mdx mice show progressive weakness and muscle deterioration with age

JOURNAL

OF THE

NEUROLOGICAL SCIENCES

ELSEVIER

Journal of the Neurological Sciences 129 (1995) 97-105

rn& mice show progressive weakness and muscle deterioration with age Christian Pastoret I, Alain Sebille * Laboratoire

de Physiologic,

Faculte’

de MLdecine

Saint-Antoine,

27 rue de Chaligny,

75571 Paris Gdex

12, France

Received 28 December 1993; revised 2 November 1994; accepted 6 November 1994

Abstract The time-course of degeneration/regeneration was investigated in leg muscles throughout the life of the r&.x mutant mouse, which is a biochemical homologue of Duchenne muscular dystrophy (DMD). In young and adult mice (up to 52 weeks old), muscle fibre necrosis was compensated by a vigorous regeneration, but in old mdr mice (65-104 weeks) this regeneration slightly declined, while the necrotic process persisted. Body and muscles weights declined strikingly after 52 weeks. Life span of mdx mutants was reduced in comparison with the control C57BL/lO animals. Immunostaining of old mdx muscles showed clusters of dystrophin-positive fibres. Muscle fibres in old mdx mice showed great variation in size, many being atrophied or split. Endomysial fibrosis became increasingly conspicuous, and there was some accumulation of adipose tissue. These progressive degenerative changes of old mak mice resemble those found in DMD and imply that basic pathological similarities between the murine and human diseasespreviously observedin diaphragmof mdx mice may be extended to other skeletal muscles. Keywords:

mdx

mouse; Muscular

dystrophy;

Skeletal muscle; Necrosis; Regeneration;

1. Introduction The mdu mutant (X-linked muscular dystrophy) was initially identified in a colony of C57BL/lOScSn mice on the basis of elevated levels of pyruvate kinase in serum and histological lesions suggestive of a muscular dystrophy (Bulfield et al., 1984). Further genetic studies showed that the affected murine gene was homologous with the gene involved in Duchenne muscular dystrophy (DMD), and that a sarcolemmal protein, dystrophin, was lacking in both human and the murine diseases(Hoffman et al., 1987; Sicinski et al., 1989). Schmalbruch (1982) defined the muscular dystrophies as “a group of genetically determined disorders which cause progressive weakness and wasting of skeletal muscles”, but early investigators of the mdu mouse were struck by the regenerative response to muscle necrosis, leading to full replacement of muscle mass

40

* Corresponding 01 14 99.

author. Tel.: (+33-l)

43 42 10 87; Fax: (+33-l)

1 Present address: Muscle Cell Biology Group, MRC Clinical Sciences Centre, Royal Postgraduate Medical School, Hammersmith Hospital, Du Cane Road, London W12 ONN, UK.

0022-510X/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI 0022-5 10X(94)00276-2

Fibrosis;

Dystrophin

with little endomysial fibrosis (Carnwath and Shotton, 1987; Torres and Duchen, 1987; Coulton et al., 1988; Marshall et al., 1989). This contrasts with the impaired regeneration and the accumulation of connective and adipose tissue prominent in DMD muscles (Bell and Conen, 1968; Dubowitz, 1985; Hoffman and Gorospe, 1991) a discrepancy which led to the mdu mutant being considered by some authors as a useful model of muscle regeneration rather an homologous pathological model of DMD (Dangain and Vrbova, 1984; Anderson et al., 1988). More recently, however, the diaphragm of adult mdx mice was shown to exhibit a pattern of degeneration and fibrosis similar to that of DMD limb muscles (Stedman et al., 1991; DuPont-Versteegden and McCarter, 19921, and it has been suggested that dystrophin-deficient muscles have a low threshold for work-induced injury (Weller et al., 1990; Stedman et al., 1991; Dick and Vrbovh, 19931,the diaphragm being sufficiently sensitive to exhibit a progressive dystrophic degenerative pattern as a consequence of its normal activity. To determine whether similar dystrophic changes eventually occur in other mdx muscles as a result of the cumulative damage, we have undertaken

