Spheroid culture enhances osteogenic potential of periodontal ligament mesenchymal stem cells

OBJECTIVE AND BACKGROUND

Human periodontal ligament mesenchymal stem cells (hPDLMSCs) are reported to be responsible for homeostasis and regeneration of periodontal tissue. Although hPDLMSCs are commonly cultured in monolayers, monolayer cultures have been reported as inferior to 3-dimensional cultures such as spheroids, which are spherical clusters of cells formed by self-assembly. The aim of this study was to examine the osteogenic phenotype of spheroids of hPDLMSCs, compared with monolayer cultures of hPDLMSC, in vitro and in vivo.

MATERIAL AND METHODS

Spheroids were formed using microwell chips that were tagged with polyethylene glycol. Mesenchymal stem cell (MSC) markers in hPDLMSC spheroids were examined by flow cytometer. Real-time polymerase chain reaction analysis was examined to measure the expressions of stemness markers and osteogenesis-related genes in monolayer and spheroid-cultured hPDLMSCs. Immunofluorescence analysis was performed to confirm protein expressions of stemness markers in PDLMSC spheroids. Nodule formation assay, alkaline phosphatase (ALP) activity assay and transplantation assay in a mouse calvarial defect model were performed to confirm the osteogenic potential of hPDLMSC spheroids. To elucidate the mechanism of spheroid culture enhanced osteogenesis in hPDLMSCs with osteoinductive medium (OIM), a small interfering RNA (siRNA) assay targeted with secreted frizzled-related protein 3 (SFRP3) was examined. The levels of SFRP3 expression in monolayer and spheroid-cultured hPDLMSCs with OIM were measured by real-time polymerase chain reaction and western blotting analysis. ALP gene expression and ALP activity were examined in SFRP3-deficient hPDLMSC spheroids.

RESULTS

The hPDLMSC spheroids expressed MSC markers, which were similar to hPDLMSCs grown in monolayer cultures. Intriguingly, the protein and mRNA expressions of transcription factors that regulate "stemness" were significantly increased in hPDLMSC spheroids, compared with hPDLMSCs in monolayer cultures. Nodule formation by hPDLMSCs was significantly increased in spheroid cultures grown with OIM, compared with monolayer-cultured hPDLMSCs. ALP activity and expression of osteogenesis-related genes were also significantly enhanced in hPDLMSC spheroids, compared with monolayer cultures. Treatment with hPDLMSC spheroids significantly enhanced new bone formation in a murine calvarial defect model, compared with hPDLMSCs in monolayer culture. Finally, to elucidate mechanisms by which spheroid culture enhances ALP activation in hPDLMSCs grown with OIM, an siRNA assay was used to manipulate expression of SFRP3, a Wnt signaling antagonist. Knockdown of SFRP3 suppressed ALP gene expression in hPDLMSCs grown in OIM; further, it suppressed ALP activity in spheroid culture. These data suggest that the enhancement of osteogenic potential in hPDLMSC spheroids is regulated through SFRP3-mediated ALP activation.

CONCLUSION

Spheroid cultures of hPDLMSCs may be a novel and useful tool in regenerative medicine.

Gingival epithelial cells support osteoclastogenesis by producing receptor activator of nuclear factor kappa B ligand via protein kinase A signaling

BACKGROUND AND OBJECTIVE

Periodontal disease is dental plaque-induced inflammatory disease of the periodontal tissues that results in bone loss in the affected teeth. During bone resorption, receptor activator of nuclear factor kappa B ligand (RANKL) is an essential factor that regulates osteoclastogenesis. Recently, we found that gingival epithelial cells (GECs) in periodontal tissue produce RANKL, the expression of which is regulated by tumor necrosis factor-α and protein kinase A signaling. In this study, we asked whether RANKL-producing GECs induce bone marrow macrophages (BMMs) to form osteoclasts in a co-culture system.

MATERIAL AND METHODS

Ca9-22 GECs and osteoclast precursor BMMs were co-cultured with or without the protein kinase A signaling activator forskolin or inhibitor H89 to examine whether the RANKL-producing GECs could be induced to form osteoclasts, as determined using a pit formation assay.

RESULTS

Osteoclasts formed spontaneously in co-cultures of Ca9-22 cells and BMMs, even in the absence of RANKL. The cells were cultured on bone slices for 14 d, at which time resorption pits were observed. Forskolin treatment significantly increased osteoclast numbers in these co-cultures, but forskolin alone did not induce osteoclast formation by BMMs.

