Mesothelial cells of peritoneal fluid.

This study looks at the cells found in the peritoneal fluid of 159 horses, focusing particularly on normal, activated, and transformed mesothelial cells to better understand their characteristics under different conditions such as acute or chronic inflammation.

Study Methodology

• The researchers collected peritoneal fluid samples from 159 horses. These peritoneal fluids were then prepared with a Giemsa stain, which is a type of dye commonly used in biology to highlight cellular structures under a light microscope.

Characteristics of Mesothelial Cells

• The study identified three different states of mesothelial cells present in the peritoneal fluid: normal, activated, and transformed.
• In their normal state, the mesothelial cells exhibited an oval nucleus with finely reticular chromatin — genetic material found in the nucleus of a cell — and a pale blue cytoplasm when observed under stained preparations.

Observations on Activated Mesothelial Cells

• Under acute or subacute non-septic conditions, the mesothelial cells were observed to become ‘activated’. Activated cells were discovered to be more diverse in form (pleomorphic) and to exhibit intense basophilia.
• Basophilia is a term used to describe the property of a cell staining strongly with a basic dye such as Giemsa. In this context, the intense basophilia indicates a higher level of RNA production which could suggest a heightened rate of protein synthesis and cell activity.
• The enhanced basophilia in activated mesothelial cells could mimic the appearance of neoplastic cells, cells that proliferate abnormally, often forming a mass or tumor which can be benign or malignant.

Observations on Transformed Mesothelial Cells

• Transformed mesothelial cells were set apart by their phagocytic function and notable cytoplasmic vacuolation. These cells were typically found in fluids associated with chronic inflammation.
• Phagocytic cells have the ability to ‘eat’ foreign substances, such as bacteria or dead cells, which helps to fight infections and inflammation. Cytoplasmic vacuolation refers to the presence of empty spaces (vacuoles) within the cell’s cytoplasm. Vacuolation can be a sign of cellular stress, injury, or disease.