[Study of the results scleral-fixated intraocular lenses in the absence of capsular support]. / Étude des résultats de l'implantation fixée à la sclère en l'absence de plan capsulaire.

INTRODUCTION: In the absence of sufficient capsular support, scleral fixation of the intraocular lens is an interesting alternative. The goal is to evaluate this implantation technique when traditional implantation is impossible. PATIENTS AND METHODS: This is an observational, retrospective, monocentric study at the Amiens university medical center between August 2013 and March 2016. Patients all underwent scleral fixation of a three-piece implant without suturing of the haptics, after posterior vitrectomy. All patients requiring implantation in the absence of stable capsular support were included. Patients with adequate iris or capsular support were excluded from our study. RESULTS: Eighteen patients were included, with an average age of 69.3±16.9 years. The surgical indications were: complicated surgery, trauma and endothelial decompensation. The preoperative mean corrected visual acuity was 1.2±0.4 LogMAR while the postoperative acuity was 0.7±0.5 LogMAR. The mean postoperative corneal astigmatism was 1.9±1.9 diopters. The main complications observed were ocular hypertension, macular edema, retinal detachment, iris incarceration and exteriorization of the haptic. DISCUSSION: There are two alternatives when faced with lack of a sufficient capsular support: scleral fixation or iris fixation. Our technique is the only one achievable in the presence of iris atrophy. Furthermore, it induces less astigmatism and enables the repositioning of a three-piece implant dislocated into the vitreous. CONCLUSION: Scleral fixation is a technique allowing both a satisfactory and a lasting functional result and is to be considered when faced with a lack of sufficient capsular support.

Oval cell proliferation in early stages of hepatocarcinogenesis in simian virus 40 large T transgenic mice.

In transgenic mice bearing the Simian Virus 40 large T antigen under the control of the human antithrombin III regulatory sequences, a stepwise progression toward hepatocellular carcinoma is observed. We have used two monoclonal antibodies (A6 and G7) developed against a surface antigen expressed in oval cells from dipin-treated mice, to analyze the emergence of such preneoplastic populations in the livers of antithrombin III Simian Virus 40 T transgenic mice. We show that a unique population of small heterogeneous epithelial cells, which probably corresponds to oval and/or transitional cells according to their morphological features, consistently appears at approximately the 10th week after birth and proliferates thereafter. This oval cell-like population stained positively for A6 and G7 monoclonal antibodies. Furthermore, different subpopulations usually recognized as possible precursors of carcinoma cells including hyperplastic foci and neoplastic nodules as well as carcinoma cells, were also positive for A6 but not G7 monoclonal antibodies. Stimulation of cell proliferation by partial hepatectomy performed at the time of emergence of the oval-like cells resulted in a rapid increase in the number of oval/transitional A6-positive cells. Our findings support the view that a common mechanism may be involved in the development of carcinomas that are induced by chemical carcinogens and in transgenic mice expressing a potent oncogene under the control of a hepatic specific promoter. In addition, our findings demonstrate a specific precursor-product relationship between the appearance of the oval/transitional cells and the development of neoplastic hepatocytes in this transgenic model.

Retroviral infection of primary hepatocytes from normal mice and mice transgenic for SV40 large T antigen.

Cultured adult rodent hepatocytes are extensively used as a model system for gene transfer in vitro. In the present study, we examined the influence differentiation status and growth capacity of the hepatocytes on their infectivity in vitro by a retroviral vector. These parameters were initially studied in primary cultures of rat hepatocytes transduced with an ecotropic retroviral vector containing Escherichia coli beta-galactosidase. However, significant differences observed in the infectivity of hepatocytes from 12-day-old and adult rats led us to also examine hepatocytes from a transgenic mouse strain in which the SV40 large T antigen is fused to the regulatory sequences of the human anti-thrombin III gene. The large T antigen is expressed in the liver and these mice develop hepatoma within 7 months. A comparison of infectivity of hepatocytes from normal and transgenic mice of different ages indicated that in contrast to previous reports, hepatocytes which express differentiated functions during the first week of culture can still be efficiently infected by retroviral vectors. Optimal infection was observed between the second and fourth day of culture and does not appear to be due to transient cell dedifferentiation, but is more likely due to transient mitotic activity of mice cells since the role of growth factors seems crucial for infection. The peak of infection did not appear to correspond to transient cell dedifferentiation. We also found differences of infectivity between hepatocytes from normal and transgenic mice of different ages. Such differences are correlated with differences in in vitro BrdU incorporation, which was used to determine the proportion of dividing hepatocytes. These results indicate that the efficiency of infectivity of hepatocytes by recombinant retrovirus is probably related to their normal proliferative potential and not to some dedifferentiated stage. Hence these findings provide a model for efficient gene transfer in differentiated cells and suggest an approach for studies of liver-specific gene regulation and for somatic gene therapy of metabolic diseases as well.

Retroviral-mediated transfer and expression of human beta-globin genes in cultured murine and human erythroid cells.

We have cloned human beta-globin DNA sequences from a genomic library prepared from DNA isolated from the human leukemia cell line K562 and have used the retroviral vector pZip-NeoSV(X)1 to introduce a 3.0-kilobase segment encompassing the globin gene into mouse erythroleukemia cells. Whereas the endogenous K562 beta-globin gene is repressed in K562 cells, when introduced into mouse erythroleukemia cells by retroviral-mediated gene transfer, the beta-globin gene from K562 cells was transcribed and induced 5-20-fold after treatment of the cells with dimethyl sulfoxide. The transcripts were correctly initiated, and expression and regulation of the K562 gene were identical to the expression of a normal human beta-globin gene transferred into mouse erythroleukemia cells in the same way. We have also introduced the normal human beta-globin gene into K562 cells using the same retrovirus vector. SP6 analysis of the RNA isolated from the transduced cells showed that the normal beta-globin gene was transcribed at a moderately high level, before or after treatment with hemin. Based on these data, we suggest that the lack of expression of the endogenous beta-globin gene in K562 cells does not result from an alteration in the gene itself and may not result from a lack of factor(s) necessary for beta-globin gene transcription. Retroviral-mediated transfer of the human beta-globin gene may, however, uniquely influence expression of the gene in K562 cells.

Regulated expression of a complete human beta-globin gene encoded by a transmissible retrovirus vector.

We introduced a human beta-globin gene into murine erythroleukemia (MEL) cells by infection with recombinant retroviruses containing the complete genomic globin sequence. The beta-globin gene was correctly regulated during differentiation, steady-state mRNA levels being induced 5- to 30-fold after treatment of the cells with the chemical inducer dimethyl sulfoxide. Studies using vectors which yield integrated proviruses lacking transcriptional enhancer sequences indicated that neither retroviral transcription nor the retroviral enhancer sequences themselves had any obvious effect on expression of the globin gene. Viral RNA expression also appeared inducible, being considerably depressed in uninduced MEL cells but approaching normal wild-type levels after dimethyl sulfoxide treatment. We provide data which suggest that the control point for both repression and subsequent activation of virus expression in MEL cells lies in the viral enhancer element.