Sox9 and adult bone marrow derived mesenchymal stem cells (MSC)
Final Report Abstract
Sox9 is a key transcription factor in early chondrogenesis with distinct roles in differentiation processes during embryonic development. Here, we report that Sox9 modulates, via the p38 MAPK pathway, on the one hand cell viability in adult mesenchymal stem cells (MSC), especially by affecting proliferation and apoptotic activity, and, on the other hand, the differentiation capacity of MSC. The inhibition of Sox9 activates apoptosis through a caspase 3/7-Bcl-2-Bax-dependent mechanism and, in addition, by the accumulation of p21 in the nucleus. Nuclear p21 inhibits cell cycle progression and leads to a decrease of the S-phase population and subsequently to a decrease in proliferation. The p21 induction in Sox9 knockdown cells is Cyclin D1-dependent. The Cyclin D1 protein in turn, is stabilized via impaired activation (phosphorylation) of p38. Cyclin D1 affects the regulation of osteocalcin, and by that, alters the osteogenic differentiation potential of MSC. We could confirm the proosteogenic, as well as the anti-proliferative effect of a Sox9 knockdown and the influence on the p21 and Cyclin D1 expression in ASC, proofing a general mechanism in MSC, regardless of the source of the cells. Interestingly, the induction of apoptosis after Sox9 silencing is not such a general mechanism as it was not detected in rASC. Adipogenic differentiation capacity is affected by inhibition of C/EBPß expression, probably via p38-mediated mRNA destabilization. Reduction of C/EBPß may also inhibit the anti-apoptotic gene Bcl-2 via direct binding and thus, contributes to increased apoptosis and, ultimately, to decreased proliferation via regulation of proliferation associated transcription factors. Employing a 3D culture model, preliminary results suggest a positive impact of Sox9 on early chondrogenic differentiation by altering expression of adapter proteins, and by influencing diameter and morphology of the aggregates. Our results clearly show that Sox9 is more than only the chondrogenic master transcription factor. We identified Sox9 as an important link between differentiation, proliferation and apoptosis in undifferentiated mesenchymal stem cells. Moreover, we emphasize the importance of the delicate balance of a precisely regulated Sox9 activity in MSC, not only for proper skeletal development during embryogenesis, but likely also for successful repair and regeneration of tissues and organs in adults. For that, it is necessary to understand the biology of mesenchymal stem cells - regardless which origin - in detail for a safe application of MSC for future therapeutical strategies.
Publications
- Retroviral induced in vitro inhibition of the transcription factor SOX9. Osteoarthritis Cartilage, Suppl. 15: C27, 2007
Gregan B., Ahmed N., Göttl C., Grifka J., Grässel S.
- Gene and protein expression profile of naïve and osteogenically differentiated rat bone marrow derived mesenchymal progenitor cells. Int. J. Mol. Med. 23: 745-755, 2009
Grässel S., Ahmed N., Göttl C., Grifka J.
- In vitro gene knockdown of Sox9 in rat MSC affects cell cycle progression. Osteoarthritis Cartilage, 17, Suppl. 1: S260- 261, 2009
Stöckl S., Göttl C., Grifka J., Grässel S.
- The cartilage specific transcription factor Sox9 regulates AP-2 expression in chondrocytes. FEBS J. 276(9):2494-504, 2009
Wenke AK., Grässel S., Moser M., Bosserhoff AK.
- Enhanced cartilage regeneration in MIA/CD-RAP deficient mice. Cell Death Dis., 1:e97-107, 2010
Schmid R., Schiffner S., Opolka A., Grässel S., Schubert T., Moser M., Bosserhoff A.K.
- In vitro gene knockdown of Sox9 in rat MSC affects Bcl2 expression. European Journal of Cell Biology 89, Suppl. 1: S14, 2010
Stöckl S., Göttl C., Grifka J., Grässel S.
- In vitro gene knockdown of Sox9 affects cell survival and osteogenic differentiation of rMSC. Osteoarthritis Cartilage, 19, Suppl.1:S29, 2011
Stöckl S., Göttl C., Grifka J., Grässel S.
- Isolation, culture and osteogenic/chondrogenic differentiation of bone marrow derived mesenchymal stem cells. Methods Mol. Biol. 2012;879:203-67
Grässel S., Stöckl S., Jenei-Lanzl Z.
- Sox9 modulates cell survival and adipogenic differentiation of multipotent adult rat mesenchymal stem cells. J. Cell Sci. 2013 Apr 19. [Epub ahead of print]
Stöckl S., Bauer R., Bosserhoff A., Göttl C., Grifka J., Grässel S.
(See online at https://doi.org/10.1242/jcs.124305) - Sox9 modulates proliferation and expression of osteogenic markers of adipose-derived stem cells (ASC). Cell. Physiol. Biochem. 2013; 31(4-5): 703-17
Stöckl S., Göttl C., Grifka J., Grässel S.
(See online at https://doi.org/10.1159/000350089)
