1: BMC Dev Biol. 2005 Jan 26;5(1):1. 

Induction of chondro-, osteo- and adipogenesis in embryonic stem cells by bone
morphogenetic protein-2: effect of cofactors on differentiating lineages.

zur Nieden NI, Kempka G, Rancourt DE, Ahr HJ.

Molecular & Genetic Toxicology, Bayer HealthCare AG, Wuppertal, Germany.
nicole.zur.nieden@gmx.net

BACKGROUND: Recently, tissue engineering has merged with stem cell technology
with interest to develop new sources of transplantable material for injury or
disease treatment. Eminently interesting, are bone and joint injuries/disorders
because of the low self-regenerating capacity of the matrix secreting cells,
particularly chondrocytes. ES cells have the unlimited capacity to self-renew
and maintain their pluripotency in culture. Upon induction of various signals
they will then differentiate into distinctive cell types such as neurons,
cardiomyocytes and osteoblasts. RESULTS: We present here that BMP-2 can drive ES
cells to the cartilage, osteoblast or adipogenic fate depending on supplementary
co-factors. TGFbeta1, insulin and ascorbic acid were identified as signals that
together with BMP-2 induce a chondrocytic phenotype that is characterized by
increased expression of cartilage marker genes in a timely co-ordinated fashion.
Expression of collagen type IIB and aggrecan, indicative of a fully mature
state, continuously ascend until reaching a peak at day 32 of culture to
approximately 80-fold over control values. Sox9 and scleraxis, cartilage
specific transcription factors, are highly expressed at very early stages and
show decreased expression over the time course of EB differentiation. Some
smaller proteoglycans, such as decorin and biglycan, are expressed at earlier
stages. Overall, proteoglycan biosynthesis is up-regulated 7-fold in response to
the supplements added. BMP-2 induced chondrocytes undergo hypertrophy and begin
to alter their expression profile towards osteoblasts. Supplying mineralization
factors such as beta-glycerophosphate and vitamin D3 with the culture medium can
facilitate this process. Moreover, gene expression studies show that adipocytes
can also differentiate from BMP-2 treated ES cells. CONCLUSIONS: Ultimately, we
have found that ES cells can be successfully triggered to differentiate into
chondrocyte-like cells, which can further alter their fate to become
hypertrophic, and adipocytes. Compared with previous reports using a brief BMP-2
supplementation early in differentiation, prolonged exposure increased
chondrogenic output, while supplementation with insulin and ascorbic acid
prevented dedifferentiation. These results provide a foundation for the use of
ES cells as a potential therapy in joint injury and disease.

PMID: 15673475 [PubMed - in process]


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