98

C. Pastoret,

A. Sebille /Journal

of the Neurological

Sciences 129 (I 995) 97-l 05

C. Pastoret,

A. Sebille /Journal

of

the Neurological

histopathological observations in hindlimb muscles of young and old m& mice. Our observations strongly suggest that late m& muscular abnormalities are similar to those of DMD and dystrophin deficient dog (Valentine et al., 1986; Kornegay et al., 1988). 2. Materials

and methods

Animals

Breeding pairs of ma!x mice (courtesy of J.-L. Guenet, Institut Pasteur, Paris) and of C57BL/lO mice were maintained and housed in our own animal facilities. Animals were fed with standard cube diet and tap water ad libitum. Diurnal cycle was regulated by natural lighting. To eliminate intersexual variations, only male animals were studied. Animals were regularly checked and 487 C57BL/lO mice and 581 mdx mice were weighed. The muscle samples were obtained from animals under chloral hydrate 3.5% (1.5 ml/100 g body weight) anaesthesia. Animals were killed by overdose after muscle excision. Morphological

methods and quantitative

analysis

Four leg muscles were studied: tibialis anterior (TA), extensor digitorum longus (EDL), plantaris (PL) and soleus (SOL). The muscles were removed from 170 C57BL/lO and 276 mdx mice at the ages of 2, 3, 4, 6, 8, 13, 26, 39, 52, 65, 78, 91 and 104 weeks. After excision and weighing, the muscles were frozen in isopentane cooled in liquid nitrogen and stored at - 80” C. Transverse serial cryostat sections (6 or 10 pm thick) were cut and stained with haematoxylin-eosin (H.E), Van Gieson (VG) and oil red 0. Quantitative analysis of degeneration and regeneration (Dubowitz, 1985) was performed on microphotographs (X 125) of 276 muk muscles, according to Dubowitz’s criteria: opaque fibres as well as fibres faintly coloured, frequently filled with phagocytes were considered as degenerating. Small strongly basophilic fibres in which the cytoplasm takes on a uniformly bluish colour, with central vesicular nuclei were classified as regenerating fibres. Fibres with non peripheral nuclei and eosinophilic cytoplasm were considered as regenerated. Degenerating fibre numbers were expressed as a percentage of the total number of fibres in each m&

Sciences

129 (1995)

97-105

99

muscle. Quantitative assessment of muscle regeneration included the percentage of regenerating fibres, and the percentage of fibres containing one or more non peripheral nuclei (Torres and Duchen, 1987). The percentage of fibres with nonperipheral nuclei was also calculated in 33 C57BL/lO TA muscles. Dystrophin immunostaining was performed, on muscle sections from old mdx mice (65-104 weeks, n = 6) to demonstrate dystrophin-positive fibres (Hoffman et al., 1990) as described in Partridge et al. (1989). Normal age-matched C57BL/lO muscles were used as positive controls.

3. Results Animals,

weights and histopathology

C57BL/lO mice retained unimpaired ability to access food and water beyond 104 weeks of age, the majority survived beyond 108 weeks of age (25 months). 170 muscles were examined histologically up to 104 weeks of age. The muscle fibres were polygonal, of constant diameter with peripheral nuclei. Connective and adipose tissues were never observed, even after 104 weeks of age (Fig. 1A). In 2-week-old mdx mice, a few abnormalities such as opaque fibres, small scattered foci of degenerating fibres surrounded by cellular infiltration, and groups of small regenerating fibres with central nuclei were detected in occasional muscles. From 3 weeks these abnormalities become conspicuous and widespread in all the muscles studied. The EDL was the last muscle in which the onset of necrosis was observed. From the age of 8 weeks, in all muscles, most of the mature fibres exhibited non peripheral nuclei. In all of the muscles, hypertrophied fibres co-existed with foci of myotubes or small fibres at various stages of maturation, leading to an increase in variability of muscle fibre diameters. Split fibres were not uncommon, but connective and adipose tissues were not conspicuous up to 52 weeks of age. From 78 weeks, the mdx mice had difficulty in obtaining food and water unaided, and they failed to groom themselves. They lost weight (Fig. 2) and a majority of them died before 91 weeks. Only 2 mdx mice (8%) survived until 104 weeks of age (24 months)

