Figure 1 Schematic diagram illustrating an overview of cellular injury and inflammatory-mediated
steps in development of leiomyoma as compared with uterine scar formation caused by
mechanical injury (i.e., myomectomy and cesarean delivery). Cellular/tissue injuries
and generation of an inflammatory response, either at a small scale (microenvironment)
or an extended area (myomectomy/cesarean delivery), result in individual and combined
regulatory interactions among several proinflammatory and profibrotic mediators. These
mediators, including cytokines, chemokines, growth factors, eicosanoids, proteases,
and extracellular matrix (ECM), activate to cause myoblasts and resident fibroblasts
to differentiate into myofibroblastic phenotype. In addition, possible participation
of fibrocytes, which are derived from bone marrow and through circulation reside at
the site of inflammation/injury, as well as the transformation of vascular endothelial
cells into mesenchymal cells, exist to transform into myofibroblastic phenotype. Collectively,
myofibroblasts are highly responsive to the actions of many of the previously mentioned
mediators, including profibrotic cytokines; they produce and deposit various components
of ECM that are essential for tissue repair process. Continuous inflammation, excess
myofibroblastic transformation, and production of a large quantity of ECM, with concurrently
reduced degradation, represent a pathway that leads to development of either leiomyoma
and/or scar tissue formation.
EGF, endothelial growth factor; FGF, fibroblast growth factor; GM-CSF, granulocyte-macrophage
colony-stimulating factor; IGF, insulinlike growth factor; IL, interleukin; LT, leukotriene;
MCP, monocyte chemoattractant protein; MIP, macrophage inflammatory protein; MMP,
metalloproteinase; PAI, plasminogen activator inhibitor; PG, prostaglandin; RANTES,
regulated upon activation, normal T-cell expressed and secreted; TBX, thromboxane;
TGF, transforming growth factor; TNF, tumor necrosis factor; TIMP, tissue inhibitor
of metalloproteinase; tPA, tissue plasminogen activator; VEGF, vascular endothelial
growth factor.