M. Neo et al., ANALYSIS OF OSTEOBLAST ACTIVITY AT BIOMATERIAL-BONE INTERFACES BY IN-SITU HYBRIDIZATION, Journal of biomedical materials research, 30(4), 1996, pp. 485-492
To investigate the effects of bioactive materials on bone formation in
vivo, a new experimental model using in situ hybridization has been d
eveloped. A hole was drilled bilaterally in the distal epiphysis of ra
bbit femurs with subsequent implantations of beta-tricalcium phosphate
(beta-TCP) cylinders in a press-fit manner. Specimens were collected
at 3, 7, 14, and 28 days after operation. Femurs with empty drilling h
oles, and normal distal femurs without operation were used as controls
. All specimens were decalcified and hybridized with a procollagen alp
ha 1(I) complementary RNA probe labeled with digoxygenin. In normal-bo
ne sections, procollagen alpha 1(I) RNA was clearly demonstrated in pe
riosteal osteoblasts, in osteoblasts in the mineralizing zone adjacent
to growth plates, and in osteoblasts lining remodeling canals. As for
beta-TCP, labeled osteoblasts around the material were not found at d
ay 3, whereas they were most intensively observed at day 7 and a littl
e less at day 14, in accordance with new-bone formation around the mat
erial. Weaker signals were also detected in fibroblasts at day 7. At d
ay 28, osteoblasts lining the surface of newly formed bone were mainly
negative, whereas those adjacent to the resorption sites of the beta-
TCP showed positive signals, demonstrating an active remodeling at the
material surface. The temporal expression of procollagen alpha 1(I) R
NA in the beta-TCP specimens was fundamentally the same as that in the
empty-hole specimens, suggesting no remarkable acceleration or suppre
ssion of bone-forming activity of osteoblasts by beta-TCP, which is co
nsistent with osteoconductive bone formation. This in situ hybridizati
on method was suggested to be a powerful tool in analyzing the biologi
cal effects of bioactive materials. (C) 1996 John Wiley & Sons, Inc.