Fig. 1. Histopathology of old normal C57BL/lO (A) and mdr muscles (B,C,D,E,F). A: C57BL/lO, tibialis anterior, 112 weeks of age: normal muscle fibres with peripheral nuclei. B: mdr, tibialis anterior 104 weeks of age: muscle showing perimysial and endomysial collagen. Most of the fibres have internal nuclei and there is a focus of lymphocytic infiltration. Compare the muscle fibre diameters with the normal muscle in (A), at the same magnification. C: mdr, soleus, 91 weeks of age: there is conspicuous perimysial and endomysial fibrosis. The fibres vary in size and most have internal nuclei. D: mdx, soleus, 104 weeks of age: muscle showing prominent endomysial fibrosis and variation in muscle fibre size. E: mdx, tibialis anterior, 65 weeks of age: group of degenerating fibres associated with an infiltration of lymphocytes and macrophages. F: mdu, tibialis anterior, 104 weeks of age: there is an increase in fibrous and adipose tissue together with marked variation in fibre sizes. Internal nuclei are frequent. (A,B,C,D): Van Gieson; (E,F): haematoxylin and eosin. A,B: X 110; C: X 200; D: X 25; E: X 140; F: X 100.

100

C. Pastoret,

0

10

Ape Fig. 2. Body (A) and tibialis C57BL/lO and mdr mutant

A. Sebille /Journal

hO

X0

of the Neurological

Sciences 129 (1995)

97-105

1,w

(weeks)

anterior (B) muscles weights of normal mice related to the age (mean k SEM).

(Fig. 3). At the time of removal, the leg muscles of these old mdx mice were observed to be flat and atrophied. In the T.A, for example, in contrast to the marked hypertrophy of mdx muscle at 6 months, the weight fell to below normal control levels by 21 months (Fig. 2). Histologically, degenerating fibres were seen until 104 weeks of age (Fig. lE), in groups as large as observed in younger mdx mutant muscles. Large areas of all the muscles were composed of small or atrophic muscle fibres (Fig. 1B) surrounded by endomysial fibrosis (Fig. 1D). Occasional fatty tissue was also found (Fig. 1F). Split fibres were very numerous in all of the older muscles resulting in a great variability of the muscle fibres diameter (Fig. 10. Small foci of small regenerating basophilic fibres, some of them embedded by dense collagen, were detectable in 65-week-old mdx mice but were rare after 91 weeks. Dystrophin immunostaining of old mdx muscles showed clusters of dystrophin-posi-

‘E cc .E .> t 2

I

L_

20

$ lo2 E H n78

86

Age (week;

104

Fig. 3. Survival of oldest normal C57BL/lO and mdr mutant mice. On an equivalent number of animals (n = 23 and n = 24, respectively) at 78 weeks, 16 C57BL/lO (70%) and 2 mdx mutants (8%) were alive at 104 weeks.

Fig. 4. Dystrophin immunostaining of old ma& muscles, (A) soleus, 91 weeks (B,C) tibialis anterior, 104 weeks. A: large cluster of dystrophin-positive fibres. B,C: serial sections showing dystrophinpositive fibres hypertrophied and split. A,B,C: 60 kDa antibody, visualised by Texas red; A: x 100; B,C: X 200.

C. Pastoret,

A. Sebille /Journal

TIBIALIS

of the Neurological

Sciences

129 (1995)

97-105

101

E.D.L

ANTERIOR

1

“3

4

6

*

II

26

39

52

65

18

PI

Ku

3

1

6

8

13

26

39

52

61,

78

‘II

103

Age (weeks) Fig. 5. Percentage

of degenerating

fibres in mdx

mice related

to the age in four

tive fibres (Fig. 4); many of these dystrophin-positive fibres were hypertrophied and/or split (Fig. 4). Quantitative analysis of degeneration and regeneration Degenerating fibres were observed in all the ma!x

muscles. From 3 to 104 weeks, the values were generally from 0.5 to 1% (Fig. 5), and the maximal values detected were 7.5% in SOL at 3 weeks and 2-3% in TA and EDL at 65 and 78 weeks. This early peak of

TIBIALIS

ANTERIOR

.-zF 5 $5 0 t? PLANTARIS

leg muscles.

Mean

percentage

from

2-13

muscles rt SEM.

necrosis in SOL is contemporary with the weaning of young mice and the increase of their mobility within the cage. Later, the percentages of necrotic fibres persisted with a value of 2%, as seen in TA and EDL. Whatever the muscle considered, we did not find a significant decrease in the percentage of degenerating fibres with age. Large inter-individual variations were a constant feature whatever the muscle and the age. Whenever muscles were removed from both legs, sym-

E.D.L 1

SOLEUS

Age (weeks) Fig. 6. Percentage

of regenerating

fibres

in mdx

mice related

to the age in four

leg muscles.

Mean

percentage

from

2-13

muscles f SEM.

