Compositions and methods for growth factor modulation

An antibody produced by a method comprising the steps of:

• i. expressing proGDF-8 (SEQ ID NO:
• 5);
• ii. forming a growth factor prodomain complex (GPC) by subjecting the expressed proGDF-8 (SEQ ID NO:
• 5) to enzymatic cleavage with one or more of furin, bone morphogenetic protein-1 (BMP-1), mammalian tolloid protein (mTLD), mammalian tolloid-like 1 (mTLL1), and mammalian tolloid-like 2 (mTLL2);
• iii. carrying out solid-phase or solution-phase enrichment with an antibody fragment phage display library, wherein the GPC formed by enzymatic cleavage is used as a target antigen;
• iv. selecting phage particles bound to the GPC formed by enzymatic cleavage;
• and
• v. producing recombinant antibodies having complementarity determining region (CDR) amino acid sequences derived from the antibody fragments expressed at the surface of the selected phage particles.