Application of digital pathology to assess the effect of hormone treatment on placental histomorphometry in mares with induced ascending placentitis.

Overview

• This study investigated how hormone treatments affect the microscopic structure of placentas in mares with experimentally induced ascending placentitis, using digital pathology to quantitatively analyze tissue changes.
• The research demonstrated that estradiol cypionate (ECP) treatment notably improves placental vascularization and structure, suggesting its potential to aid placental recovery in infected mares.

Study Objectives

• To evaluate the effect of hormone treatments—altrenogest (ALT) and estradiol cypionate (ECP)—on placental histomorphometry in mares with experimentally induced ascending placentitis.
• To use digital pathology as a quantitative method for assessing changes in placental microstructure after treatment.

Background Information

• Ascending placentitis is an infection of the placenta in mares that can cause pregnancy complications and impact fetal health.
• Hormonal treatments such as ALT and ECP are considered for supporting pregnancy maintenance and placental function.
• Histomorphometry involves measuring microscopic structures of the placenta, focusing on elements like microcotyledons (small placental projections) and capillaries essential for nutrient and gas exchange.
• Digital pathology with image analysis tools (e.g., NIH ImageJ) provides quantitative and objective data on tissue morphology.

Study Design and Methods

• A total of 30 pregnancies from 27 Criollo-type mares were included and divided into six groups:
• Healthy controls (n=5) – no placentitis or treatment
• Basic treatment (n=5) – treated with antibiotics trimethoprim-sulfamethoxazole (TSM) and anti-inflammatory flunixin meglumine (FM)
• ALT group (n=5) – received altrenogest plus basic treatment
• ECP group (n=5) – received estradiol cypionate plus basic treatment
• ALT + ECP group (n=5) – received both hormones in addition to basic treatment
• Untreated placentitis group (n=5) – no treatment given for placentitis
• Mares were experimentally induced with ascending placentitis to simulate the disease state.
• After parturition, placental tissue samples were collected from three locations: cervical star, uterine body, and both uterine horns.
• Samples were digitally imaged, and NIH ImageJ software was used to measure areas of microcotyledons and capillaries per microscopic field.
• Key parameters assessed included gestation length, placental weight, expulsion time, capillary area, and total microcotyledonary area.

Key Findings

• Gestation length: The ECP group had gestation lengths similar to healthy mares, implying that ECP may help maintain a normal pregnancy duration despite infection.
• Placental weight and expulsion time: No significant differences were noted among groups, indicating treatments did not adversely affect these parameters.
• Histomorphometric results:
• Mares treated with ECP showed a significant increase in capillary area and total microcotyledonary area compared to other placentitis groups, reflecting enhanced placental vascularization and structure.
• This enhanced microvascularization suggests ECP promotes recovery and healthy development of placental tissue despite infection.
• These findings collectively point to the beneficial role of ECP in improving placental health during infectious challenges.

Significance and Implications

• Therapeutic potential: ECP could be a valuable adjunct treatment in mares with ascending placentitis to support placental function and fetal health.
• Placental recovery: Enhancing capillary density and microcotyledon structure may improve nutrient and oxygen delivery to the fetus, reducing adverse pregnancy outcomes.
• Digital pathology utility: The study demonstrates how quantitative image analysis can objectively measure subtle microscopic changes in placental tissue, facilitating more precise evaluation of treatment effects.
• Future research: These results provide a foundation for clinical trials and development of improved hormone-based therapies for placentitis in equine veterinary medicine.

Conclusion

• This study successfully applied digital pathology techniques to quantify histomorphometric changes in equine placentas affected by ascending placentitis.
• Estradiol cypionate treatment enhanced placental vascularization and microcotyledon structure, potentially aiding in placental recovery and maintenance of uterine homeostasis.
• The research supports the use of ECP as part of therapeutic strategies for managing placentitis and highlights the benefit of digital pathology in veterinary placental research.