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Biomedical subjects

J M Legeais

Publications and source records attributed to J M Legeais.

At least 19 recordsLinked to original sources
PubMed2001

Chemotactic penetration of keratocytes in ePTFE polymer in vitro.

Expanded polytetrafluoroethylene (ePTFE) is used as a support for artificial corneas. Implanted in corneas, most of the time this polymer is colonized by corneal host cells. The absence of colonization often coincides with extrusion of the polymer. Therefore, we decided to introduce keratocytes into ePTFE in vitro before implantation. Because keratocytes do not spontaneously enter ePTFE, we used several chemoattractants, separately and in a mixture, to stimulate the penetration of cultured keratocytes into the polymer. The influence of the passage number on cell penetration was also studied. No significant differences were observed up to the seventh passage, although seventh-passage cells penetrated somewhat more slowly than younger cells. Satisfactory results were obtained with four of the tested chemotactic factors: IL-6, type alpha transforming growth factor (TGF-alpha), platelet derived growth factor isoform BB (PDGF-BB), and fibroblast growth factor-2 (FGF-2). Under our experimental conditions, two to more than six million keratocytes entered the polymer discs with a volume of 706.5 mm(3) in the presence of these four chemoattractants. TGF-alpha was the most efficient and was selected for further in vitro and in vivo studies.

Biocompatible Materials↗
PubMed2001

Effect of hyaluronan on MMP expression and activation.

Matrix metalloproteases (MMPs) play a crucial role in tissue remodelling in a variety of physiological and pathological processes. Hyaluronan is also involved in the same processes. Several cytokines and growth factors are involved in the regulation of the biosynthesis of hyaluronan and also of MMPs. The activity of MMPs has been shown to be regulated at the level of transcription and activation of the zymogen form. In order to explore the possible relationship between matrix components and especially hyaluronan, we studied the effect of hyaluronan on MMP expression (biosynthesis and activation) in the culture of human skin fibroblasts and corneal keratocytes (explant cultures and cell cultures). These cells were shown to exhibit distinct phenotypes as far as matrix biosynthesis is concerned. Using a synthetic substrate N-Suc(ala)3pNA, we measured elastase-type endopeptidase activity produced by fibroblasts and keratocytes and characterized the MMPs by zymography. Hyaluronan added to fibroblast cultures stimulated the membrane-bound elastase-type endopeptidase activity in a dose dependent fashion. Similar results were obtained with keratocyte cultures. In the presence of 1 mg/ml hyaluronan there was an increase in MMP expression and also an activation of latent MMPs both by fibroblasts and keratocytes.

Cells, Cultured↗
PubMed2001

Corneal collagens.

Cornea is a highly differentiated tissue rich in extracellular matrix (ECM) specifically distributed in space in order to insure its dual role--transparency and protection of inner eye-tissues. Corneal ECM is especially rich in collagens. Since the characterisation of a number of distinct collagen types it appeared that most of them are present in the cornea. Their synthesis follows a specific program of sequential expression of the different collagen types to be synthesised during the development and maturation of the cornea. The precise regulation of the diameter and orientation of fibers, and of the interfibrillar spaces is partially at least attributed to interactions between glycosaminoglycans and collagens. The 'program' of vectorial collagen synthesis and GAG-collagen interactions changes also with age and in several pathological conditions as corneal dystrophies and wound healing. The Maillard reaction, especially in diabetes, is one of these important factors involved in age-dependent modifications of corneal structure and function. Far from being inert, corneal collagens were shown to have relatively short half-lives. The biosynthesis of corneal collagens was studied also during wound healing. The refibrillation of wounded corneas does not follow the original 'program' of ECM-synthesis as shown by the comparative study of wound healing using biochemical and morphometric methods. This review recapitulates briefly previous and recent studies on corneal collagens in order to present to clinicians and scientists an overview of the state of the art of this important field at the intersection of eye research and matrix biology.

Aging↗
PubMed2001

Effect of procyanidolic oligomers on the permeability of the blood-brain barrier.

