Effects of Porphyromonas gingivalis 2561 extracts on osteogenic and osteoclastic cell function in co-culture

Osteoblast-osteoclast co-cultures: A systematic review and map of available literature

Drug research with animal models is expensive, time-consuming and translation to clinical trials is often poor, resulting in a desire to replace, reduce, and refine the use of animal models. One approach to replace and reduce the use of animal models is to use in vitro cell-culture models. To study bone physiology, bone diseases and drugs, many studies have been published using osteoblast-osteoclast co-cultures. The use of osteoblast-osteoclast co-cultures is usually not clearly mentioned in the title and abstract, making it difficult to identify these studies without a systematic search and thorough review. As a result, researchers are all developing their own methods, leading to conceptually similar studies with many methodological differences and, as a consequence, incomparable results. The aim of this study was to systematically review existing osteoblast-osteoclast co-culture studies published up to 6 January 2020, and to give an overview of their methods, predetermined outcome measures (formation and resorption, and ALP and TRAP quantification as surrogate markers for formation and resorption, respectively), and other useful parameters for analysis. Information regarding these outcome measures was extracted and collected in a database, and each study was further evaluated on whether both the osteoblasts and osteoclasts were analyzed using relevant outcome measures. From these studies, additional details on methods, cells and culture conditions were extracted into a second database to allow searching on more characteristics. The two databases presented in this publication provide an unprecedented amount of information on cells, culture conditions and analytical techniques for using and studying osteoblast-osteoclast co-cultures. They allow researchers to identify publications relevant to their specific needs and allow easy validation and comparison with existing literature. Finally, we provide the information and tools necessary for others to use, manipulate and expand the databases for their needs.

The effect of recombinant human bone morphogenetic protein-4 on the osteoblastic differentiation of mouse calvarial cells affected by Porphyromonas gingivalis

BACKGROUND

A number of studies have shown effective bone regeneration induced by bone morphogenetic proteins (BMPs), but it is not clear whether the presence of periodontopathic bacteria has any significant modulation effect on the bone regeneration ability of BMPs. The present study examined whether pretreatment of mouse calvarial cells with Porphyromonas gingivalis extracts can make a difference in their osteoblastic differentiation exerted by recombinant human bone morphogenetic protein-4 (rhBMP-4).

METHODS

Primary mouse calvarial osteoblastic (MCO) cells were cultured until they reached confluence. At confluence, cells were untreated or pretreated with 1 microgram/ml of sonicated P gingivalis extracts (SPEs) for 2 days. After washing, the cells were further incubated in the presence of rhBMP-4 (0 to 100 ng/ml) for 3 days. At the end of the treatment, the cells were harvested and lysed for measurement of the alkaline phosphatase (ALP) activity. Total RNA was extracted, and reverse transcription-polymerase chain reaction (RT-PCR) analysis for expression of ALP mRNA was conducted. The amount of prostaglandin E2 (PGE2) secreted into the culture supernatant was determined using an enzyme immunoassay.

RESULTS

The stimulatory effect of rhBMP-4 on ALP activity was observed in both untreated MCO cells and in cells pretreated with 1 microgram/ml of SPEs in a dose-dependent manner. The ALP activities were significantly reduced in the cells pretreated with SPEs at all concentrations of rhBMP-4 used in the study when compared to untreated cells. Similar results were obtained in the RT-PCR analysis for ALP mRNA. Cells pretreated with SPEs released significantly larger amounts of PGE2 than untreated cells, but the treatment with 100 ng/ml of rhBMP-4 had no significant effect on the amount of PGE2 released. These results suggest that the stimulatory effect of rhBMP-4 on osteoblastic differentiation might be significantly reduced by P gingivalis, possibly through the endogenous PGE2 pathway, but rhBMP-4 still has a stimulatory effect on osteoblastic differentiation of mouse calvarial cells affected by P gingivalis.

CONCLUSION

Our results suggest that supplemental BMPs would be beneficial for improved treatment of osseous defects, although their biologic effect might be significantly reduced by periodontopathic bacteria.