Viability of Equine Chondrocytes After Exposure to Mepivacaine and Ropivacaine In Vitro.

The article explores the effects of local anesthetics, specifically mepivacaine and ropivacaine, on the health of chondrocytes (cartilage cells) in horse joints. Preliminary findings suggest that short-term exposure to ropivacaine may be less harmful (chondrotoxic) to these cells than mepivacaine.

Study Design and Methods

• The researchers used articular cartilage from the metacarpophalangeal joints (knuckle joints) of five horse cadavers to establish cultures of chondrocytes, the cells that make up cartilage.
• After one week, these cells were exposed to either a standard culture medium (DMEM), different concentrations of ropivacaine (ROP7.5 and ROP10) or mepivacaine (MEP20 or MEP30), or a saline solution (SAL).

Assessment of Chondrocyte Viability

• The viability, or health and structural integrity, of the chondrocytes was evaluated using three different assays: trypan blue exclusion, MTT, and flow cytometry.
• Trypan blue is a dye that is absorbed by dead cells but not by living cells, allowing the researchers to estimate the proportion of cells that remained alive after exposure to the anesthetics.
• The MTT assay is a colorimetric method for measuring the activity of enzymes that reduce MTT to formazan, an insoluble purple compound detected using a spectrophotometer – a high activity suggests high cellular viability.
• Flow cytometry is a technique that counts and characterizes cells in a solution, including the proportion of dead cells, represented by those which absorb the propidium iodide stain.

Results Interpretation

• The trypan blue exclusion assay showed no significant differences in chondrocyte viability between the various treatments. However, the other two assays (MTT and flow cytometry) yielded different results.
• MTT assay results revealed a significant drop in cellular viability in all treatment groups compared to the DMEM group. Mepivacaine at concentrations of 20 and 30 mg/ml showed the greatest decrease in cellular viability.
• In the flow cytometry assay, cellular viability decreased in all groups as compared to DMEM and ROP7.5.
• Despite the differences in assay results, the study suggests that ropivacaine might cause less damage to chondrocytes than mepivacaine, following short-term exposure.

Implications and Further Research

• These findings have potential implications for the use of local anesthetics for pain management in equine veterinary medicine, particularly considering the effects on joint integrity.
• However, as these tests were performed in vitro (i.e., outside a living organism), further research is needed to investigate these effects in vivo (i.e., inside a living organism).