Identification of Distinct Populations of Prostasomes That Differentially Express Prostate Stem Cell Antigen, Annexin A1, and GLIPR2 in Humans1

Abstract

In addition to sperm cells, seminal fluid contains various small membranous vesicles. These include prostasomes, membrane vesicles secreted by prostate epithelial cells. Prostasomes have been proposed to perform a variety of functions, including modulation of (immune) cell activity within the female reproductive tract and stimulation of sperm motility and capacitation. How prostasomes mediate such diverse functions, however, remains unclear. In many studies, vesicles from the seminal plasma have been categorized collectively as a single population of prostasomes; in fact, they more likely represent a heterogeneous mixture of vesicles produced by different reproductive glands and secretory mechanisms. We here characterized membranous vesicles from seminal fluid obtained from vasectomized men, thereby excluding material from the testes or epididymides. Two distinct populations of vesicles with characteristic sizes (56 ± 13 nm vs. 105 ± 25 nm) but similar equilibrium buoyant density (∼1.15 g/ml) could be separated by using the distinct rates with which they floated into sucrose gradients. Both types of vesicle resembled exosomes in terms of their buoyant density, size, and the presence of the ubiquitous exosome marker CD9. The protein GLIPR2 was found to be specifically enriched in the lumen of the smaller vesicles, while annexin A1 was uniquely associated with the surface of the larger vesicles. Prostate stem-cell antigen (PSCA), a prostate-specific protein, was present on both populations, thereby confirming their origin. PSCA was, however, absent from membrane vesicles in the seminal fluid of some donors, indicating heterogeneity of prostasome characteristics between individuals.

Annexin A1–containing extracellular vesicles and polymeric nanoparticles promote epithelial wound repair

“…Furthermore, in vivo, local administration of synthetic NPs containing Ac2-26 mimics the prorepair effects of epithelial and immune cell-derived EVs. Additionally, a previous study reported ANXA1 association with the exoplasmic surface of vesicles secreted by prostate epithelial cells into the seminal fluid or prostasomes may contribute to suppression of the immune response in the female reproductive tract (39).…”

Proteomic comparison defines novel markers to characterize heterogeneous populations of extracellular vesicle subtypes

“…2A). Overlaying the gradient on top of the EV pellet ensured that membrane-enclosed vesicles floated upwards, whereas protein aggregates could not float into the gradient and remained in the dense fractions (14,15). Ten fractions were recovered and analyzed for the presence of protein markers previously detected in both pellets.…”

Strategies for Isolation of Exosomes

“…In subsequent years, many additional cell types of both hematopoietic and nonhematopoietic origin, such as cytotoxic T cells, platelets, mast cells, neurons, oligodendrocytes, Schwann cells, and intestinal epithelial cells, have been shown to release exosomes (Simons and Raposo 2009;Théry et al 2009). Furthermore, exosomes have been found in many body fluids, including blood (Caby et al 2005), semen (Aalberts et al 2012), urine (Pisitkun et al 2004), saliva (Ogawa et al 2011), breast milk (Admyre et al 2007), ascites fluid (Andre et al 2002), amniotic fluid (Asea et al 2008), cerebrospinal fluid (Vella et al 2007), and bile (Masyuk et al 2010). …”