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Prolonged exposure to bacterial toxins downregulated expression of toll-like receptors in mesenchymal stromal cell-derived osteoprogenitors.

Mo IF, Yip KH, Chan WK, Law HK, Lau YL, Chan GC - BMC Cell Biol. (2008)

Bottom Line: We found that during osteogenic differentiation, MSC-derived osteoprogenitors gradually expressed TLR2 and TLR4 by Day 12.But under prolonged incubation with LPS, MSC-derived osteoprogenitors had reduced TLR2 and TLR4 gene expression.In conclusion, our findings support the potential of using human MSCs as a biological graft, even under a bacterial toxin-rich environment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Paediatrics and Adolescent Medicine, Faculty of Medicine, The University of Hong Kong, Hong Kong, PR China. irene_hku@yahoo.com

ABSTRACT

Background: Human mesenchymal stromal cells (MSCs, also known as mesenchymal stem cells) are multipotent cells with potential therapeutic value. Owing to their osteogenic capability, MSCs may be clinically applied for facilitating osseointegration in dental implants or orthopedic repair of bony defect. However, whether wound infection or oral microflora may interfere with the growth and osteogenic differentiation of human MSCs remains unknown. This study investigated whether proliferation and osteogenic differentiation of MSCs would be affected by potent gram-positive and gram-negative derived bacterial toxins commonly found in human settings.

Results: We selected lipopolysaccharide (LPS) from Escherichia coli and lipoteichoic acid (LTA) from Streptococcus pyogenes as our toxins of choice. Our findings showed both LPS and LTA did not affect MSC proliferation, but prolonged LPS challenge upregulated the osteogenic differentiation of MSCs, as assessed by alkaline phosphatase activity and calcium deposition. Because toll-like receptors (TLRs), in particularly TLR4 and TLR2, are important for the cellular responsiveness to LPS and LTA respectively, we evaluated their expression profiles serially from MSCs to osteoblasts by quantitative PCR. We found that during osteogenic differentiation, MSC-derived osteoprogenitors gradually expressed TLR2 and TLR4 by Day 12. But under prolonged incubation with LPS, MSC-derived osteoprogenitors had reduced TLR2 and TLR4 gene expression. This peculiar response to LPS suggests a possible adaptive mechanism when MSCs are subjected to continuous exposure with bacteria.

Conclusion: In conclusion, our findings support the potential of using human MSCs as a biological graft, even under a bacterial toxin-rich environment.

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Related in: MedlinePlus

TLR4 and TLR2 constitutive gene expression in MSCs and PBMCs. Quantitative PCR revealed that constitutive expression of (A) TLR4 was higher in PBMCs than in MSCs, while (B) TLR2 was not expressed in MSCs. The data are pooled from three experiments, each done in duplicates, and expressed as mean ± SEM. * P < 0.05; ** P < 0.01.
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Figure 3: TLR4 and TLR2 constitutive gene expression in MSCs and PBMCs. Quantitative PCR revealed that constitutive expression of (A) TLR4 was higher in PBMCs than in MSCs, while (B) TLR2 was not expressed in MSCs. The data are pooled from three experiments, each done in duplicates, and expressed as mean ± SEM. * P < 0.05; ** P < 0.01.

Mentions: Because only the osteogenic function but not the proliferation of MSCs was affected by LPS, we hypothesized that MSC may not express TLR4 (the major LPS receptor) until osteogenic differentiation is triggered. We thus evaluated TLR4 and TLR2 mRNA levels by quantitative PCR. The constitutive gene expressions of TLR4 and TLR2 on MSCs were determined using PBMCs as a positive control because these cells express all TLRs constitutively. As expected, the basal level of TLR4 mRNA in MSCs was much lower than that of PBMCs (n = 3, P < 0.05) (Figure 3A). A similar result was observed for the TLR2 mRNA level, which was virtually undetectable in MSCs (n = 3, P < 0.01) (Figure 3B).


