Recent advances in ovulation synchronization and superovulation in ...

Abstracts. II International Symposium on Animal Biology of Reproduction, Nov. 19-22, 2008, São Paulo, SP, Brazil.
Human luteolysis
A.R. Baerwald
Obstetrics, Gynecology and Reproductive Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Objectives
To discuss luteolysis during the human menstrual cycle and pregnancy.
Materials and Methods
Studies to evaluate the regression of the corpus luteum (CL) during the human menstrual cycle and pregnancy using histology,
ultrasonography, and molecular and cellular techniques are discussed.
Results
Luteolysis occurs approximately 7 days after ovulation in the absence of conception (1, 10). The corpus albicans can be detected,
but is not functional, during the follicular phase of the menstrual cycle (1). Following conception, the syncytiotrophoblast cells of
the developing conceptus secrete human chorionic gonadotropin which maintains the CL until approximately 20 weeks gestation,
at which time the luteal-placental shift has occurred and the CL regresses (8). The signal for luteolysis in women is not well
known; however, it is thought that the signal may involve a loss of gonadotropic support (9). Recent evidence indicates that both
apoptotic (12, 14) and authophagic (6) processes are involved in luteal regression. Luteolysis is characterized by decreasing size
and number of luteal cells (11), decreasing vascularity (13), tissue remodeling (4), and infiltration of lymphocytes and
macrophages (7). Luteal diameter and area decrease during luteolysis (1,10), in association with a decline in serum progesterone
and estradiol concentrations (1). In addition to endocrine hormones, growth factors (2,16), cytokines (3), reactive oxygen species
(15) and nitric oxide (5) appear to modulate luteal regression in women. The timing of the onset of luteal regression, peak
progesterone concentrations and peak estradiol concentrations have not yet been shown to differ in women with 2 versus 3
follicular waves during the menstrual cycle (1).
Conclusions
Luteolysis is a complex phenomenon, regulated by a precise network of endocrine, autocrine, and paracrine factors. Morphologic
changes in the CL during the human menstrual cycle and pregnancy have been well-documented, due to marked improvements in
ovarian imaging. Significant advances in cellular and molecular techniques are providing new insight into the biologic
mechanisms underlying luteolysis, which will assist in the treatment of women experiencing luteal deficiency.
References
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E-mail: angela.baerwald@usask.ca.
Anim. Reprod., v.6, n.1, p.199, Jan./Mar. 2009 199