Age-related effects on markers of inflammation and cartilage metabolism in response to an intra-articular lipopolysaccharide challenge in horses.

This study investigates the impact of age on inflammation and cartilage turnover in horses, with a specific emphasis on the reaction to the injection of lipopolysaccharide (LPS), an inflammation-inducing substance. The test involved eighteen Quarter Horses of varying age groups and suggested that the response differences may be influenced by the age of the horse.

Study Population and Experimental Design

• A randomized complete design experimental method was used involving eighteen Quarter Horses of differing ages: yearlings, 2 to 3-year-olds, and mature horses aged between 5 to 8 years.
• All horses were individually housed and fed diets that met or exceeded requirements. The experiment lasted for 28 days.

Induction of Inflammation

• An inflammatory response was instigated on day 14 of the experiment with an intra-articular injection of LPS into the horses’ radial carpal joint.
• As a control measure, some horses received a sterile lactated Ringer’s solution instead of the LPS solution.
• Synovial fluid (the lubricant in joints) samples were collected at various times before and after the injection for analysis.

Data Collection and Analysis

• The collected synovial fluid was analyzed for the presence of inflammation and cartilage metabolism markers – these included Prostaglandin E (PGE), collagenase cleavage neoepitope (C2C), and carboxypropeptide of type II collagen (CPII).
• The horses’ heart rate, respiratory rate, and rectal temperature were monitored and joint circumference and surface temperature were recorded.
• Data evaluation used PROC MIXED of the SAS software.

Results

• The study did not find any variation in joint circumference with age. However, there was an observed increase over time in joint circumference and surface temperature across all age groups.
• While heart and respiratory rates stayed within the normal range for all age groups, heart rate and rectal temperature were seen to be influenced by age.
• The youngest animals had a lower concentration of synovial PGE compared to the mature horses, suggesting an age-influenced differential in the inflammatory response.
• Elevated levels of synovial C2C and CPII were recorded in the mature horses when compared to the yearlings and 2 to 3-year-olds.
• The ratios of CPII (anabolic or ‘building’ phase) to C2C (catabolic or ‘breaking down’ phase) varied according to age, with higher values observed in mature and 2/3-year-old horses compared to the yearlings.

Conclusion

• The study concludes that the response to inflammation and the related cartilage turnover process as a result of LPS administration varies according to the age of the horse.