leading cause of global disability and are a burden on society and to public health. Currently, there is no comprehensive, evidence-based model of care for spine-related disorders, which includes back and neck pain, deformity, spine injury, neurological conditions, spinal diseases, and pathology, that could be applied in global health care settings. The purposes of this paper are to propose: (1) principles to transform the delivery of spine care; (2) an evidence-based model that could be applied globally; and (3) implementation suggestions. METHODS: The Global Spine Care Initiative (GSCI) meetings and literature reviews were synthesized into a seed document and distributed to spine care experts. After three rounds of a modified Delphi process, all participants reached consensus on the final model of care and implementation steps. RESULTS: Sixty-six experts representing 24 countries participated. The GSCI model of care has eight core principles: person-centered, people-centered, biopsychosocial, proactive, evidence-based, integrative, collaborative, and self-sustaining. The model of care includes a classification system and care pathway, levels of care, and a focus on the patient\u27s journey. The six steps for implementation are initiation and preparation; assessment of the current situation; planning and designing solutions; implementation; assessment and evaluation of program; and sustain program and scale up. CONCLUSION: The GSCI proposes an evidence-based, practical, sustainable, and scalable model of care representing eight core principles with a six-step implementation plan. The aim of this model is to help transform spine care globally, especially in low- and middle-income countries and underserved communities. These slides can be retrieved under Electronic Supplementary Material

The Global Spine Care Initiative: methodology, contributors, and disclosures.

PURPOSE: The purpose of this report is to describe the Global Spine Care Initiative (GSCI) contributors, disclosures, and methods for reporting transparency on the development of the recommendations. METHODS: World Spine Care convened the GSCI to develop an evidence-based, practical, and sustainable healthcare model for spinal care. The initiative aims to improve the management, prevention, and public health for spine-related disorders worldwide; thus, global representation was essential. A series of meetings established the initiative\u27s mission and goals. Electronic surveys collected contributorship and demographic information, and experiences with spinal conditions to better understand perceptions and potential biases that were contributing to the model of care. RESULTS: Sixty-eight clinicians and scientists participated in the deliberations and are authors of one or more of the GSCI articles. Of these experts, 57 reported providing spine care in 34 countries, (i.e., low-, middle-, and high-income countries, as well as underserved communities in high-income countries.) The majority reported personally experiencing or having a close family member with one or more spinal concerns including: spine-related trauma or injury, spinal problems that required emergency or surgical intervention, spinal pain referred from non-spine sources, spinal deformity, spinal pathology or disease, neurological problems, and/or mild, moderate, or severe back or neck pain. There were no substantial reported conflicts of interest. CONCLUSION: The GSCI participants have broad professional experience and wide international distribution with no discipline dominating the deliberations. The GSCI believes this set of papers has the potential to inform and improve spine care globally. These slides can be retrieved under Electronic Supplementary Material