Cyclic stretching modulates type i and III collagen expression in human tendon fibroblasts

Objective: To determine collagen (col) I and III expression in human patellar tendon fibroblasts under cyclic strain. Understanding the response of tendon fibroblasts to mechanically strain may provide useful knowledge for engineering of cell/collagen composites. Methods: Human patellar tendon fibroblasts were obtained from specimens of 5 donors ( 18-40 years) undergoing surgical treatment of knee joint instability. Fibroblasts were cultured and 5xl05 2nd passage cells from each donor were plated on flexible silicon dishes. Monolayers of these subconfluently grown cells were then stretched along their longitudinal axes by an electromechanical device. Cyclic strain (5%, 1 Hz) was applied for 15′ and 60′, respectively. Col I and III mRNA was measured by RT-PCR: 0′, 15′, 30′ and 60′ after stretching, respectively. Fibroblasts from each donor without any mechanical stimulation served as individual control. The paired t-test was used for statistical analysis (p<0.05). Results: 15' of stretching results in a significant increase in col I mRNA 30′ (67%) and 60′ (69%) after stretching, respectively. After 60′ of stretching, no significant increase in col I mRNA was ob-served. Similar results were observed in col III mRNA expression. The changes in col III mRNA after 15' of stretching were more moderate than observed for col I (30': 43%, 60': 48%). Conclusion: Dependent on stress time, fibroblasts respond differentially to cyclic stretching. Cyclic stretching of engineered tendon and ligament tissues may affect mechanical properties of cell/collagen composites used to reconstruct tendons and ligaments. With different stretch time periods, the quality and thus the mechanical properties of engineered tissues could be modulated.