Pretreatment of myoblast cultures with basic fibroblast growth factor increases the efficacy of their transplantation in mdx mice

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Abstract
The effect of pretreatment of cultures with basic fibroblast growth factor (bFGF) on myoblast allotransplantation to C57BL/10ScSn mdx/mdx mouse (mdx mouse) muscles not previously damaged and not irradiated was studied. Transgenic CD1 mice which have a β‐galactosidase gene under the control of the promoter of the quail fast skeletal muscle troponin I gene, were used as donors. The myoblasts were grown with 100 ng/mL bFGF during the last 2 days before injecting them in the left tibialis anterior (TA) muscles of mdx mice. Myoblasts from the same primary cultures were also grown without bFGF and injected in the right TA muscles as control. The recipient mice were immunosuppressed with FK 506. Twenty‐eight days after myoblast transplantation, the percentage of β‐galactosidase‐positive fibers was significantly higher (more than fourfold) following culture with bFGF than without bFGF. Almost all β‐galactosidase‐positive fibers were also dystrophin positive. Direct intramuscular injections of bFGF or of Hank's balanced salt solution (HBSS) at the time of myoblast transplantation and at several intervals afterwards were also investigated. The percentage of β‐galactosidase‐positive fibers did not differ significantly following intramuscular injection of bFGF from controls injected with HBSS. In vitro, this high concentration of bFGF significantly reduced the formation of myotubes, and the percentage of mononuclear cells which were myoblasts was significantly increased by 34%. These observations alone do not account for the fourfold increase in transplantation success. The presence of bFGF in the culture did not significantly increase the cell survival 3 days after their transplantation. Our results indicate that culture of myoblasts with bFGF permits to obtain a high percentage of hybrid muscle fibers following myoblast transplantation without using damaging treatments such as notexin injection and irradiation. This suggests that such pretreatment may be helpful for myoblast transplantation in humans. The mechanism of this effect is still unclear. © 1995 John Wiley & Sons, Inc.