C. Pastoret,

102

A. Sebille /Journal

of the Neurological

Skeletal muscle necrosis has been routinely found in growing and young adult ma? mice, while intramuscular nerves, vascularization and intrafusal fibres remained unaffected (Bulfield et al., 1984; Anderson et al., 1987; Carnwath and Shotton, 1987; Torres and Duchen, 1987; Cullen and Jaros, 1988). Here, we consistently observed degenerating fibres at all ages and in a variety of muscles of even very old mice (up to 104 weeks of age), indicating that necrosis is a permanent feature in mdx muscles, the muscle fibres being not protected against at least one new episode of necrosis once they had regenerated (Karpati et al., 1988; DiMario et al., 1991). Furthermore, by 26 weeks, 80-90% of muscle fibres exhibited one or more non peripheral nuclei, as a result of at least one degeneration-regeneration cycle. This plateau was maintained (in the presence of continued degeneration), from 26 weeks to 104 weeks, suggesting that the degeneration-regeneration cycles are persistent. Another explanation would be that the nuclei have lost their capacity to migrate to the periphery of the regenerated muscle fibres, but four additional arguments support the concept of a chronic degeneration of mdx skeletal muscle fibres: (i) the continuous leakage of serum muscular enzymes (Coulton et al., 1988; Glesby et al., 1988; Jockusch et al., 1990); (ii) the permanent high turn-over of muscle protein in adults (MacLennan and Edwards, 1990); (iii) the presence of multiple layers of external lamina around some regenerated fibres which could indicate successive cycles of degeneration-regeneration (Anderson et al., 1987); and (iv) the observation of Tamaki et al. (1993) in the soleus of l-year-old mdx mice of an

metry was observed, with regard to the spatial distribution of degenerating or regenerating areas. The percentage of regenerating fibres rarely exceeded 5% whatever the muscle and the age (Fig. 6), the highest values being observed at 4 weeks in T.A and SOL, 8 weeks in PL and 39 weeks in E.D.L. Beyond 78 weeks, the percentages of regenerating fibres were generally smaller, the lowest values being observed at 91-104 weeks in TA and SOL, and 104 weeks in EDL and PL. The percentage of muscle fibres with non peripheral nuclei in relation to the age of mdr mice is shown in Fig. 7. From 3 to 4 weeks, this percentage in SOL jumped from near 0% to more than 60%. Other muscles gradually reached a SO-90% plateau at 26 weeks, remaining at this level between up to 104 weeks. 4. Discussion

This histopathological study of four hindlimb muscles in aging mdx mice demonstrates that many mdx skeletal muscles exhibit degenerative changes similar to those shown by DMD muscles, i.e fiber atrophy, frequent splitting and a conspicuous progressive endomysial fibrosis. In addition, this study shows that necrotic fibres are readily detectable throughout the life in m& muscles. The weight of the TA, from being strikingly hypertrophic at 6 months, was shown to decrease markedly between 15 and 24 months, in parallel with a relative diminution of body weight and difficulty in obtaining food and water.

TIBIALIS .d 2 y c 7 5 ._a a= & a c 2 St .z 3 g 2 % is

Sciences I29 (199.5) 97-105

ANTERIOR

E.D.L

loo

loo 1

80 60

40

20 0 SOLEUS

PLANTARIS ‘09 80

60

3

4

6

8

13

26

39

52

6.5

78

91

104

3

4

6

8

13

26

39

52

6.5

78

91

104

Age (weeks) Fig. 7. Percentage of non peripherally muscles +_ SEM. The full squares plotted the age.

nucleated in tibialis

fibres in mdu mice related to the age in four leg muscles. Mean anterior are the values of normal C57BL/lO muscles, which remained

