Lactoferrin and parathyroid hormone are not harmful to primary tenocytes in vitro, but PDGF may be.

Introduction Recently, bone-active factors such as parathyroid hormone and lactoferrin, have been used in pre-clinical models to promote tendon healing. How-ever, there is limited understanding of how these boneactive factors may affect the cells of the ten-don themselves. Here, we present an in vitro study assessing the effects of parathyroid hor-mone and lactoferrin on primary tendon cells (tenocytes), and compare their responses to the tenogenic factors, PDGF, IGF-1 and TGF-β. Materials and Methods Tenocyte proliferation and collagen production were assessed by alamarBlue® and Sirius red as-says, respectively. To assess tenocyte trans-differentiation, changes in the expression of genes important in tenocyte, chondrocyte and osteoblast biology were determined using real-time PCR. Results Parathyroid hormone and lactoferrin had no effect on tenocyte growth or collagen production, with minimal changes in gene expression and no detrimental effects observed to suggest trans-differentiation away from tendon cell behaviour. Tenogenic factors PDGF, IGF-1 and TGF all increasetenocyte collagen production, however, the gene expression data suggests that PDGF promotes severe de-differentiation of the tenocytes. Discussion Our findings suggest that using parathyroid hormone or lactoferrin as a singular factor to promote tendon healing may not be of benefit, but for use in tendon-bone healing there would be no detrimental effect on the tendon itself.