Characterization of exosomal release in bovine endometrial intercaruncular stromal cells

Cell-to-cell communication between the blastocyst and endometrium is critical for implantation. In recent years, evidence has emerged from studies in humans and several other animal species that exosomes are secreted from the endometrium and trophoblast cells and may play an important role in cell-to-cell communication maternal-fetal interface during early pregnancy. Exosomes are stable extracellular lipid bilayer vesicles that encapsulate proteins, miRNAs, and mRNAs, with the ability to deliver their cargo to near and distant sites, altering cellular function(s). Furthermore, the exosomal cargo can be altered in response to environmental cues (e.g. hypoxia). The current study aims to develop an in vitro system to evaluate maternal-embryo interactions via exosomes (and exosomal cargo) produced by bovine endometrial stromal cells (ICAR) using hypoxia as a known stimulus associated with the release of exosomes and alterations to biological responses (e.g. cell proliferation).

Researchers from the University of Queensland evaluated ICAR cells cultured under 8 % O2 or 1 % O2 for 48 h and changes in cell function (i.e. migration, proliferation and apoptosis). Exosome release was determined following the isolation (via differential centrifugation) and characterization of exosomes from ICAR cell-conditioned media. Exosomal proteomic content was evaluated by mass spectrometry.

Under hypoxic conditions (i.e. 1 % O2), ICAR cell migration and proliferation was decreased (~20 and ~32 %, respectively) and apoptotic protein caspase-3 activation was increased (∼1.6 fold). Hypoxia increased exosome number by ~3.6 fold compared with culture at 8 % O2. Mass spectrometry analysis identified 128 proteins unique to exosomes of ICAR cultured at 1 % O2 compared with only 46 proteins unique to those of ICAR cultured at 8 % O2. Differential production of proteins associated with specific biological processes and molecular functions were identified, most notably ADAM10, pantetheinase and kininogen 2.

Proteomic analysis of bovine endometrial ICAR-derived exosomes


Mass spectrometric analyses of ICAR cell-derived exosome proteins. a Representative Venn diagram of common and unique proteins identified by 5600 Triple TOF MS (ABSciex) from exosomes released by ICAR cells at 48 h at both 8 % O2 and 1 % O2. b The gene ontology classification of ICAR cell-derived exosome proteins, on the basis of their involvement in biological process, identified clusters that are unique to and present only in exosomes of ICAR cultured at 1 % O2 but not those at 8 % O2. These biological processes were: growth (0.7 %), locomotion (0.7 %) and reproduction (1.4 %). c Molecular function (using PANTHER and Gene Ontology algoritnms) of exosome proteins were mostly related to binding and catalytic activity in both ICAR cultured at 1 % O2 and at 8 % O2

These data demonstrate that a stimulus such as hypoxia can alter both the cellular function and exosome release of ICAR cells. Alterations to exosome release and exosomal content in response to stimuli may play a crucial role in maternal-fetal crosstalk and could also affect placental development.

Koh YQ, Peiris HN, Vaswani K, Reed S, Rice GE, Salomon C, Mitchell MD. (2016) Characterization of exosomal release in bovine endometrial intercaruncular stromal cells. Reprod Biol Endocrinol 14(1):78. [article]

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