The effect of platelet releasate on oocytes has a detrimental impact on early mammalian embryos

Background: Blood-derived products are a growing area of therapeutic treatments for a
diverse range of conditions, including hair loss, scarring, muscle injury, wounds,
arthritis, and symptoms related to the menopause. Platelet-rich plasma (PRP) is one
blood product being trialled on the menopausal ovary. Emerging data from ongoing
trials suggest that PRP injection might promote resumption in ovarian function, and an
increase in both spontaneous and assisted conception. However, knowledge of the
direct cellular effects of PRP on oocytes and early embryos is limited.
Hypothesis & Aim: We hypothesised that platelet releasate would influence embryo
development. This study aimed to determine the extent to which the embryo is
affected by releasate. We further hypothesised that oocytes (mature and dead) and
cumulus cells would activate platelets. This study aimed to determine the extent to
which oocytes and cumulus cells were able to induce platelet activation.
Method: Oocytes were collected from abattoir-derived bovine ovarian tissue and
incubated for 22 hours in in the presence of either 10% platelet releasate (derived from
whole human blood) or 10% foetal calf serum (FCS) (control). A proportion of oocytes
were selected for nuclear staining to establish maturation status. The majority of the
oocytes were fertilised with bull sperm and allowed to develop into embryos. The
number of embryos that reached the 2-cell stage by day 2 (cleavage rate) and blastocyst
stage by day 9 (blastocyst rate) were recorded, as were a variety of blastocyst
endpoints: blastocyst metabolism, mitochondrial function, and expression of the
epigenetic marker, H3K27me3. Separately, the effect of oocytes on platelets was
investigated. Mature oocytes, dead (unexpanded) oocytes, culture media, and cumulus
cells were added to PRP to determine their capability to activate platelets via a series of
aggregations.
Results: Platelet releasate had no discernable effect on metaphase II rate in oocytes
matured in vitro. There was no significant difference between the cleavage rate of
platelet releasate and FCS derived oocytes, however the blastocyst rate of platelet
releasate derived embryos was significantly lower than that of the FCS group. No
significant difference was found in lactate release and pyruvate depletion of platelet
ii
releasate and FCS derived embryos. However, glucose depletion was significantly
reduced in platelet releasate derived embryos in comparison to the FCS control. Oxygen
consumption rate, used as a measure of mitochondrial function, did not differ
significantly between the groups, and neither did H3K27me3 expression – both platelet
releasate derived embryos and FCS derived embryos expressed the modification. No
significant difference in platelet activation of PRP was observed between mature
oocytes, dead oocytes, culture media, and cumulus cells exposure, although repeats
were inconsistent.
Conclusion: Oocyte exposure to platelet releasate did not lead to differences in nuclear
maturation, the oocytes’ capability to be fertilised was similar between the releasate
group and FCS control. The number of oocytes that were able to cleave after fertilisation
was unaffected by prior supplementation with platelet releasate. However, platelet
releasate derived embryos were significantly less likely to develop into blastocysts. In
comparison with the FCS control, platelet releasate derived embryos that did develop
into blastocysts, had a reduced consumption of glucose but a normal pyruvate
consumption and lactate production, they also had a normal oxygen consumption rate
and normal H3K27me3 expression. Neither mature oocytes, nor dead oocytes, nor
cumulus cells, showed ability to activate platelets to a further extent than culture
media.
While platelet-derived factors injected into the ovary might stimulate resumption of
ovarian activity, the oocytes exposed to such factors may have diminished
developmental competence once they form embryos.