Browsing by Subject "Collagen fibrils"

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    Alteration in epithelium and stroma of post-INTACS cornea: Ultrastructure and 3D transmission electron tomography
    (2026) Omar Kirat2; Adrian Smedowski; Aljohara Alkanaan; Fahad Almoqbel; Turki Almubrad; Saeed Akhtar; Biología Celular e Histología; Universidad de Murcia, Departamento de Biologia Celular e Histiologia
    This study was conducted to investigate the ultrastructure of the epithelium and stroma of post INTACS corneas. INTACS were surgically inserted into the corneas of three patients to remodel the keratoconus shape. INTACS were inserted with the IntraLase femtosecond laser. Patients 1, 2, and 3 returned to the clinic 8, 6, and 9 years, respectively, after surgery due to their deteriorating vision. The lamellae above the INTACS were removed surgically and processed for light and electron microscopy. 2D and 3D digital images of lamellae, collagen fibrils (CFs), and proteoglycans (PGs) were captured by a bottom-mounted camera and analysed using iTEM software. The epithelium and stromal lamellae had degenerated. A large number of aggregates of microfilaments were present in the Bowman’s layer (BW) and throughout the stroma. In the stroma, just above the INTACS insertion, lamellae were completely disorganised and running randomly in the large electron-lucent spaces. The CF diameter was significantly smaller than in the normal cornea. 3D images showed microfibrils within the CF were less in the post-INTACS cornea than in the normal cornea. We believe that insertion of the INTACS disturbed the lamellar organisation and uniform distribution of CFs. This non-uniform CF distribution increased over time, resulting in vision impairment.
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    The role of proteoglycans in maintaining collagen fibril morphology
    (Murcia : F. Hernández, 1995) Dell`Orbo, Carlo; De Luca, G.; Gioglio, L.; Quacci, Daniela; Soldi, C.
    The aortic wall contains various heterogeneous proteoglycan populations which interact in different ways with other components of extracellular matrix. Proteoglycans (PGs) are known to provide structural support to the vessel wall as well as to influence specific physiological functions of the tissues. The aim of the present study was to investigate the effects of Chondroitinase AC (Chase), Streptococcal Hyaluronidase (Hyase) and Heparanase on human aortic wall collagen which had been treated previously with 4M GuHCl, in order to verify the effects of selective glycanolytic treatment on type 1 collagen fibril ultrastructure. Following 4M GuHCl treatment, collagen fibrils are seen to have a clearly visible period. Subsequent to GuHCl and Streptococcal Hyase treatment al1 collagen fibrils appear to be completely swollen in thin aperiodic filaments; the typical 64 nm collagen period is completely undetectable. After GuHCl and Chase treatment a small number of collagen fibrils are seen to be swollen in thin fibrils which are mainly localized at some distance from elastic fibres. Following GuHCl and HeparanaseIHeparitinase 111 treatment a considerable number of collagen fibrils appear to be swollen in thin fibrils; the majority of which are situated in the vicinity of elastic fibrils. The swelling of collagen fibrils underlines the fundamental role of proteoglycans in maintaining collagen fibril integrity and periodicity. It is as yet impossible to precisely map interactions between these proteoglycans and collagen fibres. The role of Hyaluronic acid requires further investigation, although the nature of this interaction is undoubtedly a matter of considerable interest.
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    Ultrastructure and 3D transmission electron tomography of collagen fibrils and proteoglycans of swollen human corneal stroma
    (Universidad de Murcia. Departamento de Biología Celular e Histología, 2019) Akhtar, S.; Petrovski, G.; Albert, R.; Alkanaan, A.; Kirat, O.; Khan, A.D.; Almubrad, T.
    Background. The transparency of the cornea is regulated by the unique organization of collagen fibrils (CFs) which is maintained by proteoglycans (PGs). The interlacing of CF lamellae in the anterior stroma provides the biomechanical properties of the cornea. Objective. To investigate the alterations of CFs and PGs in the swollen cornea, with special reference to the anterior stroma by using electron microscopy and 3D ultrastructural tomography. Method. Nine healthy normal scleral corneal rings (age from 40 to 65 years) were hydrated individually in deionised water to induce swelling in the cornea. Three of them were hydrated for 2hr whereas the other three were hydrated for 48hr. The remaining three scleral normal corneal rings were used as a control.The corneas were processed for electron microscopy (E M) to study the CFs and PGs. Ultrathin sections were observed using transmission electron microscopy (JOEL 1400) and digital images of CFs, PGs and lamellae were captured using a bottom mounted Quemesa camera and iTEM Soft Imaging System. The software program ‘Composerx64, version 3.4.2.0’ was used to construct individual 3D images from 120 digital images taken from -60 to +60 degree angles. Results. The 3D tomography showed the degeneration of microfibrils within the CFs of the swollen cornea. The CF diameter was significantly reduced and the interfibrillar spacing significantly increased in both the 2hr and 48hr hydrated corneas compared to the normal cornea. Within the hydrated corneas, the CF diameter was smaller and the interfibrillar spacing was increased in the middle and posterior stroma compared to the anterior stroma. The PG area in both the 2hr and the 48hr hydrated cornea was reduced in the anterior stroma, whereas it was increased in middle and posterior stroma compared to the normal cornea. The density of the PGs in both the 2hr and the 48hr samples, was reduced compared to the density of PGs in the normal cornea. Conclusion. The CFs, PGs and lamellae had degenerated, caused by swelling. 3D imaging demonstrated that the impairment of the microfibrils and PGs within the CF, is caused by the excessive hydration or swelling in the anterior as well as in the middle and posterior stroma. The lamellae of the anterior stroma which provides the biomechanical strength in the normal cornea, had degenerated in the swollen corneas due to the presence of the damaged CFs and PGs.