ABSTRACT
This article is designed to provide basic introductory information for nonbiologists
who want to learn more about the cellular and molecular mechanisms that may form the
basis of future directions for therapies aimed at preventing or reversing hearing
loss. The first section reviews basic cell biology and mechanisms of the cell cycle.
Molecular factors that regulate the cell cycle, such as cyclin-dependent kinases,
growth factor, and tumor suppressor proteins, are described in terms of their functions
in regulating each stage of the cell cycle. These regulating factors are discussed
in light of their potential roles for inducing cells to reinitiate the cell cycle
and thus produce new cells. Regulatory proteins, immunologic elements, and growth
factors are discussed in terms of their roles in stimulating these new cells to differentiate
into hair cells. Specific examples from the auditory system are provided. The second
section reviews basic mechanisms of cell death. Two types of cell death, necrosis
and apoptosis, are defined. Multiple apoptotic pathways are described, including cell
death triggered by ligation of cell surface "death receptors" (Fas, TNF-α-R) and cell
death triggered by damage to specific cellular organelles, such as mitochondria. Finally,
mechanisms of cell rescue and repair are discussed in light of the presence of cell
survival signals and cell death signals. Cell survival signals, such as Bcl-2 and
glutathione act to promote cell survival in the presence of a potentially death-inducing
stimulus. These signals and the ways in which they might be used in the future to
prevent hair cell death resulting from aging, noise, or drug exposure are briefly
introduced.
KEYWORDS
Cell cycle - mitosis - cyclin-dependent kinase - apoptosis - caspase
