Anti-ACVR2B monoclonal antibody

Background: We recently reported on the effects of exogenous growth differentiation factor 9 (GDF9) in enhancing activin A-induced inhibin beta(B)-subunit mRNA and inhibin B levels in human granulosa-lutein (hGL) cells by modulating key components of the activin signaling pathway. We undertook the following study to characterize the role of endogenous GDF9 in this regard. Methods: We compared inhibin subunit (alpha, beta(A), and beta(B)) mRNA and inhibin B levels and activation of activin receptors (ACVRs) and Smad signaling pathway in hGL cells obtained from women undergoing in vitro fertilization and cultured with and without activin A treatment after GDF9-targeting small interfering RNA transfection. GDF9, inhibin subunits, ACVR2B/1B and Smad2/3/4/7 mRNA and/or protein levels, Smad phosphorylation, and inhibin B were assessed with RT-PCR, immunoblotting, and ELISA. Data were analyzed by ANOVA followed by Tukey's test. Results: GDF9 was detected as mRNA and protein in hGL cells and protein in follicular fluid from all 11 patients tested. Reduced endogenous GDF9 expression after targeting small interfering RNA transfection was associated with decreased ACVR2B/1B and Smad2/3/4 but increased inhibitory Smad7 mRNA and protein levels and, consequently, reduced activin A-induced beta (B)-subunit mRNA and inhibin B levels. Conclusions: We report here for the first time autocrine roles for endogenous GDF9 in hGL cells in enhancing activin A-induced beta(B)-subunit mRNA and inhibin B levels via key components of the activin signaling pathway. However, the relative contributions of GDF9 in granulosa cells vs. oocyte as autocrine/paracrine regulators of beta(B)-subunit and inhibin B production in normal and abnormal human ovarian functions remain to be determined. (J Clin Endocrinol Metab 94: 5108-5116, 2009)

Myostatin is a secreted protein that normally functions as a negative regulator of muscle growth. Agents capable of blocking the myostatin signaling pathway could have important applications for treating human muscle degenerative diseases as well as for enhancing livestock production. Here we describe a potent myostatin inhibitor, a soluble form of the activin type IIB receptor (ACVR2B), which can cause dramatic increases in muscle mass (up to 60% in 2 weeks) when injected into wild-type mice. Furthermore, we show that the effect of the soluble receptor is attenuated but not eliminated in Mstn(-/-) mice, suggesting that at least one other ligand in addition to myostatin normally functions to limit muscle growth. Finally, we provide genetic evidence that these ligands signal through both activin type II receptors, ACVR2 and ACVR2B, to regulate muscle growth in vivo.