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Distribution of acidic fibroblast growth factor-like immunoreactivity in rat skeletal muscle fibers
T Junttila1, L Rechardt, Y Cao
1Department of Anatomy, University of Tampere, Finland.
Abstract:
Acidic fibroblast growth factor (aFGF) is a mitogenic, angiogenic and neurotrophic growth factor which promotes proliferation, but delays differentiation of cultured myoblasts. Its mRNA is expressed in the skeletal muscle, however, the distribution of aFGF in the postnatal skeletal muscle is poorly characterized. In the present study, the distribution of aFGF-like immunoreactivity (LI) was examined in developing and adult rat skeletal muscle fibers. In addition, the effect of the transection of the sciatic nerve on aFGF-LI in calf muscle fibers was examined. From the first postnatal day on, aFGF-immunoreactive (IR) muscle fibers were observed in different calf muscles. From the 7th postnatal day on a large number of muscle fibers exhibited aFGF-LI in the soleus muscle, some in plantaris and only few in gastrocnemius and extraocular muscles. Double-labelling with fast-myosin antibody showed that aFGF-LI was restricted to the slow oxidative muscle fibers. aFGF-IR intrafusal muscle fibers were seen in developing and mature muscle spindles. In addition, aFGF-IR nerve fibers and myoneural junctions were observed in different muscles. Transection of the sciatic nerve did not noticeably alter the expression pattern of aFGF-LI in calf muscles during two-week period. The present study demonstrates aFGF-LI in the rat slow oxidative muscle fibers where it may have fiber-type specific functions in addition to its known trophic effects.
Insights
Acidic fibroblast growth factor (aFGF) is found in rat slow oxidative muscle fibers, suggesting specific roles beyond general trophic effects. Sciatic nerve transection did not impact aFGF distribution in calf muscles.
Area of Science:
- Muscle physiology
- Neuroscience
- Biochemistry
Background:
- Acidic fibroblast growth factor (aFGF) is known for its roles in cell proliferation, angiogenesis, and neuronal support.
- While aFGF mRNA is present in skeletal muscle, its protein distribution in postnatal muscle fibers is not well understood.
- Understanding aFGF localization is crucial for elucidating its functions in muscle development and maintenance.
Purpose of the Study:
- To investigate the distribution of acidic fibroblast growth factor-like immunoreactivity (aFGF-LI) in developing and adult rat skeletal muscle fibers.
- To examine the impact of sciatic nerve transection on aFGF-LI expression in calf muscle fibers.
- To determine if aFGF exhibits fiber-type specificity in skeletal muscle.
Main Methods:
- Immunohistochemistry was used to detect aFGF-like immunoreactivity (aFGF-LI) in rat skeletal muscle.
- Double-labeling with fast-myosin antibodies differentiated muscle fiber types.
- Sciatic nerve transection was performed to assess the neurotrophic influence on aFGF distribution.
Main Results:
- aFGF-immunoreactive (IR) muscle fibers were detected from the first postnatal day onwards.
- aFGF-LI was predominantly found in slow oxidative muscle fibers, particularly in the soleus muscle.
- aFGF-IR nerve fibers and myoneural junctions were observed, but transection of the sciatic nerve did not alter aFGF-LI patterns over two weeks.
Conclusions:
- Acidic fibroblast growth factor (aFGF) is localized in slow oxidative muscle fibers in rats, indicating potential fiber-type-specific functions.
- The presence of aFGF in muscle spindles and nerve fibers suggests roles in neuromuscular development and function.
- aFGF distribution in calf muscles appears independent of sciatic nerve integrity in the short term.