Blood vessel growth in the endometrium.

Angiogenesis, or formation of new blood vessels by sprout formation from existing vessels, is generally considered to be the only mechanism by which blood vessel growth occurs. This traditional concept of angiogenesis has been derived largely from observations of experimental systems. Relatively fewer studies on angiogenesis have been carried out using normal angiogenic situations where vessel growth occurs in a controlled three-dimensional fashion throughout the tissue. Recent advances in the treatment of infertility and outpatient gynecological procedures have led to greater accessibility to normal human endometrium, thus providing new opportunities to study the process of angiogenesis in a physiological context. However, to date, it appears that very little work had been done in relation to endometrial angiogenesis apart from the location of numerous angiogenic and other growth factors with potential to influence angiogenesis in the endometrium, and here there have been few attempts to link these observations with actual angiogenic events. The purpose of this review is to summarize the literature regarding angiogenesis in the endometrium, including work from our own laboratory, and to suggest that blood vessel growth in the endometrium may occur by a mechanism that differs from classical angiogenesis.