percentage from 2-13 2-3% stable whatever

C. Pastoret,

A. Sebille /Journal

of the Neurological

increasing complexity of fibre branching with age, a picture consistent with long term repetition of degeneration and regeneration cycle. Another feature commonly described in young and adult mdx muscles is the great variation in muscle fibre shapes and diameters (Bulfield et al., 1984; Tanabe et al., 1986; Torres and Duchen, 1987; Co&on et al., 1988). This feature is enhanced in old mdu muscles, in which a great number of hypertrophied split and atrophic fibres were observed. Such irregularities of fibre size and morphology are a common feature of animal and human muscular dystrophies (Bell and Conen, 1967; Bray and Banker, 1970; Kornegay et al., 1988; Carpenter et al., 1989) resulting in part from the small diameter of regenerating fibres, but also from the irregular fusion of myotubes (Ontell et al., 1984) and the “splitting” of fibres during regeneration (Bradley, 1979; Snow and Chortkoff, 1987) especially in old animals (Blaivas and Carlson, 1991; Tamaki et al., 1993). The cause of the muscle fibre hypertrophy in association with muscle degeneration and regeneration remains unclear, but it could be related to an increased work-load on some fibres resulting from the loss of function of necrotic fibres, as has been suggested in DMD (Adstrom and Adams, 1981). Assuming that fibre “splitting” is a consequence of muscle regeneration (Schmalbruch, 19761, the observation of split dystrophin-positive fibres implies that these fibres were not originally in the muscle, but appeared after at least one cycle of degeneration-regeneration. Furthermore, the observation of hypertrophied dystrophin-positive fibres suggests that they have not undergone successive rounds of degeneration, but were left intact, as surrounding dystrophin-negative fibres degenerated and were lost. This could explain the grouping of revertant fibres in clusters, as observed in younger animals (Hoffman et al., 1990; Tanaka et al., 1991; Danko et al., 1992). It is also possible that each cluster of dystrophin-positive fibres is the descendant of a single stem cell in which the defective dystrophin gene is transcribed in a translatable form. Rare foci of regenerating fibres were observed even in muscles of very old animals (91-104 weeks old). The ability of muscle to regenerate is known to decrease with age in normal animals of all species (Carlson, 1992) and mdx mice seem not to escape this rule (Anderson et al., 1987; DiMario et al., 1991; Zacharias and Anderson, 1991; McGeachie et al., 1992,1993). The mechanisms leading to the decrease of muscle regeneration in old animals are unknown, but could be related to the progressive reduction of the satellite cell number and their diminished capacity to proliferate and fuse. On the other hand, the phagocytic function of inflammatory cells in the removal of cellular debris may also decrease ‘with age (Zacks and Sheff, 1982). Thus, it seems likely that the fibrosis (Goldspink et al.,

Sciences 129 (1995)

97-105

103

1994) and atrophy result from the failure of the waning regenerative response to balance the persisting necrosis, as has been suggested in DMD (Hudgson et al., 1967; Bell and Conen, 1968). This striking progressive loss of muscle bulk together with the progression of fibrosis may be one cause of the observed premature death of mdx mice by comparison with C57BL/lO control mice, in concert perhaps with heart and diaphragm abnormalities (Bridges, 1986; Carnwath and Shotton, 1987; Coulton et al., 1988; Sicinski and Barnard, 1990; Stedman et al., 1991; DupontVersteegden and McCarter, 1992). All these observations strongly suggest that the mdx mutant mouse is a closer model of the pathology of DMD than has been appreciated hitherto. In recent years the diaphragm has become accepted as a valid model of dystrophic pathogenesis in this animal (Stedman et al., 19911, but it is generally regarded as an exceptional muscle in this respect. Our findings suggest that it is merely the vanguard of a general progression into the dystrophic phenotype and is subsequently followed along this path by other muscles, particularly those concerned with permanent tonic antigravitational activity such as the soleus, as degeneration and regeneration occurred earlier in this muscle than in the three other muscles studied, the EDL being the least and the latest affected. This difference between muscles is also manifested in the greater severity of the late pathological changes in soleus as compared with the other three muscles. These features greatly extend the usefulness of the mdx mouse, not only as a basis for study of the pathogenesis of dystrophinopathies but also as an experimental model on which to make preliminary trials of potential therapies, permitting, as it does, the inclusion of functional tests of muscle condition in addition to the biochemical criteria used in previous evaluations of cell transplantation (Partridge, 1991a,b) or gene transfer therapy (Acsadi et al., 1991; Ragot et al., 1993; Dunckley et al., 1993). Its value vis a vis the other animal models of dystrophinopathy, the dog (Valentine et al., 1986; Kornegay et al., 1988) and the cat (Carpenter et al., 1989; Gaschen et al., 1992) is dependent on the nature of the study. It is somewhat of a disadvantage that the DMD-like changes do not occur until close to the end of the life span of the mouse with the consequence that experiments will be long-term and will involve a substantial loss of experimental animals in the course of the study, although in evaluation of whole body therapies, this latter would be a powerful test criterion. Against this must be set the fact that even allowing for the extra effort and costs involved, it will probably still be much cheaper to conduct such experiments on significant numbers of animals in the mdw mouse than in either of the other species-models currently available.

