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Biomedical subjects

G Renard

Publications and source records attributed to G Renard.

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

Three-dimensional supramolecular organization of the extracellular matrix in human and rabbit corneal stroma, as revealed by ultrarapid-freezing and deep-etching methods.

The present work was carried out to clarify the three-dimensional fine structure of extracellular matrix in the cornea, using ultrarapid-freezing and deep-etching methods for electron microscopy. Fresh and glutaraldehyde-fixed samples of human and rabbit posterior corneas were ultrarapidly-frozen onto a copper block cooled by liquid helium or liquid nitrogen, freeze-fractured, deeply etched for 8-10 min and rotary replicated with platinum-carbon. Replicas were examined in a transmission electron microscope equipped with a tilting device. Only structures with repeatedly observed, similar architectural profiles free from ice crystal damage, were taken into account. The very recognizable major collagen fibrils revealed 8-10 nm subfibrils running helically along the fibril long axis. The other extracellular matrix components consisted of: (1) 8-12 nm interfibrillar bridging filaments, frequently ornamented with globular domains, joining neighbouring collagen fibrils like steps of a ladder; (2) 10-20 nm filaments with relatively large globular domains, running on the surface of collagen fibrils along their long axes, and projecting finger-like structures into interfibrillar spaces sometimes attaching to adjacent collagen fibrils; (3) 10-15 nm beaded filaments with a periodicity of 75-110 nm, forming extended networks, especially at the interlamellar interfaces; and (4) 8-14 nm straight or sinuous strands consisting of 4-6 nm repeating subunits or modules, forming extended sheets by lateral association at the Descemet's membrane/stroma interface. In the light of the information available from studies on the localization of extracellular matrix components in the cornea, and by reference to the structural models of extracellular matrix molecules and macromolecular assemblies, we have related the deep-etched extracellular matrix structures described above to: (1) proteoglycans; (2) fibril-associated collagens with interrupted triple helices or FACIT collagens; (3) type VI collagen; and (4) fibronectin, respectively.

Animals↗
PubMed2001

Silicone punctal plug extrusion resulting from spontaneous dissection of canalicular mucosa: A clinical and histopathologic report.

PURPOSE: To report on an uncommon, previously unidentified, progressive silicone punctal plug extrusion. DESIGN: Small, retrospective case series. PARTICIPANTS: Five cases of punctal plug extrusion were identified among a series of 424 consecutive implantations. Histopathologic analysis was obtained in one case. One additional referred case was included in this report. RESULTS: The plugs were completely extruded from the punctal lumen 6 to 14 months after insertion after an otherwise uncomplicated postoperative course. All plugs were retained at the punctal margin by an encircling band of vascularized mucosal tissue originating from the canalicular lumen. The band consisted of connective tissue of canalicular mucosal origin, attached just below the junction of the punctal and canalicular epithelium. Mild mononuclear infiltration was present in the connective tissue component of the punctal region. There was no cytologic or architectural evidence of abnormal epithelium or connective tissue or of pyogenic granuloma. CONCLUSIONS: These observations suggest that progressive lacrimal punctal plug extrusion may relate to mucosal dissection by the plug edges. We speculate that mechanical stress induced by eyelid closure on an improperly sized or placed implant may result in plug tilt. Subsequent epithelial hyperplasia further enhances the tilt, and the sharper edge of the conical bulb promotes separation of the canalicular mucosa from its distal luminal aspect. At the completion of the extrusion, the mucosal surface is separated from its connective tissue base, at a proximal subpunctal level, causing formation of an encircling tissue band.

Adult↗
PubMed2001

Histologic phenotype-genotype correlation of corneal dystrophies associated with eight distinct mutations in the TGFBI gene.

PURPOSE: To establish a phenotype-genotype correlation of various autosomal-dominant corneal dystrophies among French subjects. DESIGN: Retrospective molecular genetic study and clinicopathologic correlation. PARTICIPANTS: Forty-four subjects from 26 unrelated French families were included in this study, and 60 corneal buttons could be examined at the histologic and ultrastructural levels. METHODS: Light microscopy and transmission electron microscopy were performed on corneal specimens obtained during keratoplasty. Blood samples were collected for DNA analysis. MAIN OUTCOME MEASURES: After genomic DNA extraction from peripheral blood leukocytes of each family member, exons of the TGFBI gene were amplified by polymerase chain reaction (PCR), and the PCR products were directly sequenced on both strands. RESULTS: Four different mutations were found to be responsible for dystrophy of granular type (R555W, R124L, R124H, and R124L+delT125-delE126), three other different mutations produced a lattice type (R124C, H626R, and A546T), and the last mutation identified was associated with the honeycomb-shaped dystrophy (R555Q). Each subtype of dystrophy showed, histologically and ultrastructurally, specific characteristics that are easily recognizable. However, besides these stereotyped forms, differential histologic diagnosis of atypical forms remains difficult, and these forms could be misdiagnosed. CONCLUSIONS: The characteristic biomicroscopic appearance and histopathologic features of each "classic" dystrophy present a significant degree of specificity and generally provide an accurate diagnosis. However, atypical forms in which clinical and histologic data alone could be misleading, are unequivocally diagnosed after DNA analysis.

Cornea↗
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

Methylprednisolone concentrations in the vitreous and the serum after pulse therapy.