Blood-brain barrier (BBB) is the site of regulatory mechanisms which control the exchange of substances between the brain and the blood through the wall of 'true' brain capillaries with tight junctions between endothelial cells. In some pathological situations the permeability of the BBB is increased because of a partial proteolytic degradation of some constituents of the capillary basement lamina. In such cases it is important to restore normal permeability. The effect of procyanidolic oligomers (PCO) on the BBB was investigated in vivo with quantitative morphologic procedures. We also investigated the action of this drug on collagen and basement lamina constituents (Matrigel) in vitro. Collagenase injected in lateral brain ventricles was shown to increase BBB permeability. Per os administration of PCO to rats greatly increased the resistance of brain capillaries to bacterial collagenase, as shown by the inhibition of the diffusion of fluorescein-isothiocyanate-marked dextran particles from the blood-stream into the brain tissues. Calf skin collagen pretreated in vitro with PCO became more resistant to the hydrolytic action of collagenase. Similar, even more intense protective effect was seen when basal lamina constituents containing type IV collagen was incubated with PCO before exposure to pronase. These in vitro effects may partly explain the in vivo protective effect of PCO against the alteration of brain capillaries by i.v. injected bacterial collagenase.

Animals↗
PubMed2001

Nineteen years of penetrating keratoplasty in the Hotel-Dieu Hospital in Paris.

PURPOSE: To identify changing trends in penetrating keratoplasties (PKs) performed at the Hotel-Dieu Hospital in Paris between January 1980 and December 1999 and to explain the reasons for the changes. METHODS: We retrospectively reviewed 3,736 of the 3,836 PKs performed between January 1, 1980, and December 31, 1999, and classified them into diagnostic categories. RESULTS: The most common indications for PK were keratoconus (28.8%), herpetic infections (10.9%), graft failures (9.9%), aphakic and pseudophakic corneal edema (9.9%), Fuchs' endothelial dystrophy (9.4%), and nonherpetic leucoma (7.7%). Other indications represented 23.4% of the cases. The incidence of aphakic and pseudophakic corneal edema progressively increased between 1980 and 1991, became the most frequent indication in 1991 (21.4%), and then progressively decreased. The annual number of PKs increased between 1980 and 1986, decreased between 1987 and 1997, and increased again after September 1997. The decrease was caused by both a shortage of corneal buttons, and, in 1987, the fear of transmitting diseases through corneal transplantation, particularly human immunodeficiency virus. Beginning in 1992, decreases were also associated with stringent governmental regulations of eye bank tissue. CONCLUSION: Changes in the incidence and management of corneal disorders were the primary factors leading to modifications of grafting until 1987. After 1987, corneal button shortage probably corresponded to the acquired immune deficiency syndrome epidemic. Governmental regulations of eye banking led to a severe corneal button shortage between 1992 and 1997. Despite an increase in the number of PKs performed after 1997, corneal buttons are still preferentially allocated to patients in whom there is a high probability of graft success.

Adolescent↗
PubMed2001

[Histologic evaluation in rabbits of the biocompatibility of episcleral implant material: S-PTFEe (silicone core covered with expanded polytetrafluoroethylene)].

PURPOSE: To study the tolerance of a silicone band wrapped with expanded polytetrafluoroethylene (e-PTFE) in "fauve de Bourgogne" rabbits. METHODS: A 5.7mmx3.2mm band of S-PTFE (silicone-polytetrafluoroethylene, France Chirurgie Instruments) was used. A tight seal was produced between the two materials by silicone gluing. Eight eyes were implanted episclerally and fixed with Mersilene 5-0. One silicone band was used on a control eye. RESULTS: Three eyes were removed at 4 weeks, one at 8 weeks and four at 12 weeks. No extrusion was observed except for the silicone band rejected 2 weeks after implantation. On histopathologic examination, PTFE colonisation was present in all eyes with fibroblast, inflammatory cells, and neovascularization. CONCLUSION: The S-PTFE implant was colonized and well tolerated in rabbit eyes. Advantages of silicone band (quality, stability of indentation) are combined to the tolerance of PTFE.

