An investigation of the osteoinductive properties of Colloss
Colloss is a sterile extract of bovine bone matrix which consists predominantly of collagen type 1, but also contains several growth factors associated with bone matrix. The ability of Colloss to stimulate bone formation adjacent to titanium implants in vivo and its effect on the proliferation and differentiation of multipotential human bone marrow stromal stem cells (BMSSCs) in vitro and on titanium and hydroxyapatite (HA) was investigated. When BMSSCs were cultured with a solution of Colloss in vitro for 21 days, evidence of osteogenic differentiation was signified by the expression of Alkaline Phosphatase (ALP), collagen type I, calcium deposition and changes in cell morphology. When BMSSCs were cultured on titanium pre-treated with Colloss, there was increased expression of the osteoblastic markers ALP at day 7 and osteopontin on days 14 and 21 compared to BMSSCs cultured on untreated titanium. BMSSCs cultured on porous hydroxyapatite pre-treated with Colloss showed no difference in the expression of the osteogenic markers ALP and osteopontin compared to BMSCCs cultured on untreated porous hydroxyapatite. However there was an increase in collagen type I synthesis, which was 3 times that of control cultures of BMSSCs on untreated HA at 21 days. When Colloss was used to fill 1 and 2 mm defects adjacent to shot blasted titanium implants placed in tibia of sheep, there was no difference in the area of new bone formation or the degree of mineralisation of bone between the control and Colloss containing defects. These findings show that Colloss can induce the osteogenic differentiation of bone marrow stromal stem cells cultured in monolayer and on smooth polished titanium. Results of BMSSCs cultured on hydroxyapatite were inconclusive, although evidence of collagen type I synthesis was suggestive of matrix deposition. Colloss did not enhance bone formation within defects adjacent to titanium implants in vivo.