Induction of human beta-cell proliferation and engraftment using a single G1/S regulatory molecule, cdk6.
OBJECTIVE
Most knowledge on human beta-cell cycle control derives from immunoblots of whole human islets, mixtures of beta-cells and non-beta-cells. We explored the presence, subcellular localization, and function of five early G1/S phase molecules-cyclins D1-3 and cdk 4 and 6-in the adult human beta-cell.


METHODS
Immunocytochemistry for the five molecules and their relative abilities to drive human beta-cell replication were examined. Human beta-cell replication, cell death, and islet function in vivo were studied in the diabetic NOD-SCID mouse.


RESULTS
Human beta-cells contain easily detectable cdks 4 and 6 and cyclin D3 but variable cyclin D1. Cyclin D2 was only marginally detectable. All five were principally cytoplasmic, not nuclear. Overexpression of the five, alone or in combination, led to variable increases in human beta-cell replication, with the cdk6/cyclin D3 combination being the most robust (15% versus 0.3% in control beta-cells). A single molecule, cdk6, proved to be capable of driving human beta-cell replication in vitro and enhancing human islet engraftment/proliferation in vivo, superior to normal islets and as effectively as the combination of cdk6 plus a D-cyclin.


CONCLUSIONS
Human beta-cells contain abundant cdk4, cdk6, and cyclin D3, but variable amounts of cyclin D1. In contrast to rodent beta-cells, they contain little or no detectable cyclin D2. They are primarily cytoplasmic and likely ineffective in basal beta-cell replication. Unexpectedly, cyclin D3 and cdk6 overexpression drives human beta-cell replication most effectively. Most importantly, a single molecule, cdk6, supports robust human beta-cell proliferation and function in vivo.
Fiaschi-Taesch
Nathalie M
NM
Division of Endocrinology, the University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA. taeschn@dom.pitt.edu
Salim
Fatimah
F
Kleinberger
Jeffrey
J
Troxell
Ronnie
R
Cozar-Castellano
Irene
I
Selk
Karen
K
Cherok
Edward
E
Takane
Karen K
KK
Scott
Donald K
DK
Stewart
Andrew F
AF
D000328:Adult; D000818:Animals; D015153:Blotting, Western; D002455:Cell Division; D056741:Cyclin D / Q000502:physiology*; D019938:Cyclin D1 / Q000502:physiology; D056742:Cyclin D2 / Q000502:physiology; D056743:Cyclin D3 / Q000502:physiology; D051361:Cyclin-Dependent Kinase 6 / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D016193:G1 Phase / Q000502:physiology; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000502:physiology* / Q000637:transplantation*; D007515:Islets of Langerhans / Q000166:cytology; D051379:Mice; D016196:S Phase; D013045:Species Specificity
C530104:CCND1 protein, human; C080336:CCND2 protein, human; C534696:CCND3 protein, human; D056741:Cyclin D; D056742:Cyclin D2; D056743:Cyclin D3; D019938:Cyclin D1; C495911:CDK6 protein, human; D051361:Cyclin-Dependent Kinase 6