PURPOSE: Intravenous (i.v.) pulse of corticosteroids has been used to treat severe eye inflammation from different origins. Whether such large doses result in vitreous levels that differ either in magnitude or duration from more conventional corticotherapy remain unsolved issues. The authors therefore determined levels of methylprednisolone hemisuccinate and methylprednisolone in the vitreous and serum of patients at different times after a single i.v. perfusion of methylprednisolone hemisuccinate. METHODS: Fifty patients scheduled for a first vitrectomy received an i.v. injection of 500 mg hemisuccinate methylprednisolone at different times before surgery (from 15-24 hours). Patients were divided into two groups: those with (n = 21) and without (n = 29) retinal detachment (RD). Pure vitreous samples were analyzed by high-pressure liquid chromatography. RESULTS: Both the ester and the nonester methylprednisolone forms were sampled in the vitreous, showing a slower rate of hydrolysis compared to the serum. On average, the highest concentration of total methylprednisolone in the vitreous was found at 2.5 hours and rapidly decreased for the group of patients with RD. In the group of patients without RD, the highest concentration was reached at 6 hours and then slowly decreased. The antiinflammatory potency in the nondetached retina eyes was approximately 500 times more than in the physiologic vitreous, but despite the route of administration (i.v. or oral), only 1/10 of the corticosteroid serum concentration was measured in the vitreous. CONCLUSION: High concentration of methylprednisolone is achieved by i.v. pulse therapy without changing the kinetic of entry in the vitreous of nondetached retina eyes when compared to conventional oral corticotherapy. Hydrolysis occurs in the vitreous resulting in high rate of active form. Pulse therapy could be considered in cases of severe ocular inflammation involving the posterior segment of the eye.

Adolescent↗
PubMed2001

A new poly(ortho ester)-based drug delivery system as an adjunct treatment in filtering surgery.

PURPOSE: Pharmacologic modulation of wound healing after glaucoma filtering surgery remains a major clinical challenge in ophthalmology. Poly(ortho ester) (POE) is a bioerodible and biocompatible viscous polymer potentially useful as a sustained drug delivery system that allows the frequency of intraocular injections to be reduced. The purpose of this study was to determine the efficacy of POE containing a precise amount of 5-fluorouracil (5-FU) in an experimental model of filtering surgery in the rabbit. METHODS: Trabeculectomy was performed in pigmented rabbit eyes. An ointmentlike formulation of POE containing 1% wt/wt 5-FU was injected subconjunctivally at the site of surgery, during the procedure. Intraocular pressure (IOP), bleb persistence, and ocular inflammatory reaction were monitored until postoperative day 30. Quantitative analysis of 5-FU was performed in the anterior chamber. Histologic analysis was used to assess the appearance of the filtering fistula and the polymer's biocompatibility. RESULTS: The decrease in IOP from baseline and the persistence of the filtering bleb were significantly more marked in the 5-FU-treated eyes during postoperative days 9 through 28. Corneal toxicity triggered by 5-FU was significantly lower in the group that received 5-FU in POE compared with a 5-FU tamponade. Histopathologic evaluation showed that POE was well tolerated, and no fibrosis occurred in eyes treated with POE containing 5-FU. CONCLUSIONS: In this rabbit model of trabeculectomy, the formulation based on POE and containing a precise amount of 5-FU reduced IOP and prolonged bleb persistence in a way similar to the conventional method of a 5-FU tamponade, while significantly reducing 5-FU toxicity.

Animals↗
PubMed2001

[Neovascular glaucoma following proton-beam therapy. Case report].

A 52-year-old-male patient was treated for a posterior choroid melanoma of the right eye. When it was diagnosed, it measured 6mm in thickness and 11.9mm for the largest diameter and had a typical mushroom shape. General investigations found no metastatic disease. It was treated with proton-beam irradiation. Seven years later, the patient experienced increased intraocular pressure associated with cataract and pain. The patient finally accepted enucleation, as the vision of this eye was completely lost and the eye had become painful. Histologic analysis of the eye showed changes affecting both the anterior and the posterior segments of the eye, mostly related to the tumor and the consequences of treatment. Neovascular glaucoma is a major complication that very often leads to enucleation.

Cataract↗
PubMed2001

[Papillomatous and nevus of the caruncle].

A 63-year-old male patient was operated of a single conjunctival papillomatous lesion located on the left caruncle. The curative tumoral excision was followed by its histological analysis. Histologically, the tumor associated an epithelial squamous papilloma with a subepithelial nevus, confirming a combination of two different lesions.

Conjunctiva↗
PubMed2001

[Retinal lesion due to an obstetrical traumatism: a case report].

The authors report a case of unilateral, stable, localized, and well-circumscribed choriocapillaris atrophy associated with retinal pigment epithelium dispersion and atrophy. The anterior segment was normal. Facial examination revealed a homolateral malar hypoplasia. The other eye was normal. The electrophysiologic study did not confirm pigmentary degeneration of the retina. The patient's history included a difficult delivery using obstetrical forceps. The authors review the main ocular lesions secondary to birth trauma. In this case, they favored a traumatic chorioretinal lesion secondary to an obstetrical traumatism. In this context, progressive facial hemiatrophy is the main differential diagnosis.

Atrophy↗