Serum Amyloid P Attenuates Hypertrophic Scarring in Large Animal Models

This study's purpose was to (1)determine the effect of locally administered serum amyloid P (SAP) on the development of hypertrophic scars (HTS) in porcine and rabbit HTS models and (2)determine the pharmacokinetics of systemically administered SAP and its effect on circulating fibrocyte quantities.

Two large animal (New Zealand White Rabbit and Female Red Duroc Pigs) HTS models were utilized to study the effects of daily local injections of SAP immediately post wounding (x5 d in rabbits; x7 d in pigs) on HTS development as measured by scar elevation index , scar area, wound closure, and molecular expression studies of scar components. For SAP pharmacokinetics, total and human SAP levels in porcine blood were measured at regular intervals following intravenous administration of human SAP. Fibrocyte quantities were determined prior to and 1 h following human SAP intravenous administration.

In the rabbit model, local SAP significantly decreased the level of tissue inhibitor of metalloproteinases-1 mRNA expression and maintained matrix mettaloproteinase-9 expression, while control and vehicle groups significantly declined. In the pig model, there was a significant decrease in the trend of scar elevation indexes treated with local SAP versus controls over the study period. This decrease was statistically significant at days 14 and 84. Human SAP administered intravenously is degraded within 24 h and does not influence circulating fibrocyte quantities.

This is the first study to demonstrate attenuation of HTS formation using locally administered SAP in large animal HTS models. Local SAP administration reduces HTS formation by maintaining matrix mettaloproteinase-9 and decreasing tissue inhibitor of metalloproteinases-1. Intravenous administration of SAP is not as effective.