104

C. Pastoret,

A. Sebille /Journal

of the Neurological

Acknowledgements

The authors are infinitely grateful to Professor T.A. Partridge (Charing Cross and Westminster Medical School, London) for his contribution to this manuscript. C.P would like to thank Dr. J.E. Morgan and Dr. D. Woodrow for advice and fruitful discussions, and Mr. Ron Barnett for photography. We would like to thank Dr. J.-P. Lefaucheur for his help, Ms. N. Cerise1 and Ms. N. Ouvrard for the care of animals, Ms. J. Chandellier and Mr. R. Fletcher for their invaluable technical assistance. C57BL/lO mice were provided Dr. M. Pla, INSERM U93, Paris, and Dr. M.-H. Fraqois, CNRS URA 656, Paris. C.P. holds a grant from the Association Frangaise contre les Myopathies and the Singer-Polignac foundation. This research was supported by the Association Fraqaise contre les Myopathies and the French Ministry of Research and Technology (Grant #88(30564X

References Acsadi, G., G. Dickson, D.R. Love, A. Jani, F.S. Walsh, A. Gurusinghe, J.A. Wolff, and K.E. Davies (1991) Human dystrophin expression in mdx mice after intramuscular injection of DNA constructs. Nature, 352: 815-818. Adstrom, K.E. and R.D. Adams (19811 Pathological reactions of the skeletal muscle fibre in man. In: J. Walton (Ed.), Disorders of Voluntary Muscle, Churchill-Livingstone, Edinburgh, p. 151. Anderson, J.E., W.K. Qvalle and B.H. Bressler (1987) Electron microscopic and autoradiographic characterisation of hind limb muscle regeneration in the mdu mouse. Anat. Rec., 219: 243-257. Anderson, J.E., B.H. Bressler and W.K. Ovalle (19881 Functional regeneration in the hindlimb skeletal muscle of the tndr mouse. J. Muscle Res. Cell Motil., 9: 499-515. Bell, C.D. and P.E. Conen (1967) Change in fibre size in Duchenne muscular dystrophy. Neurology, 17: 902-913. Bell, C.D. and P.E. Conen (1968) Histopathological changes in Duchenne muscular dystrophy. J. Neurol. Sci., 7: 529-544. Blaivas, M. and B.M. Carlson (1991) Muscle fibre branching Difference between grafts in old and young rats. Mech. Ageing Dev., 60: 43-53. Bradley, W.G. (1979) Muscle fibre splitting. In: A. Mauro (Ed.), Muscle Regeneration, Raven Press, New York, NY, p. 215. Bray, G.M. and B.Q. Banker (1970) An ultrastructural study of degeneration and necrosis of muscle in the dystrophic mouse. Acta Neuropathol. Berl., 15: 34-44. Bridges, L.R. (1986) The association of cardiac muscle necrosis and inflammation with the degenerative and persistent myopathy of mdx mice. J. Neurol. Sci., 72: 147-157. Bulfield, G., G.W. Siller, P.A.L. Wight, and K.J. Moore (1984) X-chromosome linked muscular dystrophy mdw in the mouse. Proc. Natl. Acad. Sci. USA, 81: 1189-1192. Carlson, B.M. (1992) Muscle regeneration and aging. Monogr. Dev. Biol., 23: 189-195. Carnwath, J.W. and D.M. Shotton (1987) Muscular dystrophy in the mdu mouse: histopathology of the soleus and extensor digitorum longus muscles. J. Neurol. Sci., 80: 39-54. Carpenter, J.L., E.P. Hoffman, F.C.A. Romanul, L.M. Kunkel, R.K. Resales, N.S.F. Ma, J.J. Dasbach, J.F. Rae, F.M. Moore, M.B.

Sciences 129 (1995)

