Endocrine Abstracts

The 'Stem Cell Programme' has critically depended upon the discovery of specific growth factors that maintain and regulate the differentiation of specific stem cell populations. Understanding the identity and actions of these agents is therefore critical for realising the promised therapeutic applications of stem cells in tissue repair and gene therapy.

In the past discovery of growth factors controlling the behaviour of stem cell populations was dependent on luck, guesswork or hard work. With the completion of the human transcriptome we now know the complete repertoire of growth factors encoded in the human genome. These agents fall into a relatively small number of families which function through signaling pathways that exhibit shared designs and effectors. Growth factors function in regulatory circuits in which the action of one agent is modified by the concurrent or historical activity of another: a complete understanding of growth factor action on stem cell populations therefore requires an appreciation of the complete growth factor circuitry acting in the system rather than knowledge of one or two players. These circuits seem to have generic features in different systems. A significant and emerging feature of growth factor action is the importance of signaling dynamics in growth factor action. Not only is the ability of growth factors to interact with target cells subject to modifying mechanisms but also the speed and location of signal propagation can dictate the regulatory outcome.