Extracellular vesicles (EVs) are released from almost all cells and tissues. They are able to transport substances (e.g. proteins, RNA or DNA) at higher concentrations than in their environment and may adhere in a receptor-controlled manner to specific cells or tissues in order to release their content into the respective target structure. Blood contains high concentrations of EVs mainly derived from platelets, and, at a smaller amount, from erythrocytes. The female and male reproductive tracts produce EVs which may be associated with fertility or infertility and are released into body fluids and mucosas of the urogenital organs. In this review, the currently relevant detection methods are presented and critically compared. During pregnancy, placenta-derived EVs are dynamically detectable in peripheral blood with changing profiles depending upon progress of pregnancy and different pregnancy-associated pathologies, such as preeclampsia. EVs offer novel non-invasive diagnostic tools which may reflect the situation of the placenta and the foetus. EVs in urine have the potential of reflecting urogenital diseases including cancers of the neighbouring organs. Several methods for detection, quantification and phenotyping of EVs have been established, which include electron microscopy, flow cytometry, ELISA-like methods, Western blotting and analyses based on Brownian motion. This review article summarises the current knowledge about EVs in blood and cord blood, in the different compartments of the male and female reproductive tracts, in trophoblast cells from normal and pre-eclamptic pregnancies, in placenta ex vivo perfusate, in the amniotic fluid, and in breast milk, as well as their potential effects on natural killer cells as possible targets.

Tendon properties do not seem to be influenced by the COL5A1 rs12722 gene variant. Although the COL5A1 rs12722 polymorphism has previously been associated with the risk of tendon pathology, that association is unlikely to be mediated via underlying tendon dimensional and functional properties.

Sequence variations in genes that code for proteins involved in homeostatic processes within tendons may influence tendon mechanical properties. Since variants of the four genes COL5A1, TNC, MMP3 and GDF5 have been implicated in the aetiopathogenesis of tendinopathies, which is ultimately characterised by abnormal structural and regulatory processes, sequence variations in these four genes may also influence how the tendon functions mechanically, even in the absence of tendinopathy. For example, two reports of association between variation in the COL5A1 gene and measures of flexibility complement reported associations between genotype and incidence of tendinopathy. Non-genetic factors such as age, body mass and physical activity status influence risk of tendon injury and physical performance potential independently from genomics, and also in gene-environment interactions. However, these non-genetic factors are often not considered in genetic association studies, probably due to their retrospective nature. Further research examining COL5A1, TNC, MMP3 and GDF5, as well as other genes that may influence the maintenance of tendon homeostasis such as COL1A1 which regulates the production of collagen type 1, the most abundant structural component of tendon is encouraged. Establishing the genetic basis of tendon properties in asymptomatic populations may advance understanding of some aspects relevant to physical performance and of the aetiology of tendinopathies. To improve understanding, accurate and reproducible assessments of tendon properties are required. However, no valid and reliable assessments of tendon properties, such as those involving in vivo ultrasound imaging techniques, have yet been applied to genetic association studies in humans.

Patellar tendon properties do not seem to be influenced by the MMP3 gene variants measured. Although these MMP3 gene variants have previously been associated with the risk of tendon pathology, that association is unlikely to be mediated via underlying tendon dimensional and functional properties.