Inverse computational analysis of in vivo corneal elastic modulus change after collagen crosslinking for keratoconus

Corneal collagen crosslinking with riboflavin photosensitization and ultraviolet irradiation is a novel approach to limiting the progression of keratoconus in patients by increasing the elastic modulus of the degenerate cornea. Beneficial reductions in corneal steepness and aberrations after crosslinking also frequently occur. In a previous study, we described a computational modeling approach to simulating topographic progression in keratoconus and regression of disease with corneal collagen crosslinking. In the current study, this model has been expanded and applied to the inverse problem of estimating longitudinal time-dependent changes in the corneal elastic modulus after crosslinking using in vivo measurements from 16 human eyes. Topography measured before crosslinking was used to construct a patient-specific finite element model with assumed hyperelastic properties. Then the properties of the cornea were altered using an inverse optimization method to minimize the difference between the model-predicted and in vivo corneal shape after crosslinking. Effects of assumptions regarding sclera-to-cornea elastic modulus ratio and spatial attenuation of treatment effect due to ultraviolet beam characteristics on the predicted change in elastic modulus were also investigated. Corneal property changes computed by inverse finite element analysis provided excellent geometric agreement with clinical topography measurements in patient eyes post-crosslinking. Over all post-treatment time points, the estimated increase in corneal elastic modulus was 110.8 ± 48.1%, and slightly less stiffening was required to produce the same amount of corneal topographic regression of disease when the sclera-to-cornea modulus ratio was increased. Including the effect of beam attenuation resulted in greater estimates of stiffening in the anterior cornea. Corneal shape responses to crosslinking varied considerably and emphasize the importance of a patient-specific approach.

High frequency of submicroscopic chromosomal imbalances in patients with syndromic craniosynostosis detected by a combined approach of microsatellite segregation analysis, multiplex ligation-dependent probe amplification and array-based comparative genome hybridisation

We present the first comprehensive study, to our knowledge, on genomic chromosomal analysis in syndromic craniosynostosis. In total, 45 patients with craniosynostotic disorders were screened with a variety of methods including conventional karyotype, microsatellite segregation analysis, subtelomeric multiplex ligation-dependent probe amplification) and whole-genome array-based comparative genome hybridisation. Causative abnormalities were present in 42.2% (19/45) of the samples, and 27.8% (10/36) of the patients with normal conventional karyotype carried submicroscopic imbalances. Our results include a wide variety of imbalances and point to novel chromosomal regions associated with craniosynostosis. The high incidence of pure duplications or trisomies suggests that these are important mechanisms in craniosynostosis, particularly in cases involving the metopic suture.

Generation of myc/fos transfectant Balb-3T3 cell lines

Early and transient expression of proto-oncogenes c-fos and c-myc is involved in the mitogenic response to PDGF (platelet-derived growth factor). We used DNA-mediated transfection to approach the role played by these genes in cell growth control by PDGF and in growth deregulation (neoplasia). Cloned pFBJ-2 (v-fos) and glucocorticoid-inducible mouse c-myc were co-transfected with a neo genetic marker to allow a neutral selection on the basis of resistance to the neomycin derivative geneticin G418. pFBJ-2 transfection was found to interfere with the number of G418-resistant (G418r) colonies. By using a v-fos-deleted pFBJ-2 construct, the deleterious effect was attributed to v-fos coding sequences. Cellular fos gene disruption, by homologous recombination with exogenous v-fos, is proposed as the basis for the deleterious effect. Co-transfection with MMTV-H3-c-myc effectively counteracts the negative effects of v-fos. Different from the parental line or single myc or fos transfectants, double myc/fos transfectants are morphologically transformed. Double transfectants still retain the PDGF requirement for growth in monolayer cultures.