A preliminary study in osteoinduction by a nano-crystalline hydroxyapatite in the mini pig.

Abstract

Abstract:To test the probable osteoinductive properties of NanoBone®, a new highly non-sintered porous nano-crystalline hydroxylapatite bone substitute embedded into a silica gel matrix, granules were implanted subcutaneously and intramuscularly into the back region of 18 mini pigs. After periods of 5 and 10 weeks as well as 4 and 8 months, implantation sites were investigated using histological and histomorphometric procedures. Signs of early osteogenesis could already be detected after 5 weeks. The later periods were characterized by increasing membranous osteogenesis in and around the granules leading to the formation of bone-like structures showing periosteal and tendon-like structures with bone marrow and focal chondrogenesis. Bone formation was better in the subcutaneous than in the intramuscular implantation sites. This ectopic osteogenesis is discussed with regard to the nanoporosity and microporosity of the material, physico-chemical interactions at its surface, the differentiation of osteoblasts, the role of angiogenesis and the probable involvement of growth factors. The results of this preliminary study indicate that this biomaterial has osteoinductive potential and induces the formation of bone structures, mainly in subcutaneous adipose tissue in the pig.

Implantation of silicon dioxide-based nanocrystalline hydroxyapatite and pure phase beta-tricalciumphosphate bone substitute granules in caprine muscle tissue does not induce new bone formation

“…Despite the presence of micro- and nanopores, NB in its granular form within caprine muscle probably did not induce sufficient mineral ion influx and protein-related surface modifications, which are suggested as a requirement to trigger osteoinduction [27-29]. On the other hand, another in vivo study in mini pigs reported a marked osteoinduction within subcutaneous as well as muscle implantation sites induced by the very same NB-granules [12]. Thus, we assume that the lack of osteoinductivity of NB in the present study could be explained on the basis of its application form, i.e.…”

“…In combination with bone marrow stromal cells [31], however, and along with hydroxyapatite as biphasic calcium phosphate ceramics [32-34], it has been shown to induce different degrees of osteoinductivity, even in ectopic tissues. With regard to objectivity, it has to be considered whether the used ß-TCP granules would have shown some osteoinductive properties, when implanted into the subcutaneous or muscle tissue of the mini-pig as was done for NB [12]. Furthermore, it has to be emphasized that for ß-TCP, osteoinduction has been demonstrated in dogs [35,36].…”

“…The granular form seems to be an influential parameter to a higher extent than previously assumed. These differences might be the reason why the implantation of the NB-granules led to ectopic bone formation in the subcutaneous and the muscle tissue of mini-pigs [12], while no osteoinductive capacity was observed when the same granules were implanted into caprine muscle.…”

“…The osteoinductive potential of NanoBone ® (NB) hydroxyapatite/silicon dioxide (HA/SiO 2 )-based nanocrystalline bone substitute has been demonstrated in an in vivo study in mini pigs by Götz et al [12]. The authors reported both new bone formation and osteogenic differentiation which they claimed were better in the subcutaneous tissue than in the intramuscular implantation sites.…”

Microsphere-based scaffolds encapsulating tricalcium phosphate and hydroxyapatite for bone regeneration

“…TCP and HAp are both chemically similar to the inorganic component of bone and are osteoconductive because of their capability to bond with bone. TCP lacks osteoinductivity, while HAp is widely accepted to be osteoinductive [7, 8]. On the other hand, HAp degrades over the course of several years, whereas TCP may be resorbed into the new bone tissue [9, 10].…”