Animals↗
PubMed2000

Inhibition of lens epithelial cell proliferation by substituted PMMA intraocular lenses.

BACKGROUND: Migration and proliferation of lens epithelial cells (LECs) are based on interactions between cellular integrins and extracellular matrix proteins (ECMs). We were able to design polymers substituted with COO- and SO3- groups that counteract LEC proliferation through modification of the integrin/ECM interaction. The objective of this study was to compare the cell proliferation-inhibiting properties of differently substituted copolymers with those of a homopolymer. METHODS: Polymers were synthesized by radical polymerization and characterized by nuclear resonance spectroscopy. Second-passage rabbit LECs were cultured either on PMMA homopolymers (control) or on substituted PMMA copolymers. Cells were counted on days 2, 7, and 17. Cell vitality was evaluated by trypan blue staining. Experiments were run in quadruplicate. Statistical analysis was performed using the Wilcoxon test and the Mann-Whitney U-test. RESULTS: Compared with control, cells cultured on copolymers grew to significantly lower cell numbers. The inhibitory effect became evident at day 2 after seeding and persisted throughout the experiment. Different ratios of COO-/SO3- substitutions yielded different grades of inhibition. No toxic effect was seen on rabbit LECs. CONCLUSIONS: The tested copolymers inhibit cell proliferation and are nontoxic. Further evaluation could lead to the development of new intraocular lens materials that prevent secondary cataract.

Animals↗
PubMed2000

A new mutation (A546T) of the betaig-h3 gene responsible for a French lattice corneal dystrophy type IIIA.

PURPOSE: To characterize the betaig-h3 gene defect in a French family affected with lattice corneal dystrophy type IIIA (LCDIIIA). METHODS: Histologic examination was performed from corneal buttons of two patients. Genomic DNA was extracted from leukocytes, and exons of the betaig-h3 gene were amplified by polymerase chain reaction to be directly sequenced. RESULTS: Numerous deposits were evident in the stroma and beneath the Bowman membrane, which had all the features of amyloid deposits. Analysis of exon 12 revealed a heterozygous G to A transition on codon 546. CONCLUSION: In contrast to Japanese patients, these French patients affected with LCDIIIA carry a distinct mutation of the betaig-h3 gene (A546T instead of P501T). Therefore, it is unclear whether different mutations could result in the same dystrophy or whether we are dealing with clinical heterogeneity of LCDIIIA.

Adult↗
PubMed2000

High-frequency ultrasound characterization of microporous biointegrable polymers in cornea using acoustic parameters.

The current work deals with the use of high-frequency quantitative backscatter acoustic microscopy for the evaluation of the biointegration of microporous polymer implants used as support of artificial cornea. A three-dimensional (3-D) 80 MHz ultrasound microscope (25 microns axial resolution at focus) was used for the imaging and characterization of the progressive biointegration of polymers implanted in rabbit cornea. In-vitro and in-vivo studies were performed. Quantitative assessment of the structural changes in the biomaterial was performed using the spectral analysis of the radio frequency signal and the estimation of acoustic parameters in the 10-65 MHz frequency bandwidth. Correlation of in-vitro ultrasound data with histologic findings has shown that attenuation and backscatter coefficients are sensitive to the changes in the polymer pore content with time. Our results obtained in vivo demonstrated that 3-D 80 MHz echography coupled with quantitative characterization provide a unique tool for the non-invasive and objective follow-up of the implant biointegration and should contribute to clinical management of artificial cornea.

Acoustics↗
PubMed2000

Clinical, histologic, and ultrastructural features of the corneal dystrophy caused by the R124L mutation of the BIGH3 gene.

