Malin Sund

Adhesion of soluble fibronectin, vitronectin, and collagen type IV to intraocular lens materials ☆

Purpose: To evaluate soluble fibronectin, vitronectin, and collagen type IV adhesion to poly(methyl methacrylate) (PMMA), fluorine‐surface‐modified PMMA, silicone, hydrophobic and hydrophilic acrylate, and hydrogel intraocular lenses (IOLs) and determine whether hydrophobic and hydrophilic acrylate materials have different fibronectin‐adhesion properties. Setting: Department of Medical Biochemistry, University of Oulu, Oulu, Finland. Methods: One hundred fifty IOLs were incubated for 1 week at 37°C with radioactive‐iodine‐labeled soluble fibronectin, vitronectin, or collagen type IV. Fifty IOLs were analyzed for each protein, 5 from each of 10 different IOL models (PMMA, Alcon MC60BM; fluorine‐surface‐modified PMMA, Chiron Fluorilens Centra‐55F; silicone, Allergan Medical Optics SI‐40NB and Pharmacia & Upjohn CeeOn® 911A; hydrophobic soft acrylate, Alcon AcrySof® MA60BM and SA30AL and AMO® Sensar®; hydrophilic soft acrylate, Ioltech Stabibag and Bausch & Lomb BL27; and hydrogel, Bausch & Lomb Hydroview®). The amount of adherent protein was measured with a gamma counter at 1 and 7 days and expressed as counts per minute. Results: At 1 week, significantly more fibronectin was bound to the hydrophobic acrylate IOLs than to the 2‐hydroxyethyl methacrylate (HEMA) containing hydrophilic acrylate IOLs (P < .05 to .0001). Significantly more vitronectin was bound to the 2 silicone IOLs than to any other IOL (P < .01 to .0001) at 7 days. Collagen type IV adhered best to the hydrophilic acrylate IOLs, which were significantly different (P < .01 to .0001) than the other IOLs at 1 and 7 days. Conclusions: Each IOL material had a different affinity to each protein. Significant binding to 1 protein does not indicate that the IOL will bind significantly to all proteins; instead, each protein should be studied separately. Fibronectin bound significantly better to hydrophobic acrylate IOLs than to hydrophilic acrylate IOLs, suggesting that the HEMA‐containing IOLs should be classified with the hydrogel IOL group.

Lack of Cytosolic and Transmembrane Domains of Type XIII Collagen Results in Progressive Myopathy

Type XIII collagen is a type II transmembrane protein found at many sites of cell adhesion in tissues. Homologous recombination was used to generate a transgenic mouse line (Col13a1(N/N)) that expresses N-terminally altered type XIII collagen molecules lacking the short cytosolic and transmembrane domains but retaining the large collagenous ectodomain. The mutant molecules were correctly transported to focal adhesions in cultured fibroblasts derived from the Col13a1(N/N) mice, but the cells showed decreased adhesion when plated on type IV collagen. These mice were viable and fertile, and in immunofluorescence stainings the mutant protein was located in adhesive tissue structures in the same manner as normal alpha1(XIII) chains. In immunoelectron microscopy of wild-type mice type XIII collagen was detected at the plasma membrane of skeletal muscle cells whereas in the mutant mice the protein was located in the adjacent extracellular matrix. Affected skeletal muscles showed abnormal myofibers with a fuzzy plasma membrane-basement membrane interphase along the muscle fiber and at the myotendinous junctions, disorganized myofilaments, and streaming of z-disks. The findings were progressive and the phenotype was aggravated by exercise. Thus type XIII collagen seems to participate in the linkage between muscle fiber and basement membrane, a function impaired by lack of the cytosolic and transmembrane domains.

