Systemic Production of Human Granulocyte Colony-Stimulating Factor in Nonhuman Primates by Transplantation of Genetically Modified Myoblasts

Abstract

Clinical use of human granulocyte-colony stimulating factor (hG-CSF) to treat various diseases involving neutropenia has been previously shown to (1) successfully increase circulating neutrophils, (2) reduce condition-related infections, and (3) cause few side effects in patients. To alleviate the symptoms of neutropenia, the patient must receive frequent injections of recombinant hG-CSF. Permanent ways to deliver stable levels of the molecule to the patient are being investigated. Among them, the transplantation of hG-CSF-secreting cells has been proposed and performed successfully in rodents, using fibroblast cell lines and primary muscle cells. We thus investigated whether similar results could be obtained by intramuscular myoblast transplantation in a large animal model. When 1-3 x 10(8) myoblasts were injected into three Macaca mulatta, hG-CSF was detected at high levels (300-900 pg/ml), which in turn led to a four- to fivefold increase in circulating neutrophils. However, both the concentrations of hG-CSF and neutrophil levels were found to decrease over time. Nonetheless, neutrophils were found at higher levels from the fourth week until the end the experiment (up to 29 weeks) in G-CSF monkeys compared with control animals. These results show that transplantation of hG-CSF-secreting myoblasts may indeed be a therapeutic option for the treatment of neutropenic patients.

Apoptosis coincident with the differentiation of skeletal myoblasts is delayed by caspase 3 inhibition and abrogated by MEK-independent constitutive Ras signaling

“…1,2,4,5 While undoubtedly a vital component of development, the linkage of these two processes is obviously detrimental 12,13 to the use of myoblast transfer as a gene complementation approach for the treatment of muscular dystrophies 8 ± 11 and certain metabolic deficiencies. 36 Finding targets to manipulate that would allow abrogation of apoptosis without affecting differentiation could improve the efficacy of these approaches. We have shown that in skeletal myoblasts both differentiation and the accompanying apoptosis depend on the variables of cell density and time and that these variables are inversely related.…”

Apoptosis coincident with the differentiation of skeletal myoblasts is delayed by caspase 3 inhibition and abrogated by MEK-independent constitutive Ras signaling

“…1,2,4,5 While undoubtedly a vital component of development, the linkage of these two processes is obviously detrimental 12,13 to the use of myoblast transfer as a gene complementation approach for the treatment of muscular dystrophies 8 ± 11 and certain metabolic deficiencies. 36 Finding targets to manipulate that would allow abrogation of apoptosis without affecting differentiation could improve the efficacy of these approaches. We have shown that in skeletal myoblasts both differentiation and the accompanying apoptosis depend on the variables of cell density and time and that these variables are inversely related.…”

Myoblast‐mediated gene transfer for therapeutic angiogenesis and arteriogenesis

“…In clinical trials, the implantation of primary myoblasts for therapeutic purposes into the leg and heart has been shown to be feasible ( Gussoni et al , 1997 ; Menasche et al , 2003 ). Based on these findings and encouraging experimental evidence, the use of transduced myoblasts has been proposed as a gene delivery system for clinical studies ( Moisset et al , 2000 ; Suzuki et al , 2001 ). An important safety‐related aspect is the possibility to control the expression of the transgene by being able to determine the expression level in vitro prior to implantation or by tetracycline regulation.…”