Prolonged exposure to bacterial toxins downregulated expression of toll-like receptors in mesenchymal stromal cell-derived osteoprogenitors.

Mo IF, Yip KH, Chan WK, Law HK, Lau YL, Chan GC - BMC Cell Biol. (2008)

TLR4 and TLR2 constitutive gene expression in MSCs and PBMCs. Quantitative PCR revealed that constitutive expression of (A) TLR4 was higher in PBMCs than in MSCs, while (B) TLR2 was not expressed in MSCs. The data are pooled from three experiments, each done in duplicates, and expressed as mean ± SEM. * P < 0.05; ** P < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2567970&req=5

Figure 3: TLR4 and TLR2 constitutive gene expression in MSCs and PBMCs. Quantitative PCR revealed that constitutive expression of (A) TLR4 was higher in PBMCs than in MSCs, while (B) TLR2 was not expressed in MSCs. The data are pooled from three experiments, each done in duplicates, and expressed as mean ± SEM. * P < 0.05; ** P < 0.01.
Mentions: Because only the osteogenic function but not the proliferation of MSCs was affected by LPS, we hypothesized that MSC may not express TLR4 (the major LPS receptor) until osteogenic differentiation is triggered. We thus evaluated TLR4 and TLR2 mRNA levels by quantitative PCR. The constitutive gene expressions of TLR4 and TLR2 on MSCs were determined using PBMCs as a positive control because these cells express all TLRs constitutively. As expected, the basal level of TLR4 mRNA in MSCs was much lower than that of PBMCs (n = 3, P < 0.05) (Figure 3A). A similar result was observed for the TLR2 mRNA level, which was virtually undetectable in MSCs (n = 3, P < 0.01) (Figure 3B).

Bottom Line: We found that during osteogenic differentiation, MSC-derived osteoprogenitors gradually expressed TLR2 and TLR4 by Day 12.But under prolonged incubation with LPS, MSC-derived osteoprogenitors had reduced TLR2 and TLR4 gene expression.In conclusion, our findings support the potential of using human MSCs as a biological graft, even under a bacterial toxin-rich environment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Paediatrics and Adolescent Medicine, Faculty of Medicine, The University of Hong Kong, Hong Kong, PR China. irene_hku@yahoo.com

ABSTRACT

Background: Human mesenchymal stromal cells (MSCs, also known as mesenchymal stem cells) are multipotent cells with potential therapeutic value. Owing to their osteogenic capability, MSCs may be clinically applied for facilitating osseointegration in dental implants or orthopedic repair of bony defect. However, whether wound infection or oral microflora may interfere with the growth and osteogenic differentiation of human MSCs remains unknown. This study investigated whether proliferation and osteogenic differentiation of MSCs would be affected by potent gram-positive and gram-negative derived bacterial toxins commonly found in human settings.

Results: We selected lipopolysaccharide (LPS) from Escherichia coli and lipoteichoic acid (LTA) from Streptococcus pyogenes as our toxins of choice. Our findings showed both LPS and LTA did not affect MSC proliferation, but prolonged LPS challenge upregulated the osteogenic differentiation of MSCs, as assessed by alkaline phosphatase activity and calcium deposition. Because toll-like receptors (TLRs), in particularly TLR4 and TLR2, are important for the cellular responsiveness to LPS and LTA respectively, we evaluated their expression profiles serially from MSCs to osteoblasts by quantitative PCR. We found that during osteogenic differentiation, MSC-derived osteoprogenitors gradually expressed TLR2 and TLR4 by Day 12. But under prolonged incubation with LPS, MSC-derived osteoprogenitors had reduced TLR2 and TLR4 gene expression. This peculiar response to LPS suggests a possible adaptive mechanism when MSCs are subjected to continuous exposure with bacteria.

Conclusion: In conclusion, our findings support the potential of using human MSCs as a biological graft, even under a bacterial toxin-rich environment.

Show MeSH
Related in: MedlinePlus