Patterns of Physiological Angiogenesis in Adult Mesentery

Abstract

The structural process by which new microvessels form from pre-existing ones has been documented in classical studies of wound healing. (Folkman and Shing, 1992; Hudlicka and Tyler, 1986). However, the process by which new microvessels originate de novoand continue to expand under physiological conditions is less well understood. The physiological formation and subsequent growth of a new vascular bed is normally considered to be something that occurs predominantly during embryonic development. In mammalian systems this puts certain restrictions on the types of studies which can be done on a developing vascular bed to understand how the growth is regulated. Most tissues in the adult have little ongoing angiogenesis, with the exception of the female reproductive system. However, it has been found that the rat mesentery undergoes a spontaneous angiogenesis, leading to the formation of a two-dimensional microvascular bed which seems to be well suited for studies of angiogenesis under either physiological or pathological conditions (Hansen-Smith, Joswiak, and Baustert, 1994; Norrby, Jakobsson, and Sorbo, 1990; Rhodin and Fujita, 1989). Since this growth occurs in adults, many types of physiological studies, as well as structural and biochemical studies, are feasible to help understand not only how the initiation of angiogenesis and angiostasis are regulated, but also how microvascular patterns arise and are remodelled during the enlargement of microvascular networks.