OBJECTIVE: This study was designed to describe the clinical, histologic, and ultrastructural features of the corneal dystrophy associated with the R124L mutation of the BIGH3 gene. DESIGN: Retrospective clinical and histologic review of a new genetic mutation. PARTICIPANTS: Thirty-four patients from five unrelated French families with corneal dystrophy caused by the R124L mutation of the BIGH3 gene were studied at the clinical, histologic, and ultrastructural levels. Records of patients carrying this mutation were compared with those from three unrelated patients with corneal dystrophy of Bowman's layer (CDB) type 2 (R555Q mutation) and from three unrelated patients with classic corneal granular dystrophy (R555W mutation). INTERVENTION: The mutational genetic status of the BIGH3 gene was determined for each patient, and the histologic and ultrastructural data available after corneal graft were analyzed. MAIN OUTCOMES MEASURES: Genomic DNA was extracted from peripheral blood leukocytes. Exons 4 and 12 of the BIGH3 gene were amplified by the polymerase chain reaction (PCR), and the PCR products were directly sequenced. RESULTS: All 34 patients with the R124L mutation displayed the clinical, histologic, and electron microscopic features of the dystrophy previously described as a superficial variant of corneal granular dystrophy. Combining molecular genetics with clinical and histologic findings established a clear distinction between the R555Q and R555W dystrophies. CONCLUSIONS: The R124L mutation of the BIGH3 gene is associated with specific clinical and morphologic criteria. This indicates that molecular studies are needed for an adequate classification of corneal dystrophies. All criteria are presently available to segregate the dystrophy caused by the R124L mutation (known as CDB1) from the dystrophy caused by the R555Q mutation (known as CDB2).

Adult↗
PubMed2000

[Therapeutic photokeratectomy for the treatment of band keratopathy].

PURPOSE: This retrospective study was designed to investigate the therapeutic potential of phototherapeutic keratectomy (PTK) for the treatment of band keratopathy. PATIENTS AND METHODS: PTK was performed with the Excimed UV 200, (Summit Technology, Inc) on 27 eyes of 22 patients and with the Nidek EC5000 on 11 eyes of 10 patients with band keratopathy. Mean patient age was 57 years. The mean follow-up period was 19 months (ranged from 4 to 54 months). When possible, the change in best corrected visual acuity and spherical equivalent was evaluated at 6, 12, 18 and 24 months. RESULTS: Almost 90% of patients with smooth bands achieved visual improvement and 85% of patients with rough bands improved ocular discomfort. The mean hyperopic shift caused by tissue ablation was less than +2.0D after one year, for smooth bands. CONCLUSION: Excimer laser PTK is a safe and effective outpatient treatment and should be used as initial treatment for band keratopathy.

Corneal Diseases↗
PubMed2000

[Avellino dystrophy. Current diagnostic criteria].

We report a French family suffering from an Avellino corneal dystrophy diagnosed by using clinical, histological, ultrastructural and genetics findings. Our results indicate that direct corneal examination and routine histological examinations must always be associated with an assay for BIGH3 gene mutations to establish a modern and unambiguous diagnosis of a corneal dystrophy.

Adult↗
PubMed1999

Evaluation of teflon-coated intraocular lenses in an organ culture method.

An amorphous and transparent form of Teflon is proposed as a coating of polymethylmethacrylate (PMMA) intraocular lenses (IOLs), rendering them highly hydrophobic. We used an organ culture method to evaluate cell adhesion, proliferation, and migration on Teflon-coated IOLs. Corneal explants from 14-day-old chicken embryos were placed on a semisolid culture medium and covered with uncoated PMMA (n = 36) and Teflon-coated PMMA (n = 36) IOLs and two controls, Thermanox (n = 84) and latex (n = 36). After incubation (7 days at 37 degrees C), a digital imaging system was used to measure the areas of the cell migration layers on the materials. The cells were then removed with tripsin-ethylenediaminetetraacetic acid and the cells detached at times up to 75 min were counted (Coulter(R) Multisizer System). The values were used to construct a cell disconnecting curve for each material. The areas of cell migration layers on uncoated and Teflon-coated IOLs were significantly different (p <.05). Cell disconnecting curves demonstrated that cells adhered less strongly to Teflon-coated IOLs than to the other materials. This organ culture method demonstrated that the coating of PMMA IOLs with Teflon AF(R) is correlated with antiadhesive and antiproliferative properties.

Animals↗