Correlation Of Sperm Quality With Vascular Endothelial Growth Factor And Its Receptor In Semen

Background and ObjectiveVascular endothelial growth factor (VEGF), also known as vascular permeability factor, is a multifunctional cytokine which is secreted by many kinds of normal cells and tumor cells and is considered a potent stimulator of endothelial cell growth and angiogenesis. It is vascular endothelial specific mitogen and has the function to increase microvascular permeability. VEGF is a homodimer glycoprotein linked by disulfide bonds, with the molecular weight of34-45kD, highly conserved sequence as well as stability against heat and acid. According to its amino acid residues number, there are six kinds of isomers such as VEGF121and VEGF165. These isomers have the same biological activity.It has been found that the VEGF has a high level of expression in a variety of normal tissues. VEGF mediates angiogenesis in both physiologic and pathologic conditions, and its expression is enhanced in vascular hyperplasia. In physiological state, VEGF can have a high level expression in the placenta, many embryonic tissues and adult normal tissues with physiological angiogenesis (eg. endometrium in proliferative phase). In addition, it is also expressed in animals’and adults’normal glomerular cells, myocardial cells, prostate epithelial cells, spermatogenic cells, adrenal cortex cells and pulmonary epithelial cells. In other pathological conditions, such as rheumatoid arthritis, psoriasis and wound healing and proliferation, it also plays an important role. However, excessive expression may be harmful to the body (such as cancer).VEGF receptors (VEGFR) mainly include VEGFRl (fms-like the tyrosine kinase-1, flt-1) and VEGFR2(fetal liver kinase-1/kinase the insert domain-containing receptor flk-l/KDR). VEGFRl is the homology form of the human KDR (infant liver kinase receptor) in mice. VEGFRl and VEGFR2are similar in structure and are both transmembrane tyrosine kinase receptors, and belong to the tyrosine kinase family of c-fins. VEGF can combine with KDR and Flt-1which can open Ca2+channel to increase intracellular Ca2+, in this way producing its biological effect.In male and female reproductive system, VEGF exerts its biological function by its receptor mediating and may be involved in regulating angio genesis and vascular permeability of the various organs of the reproductive system. Flt-1and KDR is expressed on the rat sperm acrosome, neck, middle and main section of the tail, which indicate that sperm itself is one of the target cells of VEGF. Seminiferous epithelium changes in a series of morphological structure, physical and chemical properties and biological functions in the process of sperm-producing. During these complex processes of change, VEGF and its receptors play important roles in participation and regulation. VEGF level in semen has some relationship with male and female’s reproductive to some extent.However, there is little research on relationship between VEGF as well as VEGFR and sperm quality in the domestic or abroad. In order to investigate the relationship between VEGF as well as its receptors and sperm quality in the male semen, different specimens of sperm quality were chosen, CASA (Computer-aided sperm analysis) was used to detect the sperm quality; chemical method which was the WHO recommended was used to detect seminal plasma biochemical composition (acid phosphatase, seminal plasma zinc, fructose, neutral a-glucosidase); enzyme immunoassay was used to detect seminal plasma VEGF level; immunohistochemistry was used to detect expression of VEGFR in sperm. The correlation between VEGF and VEGFR and the quality of sperm in the semen was explored by statistical analysis. Materials and methods1. Semen specimens from men with no obvious reproductive system disease were selected. General characteristics of the semen (such as amount, pH, liquefacation) were determined. CASA system was used to detect sperm quality. WTO recommended method was used to detect semen plasma biochemical indicators.2.95samples with normal biochemical indicators of seminal plasma were selected. ELISA was used to detect VEGF level of seminal plasma. Immunohistochemical SABC assay was used to detect the expression of VEGFR in sperm.3. Statistic software package SPSS16.0was used to make statistical analysis for all data. P＞O.05was considered as statistical significance.Results1. The positive signals were distributed in the tail and the base of head.2. In the groups of specimens with a class sperm proportion≥25%and<25%, VEGF average level in seminal plasma was8.18±1.93ng/ml and6.24±1.68ng/ml, respectively. There was a significant difference between them (P<0.05). The average positive rate of VEGFR in the two groups was30.1±9.2%and31.1±8.9%, respectively. There was no statistical difference between them (P>0.05).3. In the groups of specimens with a+b class sperm proportion≥50%and<50%, VEGF average level in seminal plasma was8.64±2.09ng/ml and6.57±1.44ng/ml, respectively. There was a significant difference between them (P<0.05). The average positive rate of VEGFR in the two groups was30.5±9.8%and31.0±7.5%, respectively. There was no statistical difference between them (P>0.05).4. In the groups of specimens with a+b+c class sperm proportion≥50%and<50%, VEGF average level in seminal plasma was7.62±1.68ng/ml and7.04±1.76ng/ml, respectively. There was no significant difference between them (P>0.05). The average positive rate of VEGFR in the two groups was31.4±9.1%and31.8±9.7%, respectively. There was no statistical difference (P>0.05).5. In the groups of specimens with sperm concentration≥20×10~6/ml and<20X 10~6/ml, the average positive rate of VEGFR was29.1±7.8%and41.9±10.9%, respectively. There was a significant difference between them (P<0.05). VEGF average level in seminal plasma in the two groups was7.42±1.78ng/ml and7.14±1.57ng/ml, respectively. There was no statistical difference (P>0.05).6. In the groups of specimens with total sperm number in one ejaculate≥40×10~6and<40×10~6, the average positive rate of VEGFR was30.8×7.9%and43.5×11.2%, respectively. VEGF average level in seminal plasma in the two groups was7.47×1.73ng/ml and6.49×1.55ng/ml, respectively. There was no statistical difference (P>0.05).7. Analyzed by Spearman test, seminal plasma VEGF levels and normal sperm morphology rate was negatively correlated with a correlation coefficient of-0.268.Conclusion1. Seminal plasma VEGF level of the group with normal sperm motion parameter is higher significantly than that of the group with lower sperm motion parameter. However, there is no significant difference of VEGFR positive rate between the two groups. The results suggest that higher seminal plasma VEGF level may effects positively on sperm motility via binding to VEGFR.2. VEGFR positive rate of the group with normal sperm number is lower than that of the group with lower sperm number. However, there is no significant difference of seminal plasma VEGF level between the two groups. The results suggest that increased VEGFR expression may utilize more effectively VEGF to maintain the number of sperm.