Morphological study of equine amniotic compartment.

The research article examines the structure and composition of amniotic fluid (AF) and amniotic membrane (AM) in horses, using light microscopy (LM) and transmission electron microscopy (TEM). The study aims to provide the first description of equine AF cells and AM, offering insights for understanding fetal development and equine pregnancy more accurately.

Introduction

• The study acknowledges that while the morphology of human amniotic fluid has been extensively studied, no data exist for equine species. The research emphasizes the importance of understanding this, as the amniotic fluid compartment is the environment in which the fetus grows and matures, and changes in its composition can reflect fetal wellbeing and development.

Methodology

• The researchers obtained samples of amniotic fluid and amniotic membrane from mares at parturition within 5 minutes after the amniotic membrane appeared.
• Light microscopy (LM) was used to observe a sample of fresh amniotic fluid that had undergone cytocentrifugation and staining with May-Grünwald Giemsa. In addition, amniotic membrane sections were stained with H-E.
• Transmission electron microscopy (TEM) was also employed to observe the amniotic fluid and amniotic membrane. Samples for this were fixed, embedded in epoxy resins, then sectioned and stained with uranyl acetate and lead citrate solutions.

Findings

• The researchers identified nucleated and anucleated squamous cells, intensely basophilic cornified cells, polymorphonuclear cells, and clusters of eosinophilic amorphous substances in the samples.
• Certain cells presumably originating from the tracheal epithelium and small round nucleated cells presumably derived from the amniotic or urinary epithelium were also found.
• Lamellar body-like structures (LBs) were present in some epithelial cells, suggesting they could serve as a secondary source of pulmonary surfactant – a substance that reduces lung surface tension and prevents the collapse of alveoli.
• The amniotic membrane showed clearly visible epithelial, basal, and mesenchymal layers, just as described in previous research.

Conclusion and Further Research

• The research represents the first evidence-based description of the equine amniotic compartment via LM and TEM. The findings, especially regarding the presence of LBs, suggest potential similarities with human physiology, though this requires more comprehensive investigation.
• The study points out the need for further studies using samples collected at various gestational ages to enhance knowledge about the modification of AF cells during pregnancy, as well as to understand the role of the amniotic membrane as a secondary source of pulmonary surfactant more fully.
• Finally, the paper suggests that examining the cellular composition of amniotic fluid may offer useful insights for identifying and managing high-risk pregnancies in horses.