ENDOTHELIAL-CELL INDUCED MODULATION OF CARDIAC FIBROBLAST COLLAGEN-METABOLISM

Objective: The aim was to examine the influence of vascular endothelia l cells on rat cardiac fibroblast collagen synthesis and collagenase a ctivity under co-culture conditions, and to determine whether angioten sin II or aldosterone influence endothelial cell induced modulation of fibroblast collagen metabolism. Methods: Bovine aortic endothelial ce lls were grown to confluence on microporous membrane inserts and then co-cultured with cardiac fibroblasts obtained from adult rats, previou sly grown to confluence in 35 mm dishes supplemented with 0.4% fetal b ovine serum. Collagen synthesis was measured by H-3-proline incorporat ion. Experiments were also conducted under similar conditions to quant itate collagenase activity by zymography in conditioned medium from fi broblasts co-cultured with endothelial cells. Results: After 48 h co-c ulture, there was a 1.9-fold increase in fibroblast collagen synthesis when compared to fibroblasts alone (p<0.001). Aldosterone (10(-8) M) or angiotensin II (10(-7) M) added to endothelial cells did not increa se fibroblast collagen synthesis over co-cultures alone. Neither the a ldosterone receptor antagonist spironolactone (10(-8) M) nor type I (D uP 753, 10(-8) M) or type II (PD 123319, 10(-8) M) angiotensin II rece ptor antagonists altered fibroblast collagen synthesis in co-cultures. A significant increment in collagenase activity was observed in co-cu ltured fibroblasts relative to collagenase activity of fibroblasts alo ne. Conclusions: Endothelial cells modulate both cardiac fibroblast co llagen synthesis and degradation. The nature of the responsible signal (s) remains to be defined, but does not appear to be mediated or regul ated by angiotensin II or aldosterone.