Temporal and spatial patterns of osteoblast activation following implantation of ?-TCP particles into bone

Abstract

Temporal and spatial patterns of osteoblast activation around beta-TCP particles implanted into bone were analyzed by in situ hybridization with digoxygenin-labeled procollagen alpha 1(I) RNA probes. beta-TCP particles (150-300 microns in diameter) were implanted into rat tibiae, and specimens were collected 3, 5, 7, 14, and 28 days after operation. Activated osteoblasts displayed intense procollagen alpha 1(I) RNA specific labeling. At day 3, osteoblasts lining pre-existing trabeculae in places showed a specific signal. Additionally, scattered activated cells compatible with preosteoblasts also were observed in the vicinity of the trabeculae among red blood cells that filled the space between beta-TCP particles. Osteoblast activation on the surface of beta-TCP rarely was observed. At days 5 and 7, osteoblast activation and bone formation advanced centripetally. At the forefront of bone formation positive cells were scattered in the blood cell clots, and some of the positive cells colonized forming new bone matrix. Formation of new bone did not always begin at the surface of beta-TCP. At day 14, most of the beta-TCP particles were tightly associated with newly formed bone, and the number of positive osteoblasts was reduced. At day 28, absorption of the newly formed bone and the beta-TCP by multinuclear cells was sporadically demonstrated. Such cells often were accompanied by active osteoblasts, suggesting early bone remodeling. In conclusion, in situ hybridization with procollagen alpha 1(I) was employed to demonstrate precisely the mode of recruitment of bone cell precursors. beta-TCP does not positively guide collagen I expressing bone cells along its surface. It has no apparent effects on bone regeneration.

Small‐animal models for testing macroporous ceramic bone substitutes

“…They observed that the bone colonization was higher in cortico-spongious sites than in medullar sites. The osteoconductive properties of calcium phosphate ceramics 10,37,43 may explain this difference. For centripetal bone colonization of the ceramic implant, there must be close contact, and a large interface between the bone and biomaterial.…”

“…Different animal species have also been used to evaluate bone substitutes. For instance, in vivo studies have been conducted in rats, 10,15,20 rabbits, 8,16,[21][22][23][24][25] dogs, 13,26,27 sheep, 9 and goats. 28 As these animals are different in terms of their metabolisms and bone physiology, direct and strict comparison between all these studies is difficult.…”

Enhancement of Bone-Like Apatite Forming Abilities of Calcium Phosphate Ceramics in SBF by Autoclaving

“…13 Neo and Kotani et al showed that b-TCP directly bonded to bone intervening no apatite layer by in vivo tests. 4,14,15 On the other hand, Daculsi et al reported formation of carbonate apatite layer in the vicinity of implanted b-TCP. 16 However, connectivity of b-TCP with host bone was reported to be strong in general and attributed to rough surface due to degradation of implanted b-TCP.…”

Bone formation in .BETA.-tricalcium phosphate-filled bone defects of the rat femur: Morphometric analysis and expression of bone related protein mRNA

“…Osteopontin is produced by osteoblasts and facilitates the adhesion of osteoblasts to the extracellular matrix and accelerates the calcifi cation process. Neo et al (22,23) reported that collagen is found both on the β-TCP and between β-TCP granules, but that osteopontin is found mostly on β-TCP and is also found in the cytoplasm of macrophages. Ohsawa et al (28) demonstrated expression of osteopontin mRNA induced by β-TCP in rat tibia by in situ hybridization, suggesting that osteopontin may play a role in bone formation on the materials and helps to determine their biocompatibility.…”

“…Resorbable tricalcium phosphate (TCP) ceramics (such as β-TCP) of identical initial structure undergo resorption and extensive substitution under the same experimental conditions (10). Some studies have examined the behavior of osteoblasts around implanted β-TCP granules using in situ hybridization in rats (9,20,(22)(23)(24)(25) and other studies have investigated mRNA expression in osteoblasts around the β-TCP (23,28). However, little is known about cell behavior around β-TCP.…”