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Loss of the osteogenic differentiation potential during senescence is limited to bone progenitor cells and is dependent on p53.

Despars G, Carbonneau CL, Bardeau P, Coutu DL, Beauséjour CM - PLoS ONE (2013)

Bottom Line: Indeed, we show here that exposure to IR prevented the differentiation and mineralization functions of MSC, an effect we found was limited to this population as more differentiated OB-SC could still form mineralize nodules.This is in contrast to adipogenesis, which was inhibited in both IR-induced senescent MSC and 3T3-L1 pre-adipocytes.Furthermore, we demonstrate that IR-induced loss of osteogenic potential in MSC was p53-dependent, a phenotype that correlates with the inability to upregulate key osteogenic transcription factors.

View Article: PubMed Central - PubMed

Affiliation: Centre de recherche du CHU Ste-Justine, Montréal, Québec, Canada.

ABSTRACT
DNA damage can lead to the induction of cellular senescence. In particular, we showed that exposure to ionizing radiation (IR) leads to the senescence of bone marrow-derived multipotent stromal cells (MSC) and osteoblast-like stromal cells (OB-SC), a phenotype associated with bone loss. The mechanism by which IR leads to bone dysfunction is not fully understood. One possibility involves that DNA damage-induced senescence limits the regeneration of bone progenitor cells. Another possibility entails that bone dysfunction arises from the inability of accumulating senescent cells to fulfill their physiological function. Indeed, we show here that exposure to IR prevented the differentiation and mineralization functions of MSC, an effect we found was limited to this population as more differentiated OB-SC could still form mineralize nodules. This is in contrast to adipogenesis, which was inhibited in both IR-induced senescent MSC and 3T3-L1 pre-adipocytes. Furthermore, we demonstrate that IR-induced loss of osteogenic potential in MSC was p53-dependent, a phenotype that correlates with the inability to upregulate key osteogenic transcription factors. These results are the first to demonstrate that senescence impacts osteogenesis in a cell type dependent manner and suggest that the accumulation of senescent osteoblasts is unlikely to significantly contribute to bone dysfunction in a cell autonomous manner.

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IR-induced senescent MSC failed to generate bone in vivo.(A) Schematic of the experiment. Control or IR-induced senescent MSC were mixed with HA/TCP particles along with collagen and injected subcutaneously to the flank of mice. 10 weeks post injection, implants were retrieved from the animals, embedded in plastic, sectioned and stained with Goldner’s trichrome to detect bone formation. (B) Representative images from n= 6 implants per group showing mineralization (Goldner’s trichrome in green) from control or IR-induced senescent MSC. Implants were counterstained with hematoxylin eosin. Scale bar: 300µm.
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pone-0073206-g004: IR-induced senescent MSC failed to generate bone in vivo.(A) Schematic of the experiment. Control or IR-induced senescent MSC were mixed with HA/TCP particles along with collagen and injected subcutaneously to the flank of mice. 10 weeks post injection, implants were retrieved from the animals, embedded in plastic, sectioned and stained with Goldner’s trichrome to detect bone formation. (B) Representative images from n= 6 implants per group showing mineralization (Goldner’s trichrome in green) from control or IR-induced senescent MSC. Implants were counterstained with hematoxylin eosin. Scale bar: 300µm.

Mentions: Finally, because the osteogenic differentiation condition established in vitro may not adequately reflect in vivo conditions, one may argue that loss of mineralization potential observed in senescent MSC is a culture artifact and that senescent MSC may still be able to differentiate in vivo. To address this important question, we used a heterotopic bone formation model in which MSC, when mixed with hydroxyapatite/tricalcium phosphate particles and collagen can form bone subcutaneously in mice (Figure 4A). Using this model, we observed robust heterotopic bone formation in MSC implants as shown by Goldner’s Trichrome staining (Figure 4B). In contrast, senescent MSC were unable to mineralize bone in vivo, indicating that the loss in ostegenic differentiation potential following exposure to IR likely takes place under physiological conditions as well. Importantly, lack of mineralization in vivo was not due to the death/clearance of senescent MSC as we have injected IR-induced senescent MSC subcutaneously in mice before and never observed reduced viability of these cells compared to control non-irradiated MSC [30]. Together, these results suggest that the net bone loss observed following exposure to IR may not only arise as the consequence of the depletion of bone progenitor cells but also as a result of impaired functionality from DNA damaged MSC.


