Reproduction, Fertility and Development Reproduction, Fertility and Development Society
Vertebrate reproductive science and technology

Caspase-3-mediated apoptosis and cell proliferation in the equine endometrium during the oestrous cycle

R. P. Roberto da Costa A , P. M. Serrão B , S. Monteiro B , P. Pessa C , J. Robalo Silva B and G. Ferreira-Dias B D

A Escola Superior Agrária, Instituto Politécnico de Coimbra, Bencanta, 3040-316 Coimbra, Portugal.

B CIISA, Faculdade de Medicina Veterinária, Universidade Técnica de Lisboa (TULisbon), 1300-477 Lisbon, Portugal.

C Hospitais da Universidade de Coimbra, 3000-075 Coimbra, Portugal.

D Corresponding author. Email:

Reproduction, Fertility and Development 19(8) 925-932
Submitted: 5 December 2006  Accepted: 22 July 2007   Published: 13 September 2007


Cell proliferation and apoptosis are hormone-dependent physiological processes involved in endometrial growth and regression. The aims of the present study were: (1) to evaluate endometrial cell proliferation using proliferating cell nuclear antigen (PCNA) expression; (2) to evaluate the induction of endometrial cell death by the expression of active caspase-3 and the apoptotic phenotype visualised by DNA fragmentation; and (3) to relate these observations to endometrial tissue dynamics in the equine endometrium throughout the oestrous cycle. Endometria were assigned to follicular and luteal phases based on ovarian structures and plasma progesterone. Cell proliferation and active caspase-3-mediated apoptosis were expressed in both phases of the oestrous cycle. In the luteal phase, PCNA expression was higher than in the follicular phase. Highest PCNA activity was noted in the luminal and glandular structures. Active caspase-3 staining was increased in luminal epithelium and deep glandular cells during the luteal phase. However, in the follicular phase, stromal cells showed greater active caspase-3 expression. Only a few apoptotic endometrial cells were detected by terminal deoxyribonucleotidyl transferase-mediated dUTP–digoxigenin nick end-labelling (TUNEL) and these cells were mostly present in luminal and glandular structures. A simultaneous increase in DNA, cell proliferation and protein synthesis was observed in the endometrium during the mid-luteal phase. This suggests that cell hyperplasia occurs at the time the histotroph is needed for eventual embryo nourishment.

Additional keywords: apoptosis, mare, proliferating cell nuclear antigen, terminal deoxyribonucleotidyl transferase-mediated dUTP–digoxigenin nick end-labelling (TUNEL).


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