Production of recombinant bone-inducing proteins

In a process for producing a recombinant bone-inducing protein of the BMP-2 family which comprises culturing in a suitable culture medium a mammalian host cell grown in suspension, said host cell being transformed with a gene encoding BMP-7, and recovering the protein from said culture medium, the improvement for increasing the yield of said bone-inducing protein which comprises adding about 1 to about 1,000 .mu.g/ml dextran sulfate to said culture medium.