The effect of four different freezing conditions and time in frozen storage on the concentration of commonly measured growth factors and enzymes in equine platelet-rich plasma over six months.
Authors: McClain Andrew K, McCarrel Taralyn M
Journal: BMC veterinary research
Summary
# Editorial Summary: Freezing Conditions and Growth Factor Stability in Equine PRP Platelet-rich plasma is increasingly used to treat musculoskeletal injuries in horses, yet the expense of production kits and typical yield volumes mean that clinicians and researchers frequently freeze aliquots for later use or analysis—a practice whose optimal conditions remain poorly defined. McClain and McCarrel (2019) investigated how four storage methods (–20°C automatic defrost, –20°C manual defrost, –80°C manual defrost, and liquid nitrogen) affected concentrations of growth factors and enzymes over six months, establishing baseline measurements after a single freeze-thaw cycle. The researchers documented substantial variability in protein stability depending on freezing method and storage duration, providing critical evidence that automatic defrost freezers significantly compromised growth factor concentrations, whilst –80°C and liquid nitrogen storage maintained more consistent bioactive protein levels across the six-month period. These findings have direct implications for equine practitioners: if freezing PRP for repeated therapeutic dosing, –80°C manual defrost or liquid nitrogen storage is substantially preferable to standard –20°C freezers, and extended storage beyond three months risks meaningful degradation of therapeutic compounds. For researchers publishing PRP-based work, this study reinforces the necessity of specifying freezing methods and storage duration, as different protocols produce materially different baseline data that affect study validity and comparison across literature.
Read the full abstract on PubMed
Practical Takeaways
- •If freezing PRP for later clinical use, store at -80°C or in liquid nitrogen rather than standard -20°C freezers to preserve therapeutic factor concentrations
- •Avoid automatic defrost -20°C freezers for PRP storage; if -20°C storage is necessary, use manual defrost only
- •Plan to use frozen PRP within 3 months when possible to minimize protein degradation, though 6-month storage at -80°C/-LN2 remains viable
Key Findings
- •Freeze-thaw cycles significantly reduced concentrations of most measured growth factors and enzymes in equine PRP
- •Storage at -80°C manual defrost freezer and liquid nitrogen preserved growth factor concentrations better than -20°C freezers over 6 months
- •-20°C automatic defrost freezer showed the greatest degradation of protein concentrations due to temperature cycling
- •Storage duration up to 6 months in optimal conditions (-80°C or liquid nitrogen) maintained measurable therapeutic protein levels