Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Adipogenic and Osteogenic Switch in Differentiation of Human Mesenchymal Stem Cells (hMSCs) Is Triggered by Hypoxia in a HIF-1 Dependent Manner.

Wagegg3,  Markus, Gaber1,  Timo, Lohanatha1,  Ferenz, Jakstadt1,  Manuela, Kasper2,  Grit, Duda2,  Georg, Kolar3,  Paula

Berlin-Brandenburg Center for Regenerative Therapies (BCRT)
Charité University Hospital, Center for Musculoskeletal Surgery, Berlin, Germany
Charité University Hospital, Department of Rheumatology and Clinical Immunology, Berlin, Germany
Charité University Hospital, Department of Rheumatology and Clinical Immunology, Berlin, Germany
Charite University Med-Berlin, Berlin, Germany

Background:

Bone regeneration is often impaired in elderly people as well as in people suffering from autoimmune diseases such as rheumatoid arthritis (RA). Bone fractures initiate series of cellular and molecular events that commence with hematoma formation, induction of inflammatory cascades which regulate hMSCs recruitment and finally differentiation. Due to the disruption of supplying blood vessels, hypoxia and the induction of the transcription factor hypoxia-inducible factor (HIF)-1 are considered to have considerable influence on these events.

Objectives:

Here, we analyzed the impact of hypoxia and HIF-1 on the adipogenic and osteogenic differentiation potential of hMSCs.

Methods:

Human MSCs isolated from bone marrow were characterized for their ability to differentiate into adipogenic, osteogenic and chondrogenic lineage cells and for their expression of surface markers. Adipogenesis and osteogenesis were induced by respective conditioned media. The cells were cultured for 14 and 28 days under normoxia (20% O2 air fraction) and hypoxia (<2% O2 air fraction), respectively. Adipogenic differentiation was assessed by oil-red staining, osteogenic differentiation by von Kossa staining. Additionally, the expressions of the adipogenic gene peroxisome proliferator-activated receptor g (PPARg), and the osteogenic genes osteopontin (SPP1) and runt-related transcription factor 2 (RUNX2) were measured by real-time PCR. For defining the role of HIF-1, a knockdown of HIF-1a (the oxygen-sensitive a-subunit of HIF-1) by lentiviral transduction was performed, and the ability of the transduced MSCs to differentiate into adipogenic and osteogenic lineage cells was analyzed.

Results:

Hypoxia led to the induction of HIF-1a, suppressed adipogenesis, and further enhanced osteogenesis in hMSCs. In case of adipogenesis, we observed a 13fold induction of PPARg after 28 days under normoxia when compared to hypoxia. In the event of osteogenesis, SPP1 and RUNX2 were both found to be up-regulated under hypoxia when compared to normoxia (SPP1: 2fold; RUNX2 10.5fold; after 14 days). Furthermore, shRNA mediated knockdown of HIF-1a enhanced adipogenesis under both normoxia and hypoxia. In addition knockdown of HIF-1a suppressed hypoxia-induced osteogenesis.

Conclusion:

We show that hypoxia considerably influences bone healing by promoting osteogenesis while suppressing adipogenesis of hMSCs in a HIF-1 dependent manner. Therefore, stem cell therapy in combination with chemically induced hypoxia might be a novel approach to improve fracture healing in elderly people with an impaired bone healing and in patients suffering from autoimmune diseases such as RA.

To cite this abstract, please use the following information:
Wagegg, Markus, Gaber, Timo, Lohanatha, Ferenz, Jakstadt, Manuela, Kasper, Grit, Duda, Georg, et al; Adipogenic and Osteogenic Switch in Differentiation of Human Mesenchymal Stem Cells (hMSCs) Is Triggered by Hypoxia in a HIF-1 Dependent Manner. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :630
DOI: 10.1002/art.28398

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