Angiogenesis, i.e. the development and growth of blood vessels, is a major topic of research as it plays an important role in normal development and in various pathologies. Recent evidence revealed the existence of different mechanisms of blood vessel growth, including sprouting and intussusceptive angiogenesis, vascular mimicry, and blood vessel cooption. The latter two have only been observed in tumor growth, but sprouting and intussusceptive angiogenesis also occur in healthy, physiologically growing tissues. Despite this variety of angiogenic mechanisms, most of the current research is focused on the mechanism of sprouting angiogenesis because this mechanism was first described and because most existing experimental models are related to sprouting angiogenesis. Consequently, the mechanism of intussusceptive angiogenesis is often overlooked in angiogenesis research. Here, the mechanism of intussusceptive angiogenesis is reviewed and the current techniques and models for investigating intussusceptive angiogenesis are summarized. In addition, other mechanisms of vascular growth are briefly reviewed.

In the course of new blood vessel formation, two different processes--vasculogenesis and angiogenesis--have to be distinguished. The term vasculogenesis describes the de novo emergence of a vascular network by endothelial progenitors, whereas angiogenesis corresponds to the generation of vessels by sprouting from pre-existing capillaries. Until recently, it was thought that vasculogenesis is restricted to the prenatal period. During the last decade, one of the most fascinating innovations in the field of vascular biology was the discovery of endothelial progenitor cells and vasculogenesis in the adult. This review aims at introducing the concept of adult vasculogenesis and discusses the efforts to identify and characterize adult endothelial progenitors. The different sources of adult endothelial progenitors like haematopoietic stem cells, myeloid cells, multipotent progenitors of the bone marrow, side population cells and tissue-residing pluripotent stem cells are considered. Moreover, a survey of cellular and molecular control mechanisms of vasculogenesis is presented. Recent advances in research on endothelial progenitors exert a strong impact on many different disciplines and provide the knowledge for functional concepts in basic fields like anatomy, histology as well as embryology.

BackgroundHigher rates of depression, suicidal ideation and suicide risk have been reported for veterinarians in various studies worldwide. This study investigates whether this is also true for German veterinarians.MethodsA total of 3.118 veterinarians (78.8 per cent female, mean age 41.3 years) between 22 and 69 years were included and compared with two general population samples of the same age range using the Suicide Behaviours Questionnaire-Revised and Patient Health Questionnaire.ResultsCurrent suicidal ideation was found in 19.2 per cent of veterinarians, compared with only 5.7 per cent in the general population. 32.11 per cent of veterinarians were classified with increased suicide risk, compared with 6.62 per cent in the general population. 27.78 per cent of veterinarians screened positive for depression, compared with 3.99 per cent of the general population.ConclusionThe study shows that veterinarians have an increased risk of depression and suicidal ideation and suicide risk compared with the general population in Germany. Similar to previous findings, the level of depression was higher among veterinarians than in the general population. However, this study does not explore causes for higher rates in depression, suicide risk and suicidal ideation. Since other studies strongly suggest specific risk factors lead to higher suicide risk and consequently elevated numbers of completed suicides, future research should focus on identifying and preventing causes.

Angiogenesis is defined as the sprouting of new capillaries from pre-existing ones. Angiogenesis is a prerequisite for growth and differentiation of organs and tissues and is involved in many pathological processes, for example growth and metastasis of tumours. Numerous in vivo and in vitro models of angiogenesis have been developed in order to identify and analyse pro-and antiangiogenic factors. This review aims at outlining the topic of quantitation of angiogenesis and antiangiogenesis in these models.

In vitro angiogenesis assays constitute an important tool for studying the mechanisms of angiogenesis and for identification of pro- and anti-angiogenic substances. Therefore, endothelial cell and media systems used for in vitro angiogenesis assays are required to mimic the angiogenic process in vivo including endothelial capability to express collagen type IV as a component of the basement membrane. In this study, the expression of collagen type IV and its α chains (α1-6) was investigated in different endothelial cell culture systems in vitro qualitatively and quantitatively. These systems included four different batches of microvascular endothelial cells derived from the human skin, heart and lung, from which only two batches were found to be angiogenic and two batches were classified as non-angiogenic. Distribution of the transcripts of the α chains of collagen type IV was similar in all cell and media systems investigated. However, secretion and deposition of a stable extracellular network of collagen type IV could only be observed in the angiogenic cultures. In conclusion, the consecutive steps of the angiogenic cascade in vivo as well as in vitro depend on an increasing secretion and subsequent extracellular deposition of collagen type IV.