Relation Between The Capillary Angiogenesis Modes And The Tissue Hypoxia Degree

The main modes of angiogenesis include sprouting and intussusception, which are observed in different physiological and pathologic conditions. Recent literatures show that current researches on the angiogenesis modes mainly focus on the observation and description of the phenomenon, mathematical simulation and elaborating the role of various factors in the process of sprouting and intussusceptive angiogenesis at molecular level. Angiogenesis might happen in a certain mode under a given condition, which has been rarely concerned and studied. The aim of this research is to discuss the effect of hypoxia on the angiogenesis modes. Firstly, the main angiogenesis modes were observed through anatomy of rats; secondly, the degrees of tissue hypoxia during the body growth, tumor growth and wound healing were analyzed and compared respectively via mathematical models; finally, the relation between the angiogenesis modes and the tissue hypoxia degree under different physiological and pathologic conditions have been discussed. The study includes two parts as followed:In the first part, the main angiogenesis modes in the state of chronic hypoxia during the body growth were observed. The main angiogenesis mode during the growth of extensor digitorum longus in rats was judged with capillary morphogy; then the relation between the angiogenesis modes and the degree of tissue hypoxia was discussed. The results showed that the main angiogenesis mode during the extensor digitorum longus growth is intussusception.In the second part, the effects of hypoxia on the angiogenesis modes were discussed theoretically by building the models of the tissue growth and angiogenesis. The degrees of tissue hypoxia during the body growth, tumor growth and wound healing were analyzed and compared, respectively. Therefore, this might explain the mechanism of adopting different modes of angiogenesis during different conditions. As a result, the degree of tissue hypoxia during the body growth is slighter than those during the tumor growth and wound healing, called chronic hypoxia; furthermore, intussusception is the main angiogenesis mode during this process of chronic hypoxia. The degree of tissue hypoxia during the tumor growth is larger than that of the body growth and smaller than that of the wound healing, called moderate hypoxia; the main angiogenesis mode is sprouting in the prophase of tumor growth, in the later stage, intussusception appears, so sprouting and intussusceptive angiogenesis coexist in the state of moderate hypoxia. Wound healing is a process of acute hypoxia; the main angiogenesis mode is sprouting.Knowing the relation between the angiogenesis modes and the tissue hypoxia degree is helpful to further understanding the mechanism of angiogenesis, to discussing morphology of capillary network for designing biomedical materials in favor of vascular growth and to treating diseases initiated by angiogenesis. We believe that this study has an important reference role in theoretical and clinical aspect for further understanding physiological and pathologic situations.