Electroporation as a method to induce myofiber regeneration and increase the engraftment of myogenic cells in skeletal muscles of primates.

Engraftment of intramuscularly transplanted myogenic cells in mice can be optimized after induction of massive myofiber damage that triggers myofiber regeneration and recruitment of grafted cells; this generally involves either myotoxin injection or cryodamage. There are no effective methods to produce a similar process in the muscles of large mammals such as primates. In this study, we tested the use of intramuscular electroporation for this purpose in 11 macaques.

Intramuscular transplantation of myogenic cells in primates: importance of needle size, cell number, and injection volume.

The aim of this study was to quantitatively define the main measurable technical parameters for the intramuscular transplantation of myogenic cells in primates. Myoblasts transduced with the gene coding for β-galactosidase were injected into the skeletal muscles of 15 monkeys. The following parameters were studied: needle size, number of cells per injection, and volume of cell suspension per injection.

Myopathy in a rhesus monkey with biopsy findings similar to human sporadic inclusion body myositis.

A rhesus macaque with generalized muscle atrophy and musculotendinous contractures was detected in our research center. Muscle biopsies showed myofibers with rimmed vacuoles and eosinophilic hyaline inclusions, accumulations of CD8+ and CD4+ lymphocytes and expression of major histocompatibility complex class I in myofibers. Intracellular inclusions were positive to Congo red.

Transplanted myoblasts can migrate several millimeters to fuse with damaged myofibers in nonhuman primate skeletal muscle.

A major restriction of the intramuscular transplantation of myoblasts is that the grafted cells fuse mostly with myofibers along the injection trajectories. This has been attributed to a "lack of migration ability" of the grafted myoblasts. It has been assumed that grafted myoblasts remain motionless in the sites of delivery and fuse only with myofibers with which they come into contact.

Intramuscular transplantation of human postnatal myoblasts generates functional donor-derived satellite cells.

Myogenic cell transplantation is an experimental approach for the treatment of myopathies. In this approach, transplanted cells need to fuse with pre-existing myofibers, form new myofibers, and generate new muscle precursor cells (MPCs). The last property was fully reported following myoblast transplantation in mice but remains poorly studied with human myoblasts.

A first semimanual device for clinical intramuscular repetitive cell injections.

Intramuscular cell transplantation in humans requires so far meticulous repetitive cell injections. Performed percutaneously with syringes operated manually, the procedure is very time consuming and requires a lot of concentration to deliver the cells exactly in the required region. This becomes impractical and inaccurate for large volumes of muscle.

Growth factor coinjection improves the migration potential of monkey myogenic precursors without affecting cell transplantation success.

Duchenne muscular dystrophy (DMD) is an inherited disease and a main target of myogenic cell transplantation (MT). After the failure of the first clinical trials with DMD patients, the poor migration of transplanted cells has been suspected to be a major problem for a more effective clinical application of MT. Previous investigations suggested that the quantity and dispersion of myofibers containing donor cell nuclei might be improved by increasing the migration of the transplanted cells outside the injection sites.

Ischemic central necrosis in pockets of transplanted myoblasts in nonhuman primates: implications for cell-transplantation strategies.

Background: Several cell-transplantation strategies implicate the injection of cells into tissues. Avascular accumulations of implanted cells are then formed. Because the diffusion of oxygen and nutrients from the surrounding tissue throughout the implanted cell accumulations may be limited, central ischemic necrosis could develop.

Autologous transplantation of muscle precursor cells modified with a lentivirus for muscular dystrophy: human cells and primate models.

Duchenne muscular dystrophy (DMD) is characterized by the absence of dystrophin. We tested the ability of lentiviral vectors to deliver a transgene into myogenic cells before their transplantation. Enhanced green fluorescent protein (eGFP) transgene was efficiently transferred into cells and eGFP-positive fibers were generated following transplantation.

Use of repeating dispensers to increase the efficiency of the intramuscular myogenic cell injection procedure.

Intramuscular myoblast transplantation in humans and nonhuman primates requires precise repetitive cell injections very close to each other. Performed with syringes operated manually throughout large regions, this procedure takes a lot of time, becoming tiring and thus imprecise. We tested two repetitive dispensers with Hamilton syringes as cell injection devices to facilitate this procedure.

First test of a "high-density injection" protocol for myogenic cell transplantation throughout large volumes of muscles in a Duchenne muscular dystrophy patient: eighteen months follow-up.

A 26-years old Duchenne muscular dystrophy (DMD) patient received normal muscle-precursor cells, proliferated in vitro and implanted in a thenar eminence, biceps brachii, and in a portion of a gastrocnemius by injections placed 1mm from each other or less. Saline was injected in the contralateral gastrocnemius. The patient was immunosuppressed with tacrolimus.

Dystrophin expression in muscles of duchenne muscular dystrophy patients after high-density injections of normal myogenic cells.

A clinical trial was conducted to test a new protocol of normal muscle precursor cell (MPC) allotransplantation in skeletal muscles of patients with Duchenne muscular dystrophy (DMD). Cultured MPCs obtained from one of the patient's parents were implanted in 0.25 or 1 cm of a Tibialis anterior in 9 patients with DMD.

Dystrophin expression in myofibers of Duchenne muscular dystrophy patients following intramuscular injections of normal myogenic cells.

Three Duchenne muscular dystrophy (DMD) patients received injections of myogenic cells obtained from skeletal muscle biopsies of normal donors. The cells (30 x 10 (6)) were injected in 1 cm3 of the tibialis anterior by 25 parallel injections. We performed similar patterns of saline injections in the contralateral muscles as controls.

Resetting the problem of cell death following muscle-derived cell transplantation: detection, dynamics and mechanisms.

We conducted a study in mice to reevaluate and clarify many aspects of the early survival of muscle cells following transplantation. Male mouse muscle cells (primary-cultures and T-antigen-immortalized clones) labeled with [14C]thymidine and beta-galactosidase were injected into female muscles. Each label was detected in the muscles after different time periods.

Dynamics of the early immune cellular reactions after myogenic cell transplantation.

The role of immune cells in the early donor cell death/survival following myoblast transplantation is confusing, one of the reasons being the lack of data about the immune reactions following cell transplantation. We used outbred mice as hosts for transplantation of primary cultured muscle cells and T-antigen-immortalized myoblasts. The host muscles were analyzed 1 h to 7 days after cell injection.

Efficacy of myoblast transplantation in nonhuman primates following simple intramuscular cell injections: toward defining strategies applicable to humans.

Nonhuman primates were used to define myoblast transplantation strategies applicable to humans. Nevertheless, previous experiments were based on the use of myotoxins concomitant with the myoblast injections. Since myotoxins must be avoided for clinical applications, we analyzed the efficacy of simple myoblast injections (i.