VEGF receptor mRNA expression by ACL fibroblasts is associated with functional healing of the ACL.

PURPOSE: Recent advances in the treatment of ACL ruptures employ platelet-rich plasma combined with collagen to modulate growth factor release from platelets to stimulate healing. Among the most notable of these growth factors is VEGF, which is a potent mitogen and stimulator of vascular growth and healing. However, the effect of such a growth factor on healing depends on the cellular ability to bind with its receptor. The purpose of this study was to test (1) whether the strength of a tissue-engineered ACL repair is associated with VEGF receptors' mRNA expression of ACL cells and (2) whether age influences this association.
METHOD: Nineteen female Yucatan pigs underwent enhanced ACL repair. Biomechanical testing was performed after 15 weeks of healing. Messenger RNA of VEGF receptors 1 and 2 in ACL fibroblasts was assessed by RT-PCR. The ACL structural properties were regressed on receptor expression levels in a multivariate model including serum levels of VEGF, age, and weight as potential confounders. RESULT: While maximum load and linear stiffness were independent of VEGF receptor expression, VEGF receptor 1 was associated with displacement (positively) and yield load (negatively). In a multivariate model of VEGF receptor expression and biomechanics, age was associated with maximum load and yield load.
CONCLUSION: These findings suggest that high VEGF receptor expression, even more so at higher age, results in a more compliant scar, which in turn may lead to greater knee laxity and a compromised clinical result.