Studies on in vitro evaluation for the biocompatibility of various biomaterials: inhibitory activity of various kinds of polymer microspheres on metabolic cooperation

Effects of surface chemistry prepared by self-assembled monolayers on osteoblast behavior

A surface of biomaterials is known to affect the behavior of cells after their adhesion on the surface, indicating that surface characteristics of biomaterials play an important role in cell adhesion, proliferation, and differentiation. To assess the effects of functional groups on biomaterial surface, normal human osteoblasts (NHOsts) were cultured on surfaces coated with self-assembled monolayers (SAMs) containing various functional groups, and the adhesion, proliferation, differentiation, and gap junctional intercellular communication (GJIC) of the NHOsts were investigated. In the case of SAM with terminal methyl groups (hydrophobic surface), NHOst adhesion and proliferation was less prevalent. In contrast, NHOsts were adhered well on SAMs with hydroxyl, carboxyl, amino, phosphate, and sulfate group, which are relatively hydrophilic, their proliferation and differentiation level were dependent on the type of functional groups. Especially, when they were cultured on either SAMs with phosphate or sulfate group, both their alkaline phosphate activity and the calcium deposition by them were enhanced more than those cultured on a collagen-coated dish. More interestingly, GJIC of NHOsts, which has been reported to play a role in cell differentiation as well as homeostasis of cells, were not significantly different among the SAM surfaces tested. These suggest that a specific functional group on a material surface can regulate NHOst adhesion, proliferation, and differentiation via cell-functional group interaction without influencing their homeostasis.

Hydroxy apatite microspheres enhance gap junctional intercellular communication of human osteoblasts composed of connexin 43 and 45

The aseptic loosening of artificial joints with associated periprosthetic bone resorption may be partly due to the suppression of osteoblast function to form new bone by wear debris from the joint. To assess the effect of wear debris on osteoblasts, effects of model wear debris on gap junctional intercellular communication (GJIC) of normal human osteoblasts were estimated. The GJIC activity of the osteoblasts after a 1-day incubation with the microspheres was similar to that of normal osteoblasts. However, hydroxy apatite particles, which have been reported to enhance the differentiation of osteoblasts in contact with them, enhanced the GJIC function of the osteoblasts. From RT-PCR studies, not only connexin 43 but also connexin 45 is suggested to play a role in the GJIC of the osteoblasts in an early stage of coculture with the microspheres, although it is still unclear how these connexins work and are regulated in the GJIC and differentiation. However, this study suggests that there is a relationship between the early levels of GJIC and the differentiation of the cells. Therefore, estimating the effect of biomaterials, even in the microsphere form, on the GJIC of model cells, with which the biomaterials may be in contact in vivo, can provide important information about their biocompatibility.

The response of normal human osteoblasts to anionic polysaccharide polyelectrolyte complexes

Polyelectrolyte complexes (PEC) were prepared from chitosan as the polycation and several synthesized functional anion polysaccharides, and their effects on cell attachment, morphology, proliferation and differentiation were estimated using normal human osteoblasts (NHOst). After a 1-week incubation, PEC made from polysaccharides having carboxyl groups as polyanions showed low viability of NHOst on it although the NHOst on it showed an enhancement in their differentiation level. On the other hand, NHOst on PEC made from sulfated or phosphated polysaccharides showed similar attachment and morphology to those on the collagen-coated dish. When the number of NHOst was estimated after 1 week, the number on the PEC was ranged from 70% to 130% of those on the collagen-coated dish, indicating few effects of these PEC on cell proliferation. In addition, NHOst on PEC films made from sulfated polysaccharides differentiated to a level very similar to that observed on the collagen-coated dish, indicating that these PEC films maintain the normal potential of NHOst to both proliferate and differentiate. Measurement of gap junctional intercellular communication of NHOst on PEC revealed that PEC did not inhibit communication, suggesting that PEC films have few effects on cell homeostasis. Thus, PEC made from the sulfated polysaccharide may be a useful material as a new scaffold for bone regeneration.