Organ culture studies of coupled fetal cord and adult muscle from normal and dystrophic mice

The effect of the myotoxic agent iodoacetate on dystrophic mice 129/Re

Three groups of dystrophic and non-dystrophic mice 129/Re were used for studying the effect of the myotoxic agent iodoacetate on dystrophic muscle. The mice of the first group were given intramuscular injections of iodoacetate. The mice of the second group were injected with normal saline and the third group was maintained as untreated controls. The most severe histopathological changes were found in the dystrophic mice treated with iodoacetate. The non-dystrophic mice of the same group showed a significant increase in the number of internal nuclei. Moderate changes were observed in saline-treated dystrophic controls. There was no significant decrease in the life expectancy in any of the groups. The body weight of dystrophic mice was reduced throughout the experiment. On the contrary the non-dystrophic group showed an increased in weight, regardless of the treatment. The aggravation of the histopathological changes of dystrophic mice by iodoacetate would probably give support to the cyclical necrosis/abnormal regeneration theory of pathogenesis of muscular dystrophy.

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.

Differentiation in dystrophic muscle cultures from mice of different ages

Muscle from dystrophic (129 ReJ dy/dy) mice, aged 1, 2, 3, 4, and 6 months, was cocultured with normal embryonic mouse spinal cord. Cultures were scored for regeneration (myotubes) and differentiation (cross-striated or contracting fibers) over a 28-day period. Although muscle from dystrophic mice of all ages was able to regenerate, the ability to differentiate decreased with the increasing age of the mouse. Muscle from litter-mate control mice of different ages regenerated and differentiated equally well.

The application of organotypic nerve cultures to problems in neurology with special reference to their potential use in research into neuromuscular diseases

In organotypic nerve cell cultures there is production of central and peripheral myelin as well as synapse formation and long-term survival (months) of neuronal cell types and their associated glia. These cultures can be viewed continuously by light microscopy and are amenable to both electron microscopy and electrophysiology. Organotypic cultures have been used in studies of myelin formation and of demyelination by "toxic" sera, in the search for a neurotoxic factor in motor neurone disease and in studies of neurotrophic viruses. They have also been used to demonstrate the effects of toxins such as cyanide, lead, various industrial chemicals and neurotransmitter analogues (such as kainic acid) on myelin, axons and neurones in culture. They are currently being used in conjunction with small bundles of teased adult mammalian muscle fibres. Such bundles, cultured alone, do not regenerate. However, in the presence of various foetal tissues (neuronal or non-neuronal), the muscle regenerates to form new myotubes. Only in the presence of foetal spinal cord neurones will these myotubes differentiate further to form cross-striated, contracting muscle fibres. If the spinal cord tissue is removed when contractions have just begun, the muscle fibres revert to undifferentiated myotubes.

A quantitative assessment of dystrophic mouse (129 ReJ dy/dy) myogenesis in vitro

A quantitative assessment was made of the myogenic capability in vitro of muscle cells from dystrophic (129 Rej dy/dy) and normal mice from birth to 5 months old. Seeding efficiency was increased in dystrophic cells from neonatal and 1-week-old mice compared to age-matched controls. The extent of myogenesis in cultures from neonatal and 1-week-old dystrophic mice did not differ from controls. Muscle colony formation in cultures established from 5-month-old dystrophic mice was reduced by 80% compared with normal cultures. Normal and dystrophic cultures established from 5-month-old mice contained equal numbers of fibroblast colonies. The results suggest that decreased myogenesis in cultures from 5-month-old dystrophic mice is due to a relative absence of myogenic cells rather than a numerical dilution of the cultures by fibroblasts. This may be due to population of nonviable satellite cells or to necrosis of dystrophic myotubes in vitro.

An investigation of the influence of the extracellular environment on the regeneration of the normal and dystrophic mouse muscle in vitro

The regenerative response of normal and dystrophic muscle cultured with fetal spinal cord has been investigated. Nearly all the normal muscle explants regenerated, but the dystrophic muscle gave a much more varied response as only 30% regenerated, and 38% showed total explant degradation with loss of all recognisable muscle elements. Forty-five % of the dystrophic explants, produced 'pseudostraps' in which there was an apparent block of myoblast fusion. Cultures in which cellular contact between spinal cord tissue and the normal or dystrophic muscle was prevented showed less regeneration than when it was allowed. However, the incidence of regeneration in these cultures was much higher than when the muscle was cultured in isolation. Direct cellular contact between the cord and the muscle is, therefore, not necessary to initiate regeneration which is presumably mediated in these cultures by changes in the chemical environment. This is substantiated by the almost complete absence of regeneration in cultures of muscle alone, where the fibres were shown to be devoid of nuclei within 5 days. The experiments have shown that under our conditions, a myogenic defect is apparent in the dystrophic muscle. This does not exclude a possible neuronal involvement in the aetiology of the disease, although we have no evidence to support it.

Abnormalities of the sciatic nerves of dystrophic mice with reference to the large U-axons

A statistical study using regression analysis was used to evaluate the density of axonal organelles in dystrophic peripheral nerves. The slope of the density of neurotubules (NT) in myelinated (M-) axons was different from that in small unmyelinated (U-) axons. The slope of the density of NT in large U-axons (larger than 1.5 micron in diameter) was similar to that of the M-axons in both the dystrophic and control mice. There was a higher density of NT in the dystrophic M-axons than in the controls in the anterior, posterior and mixed nerves of the sciatic nerve. There was also a higher density of NT in the dystrophic small U-axons than in the controls. There was a higher density of neurofilaments (NF) of M-axons in the dystrophic mice than in the controls. On the contrary, the NF of small U-axons were lower in density in the dystrophic mice. These results were different from our previous reports, which were observed in the distal part, depending on when the groups of U-axons were divided (Okada, Mizuhira and Nakamura 1976a).

Growth of diseased human muscle in combined cultures with normal mouse embryonic spinal cord

Normal and diseased human muscle cells have been grown in combined cultures with 12-14 day embryonic mouse spinal cord explants. Nerve endings on myotubes were found by light and scanning electron microscopy, and motor end-plates were identified by a histochemical reaction for acetylcholinesterase. Contracting myotubes, never observed in cultures of human muscle alone, were found in a culture from normal muscle. Histochemical studies demonstrated the presence of strongly and weakly reacting myotubes for both ATPase pH 9.4 and NADH-TR, but could not be related to the development of fibre types. No differences in morphology or histochemical reactions were found between normal and diseased muscle cells in these combined cultures.

Neural abnormalities in the dystrophic mouse

Neural abnormalities (area of amyelination) have been found in the cranial nerves and in the ventral cervical and lumbosacral roots and in the mixed spinal nerves of bar harbor dystrophic mice of both the severe (129 Re/J dy/dy) and benign (dy-2J DY-2J) forms. The significance of these findings is discussed.