In vitro effects of particulate bone substitute materials on the resorption activity of human osteoclasts.

Much research has been done on bone cells, but only a few studies deal with biomaterial-induced effects on human osteoclasts, which may take on an important role in the successful regeneration of bone. In order to highlight such effects, human peripheral blood mononuclear cells (PBMCs) were extracted from venous blood, differentiated to osteoclasts and then cultured in, the presence of five particulate hydroxyapatite (HA)/ß-tricalcium phosphate (TCP) biomaterials, on bovine bone slices and glass cover slips. The biomaterials, AlgOSS 50/50 (50 % HA/50 % TCP), AlgOSS 20/80 (20 % HA/80 % TCP), Algipore (98 % HA), Cerasorb (100 % TCP) and Bio-Oss (100 % HA) were chosen to assess their influence on cell morphology and numbers. Light microscopic evaluation was performed during ongoing cell culture. After 21 d of cultivation, the biomaterial-induced effects on osteoclastic resorption of the bone slices were evaluated by scanning electron microscopy (SEM). Osteoclast-like cells were identified by TRAP staining. All five biomaterials showed larger area fractions of resorbed bone than the control (5.6 ± 6.8 %), as measured on SEM images. The purely hydroxyapatite-based Algipore (9.8 ± 9.7 %) and Bio-Oss (7.9 ± 8.8 %) showed significantly elevated area fraction rates (p ≤ 0.05) of bone resorption. Light microscope evaluation revealed a significant, but inhibiting effect of Cerasorb (p = 0.05). These data indicated that introducing of small biomaterial hydroxyapatite particles may have improved the performance of bone substitute materials.

Proliferation of myocytes on different ECM-components of animal/human origin in vitro.

For the purpose of tissue regeneration gels of reconstituted basement membrane have been suggested as a vehicle to transfer autologous cells. Results do look promising, but it should be considered that extracellular matrix (ECM) gel (Matrigel) is a soluble extract of Engelbreth-Holm-Swarm (EHS) mouse tumor. Therefore objections arising concerning possible risks complicate clinical use in human subjects. Aim of this study was to determine whether ECM-components of human origin can be used as substitutes for tissue engineering tasks as proposed previously. Proliferation capability and viability of primary rat myocytes and rat myocyte cell lines were determined on days 1, 2, 4 and 8 after inocculation of the cells. Pooled data suggest that an appropriate combination of human ECM and human Collagen Type IV may represent an approach with good prospects.

[Concerning cell cultures for biocompatibility-testing: monitoring by DNA-fingerprinting]. / Ad Zellkulturen zur Biomaterialuntersuchung: Uberwachung mit DNA-Fingerabdrücken.

Cell cultures are innovative tools for e.g. biocompatibility testing of biomaterials in vitro. In our studies we used fibroblast, endothelial cell and chondrocyte cultures of human origin and of the test animal species most common for this purpose in vivo. Verification of the identity of these cells is obligatory for reproducibility of the tests and valid interpretation of the results. Cultured cells have to be checked for identity, contaminations of various origins and also for genomic mutations occuring during prolonged cultivation in vitro or due to exposition to biomaterials. Furthermore, the risk of genetic cross-contamination with other cells increases with the number of cell cultures passaged parallel in the same laboratory. Therefore, we generated reference fingerprints of the cultures in varying passages for comparative monitoring of cells purposed for in vitro tests. Minisattelite DNA polymorhism resulting in reproducible individual DNA fingerprints is very discriminatory and can be used for cell culture monitoring. The patterns are stable over several passages, although sudden changes did happen in two cases, i.e. loss/gain of bands or changes in band-intensity, indicating massive genomic mutations of the cultures in vitro. Influences of biomaterials on the prints could not be detected. Several tasks can be followed at the same time: detection of contaminant cells, identification of these cells of primary culture origin used for in vitro testing and finally, monitoring for eventual genomic mutations due to prolonged cultivation or contact to biomaterials. Inconclusive results in just one of these aspects should lead to the disqualification of the monitored cultures from usage in vitro.