97-105

McAfee and L.K. Pearce (1989) Feline muscular dystrophy with dystrophin deficiency. Am. J. Pathol., 135: 909-919. Coulton, G.R., J.E. Morgan, T.A. Partridge and J.C. Sloper (1988) The mdu mouse skeletal muscle myopathy: I. A histological, morphometric and biochemical investigation. Neuropath. Appl. Neurobiol., 14: 54-70. Cullen, M.J. and E. Jaros (1988) Ultrastructure of the skeletal muscle in the X chromosome-linked dystrophic mdr mouse: comparison with Duchenne muscular dystrophy. Acta Neuropathol. Berl., 77: 69-81. Dangain, J. and G. Vrbova (1984) Muscle development in mdu mutant mice. Muscle Nerve, 7: 700-704. Danko, I., V. Chapman and J.A. Wolff (19921 The frequency of revertants in mdx mouse. Genetic models for Duchenne muscular dystrophy. Pediatr. Res., 32: 128-131. Dick, J. and G. Vrbova (1993) Progressive deterioration of muscles in mdx mice induced by overload. Clin. Sci., 84: 145-150. DiMario, J., A. Uzman and R.C. Strohman (1991) Fibre regeneration is not persistent in dystrophic MDX mouse skeletal muscle. Dev. Biol., 148: 314-321. Dubowitz, V. (1985) Muscle Biopsy: A Practical Approach, 2nd edn., Bailliere Tindall, London. Dunckley, M.G., D.J. Wells, F.S. Walsh and G. Dickson (1993) Direct retroviral-mediated transfer of a minigene into mdu mouse muscle in vivo. Hum. Mol. Genet., 2: 717-723. DuPont-Versteegden, E.E. and R.J. McCarter (1992) Differential expression of muscular dystrophy in diaphragm versus hindlimb muscles of mdr mice. Muscle Nerve, 15: 1105-1110. Gaschen, F.P., E.P. Hoffman, J.R.M. Gorospe, E.W. Uhl, D.F. Senior, G.H. Cardinet and L.K. Pearce (1992) Dystrophin deficiency causes lethal muscle hypertrophy in cats. J. Neurol. Sci., 110: 149-159. Glesby, M.J., E. Rosenmann, E.G. Nylen and K. Wrogemann (1988) Serum CK, calcium, magnesium, and oxidative phosphorylation in mdx mouse muscular dystrophy. Muscle Nerve, 11: 852-856. Goldspink, G.K., Fernandes, P.E. Williams and D.J. Wells (1994) Age related changes in collagen gene expression in the muscles of mdx dystrophic and normal mice. Neuromusc. Disord., 4: 183191. Hoffman, E.P., R.H. Brown and L.M. Kunkel (1987) Dystrophin: the protein product of the Duchenne muscular dystrophy locus. Cell, 51: 919-928. Hoffman, E.P., J.E. Morgan, SC. Watkins and T.A. Partridge (1990) Somatic reversion/suppression of the mouse mdu phenotype in vivo. J. Neural. Sci., 99: 9-25. Hoffman, E.P. and J.R.M. Gorospe (1991)The animal models of Duchenne Muscular Dystrophy: windows on the pathophysiological consequences of dystrophin deficiency. In: J.S. Mooseker (Ed.), Current Topics in Membranes, vol. 38, Academic Press, New York, NY, p. 113. Hudgson, P., G.W. Pearce and J.N. Walton (19671 Pre-clinical muscular dystrophy: histopathological changes observed on muscle biopsy. Brain, 90: 565-576. Jockusch, H., G. Friedrich and M. Zippel(1990) Serum parvalbumin, an indicator of muscle disease in murine dystrophy and myotonia. Muscle Nerve, 13: 551-555. Karpati, G., S. Carpenter and S. Prescott (1988) Small-caliber skeletal muscle fibres do not suffer necrosis in mdr mouse dystrophy. Muscle Nerve, 11: 795-803. Kornegay, J.N., SM. Tuler, D.M. Miller and D.C. Levesque (1988) Muscular dystrophy in a litter of golden retriever dog. Muscle Nerve, 11: 1056-1064. MacLennan, P.A. and R.H.T. Edwards (1990) Protein turnover is elevated in muscle of mak mice in vivo. Biochem. J., 268,795-797. Marshall, P.A., S.P.E. Williams and G. Goldspink (1989) Accumulation of collagen and altered fiber-type ratios as indicators of

