Tierärztliche Hochschule Hannover Einfluss unterschiedlicher ...

7 Summary
Nicole Schlüter
Influence of different progesterone concentrations on bovine oocyte maturation in vivo and in
vitro
The influence of different progesterone concentrations on oocyte maturation was investigated.
In the first part of the experiments oocytes were retrieved by twice-weekly OPU. The first
OPU-session was performed on day 7 of the natural cycle (oestrus = day 0). Cumulus-oocytecomplexes
(COC) were classified by morphological criteria and mRNA expression of GDF9,
BMP15, SCL2A1, HIF2α, PGR, PGRMC1, PGRMC2 und PAQR5 was measured via RT-qPCR.
Bloodsamples were taken at every OPU-session and serum progesterone levels measured by
radioimmunoassey (RIA).
Despite twice weekly removal of all follicles > 2mm from the ovaries all animals showed
a natural cycle and formation of C.l. (induced C.l.) during the OPU period. Induced C.l. were
smaller (ind. C.l. 140,6 ±55,9 mm 2 , nat. C.l. 246,7 ±56,0 mm 2 ; P ≤0,05) and produced less
progesterone (ind. C.l. 2,8 ±1,0 ng/ml, nat. C.l. 4,6 ±1,9 ng/ml; P ≤0,05) than their natural
counterparts at the beginning of the experiment. There was neither an influence of the cycle on
number or size of follicles nor on number and quality of retreived oocytes. Messenger RNA
expression levels showed a reduced abundance of GDF9, BMP15, HIF2α, PGR, PGRMC1,
PGRMC2 und PAQR5 transcripts in oocytes of the induced c.l.-phase.
In the second part of the experiments oocytes from slaughterhouse ovaries were matured in
vitro with different progesterone concentrations (< 50 ng/ml, 150 ng/ml, 300 ng/ml, 450 ng/ml)
followed by in vitro production of embryos. Matured oocytes were rated for meiosis II stages
and the expression of GDF9, BMP15, SCL2A1, HIF2α, PGR, PGRMC1, PGRMC2 und PAQR5
was measured.
There was no influence of progesterone on maturation and cleavage rates. Oocytes of the
< 50 ng/ml group showed a significant reduction of developmental rates on day 7 and 8 when
compared to those of the control group (d7: 10,7 ±5,4 % vs. 20,7 ±6,6 %; d8: 15,8 ±5,4 %
vs. 25,4 ±8,0 %). Oocytes from all progesterone treatment groups contained less transcripts of
GDF9, HIF2α, PGR, PGRMC2 und PAQR5 compared to immature oocytes.
In conclusion, twice-weekly OPU has an influence on the natural cycle in cattle and may
induce C.l.s with different characteristics. The cycle has no influence on OPU results and morphological
quality of COC. There are alterations in the molecular structure of the oocyte that
may influence their developmental competence.
Supplementation of progesterone did not show an influence on oocyte maturation and cleavage
rates. Gene expression in oocytes matured in progesterone supplemented medium was
altered and may have negative effects on early embryonic development.
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