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Thrombopoietic-mesenchymal interaction that may facilitate both endochondral ossification and platelet maturation via CCN2.

Sumiyoshi K, Kubota S, Furuta RA, Yasui K, Aoyama E, Kawaki H, Kawata K, Ohgawara T, Yamashiro T, Takigawa M - J Cell Commun Signal (2009)

Bottom Line: In this study, we initially pursued the possible origin of the CCN2 in platelets.As suspected, CCN2 production by HCS-2/8 was significantly enhanced by the conditioned medium.We further confirmed that human platelets were able to absorb/uptake exogenous CCN2 in vitro.

View Article: PubMed Central - PubMed

ABSTRACT
CCN2 plays a central role in the development and growth of mesenchymal tissue and promotes the regeneration of bone and cartilage in vivo. Of note, abundant CCN2 is contained in platelets, which is thought to play an important role in the tissue regeneration process. In this study, we initially pursued the possible origin of the CCN2 in platelets. First, we examined if the CCN2 in platelets was produced by megakaryocyte progenitors during differentiation. Unexpectedly, neither megakaryocytic CMK cells nor megakaryocytes that had differentiated from human haemopoietic stem cells in culture showed any detectable CCN2 gene expression or protein production. Together with the fact that no appreciable CCN2 was detected in megakaryocytes in vivo, these results suggest that megakaryocytes themselves do not produce CCN2. Next, we suspected that mesenchymal cells situated around megakaryocytes in the bone marrow were stimulated by the latter to produce CCN2, which was then taken up by platelets. To evaluate this hypothesis, we cultured human chondrocytic HCS-2/8 cells with medium conditioned by differentiating megakaryocyte cultures, and then monitored the production of CCN2 by the cells. As suspected, CCN2 production by HCS-2/8 was significantly enhanced by the conditioned medium. We further confirmed that human platelets were able to absorb/uptake exogenous CCN2 in vitro. These findings indicate that megakaryocytes secrete some unknown soluble factor(s) during differentiation, which factor stimulates the mesenchymal cells to produce CCN2 for uptake by the platelets. We also consider that, during bone growth, such thrombopoietic-mesenchymal interaction may contribute to the hypertrophic chondrocyte-specific accumulation of CCN2 that conducts endochondral ossification.

No MeSH data available.


Related in: MedlinePlus

a Distribution of CCN2 in platelets. CCN2 in human platelets was visualized by immunofluorescence analysis and was viewed at a magnification of ×400. CCN2 is found in granular structures therein. b Absorption/incorporation of exogenous CCN2 to/by human platelets. After the addition of CCN2, human platelets were collected and subjected to Western blotting for the detection of CCN2. Western blotting against actin was also performed as an internal control. The intensity of the signals at 38 kDa, representing full-length CCN2, increased with time up to 40 min after the addition of CCN2. The minor bands are anticipated to be proteolytic N-terminal fragment of CCN2. Evaluation was performed with two samples from independent donors, and similar results were obtained
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Fig5: a Distribution of CCN2 in platelets. CCN2 in human platelets was visualized by immunofluorescence analysis and was viewed at a magnification of ×400. CCN2 is found in granular structures therein. b Absorption/incorporation of exogenous CCN2 to/by human platelets. After the addition of CCN2, human platelets were collected and subjected to Western blotting for the detection of CCN2. Western blotting against actin was also performed as an internal control. The intensity of the signals at 38 kDa, representing full-length CCN2, increased with time up to 40 min after the addition of CCN2. The minor bands are anticipated to be proteolytic N-terminal fragment of CCN2. Evaluation was performed with two samples from independent donors, and similar results were obtained

Mentions: Although the inclusion of CCN2 in platelets has been clearly demonstrated, its subcellular localization therein has not been analyzed. Thus, we carried out immunofluorescence analysis to investigate the mode of CCN2 distribution in platelets. As a result, CCN2 was not distributed evenly in the cytoplasm, but had accumulated in granular structures (Fig. 5a).Fig. 5


Thrombopoietic-mesenchymal interaction that may facilitate both endochondral ossification and platelet maturation via CCN2.

