Corneal cell proteins and ocular surface pathology

The cornea is a transparent and avascular tissue that functions as the major refractive structure for the eye. A wide variety of growth factors, chemokines, cytokines and their receptors are synthesized by corneal epithelial and stromal cells, and are found in tears. These molecules function in corneal wound healing and in inflammatory responses. Proteoglycans and glycoproteins are essential for normal corneal function, both at the air-epithelial interface and within the extracellular matrix. The ocular MUC mucins may play roles in forming the mucus layer of the tear film, in regulating tear film spread, and in inhibiting the adhesion of pathogens to the ocular surface. Lumican, keratocan and mimecan are the major keratan sulfate proteoglycans of the corneal stroma. They are essential, along with other proteoglycans and interfibrillar proteins, including collagens type VI and XII, for the maintenance of corneal transparency. Corneal epithelial cells interact with a specialized extracellular matrix structure, the basement membrane, composed of a specific subset of collagen type IV and laminin isoforms in addition to ubiquitous extracellular matrix molecules. Matrix metalloprotein-ases have been identified in normal corneal tissue and cells and may play a role in the development of ulcerative corneal diseases. Changes in extracellular matrix molecule localization and synthesis have been noted in other types of corneal diseases as well, including bullous keratopathy and keratoconus.     

Amniotic membrane transplantation for ocular surface reconstruction

The purpose of this study is to analyze the clinical experience and the effect of human amniotic membrane transplantation on pterygium excision and bullous keratopathy. From January 1999 to January 2001 at University Hospital "Sestre milosrdnice" amniotic membrane transplantation was performed consecutively in 21 eyes: 11 eyes with bullous keratopathy and 10 with recurrent pterygia. In the group with bullous keratopathy epithelization took place in 19.6 days in 72.7% and the reduction of pain was satisfactory. Recurrence rate in group with recurrent pterygia was 20%. Based on the presented results it could be concluded that amniotic membrane transplantation can be considered as an effective alternative for treating severe ocular surface diseases and as an alternative for penetrating keratoplasty if there is a lack of grafts.     

Amniotic membrane transplantation in ocular surface disorders

Chronic ocular surface disorders, which can result in severe functional impairment, have been viewed for decades as untreatable diseases. In 1995, the reintroduction of amniotic membrane transplantation (AMT), either alone or associated with limbal stem cell transplantation, has offered new hope of using tissue and cell therapy strategies to repair ocular surface disorders. Amniotic membrane (AM) has been found to exert its effects by acting as a substrate for the growth of ocular surface epithelia, by suppressing inflammation and scarring and by serving as an anti-microbial barrier. Moreover, AM has recently been used as a substrate for ex vivo expansion of corneal epithelial cells for ocular surface reconstruction. Notwithstanding the substantial agreement among Authors regarding its clinical efficacy, there are still many uncertainties regarding the fate of grafted AM and consequently the mechanisms through which it exerts its long-term effects. Further studies including controlled clinical trials with numerous cases are required to understand which ocular surface conditions are certain to benefit from AM transplantation and how its mechanical properties interact with the mediators produced to favor ocular surface reconstruction.     

Electrical Impedance of Isolated Amnion

The electrical impedance of the guinea pig amniotic membrane was measured, under standardized conditions, over the frequency range of 20 to 7000 cycles/second. This impedance can be represented analytically by a simple frequency-dependent function which is precisely of the form of the Debye relaxation equation. The observed data exhibit a broad dispersion centered at a frequency of 1050 cycles/second and a narrow distribution of time constants centered about 152 microseconds, both effects being due to the polydisperse nature of amniotic tissue. If the narrow time-constant distribution is approximated by a single time constant, amnion impedance can be simulated by a simple electrical circuit of frequency-independent elements. The Maxwell-Wagner interfacial treatment, although successfully adapted for cell suspensions, is shown to lose its quantitative significance in the case of the tightly structured amnion. In addition, determinations were made on the chemical composition of amniotic fluid, fetal blood and urine, and maternal blood and urine; the DC potential across the amniotic membrane was also measured.     

