Pilot study of myoblast transfer in the treatment of Becker muscular dystrophy.

We evaluated myoblast implantation therapy in three subjects with Becker muscular dystrophy who received 60 million myoblasts in one tibialis anterior (TA) muscle 2 months after beginning cyclosporine immunosuppression (5 to 10 mg/kg) that continued for 1 year. Strength of the implanted and control TA muscles was measured before and after treatment using a gauge to record TA contraction force. Our protocol controlled for the effects of cyclosporine and myoblast injections. In this pilot study, myoblast implantation did not improve strength of the implanted TA muscles.

Developmental changes in expression of myotonic dystrophy protein kinase in the rat central nervous system.

Myotonic dystrophy protein kinase (DMPK) is the protein product of the genetic locus associated with myotonic dystrophy, in which alterations of muscle excitability, cardiac conduction defects, mental retardation, and cognitive deficiencies are inherited as an autosomal dominant trait. DMPK belongs to a novel protein serine/threonine kinase family, but its regulation and physiological functions have not been specified. In a first step toward understanding the functions of DMPK in the central nervous system, we have characterized its localization and developmental pattern of expression in rat brain and spinal cord by using a monospecific rabbit antiserum produced against bacterially expressed DMPK. Expression of DMPK begins after birth and increases gradually to peak at postnatal day 21 with antibody labeling of neuronal cell types in many regions. After postnatal day 21 and proceeding to the adult, the pattern of expression becomes more restricted, with localization to certain regions or cell groups in the central nervous system. Electron microscopy reveals localization within adult spinal motor neurons to the endoplasmic reticulum and dendritic microtubules. The adult localizations suggest that DMPK may function in membrane trafficking and secretion within neurons associated with cognition, memory, and motor control.

Identification of two mutations and a polymorphism in the chloride channel CLCN-1 in patients with Becker's generalized myotonia.

Myotonia congenita is an inherited muscle disorder characterized by muscle stiffness and hypertrophy. Its clinical phenotype depends, in part, on whether it is inherited as a dominant or recessive trait, respectively designated Thomsen's disease or Becker's generalized myotonia (BGM). In either case, it is associated with abnormalities in the muscle currents that are linked to the gene (CLCN-1) on human chromosome 7q35 encoding the skeletal muscle chloride channel. Single-strand conformation polymorphism analysis was used to screen two families with the BGM for mutations in the CLCN-1 gene. Two new mutations were found (G 201ins and A317Q). The latter mutation has been previously described in Thomsen's disease.

Arterial delivery of myoblasts to skeletal muscle.

One of the major limitations of myoblast implantation as a therapy for muscular disease is that multiple injections by intramuscular implantation may be required for widespread delivery of cells. Also, some sites (eg, the diaphragm) are relatively inaccessible to injection. As an alternative, we have undertaken intra-arterial administration of myoblasts. For these experiments, we used donor cell myoblasts from the immortal L6 cell line labeled with lacZ via the beta-gal-at-gal retrovirus. In our model, target rat skeletal muscle (tibialis anterior [TA]) was injured using 0.5 ml of 0.5% bupivacaine and 15 IU of hyaluronidase; saline was injected into the contralateral side as a control. We infused 3 x 10(6) lacZ-positive cells into the abdominal aorta of previously injured, immunosuppressed (cyclosporine A) rats. At 7, 14, and 28 days, TA, liver, heart, lung, and spleen were examined for lacZ staining. In both the injured and control muscles, a few differentiated, lacZ-positive muscle cells were present, both singly and in groups, at each time point. These studies demonstrate that genetically labeled, transformed myoblasts may migrate from the arterial circulation to muscle and fuse there to form differentiated muscle cells. It is conceivable that intra-arterial delivery of myoblasts may have a role in the therapy of selected diseases of skeletal muscle.