Do cells of continually renewing populations and those stimulated from quiescence respond similarly to HU and Ara-C?

Applying computer modeling to examine complex dynamics and pattern formation of tissue growth

For research in areas such as developmental biology and cancer, understanding the formation and regrowth of tissue is of great importance. Since complex system behavior makes it difficult to interpret dynamics and pattern formation of tissue growth, it is helpful to have a way to simulate the cell systems and test hypotheses about the mechanisms by which the system is responding. Computer "modeling experiments" can serve this purpose, as we show with an example of the small intestine epithelial cells' response to cytosine arabinoside. This example demonstrates that nonhomogeneities in the cell population can play an important role and emphasizes the need to use a modeling approach, like our spatial modeling, that addresses the differences within the tissue structure. These types of "modeling experiments" can guide researchers with further experiments and provide clues as to how complex cell proliferation behavior is linked to underlying molecular phenomena.

Bromodeoxyuridine-labelled apoptosis after treatment with antimetabolites in two murine tumours and in small intestinal crypts

Antimetabolites are S-phase specific anticancer drugs. Administration of bromodeoxyuridine (BrdUrd) to tumour bearing mice was followed by treatment with cytosine arabinoside or hydroxyurea. Anti-BrdUrd immunocytochemistry visualised susceptible tumour and intestinal crypt cells at electron microscope level, showing unequivocally that cells that were in S-phase at the time of administration of the drugs subsequently died by apoptosis.

The nature of cytotoxic drug-induced cell death in murine intestinal crypts

The nature of cell death in murine small intestinal crypts caused by potentially lethal doses of four classes of cancer chemotherapeutic agents was studied. The drugs used were cytosine arabinoside, vincristine, adriamycin and nitrogen mustard. The compounds readily induced massive cell death in the proliferating compartment of the crypt. In each case, cell death was apparent within an hour, and the incidence of dead cells peaked during the following 4-8 h. By 24 h, little damage was discernible in the crypt systems. Remarkably, dead cells or dead cell fragments were phagocytosed rapidly (within about 1 h) by neighbouring healthy enterocytes. When examined by light microscopy, transmission electron microscopy and scanning electron microscopy, the dead cells showed the characteristic features of having succumbed to an apoptotic mode of cell death without any trace of cell and organelle oedema characteristic of necrosis. The study suggests that cell death by apoptosis operates even when the cells are exposed to severe pathological perturbation and that the phenomenon is not solely a process which operates in response to either physiological stimuli or to mild physical or chemical trauma.

The pharmacological mediation of epithelial cell proliferation

In the past, it has been necessary for pharmacological intervention of epithelial proliferation to mostly be limited to non-specifically arresting or killing actively proliferating cells. As our understanding of the mechanisms involved in mediating the processes of growth and differentiation increases, we can hope to see the development of a new pharmacology, in which proliferation of individual systems may be regulated in a less drastic manner.