Loss of the osteogenic differentiation potential during senescence is limited to bone progenitor cells and is dependent on p53.

Despars G, Carbonneau CL, Bardeau P, Coutu DL, Beauséjour CM - PLoS ONE (2013)

IR-induced senescent MSC failed to generate bone in vivo.(A) Schematic of the experiment. Control or IR-induced senescent MSC were mixed with HA/TCP particles along with collagen and injected subcutaneously to the flank of mice. 10 weeks post injection, implants were retrieved from the animals, embedded in plastic, sectioned and stained with Goldner’s trichrome to detect bone formation. (B) Representative images from n= 6 implants per group showing mineralization (Goldner’s trichrome in green) from control or IR-induced senescent MSC. Implants were counterstained with hematoxylin eosin. Scale bar: 300µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3756945&req=5

pone-0073206-g004: IR-induced senescent MSC failed to generate bone in vivo.(A) Schematic of the experiment. Control or IR-induced senescent MSC were mixed with HA/TCP particles along with collagen and injected subcutaneously to the flank of mice. 10 weeks post injection, implants were retrieved from the animals, embedded in plastic, sectioned and stained with Goldner’s trichrome to detect bone formation. (B) Representative images from n= 6 implants per group showing mineralization (Goldner’s trichrome in green) from control or IR-induced senescent MSC. Implants were counterstained with hematoxylin eosin. Scale bar: 300µm.
Mentions: Finally, because the osteogenic differentiation condition established in vitro may not adequately reflect in vivo conditions, one may argue that loss of mineralization potential observed in senescent MSC is a culture artifact and that senescent MSC may still be able to differentiate in vivo. To address this important question, we used a heterotopic bone formation model in which MSC, when mixed with hydroxyapatite/tricalcium phosphate particles and collagen can form bone subcutaneously in mice (Figure 4A). Using this model, we observed robust heterotopic bone formation in MSC implants as shown by Goldner’s Trichrome staining (Figure 4B). In contrast, senescent MSC were unable to mineralize bone in vivo, indicating that the loss in ostegenic differentiation potential following exposure to IR likely takes place under physiological conditions as well. Importantly, lack of mineralization in vivo was not due to the death/clearance of senescent MSC as we have injected IR-induced senescent MSC subcutaneously in mice before and never observed reduced viability of these cells compared to control non-irradiated MSC [30]. Together, these results suggest that the net bone loss observed following exposure to IR may not only arise as the consequence of the depletion of bone progenitor cells but also as a result of impaired functionality from DNA damaged MSC.

Bottom Line: Indeed, we show here that exposure to IR prevented the differentiation and mineralization functions of MSC, an effect we found was limited to this population as more differentiated OB-SC could still form mineralize nodules.This is in contrast to adipogenesis, which was inhibited in both IR-induced senescent MSC and 3T3-L1 pre-adipocytes.Furthermore, we demonstrate that IR-induced loss of osteogenic potential in MSC was p53-dependent, a phenotype that correlates with the inability to upregulate key osteogenic transcription factors.

View Article: PubMed Central - PubMed

Affiliation: Centre de recherche du CHU Ste-Justine, Montréal, Québec, Canada.

ABSTRACT
DNA damage can lead to the induction of cellular senescence. In particular, we showed that exposure to ionizing radiation (IR) leads to the senescence of bone marrow-derived multipotent stromal cells (MSC) and osteoblast-like stromal cells (OB-SC), a phenotype associated with bone loss. The mechanism by which IR leads to bone dysfunction is not fully understood. One possibility involves that DNA damage-induced senescence limits the regeneration of bone progenitor cells. Another possibility entails that bone dysfunction arises from the inability of accumulating senescent cells to fulfill their physiological function. Indeed, we show here that exposure to IR prevented the differentiation and mineralization functions of MSC, an effect we found was limited to this population as more differentiated OB-SC could still form mineralize nodules. This is in contrast to adipogenesis, which was inhibited in both IR-induced senescent MSC and 3T3-L1 pre-adipocytes. Furthermore, we demonstrate that IR-induced loss of osteogenic potential in MSC was p53-dependent, a phenotype that correlates with the inability to upregulate key osteogenic transcription factors. These results are the first to demonstrate that senescence impacts osteogenesis in a cell type dependent manner and suggest that the accumulation of senescent osteoblasts is unlikely to significantly contribute to bone dysfunction in a cell autonomous manner.

Show MeSH
Related in: MedlinePlus