Equine zona pellucida and capsule: some physicochemical and antigenic properties.

This research article investigates the capsule that surrounds the pre-attachment equine embryo and compares its properties to the zona pellucida it replaces, using physicochemical and immunological methods. The article also compares these properties to those of the rabbit blastocyst coverings.

Methods of Analysis

• The researchers conducted a thorough investigation of the physical and immunological properties of the capsule and the zona pellucida using a range of solutions and conditions.
• The capsule was exposed to trypsin solution at a pH varying between 7.5 and 9.0 and also Na borohydride, both of which completely solubilized the capsule.
• The zona pellucida was treated under conditions of extreme pH values (2.0 or 12.0), urea, high temperature (65 degrees C, 60 min or 80 degrees C, 30 min), and chemicals such as mercaptoethanol and dithiothreitol. These conditions were able to solubilize the zona pellucida but not the capsule at the concentrations used.

Immunofluorescence Observations

• Using indirect immunofluorescence on cryostat sections and whole mounts of fresh or frozen-thawed material, certain observations were recorded.
• Common antigens are shared by equine, porcine and bovine zona pellucida.
• Day 7 to day 15.5 capsule reacted with anti-capsule-serum but not with anti-zp-serum except for a few patches on the surface of the capsule, suggesting different immunological responses.
• Anti-capsule-serum, but not anti-zp-serum, reacted with the capsular material recovered along with a broken day 27.5 conceptus.
• Anti-capsule-serum does not react with rabbit blastocyst coverings, implying species-specific immune interactions.

Absorption of Anti-Capsule Antibodies and Composition of Capsule

• The study demonstrated that anti-capsule antibodies can be absorbed from the anti-capsule-serum by uterine proteins from either pregnant or non-pregnant mares, indicating that these antibodies may interact with uterine proteins.
• Furthermore, the study confirmed that the equine embryo capsule does not contain mouse laminin-like material, a protein crucial for cell adhesion and migration, implying a unique protein composition in the equine embryo capsule.