Presence of basic fibroblast growth factor in cultured rat cardiomyocytes and its release in culture medium

Vasculogenesis and angiogenesis: molecular and cellular controls. Part 1: growth factors

SUMMARY

Angiogenesis characterizes embryonic development, but also occurs in adulthood in physiological situations such as adaptation to muscle exercise, and in pathological conditions like cancer. Major advances have been made in understanding the molecular mechanisms responsible for vasculogenesis and angiogenesis, largely due to the use of "knock-out mice", i.e. mice in which the gene coding for the protein under investigation has been inactivated. Interestingly, the same growth factors and their receptors are equally involved in the different aspects of vasculogenesis and angiogenesis during development and in adulthood. This review aims to describe in detail their respective roles and how interactions between them lead to a newly formed vessel.

Differential protein localization in sarcomeric and nonsarcomeric contractile structures of cultured cardiomyocytes

The use of cardiomyocyte cell culture models allows the identification of various cell mediators that bring about changes in subcellular structures and gene expression associated with hypertrophy. The effects of insulin-like growth factor-I (IGF-I), basic fibroblast growth factor (bFGF), and triiodothyronine (T3) on gene expression and on the structural organization of myofibrillar and cytoskeletal proteins were compared in adult atrial (aARC) and ventricular (vARC) as well as in neonatal ventricular rat cardiomyocytes (vNRC) in long-term culture. Structural changes were evaluated by confocal microscopy and correlated to biochemical alterations. In vARC, IGF-I enhanced myofibrillar growth, whereas bFGF or T3 restricted sarcomere assembly to the central cell area, forming a sharp boundary in more than 50% of the cells. However, myosin occurred both in the cross-striated myofibrillar structures and in patches running along the nonsarcomeric fibrillar structures (also called stress fiber-like structures) in the cell periphery. In cells treated with either bFGF or T3, the expression of alpha-smooth muscle actin (alpha-sm actin) was greatly increased. This actin isoform was incorporated mainly into the nonsarcomeric contractile structures outside the area where myofibrils ended abruptly. alpha-sm actin protein increased up to 14- to 17-fold while the mRNA showed a moderate increase of 2- to 4-fold. This suggests that alpha-sm actin is mainly regulated at the translational or posttranslational level. In contrast, the cytoskeletal proteins alpha-actinin and vinculin increased only moderately (less than 2-fold) but also showed a relocalization in cells with restricted myofibrils. In aARC and in vNRC, alpha-sm actin was only moderately upregulated by bFGF or T3 and no drastic morphological changes were observed. In conclusion, IGF-I, bFGF, and T3 induced characteristic structural phenotypes depending on the type of cardiomyocyte. Large amounts of alpha-sm actin as expressed in bFGF and T3 treated vARC seem to be incompatible with sarcomere assembly.

Monocyte activation in angiogenesis and collateral growth in the rabbit hindlimb

We have previously shown that monocytes adhere to the vascular wall during collateral vessel growth (arteriogenesis) and capillary sprouting (angiogenesis). In this study we investigated the association of monocyte accumulation with both the production of the cytokines-basic fibroblast growth factor (bFGF) and TNF-alpha-and vessel proliferation in the rabbit after femoral artery occlusion. In particular, we studied the effects of an increase in monocyte recruitment by LPS on capillary density as well as collateral and peripheral conductance after 7 d of occlusion. Monocytes accumulated around day 3 in collateral arteries when maximal proliferation was observed, and stained strongly for bFGF and TNF-alpha. In the lower limb where angiogenesis was shown to be predominant, macrophage accumulation was also closely associated with maximal proliferation (around day 7). LPS treatment significantly increased capillary density (424+/-26.1 n/mm2 vs. 312+/-20.7 n/mm2; P < 0.05) and peripheral conductance (109+/-33.8 ml/min/100 mmHg vs. 45+/-6.8 ml/min/100 mmHg; P < 0.05) as compared with untreated animals after 7 d of occlusion. These results indicate that monocyte activation plays a major role in angiogenesis and collateral artery growth.