Authors:
Nathalie Fiaschi-Taesch, PhD, Todd A. Bigatel, MD, Brian Sicari, BS, Karen K. Takane, PhD, Fatima Salim, BS, Silvia Velazquez-Garcia, BS, George Harb, PhD, Karen Selk, BS, Irene Cozar-Castellano, PhD, and Andrew F. Stewart, MD
Summary:
Objectives - To comprehensively inventory the proteins that control the G1/S cell cycle checkpoint in the human islet, and compare them to those in the murine islet. To determine if these might therapeutically enhance human beta cell replication. To determine if human beta cell replication can be demonstrated in an in vivo model. To enhance human beta cell function in vivo.
Research Design and Methods - 34 G1/S regulatory proteins were examined in human islets. Effects of adenoviruses expressing cdk-6, cdk-4 and cyclin D1 on proliferation in human beta cells was studied both in vitro and in an in vivo model.
Results - Multiple differences between murine and human islets occur, most strikingly the presence of cdk-6 in human beta cells vs. its low abundance in the murine islet. Cdk-6 and cyclin D1 in vitro led to marked activation of retinoblastoma protein phosphorylation and cell cycle progression, with no induction of cell death. Human islets transduced with cdk-6 and cyclin D1 were transplanted into diabetic NOD-SCID mice and markedly outperformed native human islets in vivo, maintaining glucose control for the entire six weeks of study.
Conclusions - The human G1/S proteome is described for the first time. Human islets are unlike their rodent counterparts in that they contain easily measurable cdk-6. Cdk-6 overexpression, alone or in combination with cyclin D1 strikingly stimulates human beta cell replication, both in vitro as well as in vivo, without inducing cell death or loss of function. Using this model, human beta cell replication can be induced and studied in vivo.
Source:
Diabetes; (01/09/09)