C. Pustoret,

A. Sebille/Journal

of the Neurological

abnormal muscle gene expression in the mdx dystrophic mouse. Muscle Nerve, 12: 528-537. McGeachie, J.K., M.D. Grounds, T.A. Partridge and J.E Morgan (1992) Replication of myogenic cells with age, and myogenesis after experimental injury in ma!x mouse muscle: quantitative autoradiographic studies. In: A. Kakulas, J. McC. Howell and A.D. Roses (Eds.), Duchenne Muscular Dystrophy: Animal models and genetic manipulation, Raven Press, New York, NY, p. 189. McGeachie, J.K., M.D. Grounds, T.A. Partridge and J.E Morgan (1993) Age-related changes in replication of myogenic cells in mdr mice: quantitative autoradiographic studies. J. Neurol. Sci., 119: 169-179. Ontell, M., K.C. Feng, K. Klueber, R.F. Dunn and F. Taylor (1984) Myosatellite cells, growth and regeneration in murine dystrophic muscle: a quantitative study. Anat. Rec., 208: 159-174. Partridge, T.A., J.E. Morgan, G.R. Coulton, E.P Hoffman and L.M. Kunkel (1989) Conversion of mdx myofibres from dystrophinnegative to -positive by injection of normal myoblasts. Nature, 337: 176-179. Partridge, T. (1991a) Animal models of muscular dystrophy - What can they teach us? Neuropathol. Appl. Neurobiol., 17: 353-363. Partridge, T. (1991b) Myoblast transfer: a possible therapy for inherited myopathies? Muscle Nerve, 14: 197-212. Ragot, T., N. Vincent, P. Chafey, E. Vigne, H. Gilgenkrantz, D. Couton, J. Cartaud, P. Briand, J.-C. Kaplan, M. Perricaudet and A. Kahn (1993) Efficient adenovirus-mediated transfer of a human minidystrophin gene to skeletal muscle of mak mice. Nature, 361: 647-650. Schmalbruch, H. (1976) Muscle fiber splitting and regeneration in diseased human muscle. Neuropath. Appl. Neurobiol., 2: 3-19. Schmalbruch, H. (1982) The muscular dystrophies. In: F.L. Mastaglia and J. Walton (Eds.), Skeletal Muscle Pathology, Churchill Livingstone, Edinburgh, p. 235. Sicinski, P. and P.J. Barnard (1990) The mdu mouse, a model for Duchenne muscular dystrophy. J. Neurol. Sci., 98 (Suppi.): 122 (Abstract).

Sciences

129 (1995)

97-105

105

Sicinski, P., Y. Geng, A.S Ryder-Cook, E.A. Barnard, M.G. Darlinson and P.J. Barnard (1989) The molecular basis of muscular dystrophy in the ma!x mouse: a point mutation. Science, 244: 1578-1580. Snow, M.H. and B.S. Chortkoff (1987) Frequency of bifurcated fibres in bypertrophic rat soleus muscle. Muscle Nerve, 10: 312-317. Stedman, H.H., H.L. Sweeney, J.B. Shrager, H.C. Maguire, R.A. Panettieri, B. Petrof, M. Narusawa, J.M Leferovich, J.T. Sladky and A.M. Kelly (1991) The mdr mouse diaphragm reproduces the degenerative changes of Duchenne muscular dystrophy. Nature, 352: 536-539. Tamaki, T. T. Sekine, A. Akatsuka, S. Uchiyama and S. Nakano (1993) Three-dimensional cytoarchitecture of complex branched fibers in soleus muscle from mdx mutant mice. Anat. Rec., 237: 338-344. Tanabe, Y., K. Esaki and T. Nomura (1986) Skeletal muscle pathology in X chromosome-linked muscular dystrophy mdu mouse. Acta Neuropathol. Berl., 69: 91-95. Tanaka, H., K. Hayashi and E. Ozawa (1991) Positive immunostaining with dystrophin antibodies in mdu skeletal muscle. Proc. Jap. Acad., 67 (B): 148-152. Torres, L.F.B. and L.W. Duchen (1987) The mutant mak: inherited myopathy in the mouse. Morphological studies of nerves, muscles and end-plates. Brain, 110: 269-299. Valentine, B.A., B.J. Cooper, J.F. Cummings and J.F. DeLahunta (1986) Progressive muscular dystrophy in a golden retriever dog: light microscope and ultrastructural features at 4 and 8 months. Acta Neuropathol. Berl., 71: 301-310. Weller, B., G. Karpati and S. Carpenter (1990) Dystrophin-deficient mdx muscle fibers are preferentially vulnerable to necrosis induced by experimental lengthening contractions. J. Neurol. Sci., 100: 9-13. Zacharias, J.M. and J.E. Anderson (1991) Muscle regeneration after imposed injury is better in younger than older mdr dystrophic mice. J. Neurol. Sci., 104: 190-196. Zacks, S.I. and M.F. Sheff (1982) Age-related impeded regeneration of mouse minced anterior tibia1 mouse. Muscle Nerve, 5: 152-161.