Serum and Urinary Matrix Metalloproteinase-9 Concentrations in Dehydrated Horses.
Authors: van Spijk Julia N, Lo Hsiao-Chien, Merle Roswitha, Richter Ina-Gabriele, Diemar Anne, Stoeckle Sabita D, Gehlen Heidrun
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Matrix Metalloproteinase-9 as a Marker of Dehydration-Induced Kidney Stress Dehydration commonly triggers secondary renal dysfunction in horses, yet identifying early kidney injury remains challenging with conventional markers like creatinine and urea. Van Spijk and colleagues measured serum and urinary matrix metalloproteinase-9 (MMP-9)—an enzyme implicated in kidney tissue damage in humans—across 40 dehydrated horses and four healthy controls, sampling at admission and 12, 24, and 48 hours post-treatment using sandwich ELISA methodology. Serum MMP-9 concentrations were substantially elevated at presentation (median 589 ng/mL), declining significantly by 12 hours (340 ng/mL) and continuing to normalise through 48 hours (258 ng/mL), mirroring the physiological response to rehydration therapy; notably, only one horse developed acute kidney injury, whilst conventional markers showed inconsistent elevations (creatinine in 7/40, SDMA in 11/40 horses). Positive correlations emerged between serum MMP-9 and urinary casts and between urinary gamma-glutamyl transferase/creatinine ratio and serum MMP-9, suggesting the enzyme reflects acute renal epithelial stress rather than established injury. Whilst serum MMP-9 shows promise as an earlier indicator of dehydration-induced renal insult than traditional biomarkers, practitioners should view these findings as preliminary—the clinical utility remains to be established, and urinary MMP-9 did not provide additional diagnostic value in this cohort.
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Practical Takeaways
- •Serum MMP-9 may be a useful acute biomarker for monitoring kidney stress in dehydrated horses, with levels naturally declining as hydration improves over 48 hours
- •The correlation between sMMP-9, urinary casts, and GGT/creatinine suggests this biomarker could help identify subclinical kidney damage in dehydration cases, though further validation is needed
- •Urinary MMP-9 alone did not differentiate dehydrated from healthy horses, so serum samples are more diagnostically relevant if considering MMP-9 testing in practice
Key Findings
- •Serum MMP-9 concentrations were significantly elevated in dehydrated horses at admission (median 589 ng/mL) compared to measurements at 12, 24, and 48 hours post-admission
- •Healthy control horses had lower sMMP-9 levels (239 ng/mL) with no temporal variation, suggesting dehydration drives acute elevation
- •Urinary MMP-9 and urinary MMP-9/creatinine showed no significant changes over time or between dehydrated and healthy groups
- •sMMP-9 correlated with urinary casts and urinary GGT/creatinine ratio, suggesting potential utility as a kidney injury biomarker in horses