RESUMO
G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors in mammals that contain seven transmembrane helices. The human genome encodes about 800 different types of GPCRs, which are widely involved in the pathological processes underlying different diseases, e.g. metabolic diseases and tumors, rendering them popular therapeutic targets. Peptides are organic substances consisted of two to dozens of amino acids linked by peptide bonds. They are bioactive substances involved in various cellular activities. To date, over 7 000 natural peptides have been identified as hormones, neurotransmitters, growth factors, ion channel ligands and antibiotics. Peptide drugs are valued for being selective and efficacious, and at the same time relatively safe and with low costs of production. In recent years, based on the increased understanding of GPCR structures, the development of GPCR-targeting peptide drugs has made great progress. Up to now, there have been nearly 50 peptide drugs targeting GPCRs approved by FDA for the treatment of metabolic diseases, nervous system diseases, cancer or other diseases. The research and development of peptide drugs have gone through three stages: development based on human peptides, on natural peptides and by modern biotechnology. At present, most of the marketed GPCR-targeting peptide drugs are derivatives of human natural peptides. In this review, we sum up the recent marketed GPCR-targeting peptide drugs, and also summarize the current strategies and further directions of peptide drug development.
RESUMO
<p><b>OBJECTIVE</b>To establish an improved three-dimension (3D) and serum-free approach to differentiate human embryonic stem cells (hESCs) into endothelial cells, and detect the endothelial functions of the obtained cells.</p><p><b>METHODS</b>We cultured undifferentiated H9 human embryonic stem cell line in low-adhesion dishes to form embryonic bodies (EBs). After 12 days, EBs were harvested, re-suspended into rat tail collagen type I, and put into the incubator (37℃). After 30 minutes, EGM-2 culture medium was added to the solidified collagen, and the EBs were cultured for another 3 days to form embryonic body-sproutings (EB-sproutings). EB-sproutings were digested with 0.25% collagenase I and 0.56 U/ml Liberase Blendzyme for 20 minutes respectively, and the CD31(+) cells were sorted by FACS. The endothelial functions were tested by Dil-ac-LDL uptake assay and tube formation assay.</p><p><b>RESULTS</b>This approach raised the efficiency of endothelial differentiation to 18%, and also avoided the contamination with animal materials. The obtained hESC-derived endothelial cells (hESC-ECs) had the similar pattern of surface biomarkers as human umbilical vein endothelial cells (HUVECs), and their endothelial functions were confirmed by the uptake of Dil-ac-LDL and the tube formation on Matrigel.</p><p><b>CONCLUSIONS</b>The improved 3D approach can enhance the efficiency of differentiation from hESCs into endothelial cells. Furthermore, serum free differentiation system may be applied in future hESC-based therapies for various ischemic diseases.</p>