Differential adaptation of growth and differentiation factor 8/myostatin, fibroblast growth factor 6 and leukemia inhibitory factor in overloaded, regenerating and denervated rat muscles. (1/21)

Mice genetically deficient in growth and differentiation factor 8 (GDF8/myostatin) had markedly increased muscle fiber numbers and fiber hypertrophy. In the regenerating muscle of mice possessing FGF6 mutation, fiber remodeling was delayed. Although myostatin and FGF6 may be important for the maintenance, regeneration and/or hypertrophy of muscle, little work has been done on the possible role of these proteins in adult muscle in vivo. Using Western blot and immunohistochemical analysis, we investigated, in rats, the distribution of myostatin, FGF6 and LIF proteins between slow- and fast-type muscles, and the adaptive response of these proteins in mechanically overloaded muscles, in regenerating muscles following bupivacaine injection and in denervated muscles after section of the sciatic nerve. The amounts of myostatin and LIF protein were markedly greater in normal slow-type muscles. In the soleus muscle, myostatin and LIF proteins were detected at the site of the myonucleus in both slow-twitch and fast-twitch fibers. In contrast, FGF6 protein was selectively expressed in normal fast-type muscles. Mechanical overloading rapidly enhanced the myostatin and LIF but not FGF6 protein level. In the regenerating muscles, marked diminution of myostatin and FGF6 was observed besides enhancement of LIF. Denervation of fast-type muscles rapidly increased the LIF, but decreased the FGF6 expression. Therefore, the increased expressions of myostatin and LIF play an important role in muscle hypertrophy following mechanical overloading. The marked reduction of FGF6 in the hypertrophied and regenerating muscle would imply that FGF6 regulates muscle differentiation but not proliferation of satellite cells and/or myoblasts.  (+info)

Increased expression of fibroblast growth factor 6 in human prostatic intraepithelial neoplasia and prostate cancer. (2/21)

Fibroblast growth factors (FGFs) are known to play an important role in the growth of normal prostatic epithelial cells. In addition to their effects on proliferation, FGFs can promote cell motility, increase tumor angiogenesis, and inhibit apoptosis, all of which play an important role in tumor progression. To determine whether FGFs are overexpressed in human prostate cancers, we analyzed 26 prostate cancer RNAs by reverse transcription-PCR for expression of FGF3, FGF4, and FGF6, which cannot be detected in normal prostate tissue by this technique. Fourteen of 26 prostate cancers expressed FGF6 mRNA. No expression of FGF3 or FGF4 was detected. An ELISA of tissue extracts of normal prostate, high-grade prostatic intraepithelial neoplasia (PIN), and prostate cancer for FGF6 showed that this growth factor was undetectable in normal prostate but was present at elevated levels in 4 of 9 PIN lesions and in 15 of 24 prostate cancers. Immunohistochemical analysis with anti-FGF6 antibody revealed weak staining of prostatic basal cells in normal prostate that was markedly elevated in PIN. In the prostate cancers, the majority of cases revealed expression of FGF6 by the prostate cancer cells themselves. In two cases, expression was present in prostatic stromal cells. Exogenous FGF6 was able to stimulate proliferation of primary prostatic epithelial and stromal cells, immortalized prostatic epithelial cells, and prostate cancer cell lines in tissue culture. FGF receptor 4, which is the most potent FGF receptor for FGF6, is expressed in the human prostate in vivo and in all of the cultured cell lines. Thus, FGF6 is increased in PIN and prostate cancer and can promote the proliferation of the transformed prostatic epithelial cells via paracrine and autocrine mechanisms.  (+info)

Delivery of FGF genes to wound repair cells enhances arteriogenesis and myogenesis in skeletal muscle. (3/21)

Tissue repair is driven by migratory macrophages and fibroblasts that infiltrate injury sites and secrete growth factors. We now report the enhancement of skeletal muscle repair by targeting transgene delivery to these repair cells using matrix-immobilized gene vectors. Plasmid and adenovirus vectors immobilized in collagen-gelatin admixtures were delivered to excisional muscle wounds, and when encoding either fibroblast growth factor-2 (FGF2) or FGF6 transgenes, produced early angiogenic responses that subsequently remodeled into arteriogenesis. FGF2 gene delivery enhanced the number of CD31(+) endothelial cells present at treatment sites > 6-fold by day 14, and muscular arteriole density up to 11-fold by day 21 (P<0.0001). Muscle repair was also enhanced, as FGF gene-treated wounds filled with regenerating myotubes expressing the marker CD56 (an average 20-fold increase in CD56 expression versus controls, P<0.0001). These responses required transfection of a threshold level of repair cells, achievable only in injured muscles, and were transgene-driven, as neither platelet-derived growth factor-B (PDGFB) gene nor FGF2 protein delivery produced equivalent responses. In conclusion, using biomatrices to direct gene delivery to repair cells allows for relatively complex regenerative processes such as arteriogenesis and myogenesis, and therefore represents a promising approach to treating injured and ischemic muscle.  (+info)

Reduced mobility of fibroblast growth factor (FGF)-deficient myoblasts might contribute to dystrophic changes in the musculature of FGF2/FGF6/mdx triple-mutant mice. (4/21)

