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Review
. 2024 Sep;24(3):100920.
doi: 10.1016/j.repbio.2024.100920. Epub 2024 Jul 5.

Transcervical uterine flushing and embryo transfer in sheep: Morphophysiological basis for approaches currently used, major challenges, potential improvements, and new directions (alas, including some old ideas)

Joedson Dantas Gonçalves  1 , Jenniffer Hauschildt Dias  2 , Mariana Machado-Neves  2 , Gabriel Brun Vergani  1 , Bahareh Ahmadi  3 , Ribrio Ivan Tavares Pereira Batista  4 , Joanna Maria Gonçalves Souza-Fabjan  4 , Maria Emilia Franco Oliveira  1 , Pawel Mieczyslaw Bartlewski  3 , Jeferson Ferreira da Fonseca  5
Affiliations
Review

Transcervical uterine flushing and embryo transfer in sheep: Morphophysiological basis for approaches currently used, major challenges, potential improvements, and new directions (alas, including some old ideas)

Joedson Dantas Gonçalves et al. Reprod Biol. 2024 Sep.

Abstract

At present, the success of non-surgical embryo recovery (NSER) and transfer (NSET) hinges upon the cervical passage of catheters, but penetration of the uterine cervix in ewes is problematic due to its anatomical structure (i.e., long and narrow cervical lumen with misaligned folds and rings). It is a major obstacle limiting the widespread application of NSER and NSET in sheep. While initial attempts to traverse the uterine cervix focused on adapting or re-designing insemination catheters, more recent studies demonstrated that cervical relaxation protocols were instrumental for transcervical penetration in the ewe. An application of such protocols more than tripled cervical penetration rates (currently at 90-95 %) in sheep of different breeds (e.g., Dorper, Lacaune, Santa Inês, crossbred, and indigenous Brazilian breeds) and ages/parity. There is now sufficient evidence to suggest that even repeatedly performed cervical passages do not adversely affect overall health and reproductive function of ewes. Despite these improvements, appropriate selection of donors and recipients remains one of the most important requirements for maintaining high success rates of NSER and NSET, respectively. Non-surgical ovine embryo recovery has gradually become a commercially viable method as even though the procedure still cannot be performed by untrained individuals, it is inexpensive, yields satisfactory results, and complies with current public expectations of animal welfare standards. This article reviews critical morphophysiological aspects of transcervical embryo flushing and transfer, and the prospect of both techniques to replace surgical methods for multiple ovulation and embryo transfer (MOET) programs in sheep. We have also discussed some potential pharmacological and technical developments in the field of non-invasive embryo recovery and deposition.

Keywords: Assisted reproductive technologies; Biomedical engineering, microrobotics; Cervical dilation; Sheep; Transcervical passage.

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Conflict of interest statement

Declaration of Competing Interest I, Jeferson Ferreira da Fonseca, declare that I do not have any personal or financial interests that could influence or bias my actions, decisions, or judgments in any professional capacity. I have no affiliations, investments, or relationships that could create conflicts of interest. I acknowledge that conflicts of interest can compromise objectivity, fairness, and integrity, and I am committed to maintaining the highest level of ethical conduct in all my endeavors. I will disclose any potential conflicts of interest that may arise during the course of my work, and take appropriate steps to mitigate or address them transparently and in accordance with relevant laws, regulations, and organizational policies. Furthermore, I understand that any actions or decisions I take in my professional role should be based on merit, relevant expertize, and the best interests of the individuals, organizations, or entities that I serve. I will act in a fair, impartial, and transparent manner, and avoid any actions that could compromise my ability to fulfill my professional duties objectively and with integrity. I hereby affirm that the above declaration accurately reflects my current understanding and commitment to upholding high standards of integrity, transparency, and ethical conduct in all my professional endeavors.