Non-collagenous
phosphoproteins that interact with a
type-I collagen are thought to nucleate bone
mineral into
collagen networks of mineralized tissues. Previously,
phosphophoryn cross-linked to
type-I collagen was reported to be an effective nucleator of appatite. However, free
phosphophoryn molecules inhibit the formation of
apatite in vitro. On the basis of the above study, we expected a
collagen-
phosphophoryn sponge to be a good scaffold for bone-tissue engineering and examined the formation of bone in orthotopically transplanted composites of the sponge and bone marrow osteoblasts in vivo in Fischer rats. Osteoblastic primary cells were obtained from the bone shaft of femorae of Fisher rats, according to the method of Maniatopoulous et al. A
suspension of marrow cells was distributed through a flask with standard culture medium and incubated at 37 degrees C. When cultures were nearly confluent after 10 days, they were concentrated by centrifugation to 10(6) cells/ml and subcultured onto the synthesized
collagen-
phosphophoryn sponge and a
collagen sponge (control). After 14 days, the composites of
collagen-
phosphophoryn and osteoblastic cells as well as control composites were transplanted into bone-defect sites of Fisher rats (holes 2 mm in diameter) and then the
wounds were sutured. The composites were harvested at 1-8 weeks after implantation, and stained with
hematoxylin and
eosin. It was found that more bone was formed in the composites of
collagen-
phosphophoryn sponge and osteoblasts than control composites from 1 week to 8 weeks, suggesting that the
collagen-
phosphophoryn sponge is a good candidate as a scaffold for bone-tissue engineering.