Angiogenic growth factors in myocardial infarction: a critical appraisal

In the recent past, substantial advances have been made in the treatment of myocardial infarction (MI). Despite the impact of these positive developments, MI remains to be a leading cause of morbidity as well as mortality. An interesting hypothesis is that the development of new blood vessels (angiogenesis) or the remodeling of preexisting collaterals may form natural bypasses that could compensate for the occlusion of an epicardial coronary artery. A number of angiogenic factors are proven to be elicited during MI. Exogenous supplementation of these growth factors either in the form of recombinant protein or gene would enhance the collateral vessel formation and thereby improve the outcome after MI. The aim of this review is to describe the nature and potentials of different angiogenic factors, their expression, their efficacy in animal studies, and clinical trials pertaining to MI.

Integrin β3/Akt signaling contributes to platelet-induced hemangioendothelioma growth

Hemangioendothelioma (HE) is a type of angiomatous lesions that features endothelial cell proliferation. Understanding the mechanisms orchestrating HE angiogenesis can provide therapeutic insights. It has been shown that platelets can support normal and malignant endothelial cells during angiogenesis. Using the mouse endothelial-derived EOMA cell line as a model of HE, we explored the regulatory effect of platelets. We found that platelets stimulated EOMA proliferation but did not mitigate apoptosis. Furthermore, direct platelet-EOMA cell contact was required and the proliferation was mediated via integrin β3/Akt signaling in EOMA cells. SiRNA knockdown of integrin β3 and inhibition of Akt activity significantly abolished platelet-induced EOMA cell proliferation in vitro and tumor development in vivo. These results provide a new mechanism by which platelets support HE progression and suggest integrin β3 as a potential target to treat HE.

Thymidine Phosphorylase in Cancer; Enemy or Friend?

Thymidine phosphorylase (TP) is a nucleoside metabolism enzyme that plays an important role in the pyrimidine pathway.TP catalyzes the conversion of thymidine to thymine and 2-deoxy-α-D-ribose-1-phosphate (dRib-1-P). Although this reaction is reversible, the main metabolic function of TP is catabolic. TP is identical to the angiogenic factor platelet-derived endothelial-cell growth factor (PD-ECGF). TP is overexpressed in several human cancers in response to cellular stressful conditions like hypoxia, acidosis, chemotherapy and radiotherapy. TP has been shown to promote tumor angiogenesis, invasion, metastasis, evasion of the immune-response and resistance to apoptosis. Some of the biological effects of TP are dependent on its enzymatic activity, while others are mediated through cytokines like interleukin 10 (IL-10), basic fibroblast growth factor (bFGF) and tumour necrosis factor α (TNFα). Interestingly, TP also plays a role in cancer treatment through its role in the conversion of the oral fluoropyrimidine capecitabine into its active form 5-FU. TP is a predictive marker for fluoropyrimidine response. Given its various biological functions in cancer progression, TP is a promising target in cancer treatment. Further translational research is required in this area.

Myocardial expression of PDECGF is associated with extracellular matrix remodeling in experimental myocardial infarction in rats

Platelet-derived endothelial cell growth factor (PDECGF) is a potent angiogenic peptide with anti-apoptotic activity expressed widely in tumours. However, its expression in myocardial infarction (MI) is not yet established. This study aimed to assess the myocardial expression of PDECGF in rats after MI. Extracellular matrix (ECM) remodeling plays an important role in angiogenesis; hence, changes in the ECM components were investigated in the myocardium after MI, which was induced in rats by coronary artery ligation (CAL) and verified using biochemical markers and histopathology. Immunohistochemistry, RT-PCR, and activity assays identified the expression pattern of PDECGF on days 1, 2, 4, 8, 16, and 32 after CAL. The levels of TNF-alpha, MMP-2, collagen, and glycosaminoglycans in the ECM were assessed. Studies on immunohistochemistry, RT-PCR, and PDECGF activity demonstrated elevated levels of PDECGF expression from day 2 after CAL. Macrophages, endothelial cells, fibroblasts, and cardiomyocytes, especially at the border region of the lesion, showed an enhanced expression for PDECGF. Remodeling of the ECM was depicted by changes in the levels of TNF-alpha, MMP-2, collagen, and GAG. Hence, this study clearly indicated PDECGF as an important angiogenic molecule expressed during MI and the alterations in ECM components facilitated the process of angiogenesis.