Inhibition of gamma-secretases alters both proliferation and differentiation of mesenchymal stem cells.
BACKGROUND
Human mesenchymal stem cell (hMSC) proliferation and development is regulated by many signalling pathways. gamma-Secretases play an important role in Notch signalling as well as other processes that are involved in developmental decisions, but their role in hMSC proliferation and cell fate decisions has not been explored.


OBJECTIVE
To investigate the role of gamma-secretases in hMSC proliferation and differentiation.


METHODS
Using the gamma-secretase inhibitor N-[N-(3,5-Difluorophenacetyl-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), we investigated their role in hMSC growth and differentiation to chondrogenic, osteogenic and adipogenic fates.


RESULTS
We found that inhibiting gamma-secretases reduced the rate of hMSC proliferation, and altered hMSC differentiation in vitro. Addition of DAPT had an inhibitory effect on chondrogenesis resulting in impaired cartilage matrix production and altered chondrocyte morphology. DAPT treated chrodrocytic pellets had reduced levels of Hes1 and Hey1 suggesting that these effects are mediated via Notch signalling. Addition of the DAPT inhibitor to osteogenic cultures did not alter the appearance of bone markers, however, adipogenesis occurred in these cultures in a DAPT concentration-dependent manner. DAPT did not enhance adipogenesis in the presence of a potent adipogenic cocktail, but had an adipogenic effect when combined with dexamethasone only.


CONCLUSIONS
We conclude that gamma-secretases play an important role in both hMSC proliferation and differentiation.
Vujovic
S
S
Wolfson Institute for Biomedical Research, University College London, London, UK.
Henderson
S R
SR
Flanagan
A M
AM
Clements
M O
MO
D017667:Adipocytes / Q000166:cytology / Q000187:drug effects; D050156:Adipogenesis / Q000187:drug effects; D000328:Adult; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D020219:Chondrogenesis / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology; D010012:Osteogenesis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions; D000072056:Transcription Factor HES-1
D053829:Amyloid Precursor Protein Secretases; D051792:Basic Helix-Loop-Helix Proteins; D003907:Dexamethasone; D004151:Dipeptides; D004791:Enzyme Inhibitors; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D000072056:Transcription Factor HES-1; C405694:Hairy, HRT1 protein; C419410:N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester; C078493:HES1 protein, human