Expression of an engineered form of recombinant procollagen in mouse milk

We have examined the suitability of the mouse mammary gland for expression of novel recombinant procollagens that can be used for biomedical applicati ons. We generated transgenic mouse lines containing cDNA constructs encodin g recombinant procollagen, along with the alpha and beta subunits of prolyl 4-hydroxylase, an enzyme that modifies the collagen into a form that is st able at body temperature, The lines expressed relatively high levels (50-20 0 mu g/ml) of recombinant procollagen in milk, As engineered, the recombina nt procollagen was shortened and consisted of a pro alpha 2(I) chain capabl e of forming a triple-helical homotrimer not normally found in nature, Anal ysis of the product demonstrated that (1) the pro alpha chains formed disul phide-linked trimers, (2) the trimers contained a thermostable triple-helic al domain, (3) the N-propeptides were aligned correctly, and (4) the expres sed procollagen was not proteolytically processed to collagen in milk.