Pharmacological stimulation of marrow function

Studies of the pharmacological stimulation of marrow function have provided insight into mechanisms which might possibly affect cell proliferation in vivo. However, the most dramatic and clear-cut effects have come with studies employing normal marrow or populations of cells recovering in a predictable manner from suppression. Even with this, a wide number of agents appear to be active and capable of influencing the growth or cycle activity of more than one class of progenitor, including both committed and pluripotent stem cells. Perhaps the most useful clinical insight from these studies is that they provide a rationale for 'rescuing' deliberately damaged marrow (as with high dose chemotherapy) and suggest that it may be possible to reduce the period of severe hypoplasia under controlled circumstances. In cases of idiopathic marrow failure, the situation is less hopeful. The studies do not indicate that we are at a stage where we may hope to enhance marrow function significantly in the severely aplastic patient. Initial suggestions that in vitro culturing of marrow cells with various agents might lead to a programme of specifically designed therapy have resulted in limited, but negative, experiments. It is not likely that this is going to be fruitful. It seems clear, however, that the phenotypic expression of marrow failure in man masks a number of pathogenetic mechanisms, and that further attempts to characterize marrow growth in such patients are warranted. Perhaps by identifying patients with normal growth patterns it will be possible to select individuals for rational pharmacological therapy with some expectation of success.