CONCLUSION

GECs producing RANKL are able to support osteoclastogenesis in an in vitro co-culture system using GECs and BMMs, in a process promoted by forskolin.

Clarithromycin suppresses the periodontal bacteria-accelerated abdominal aortic aneurysms in mice

BACKGROUND AND OBJECTIVE

Although clarithromycin (CAM) has many biological functions, including regulation of MMPs, little is known about its effect on abdominal aortic aneurysms. Periodontopathic bacteria have been reported to be associated with several kinds of circulatory diseases. The purpose of this study was therefore to clarify the effect of CAM on periodontopathic bacteria-accelerated abdominal aortic aneurysms.

MATERIAL AND METHODS

Abdominal aortic aneurysm was produced in mice by the peri-aortic application of 0.25 m CaCl(2). The mice were inoculated once per week with live Porphyromonas gingivalis, which is one of the major periodontopathic bacteria. Test mice (n=8) were given a daily oral dose of CAM, while control mice (n=13) were not.

RESULTS

Four weeks after the operation, the P. gingivalis-injected and CAM-treated mice showed a significant decrease in the aortic diameter in comparison with the mice only injected with P. gingivalis. Histopathologically, the samples obtained from the P. gingivalis-injected and CAM-treated mice showed less elastic degradation. Moreover, the plasma MMP-2 concentration of the CAM-treated mice decreased significantly.

CONCLUSION

These findings suggest that CAM administration is useful to suppress periodontal bacteria-accelerated abdominal aortic aneurysms via MMP regulation.

Porphyromonas gingivalis promotes murine abdominal aortic aneurysms via matrix metalloproteinase-2 induction

BACKGROUND AND OBJECTIVE

Abdominal aortic aneurysm (AAA) is a common and lethal disorder, and MMPs are highly expressed in AAA lesions. Large numbers of periodontopathic bacteria have been reported to be present in specimens obtained from the aortic walls of patients with an AAA. The purpose of this study was to analyze the influence of periodontopathic bacteria on AAA dilatation.

MATERIAL AND METHODS

AAAs were produced in mice by the periaortic application of 0.25 M CaCl(2), and NaCl was used as a control. The mice were inoculated once weekly with live Porphyromonas gingivalis, live Aggregatibacter actinomycetemcomitans or vehicle.

RESULTS

Four weeks after the periaortic application of either CaCl(2) or NaCl, a significant increase was observed in the aortic diameter of P. gingivalis-challenged mice compared with the vehicle control mice (p < 0.05), whereas there was no statistically significant increase in the aortic diameter of the A. actinomycetemcomitans-challenged mice. Immunohistochemical analysis found significantly higher numbers of CD8-positive and MOMA2-positive cells and significantly higher levels of MMP-2 in the aneurysmal samples of P. gingivalis-challenged mice compared with control mice. Live P. gingivalis promoted a significant proliferation of splenocytes in comparison with P. gingivalis-lipopolysaccharide and live A. actinomycetemcomitans (p < 0.05).

CONCLUSION

These findings demonstrate that challenge with P. gingivalis, but not with A. actinomycetemcomitans, can accelerate, or even initiate, the progression of experimental AAA through the increased expression of MMPs.

CYP2C9*3 influences the metabolism and the drug-interaction of candesartan in vitro

Candesartan cilexetil is an angiotensin II receptor antagonist, and candesartan, its active metabolite, is metabolized by CYP2C9. However, the effect of CYP2C9*3 on candesartan metabolism is not established. We characterized the kinetics of candesartan by CYP2C9*1/*1 and CYP2C9*1/*3 in human liver microsomes. The difference between the two was not significant. Subsequently, CYP2C9*1 and CYP2C9*3 (Leu359) were expressed in yeast, and the kinetics of candesartan were determined. The wild-type showed the lower Km (345 vs 439 microM; 3/4) and higher Vmax/Km (1/3) than the Leu359 variant. Also, we investigated potential interaction between candesartan and warfarin with both the wild-type and the Leu359 variant. Candesartan had no effect on S-warfarin 7-hydroxylation. In contrast, S-warfarin inhibited candesartan metabolism by the wild-type (K = 17microM) greater than by the Leu359 variant (Ki = 36 microM). These findings suggest that CYP2C9*3 may change not only the metabolic activity but also the inhibitory susceptibility compared with CYP2C9*1.