Development and regeneration of muscle tissue is a highly organized, multistep process that requires cell proliferation, migration, differentiation, and maturation. Previous data implicate fibroblast growth factors (FGFs) as critical regulators of these processes, although their precise role in vivo is still not clear. We have explored the consequences of the loss of multiple FGFs (FGF2 and FGF6 in particular) for muscle regeneration in mdx mice, which serve as a model for chronic muscle damage. We show that the combined loss of FGF2 and FGF6 leads to severe dystrophic changes in the musculature. We found that FGF6 mutant myoblasts had decreased migration ability in vivo, whereas wild-type myoblasts migrated normally in a FGF6 mutant environment after transplantation of genetically labeled myoblasts from FGF6 mutants in wild-type mice and vice versa. In addition, retrovirus-mediated expression of dominant-negative versions of Ras and Ral led to a reduced migration of transplanted myoblasts in vivo. We propose that FGFs are critical components of the muscle regeneration machinery that enhance skeletal muscle regeneration, probably by stimulation of muscle stem cell migration.  (+info)

Injection of FGF6 accelerates regeneration of the soleus muscle in adult mice. (5/21)

FGF6, a member of the fibroblast growth factor (FGF) family, accumulated almost exclusively in the myogenic lineage, supporting the finding that FGF6 could specifically regulate myogenesis. Using FGF6 (-/-) mutant mice, important functions in muscle regeneration have been proposed for FGF6 but remain largely controversial. Here, we examined the effect of a single injection of recombinant FGF6 (rhFGF6) on the regeneration of mouse soleus subjected to cardiotoxin injection, specifically looking for molecular and morphological phenotypes. The injection of rhFGF6 has two effects. First, there is an up-regulation of cyclin D1 mRNA, accounting for the regulating role of a high FGF6 concentration on proliferation, and second, differentiation markers such as CdkIs and MHC I and Tn I increase and cellular differentiation is accelerated. We also show a down-regulation of endogenous FGF6, acceleration of FGFR1 receptor expression and deceleration of the FGFR4 receptor expression, possibly accounting for biphasic effects of exogenous FGF6 on muscle regeneration.  (+info)

Global transcriptional characterization of SP and MP cells from the myogenic C2C12 cell line: effect of FGF6. (6/21)

With the use of Hoechst staining techniques, we have previously shown that the C2C12 myogenic cell line contains a side population (SP) that is largely increased in the presence of fibroblast growth factor 6 (FGF6). Here, we compared transcriptional profiles from SP and main population (MP) cells from either C2C12 or FGF6-expressing C2C12. Expression profiles of SPs show that these cells are less differentiated than MPs and display some similarities to stem cells. Moreover, principal component analysis made it possible to distinguish specific contributions of either FGF6 or differentiation effects on gene expression profiles. This demonstrated that FGF6-expanded SPs were similar to parental C2C12-derived SPs. Conversely, FGF6-treated MPs differed from parental MPs and were more related to SP cells. These results show that FGF6 pushed committed myogenic cells toward a more immature phenotype resulting in the accumulation of cells with a SP phenotype. We propose that FGF6 conditioning could provide a way to expand the pool of immature cells by myoblast dedifferentiation.  (+info)

Localization of FGF-6 and FGFR-4 during prenatal and early postnatal development of the mouse sublingual gland. (7/21)

A number of fibroblast growth factors (FGFs) are involved in regulatory mechanisms of the salivary gland development. However, the role of FGF-6 unique in myogenic cells has not been elucidated in the developing sublingual gland. In the present study, temporo-spatial expression of FGF-6 and its receptor (FGFR)-4, in conjunction with some related histo-chemical properties, were investigated in the sublingual gland of the prenatal and early postnatal mice. The earliest expression of both FGF-6 and FGFR-4 was detected in immature acinar cells at gestational day 17 (GD17). The staining intensity increased gradually and some acinar cells showed a distinct staining at postnatal day 0 (PD0). The immunopositive cells had a relatively round profile and were assumed to be acinar cells. The positive staining decreased thereafter and disappeared completely by PD11. To confirm the identity of cells positive for FGF-6, double immunolabeling with anti-alphasmooth muscle actin (alphaSMA) and anti-FGF-6 antibodies was performed. The positive staining of alphaSMA, a marker of myoepithelial cells, was detected in the flattened cells surrounding the acini but not in the cells positive for FGF-6. The staining properties of secretory granules in acinar cells were also examined with periodic acid-Shiff (PAS) and alcian blue (AB). PAS-positive granules abundant in the late gestational stages (GD17 to PD0) began to be replaced with AB-positive mucous granules at early neonatal days (PD0-3), when the FGF-6/FGFR-4 expression was the strongest. These findings suggest that FGF-6/FGFR-4 might be involved in the changes of secretory granule content of acinar cells in the sublingual gland during the late gestational and early neonatal stages.  (+info)

FGF6 in myogenesis. (8/21)

Important functions in myogenesis have been proposed for FGF6, a member of the fibroblast growth factor family accumulating almost exclusively in the myogenic lineage. However, the analyses of Fgf6 (-/-) mutant mice gave contradictory results and the role of FGF6 during myogenesis remained largely unclear. Recent reports support the concept that FGF6 has a dual function in muscle regeneration, stimulating myoblast proliferation/migration and muscle differentiation/hypertrophy in a dose-dependent manner. The alternative use of distinct signaling pathways recruiting either FGFR1 or FGFR4 might explain the dual role of FGF6 in myogenesis. A role for FGF6 in the maintenance of a reserve pool of progenitor cells in the skeletal muscle has been also strongly suggested. The aim of this review is to summarize our knowledge on the involvement of FGF6 in myogenesis.  (+info)