Sumiyoshi K, Kubota S, Furuta RA, Yasui K, Aoyama E, Kawaki H, Kawata K, Ohgawara T, Yamashiro T, Takigawa M - J Cell Commun Signal (2009)

a Distribution of CCN2 in platelets. CCN2 in human platelets was visualized by immunofluorescence analysis and was viewed at a magnification of ×400. CCN2 is found in granular structures therein. b Absorption/incorporation of exogenous CCN2 to/by human platelets. After the addition of CCN2, human platelets were collected and subjected to Western blotting for the detection of CCN2. Western blotting against actin was also performed as an internal control. The intensity of the signals at 38 kDa, representing full-length CCN2, increased with time up to 40 min after the addition of CCN2. The minor bands are anticipated to be proteolytic N-terminal fragment of CCN2. Evaluation was performed with two samples from independent donors, and similar results were obtained
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2821475&req=5

Fig5: a Distribution of CCN2 in platelets. CCN2 in human platelets was visualized by immunofluorescence analysis and was viewed at a magnification of ×400. CCN2 is found in granular structures therein. b Absorption/incorporation of exogenous CCN2 to/by human platelets. After the addition of CCN2, human platelets were collected and subjected to Western blotting for the detection of CCN2. Western blotting against actin was also performed as an internal control. The intensity of the signals at 38 kDa, representing full-length CCN2, increased with time up to 40 min after the addition of CCN2. The minor bands are anticipated to be proteolytic N-terminal fragment of CCN2. Evaluation was performed with two samples from independent donors, and similar results were obtained
Mentions: Although the inclusion of CCN2 in platelets has been clearly demonstrated, its subcellular localization therein has not been analyzed. Thus, we carried out immunofluorescence analysis to investigate the mode of CCN2 distribution in platelets. As a result, CCN2 was not distributed evenly in the cytoplasm, but had accumulated in granular structures (Fig. 5a).Fig. 5

Bottom Line: In this study, we initially pursued the possible origin of the CCN2 in platelets.As suspected, CCN2 production by HCS-2/8 was significantly enhanced by the conditioned medium.We further confirmed that human platelets were able to absorb/uptake exogenous CCN2 in vitro.

View Article: PubMed Central - PubMed

ABSTRACT
CCN2 plays a central role in the development and growth of mesenchymal tissue and promotes the regeneration of bone and cartilage in vivo. Of note, abundant CCN2 is contained in platelets, which is thought to play an important role in the tissue regeneration process. In this study, we initially pursued the possible origin of the CCN2 in platelets. First, we examined if the CCN2 in platelets was produced by megakaryocyte progenitors during differentiation. Unexpectedly, neither megakaryocytic CMK cells nor megakaryocytes that had differentiated from human haemopoietic stem cells in culture showed any detectable CCN2 gene expression or protein production. Together with the fact that no appreciable CCN2 was detected in megakaryocytes in vivo, these results suggest that megakaryocytes themselves do not produce CCN2. Next, we suspected that mesenchymal cells situated around megakaryocytes in the bone marrow were stimulated by the latter to produce CCN2, which was then taken up by platelets. To evaluate this hypothesis, we cultured human chondrocytic HCS-2/8 cells with medium conditioned by differentiating megakaryocyte cultures, and then monitored the production of CCN2 by the cells. As suspected, CCN2 production by HCS-2/8 was significantly enhanced by the conditioned medium. We further confirmed that human platelets were able to absorb/uptake exogenous CCN2 in vitro. These findings indicate that megakaryocytes secrete some unknown soluble factor(s) during differentiation, which factor stimulates the mesenchymal cells to produce CCN2 for uptake by the platelets. We also consider that, during bone growth, such thrombopoietic-mesenchymal interaction may contribute to the hypertrophic chondrocyte-specific accumulation of CCN2 that conducts endochondral ossification.

No MeSH data available.


Related in: MedlinePlus