Fibronectin expression in human mesangial cell cultures and its alterations by adriamycin

Lack of integrin alpha1beta1 leads to severe glomerulosclerosis after glomerular injury

Severity of fibrosis after injury is determined by the nature of the injury and host genetic susceptibility. Metabolism of collagen, the major component of fibrotic lesions, is, in part, regulated by integrins. Using a model of glomerular injury by adriamycin, which induces reactive oxygen species (ROS) production, we demonstrated that integrin alpha1-null mice develop more severe glomerulosclerosis than wild-type mice. Moreover, primary alpha1-null mesangial cells produce more ROS both at baseline and after adriamycin treatment. Increased ROS synthesis leads to decreased cell proliferation and increased glomerular collagen IV accumulation that is reversed by antioxidants both in vivo and in vitro. Thus, we have identified integrin alpha1beta1 as a modulator of glomerulosclerosis. In addition, we showed a novel pathway where integrin alpha1beta1 modulates ROS production, which in turn controls collagen turnover and ultimately fibrosis. Because integrin alpha1beta1 is expressed in many cell types this may represent a generalized mechanism of controlling matrix accumulation, which has implications for numerous diseases characterized by fibrosis.

Increased fibronectin expression in developing embryos is associated with abnormal notochord in the Adriamycin rat model

BACKGROUND

The VACTERL association is a spectrum of clinical conditions, including esophageal atresia (EA) and tracheoesophageal fistula (TEF), which affects approximately 1 in 5,000 live human births. The administration of intraperitoneal Adriamycin to pregnant rats reliably induces anomalies, such as EA and TEF, in their offspring, in what is known as the Adriamycin rat model (ARM). In affected embryos the presence of gross notochord abnormalities is commonly found, with typical features being ectopic ventral branches and adherence of the notochord to the foregut. Fibronectin (FN) is an extracellular matrix (ECM) glycoprotein present on most cell surfaces, in extracellular fluids and in plasma. FN is involved in various functions, including cell adhesion, cell motility and wound healing. Previous studies in rats have shown that a single dose of Adriamycin can produce an appreciable rise in FN levels in various organs such as kidney and heart. We hypothesised that Adriamycin administration could promote upregulation of FN expression contributing to increased gut-notochord adherence and the development of abnormal ventral notochordal branching in the ARM. This study was designed to investigate FN expression in ARM embryos.

METHODS

Adriamycin (1.75 mg/kg) was administered intraperitoneally to pregnant rats on days 7,8 and 9 of gestation (E7, E8 and E9 respectively). Control animals were given saline. Embryos recovered on E10-E14 were fixed, embedded in paraffin and sectioned. Immunohistochemistry using an anti-FN rabbit polyclonal antibody was performed.

RESULTS

FN expression in both Adriamycin and control embryos on E10, E11 and E12 was comparable. However, the levels of FN expression in Adriamycin embryos on E13 and E14 were significantly greater in embryos with abnormal notochords than in equivalent control embryos.

CONCLUSION

Adriamycin-induced increased expression of FN, in the ARM, may contribute to abnormal notochord development leading to the VACTERL association.