"Immunolocalization and effect of low concentrations of Insulin like growth factor-1 (IGF-1) in the canine ovary".

Diogo J Cardilli,Gilson H Toniollo,Marco A Machado‐Silva,Kellen Sousa‐Oliveira,María Jesús Sánchez‐Calabuig,Faviana Azevedo‐Voorwald,José F Pérez‐Gutiérrez,Carolina Franchi‐João,João Ademir Oliveira

doi:10.1002/vms3.347

Abstract

Insulin like growth factor‐1 (IGF‐1) plays an important role in the regulation of ovarian function. Despite its extensive study in several species, there is a paucity of information about IGF‐1`s function and localization in the canine ovary. The aim of the present study was to assess the effect of IGF‐1 on oocyte nuclear maturation and to immunolocalize the IGF‐1 and its receptor (IGF‐1R) in the ovary. Cumulus‐oocyte complexes (COCs) were obtained from 34 bitches. The COCs from each bitch were incubated in TCM 199‐HEPES in the absence (n = 199) or presence (n = 204) of 100 ng/ml IGF‐1 for 96 hr at 38ºC in 5% CO2, stained and evaluated for nuclear maturation by fluorescence microscopy. The results showed that the addition of IGF‐1 did not have an effect (p ˃ 0.05) on the nuclear maturation under these conditions. The immunohistochemical study revealed nuclear and cytoplasmic staining for IGF‐1 and IGF‐1R, respectively. Both were localized in all ovarian structures including the corpus luteum, but not in the granulosa cells from primordial follicles. In addition, IGF‐1 was not localized in the oocytes in tertiary follicles. The results obtained show the presence of IGF‐1 through the stages of follicular growth and in the corpus luteum of the canine ovary. However, its role on oocyte nuclear maturation could not be demonstrated.

Highlights

The development of assisted reproductive technologies (ART) in domestic canids arouses great interest due to its critical role in conserving endangered canid species
The aim of the current study is to reveal the immunolocalization of Insulin like growth factor-1 (IGF-1) and IGF-1 receptor (IGF-1R) in all the canine ovarian compartments throughout the cycle and to assess the effects of low IGF-1 concentration (100 ng/ ml) on nuclear maturation using a long incubation time (96 hr)
The immunolocalization of IGF-1 and IGF-1R in the ovary of the bitch showed a wide distribution, suggesting that this growth factor could be involved in many functions such as follicular development, ovulation, postovulatory wound healing and corpus luteum maintenance

Summary

Introduction

The development of assisted reproductive technologies (ART) in domestic canids arouses great interest due to its critical role in conserving endangered canid species. The oocyte completes meiosis after a prolonged exposure (i.e. 2–3 days) to the oviductal environment (Songsasen & Wildt, 2007), which consists of a changing milieu in response to multiple fluctuating hormones throughout the oestrous cycle. This environment is difficult to reproduce in vitro and involves the complex interaction of a multitude of signals that likewise vary throughout the oestrous cycle (Luvoni, Chigioni, Allievi, & Macis, 2005)

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