Preoperative brush and impression cytology in ocular surface squamous neoplasms

OBJECTIVE: Preoperative cytologic diagnoses of ocular surface squamous neoplasms were evaluated and compared with histologic diagnoses. STUDY DESIGN: Impression cytology (Millipore filter paper) and brush cytology were applied to 32 patients who had conjunctival neoplasms. Papanicolaou-stained cytologic preparations and hematoxylin and eosin-stained histologic sections were examined by light microscopy. RESULTS: The brush technique was used on 27 patients; impression cytology was applied in 5 cases. Cytologic and histologic diagnoses were concordant in 26 cases. Squamous cell carcinoma or carcinoma in situ was diagnosed in 18 and dysplasia in 4 cases. Squamous metaplasia and normal-appearing conjunctival epithelial cells were diagnosed cytologically in four cases; of those histologic diagnoses, one was pterygium and three, conjunctival nevus. Four cases revealed discrepancies between the cytologic and histologic preparations. There was one false positive result, and one case was subconjunctival invasion of basal cell carcinoma of the eyelid. CONCLUSION: Impression and brush cytology are fast, cost-effective, reliable and noninvasive diagnostic tools for ocular surface squamous neoplasms. However, the brush technique has several advantages over impression cytology.     

Initiation of Bone and Amnion Banking in Turkey

There is a growing demand in Turkey for human tissue to use in surgery and wound healing. However, our country does not have facilities for local production of tissue grafts and generally depends on imported products. Under a multi-year project initiated in 1997, the International Atomic Energy Agency has provided main equipment for tissue processing and experts on Tissue Banking as well as training on tissue processing methods.In this presentation, information on various stages of the project implementation is given. Details of lay out for the process laboratories and equipment are given. Donor selection and testing criteria, processing procedures for bone and amnion, setting up product design, implementation of quality system and radiation sterilisation are described briefly. Quality procedures included preparation of quality manual, record forms, document control, non-conformance and corrective actions, training records, equipment maintenance and calibration are all in line with GMP/GLP Standards. Clinical applications of tissue grafts and medico-legal position of organ and tissue donation in Turkey are also discussed briefly.     

生物羊膜在鼓膜修补术中的应用价值研究

目的:探讨耳内镜下应用瑞济生物羊膜这一新型材料进行鼓膜修补术的可行性,为临床鼓膜修补术探索新的、更为理想的修复材料提供新的思路。方法:临床筛选18例(24耳)鼓膜紧张部中央性穿孔患者,在耳内镜下进行手术,修补材料应用瑞济生物羊膜作为移植材料,全部采用内植法行鼓膜修补术。移植材料内外均有明胶海绵支撑,术后10天取出外耳道填塞物。结果:术后随访6个月,除2例(2耳)术后感染而穿孔未愈外,其余16例(22耳)全部一期愈合,鼓膜形态完好,无手术并发症发生,成功率97.1%。结论:内镜下经外耳道鼓膜成形术具有创伤小、术后恢复快、疗效好的优点。瑞济生物羊膜来自同种异体,成分单一,抗原少,免疫排斥小,可规模化、标准化生产,手术应用操作简单方便,成功率高,可作为鼓膜修补术较为理想的移植修复材料,值得临床推广应用。     

羊膜及羊膜匀浆液在眼科学中应用的研究进展

羊膜应用于医学已有一个多世纪,应用于眼科也有70余年的历史。因种种原因,在很长一段时间里,对羊膜的研究停滞不前,但随着生物医学技术和其它相关技术的发展,羊膜的解剖结构及生物学特性研究得越来越深入。而随着羊膜的解剖和生物学特性日益明确,羊膜在医学和组织工程学中的应用也越来越广泛,并且应用前景广阔。近年来,由于羊膜的诸多解剖和生物学特性符合眼科学发展的需要,羊膜在眼科中的应用也日益广泛,并取得了良好的临床效果。羊膜的研磨提取液-羊膜匀浆液保留了羊膜中的有效生物成分,在治疗眼部疾病方面也取得了一定的进展。国内外关于羊膜及羊膜匀浆的研究文献有很多,为了更深入了解羊膜的特性及其在眼科疾病治疗方面的优势,该文将对羊膜的应用历史、羊膜及羊膜匀浆液的制备及保存、生物学特性及其在眼科学中的应用作一综述。