Distinct expression of type XIII collagen in neuronal structures and other tissues during mouse development

Type XIII collagen is a type II transmembrane protein found in adhesive structures of mature tissues. We describe here its expression and spatio-temporal localization during mouse fetal development. Type XIII collagen mRNAs were expressed at a constant rate during development, with an increase of expression towards birth. Strong type XIII collagen expression was detected in the central and peripheral nervous systems of the developing mouse fetus in mid-gestation. Cultured primary neurons also expressed this collagen, and it was found to enhance neurite outgrowth. The results suggest that type XIII collagen is a new member among the proteins involved in nervous system development. Strong expression during early development was also detected in the heart, with localization to cell-cell contacts and accentuation in the intercalated discs perinatally. During late fetal development, type XIII collagen was observed in many tissues, including cartilage, bone, skeletal muscle, lung, intestine and skin. Clear developmental shifts in expression suggest a role in endochondral ossification of bone and the branching morphogenesis in the lung. Notable structures lacking type XIII collagen were the endothelia of most blood vessels and the endocardium. Its initially unique staining pattern began to concentrate in the same adhesive structures where it exists in adult tissues, and started to resemble that of the beta1 integrin subunit and vinculin during late intrauterine development and in the perinatal period.

ArticlesAdhesion of soluble fibronectin, laminin, and collagen type IV to intraocular lens materials12☆

PURPOSE To evaluate soluble fibronectin, laminin, and collagen IV adhesion to poly(methyl methacrylate) (PMMA), heparin-surface-modified (HSM) PMMA, silicone, acrylate, and hydrogel intraocular lenses (IOLs). SETTING Department of Medical Biochemistry, University of Oulu, Oulu, Finland. METHODS Seventy-five IOLs were incubated for 24 hours at 37 degrees C with radioactive iodine labeled soluble fibronectin, laminin, or collagen type IV. Twenty-five IOLs were analyzed for each protein, 5 of each type. The amount of absorbed protein was measured with a gamma counter and expressed as counts per minute (cpm). RESULTS Fibronectin bound best to the acrylate IOL; the differences between the acrylate and the other materials, except PMMA, were significant (P < .01 to .001; PMMA P = .31). Although significantly more laminin bound to acrylate than to PMMA, HSM PMMA, or silicone (P < .05 to .001), hydrogel had the highest overall binding of this protein (P < .001 to .0001). Hydrogel also had significantly higher binding of type IV collagen than the other IOLs (P < .01 to .0001). CONCLUSIONS It can be hypothesized that if an IOL has more fibronectin bound to it, the IOL can also attach to the capsule better as it consists mainly of collagen. The stronger binding of fibronectin and laminin to acrylate IOLs could be an explanation for the better adhesion of the acrylate IOL to the anterior and posterior capsules and thus for the lower rate of posterior capsule opacification.

Abnormal adherence junctions in the heart and reduced angiogenesis in transgenic mice overexpressing mutant type XIII collagen

Type XIII collagen is a type II transmembrane protein found at sites of cell adhesion. Transgenic mouse lines were generated by microinjection of a DNA construct directing the synthesis of truncated α1(XIII) chains. Shortened α1(XIII) chains were synthesized by fibroblasts from mutant mice, and the lack of intracellular accumulation in immunofluorescent staining of tissues suggested that the mutant molecules were expressed on the cell surface. Transgene expression led to fetal lethality in offspring from heterozygous mating with two distinct phenotypes. The early phenotype fetuses were aborted by day 10.5 of development due to a lack of fusion of the chorionic and allantoic membranes. The late phenotype fetuses were aborted by day 13.5 of development and displayed a weak heartbeat, defects of the adherence junctions in the heart with detachment of myofilaments and abnormal staining for the adherence junction component cadherin. Decreased microvessel formation was observed in certain regions of the fetus and the placenta. These results indicate that type XIII collagen has an important role in certain adhesive interactions that are necessary for normal development.

Type XIII Collagen Strongly Affects Bone Formation in Transgenic Mice

To characterize the function of type XIII collagen, a transmembrane protein occurring at cell adhesion sites, we generated transgenic mice overexpressing it. High transgene expression was detected in cartilage and bone. The overexpression mice developed an unexpected skeletal phenotype marked by a massive increase in bone mass caused by increased bone formation rather than impaired resorption.