Fibroblast clones for detection of Duchenne carriers

Tissue culture studies of muscle disorders: Part 2. Biochemical studies, nerve-muscle culture, metabolic myopathies, and animal models

This review continues with studies of protein, lipid, and purine metabolism of Duchenne muscular dystrophy (DMD) cells in vitro and of muscle cells in combined culture with nerve cells. In vitro studies of human metabolic myopathies are tabulated. Results using the hamster, chicken, and mouse (dy25, dy, mdg, and mdx) myopathies are discussed. Interesting findings include suggestions of altered collagen synthesis by DMD cells. Analysis of cell proteins by two-dimensional gel electrophoresis and the use of combined nerve-muscle cultures remain important areas of development. It is disappointing that so few attempts have been made to repeat significant findings in this field, and when a number of laboratories have examined the same phenomenon, the results are often contradictory. It remains to be shown how these various abnormalities found in cells in vitro are related to each other and to those pathologic features of diseased muscle observed in vivo.

Adhesive interactions between normal and dystrophic human skin fibroblasts

The adhesive properties of skin fibroblasts from patients with Duchenne muscular dystrophy (DMD) were studied by analysing cell aggregate formation in suspensions consisting of normal and DMD fibroblasts. By the use of aggregation kinetics and fluorescent labelling, the genotypic composition of aggregates in mixed-cell suspensions could be visualised. The distribution of normal and DMD cells within these aggregates could then be compared to theoretical binomial distributions which assume no difference in the specific adhesiveness between the two genotypes. Analysis of the 3- and 4-cell aggregates which were produced by co-aggregating normal and DMD cells demonstrate that there is no qualitative (specific) difference in the adhesiveness between normal and DMD fibroblasts. However, quantitative changes in the cell-cell adhesion of DMD fibroblasts may be present, and this is supported by the relatively small proportion of intermediate size heterotypic aggregates which were formed in mixed-genotype cell suspensions. In such mixtures, fewer aggregates consisting of 5 or more cells were formed compared to fibroblast suspensions derived from pairs of normal individuals. Furthermore, cell suspensions from pairs of DMD patients produced even less greater than or equal to 5-cell aggregates than were found in the mixed-genotype experiments. These findings are considered in relation to previous reports of abnormal cell adhesiveness and other adhesion-related mechanisms in DMD cells.

Cell surface abnormality in clones of skin fibroblasts from a carrier of Duchenne muscular dystrophy

We have previously reported that skin fibroblasts from patients with Duchenne muscular dystrophy (DMD) have a lower intercellular adhesiveness than control cells, and that cells from carriers of DMD have normal adhesiveness instead of the expected intermediate value. We have now cloned skin fibroblasts from a carrier of DMD (subject AS) who is also heterozygous for G6PD B/G6PD Mediterranean and determined the intercellular adhesiveness and G6PD phenotypes of the clones. G6PD activity was determined using the 2d-G6P/G6P ratio method. Normal cells had a percentage utilisation of 7.31% and uncloned cells from AS a value of 25.16%. Of 16 clones, 15 had normal values (mean 8.72%) while one clone was G6PD Med with a value of 57.5%. Mean intercellular adhesiveness of normal and uncloned cells from AS were 2.95 and 2.90 respectively. Of 11 clones tested, nine had normal values of adhesiveness (mean 3.1) and all these clones were G6PD B. The single G6PD Med clone had a value of 0.88, compared with 1.39 for DMD cells. We have no explanation at present for the single clone that was G6PD B but DMD-like on aggregation.

Monensin-induced inhibition of cell spreading in normal and dystrophic human fibroblasts

Cultured skin fibroblasts from normal individuals and from patients with Duchenne muscular dystrophy spread equally rapidly when seeded on a glass substratum. Exposure to the ionophore monensin substantially suppresses normal and dystrophic fibroblast spreading in serum-free media for up to at least 100 min. Preincubation of normal fibroblasts with monensin causes a further reduction in cell spreading. Dystrophic fibroblasts fail to spread as well as normal cells after monensin preincubation. Such findings indicate that there is a delay in the secretion of functional adhesive surface proteins in monensin-preincubated normal fibroblasts and that this lag period is significantly longer in dystrophic fibroblasts. These data are consistent with findings of altered adhesive and secretory properties of fibroblasts from patients with Duchenne muscular dystrophy.