Tendinopathy is a common painful musculoskeletal disorder treated by injection of analgesics and nonsteroidal anti-inflammatory drugs (NSAIDs), which are believed to have cytotoxicity toward tenocytes. Ascorbic acid is an antioxidant that promotes collagen biosynthesis and prevents free radical formation. It is believed to protect tenocytes from oxidative stress. The optimal concentration of ascorbic acid, especially when used in conjunction with anesthetics and NSAIDs injection, to treat different stages of tendinopathies is unknown. Human tenocytes were isolated from a torn edge of the supraspinatus tendon of a 51-year-old male patient during arthroscopic repair. We monitored real-time changes in human tenocyte proliferation upon exposure to different concentrations of ascorbic acid, bupivacaine, and ketorolac tromethamine using the xCELLigence system. No significant changes in cell index were observed between the control group and tenocytes treated with the 3 concentrations of ascorbic acid. Tenocytes exposed to 0.5% bupivacaine and 30 or 15 mg/mL ketorolac tromethamine revealed significant reduction in tenocytes proliferation. Bupivacaine 0.5% with 250 μg/mL ascorbic acid and 15 mg/mL ketorolac tromethamine with 250 μg/mL ascorbic acid showed the least cytotoxicity against tenocytes. The optimal ascorbic acid concentration required to reduce the cytotoxic effects of bupivacaine and ketorolac tromethamine was demonstrated using this platform.

The platelet-rich plasma (PRP) has become an attractive topic for soft tissue healing therapy recently. While some clinical reports revealed the effective treatments for knee osteoarthritis, lateral epicondylitis, and rotator cuff tears, other case studies showed that there was no statistically significant healing improvement. The efficacy of the PRP therapy is still unclear clinically. Thus, a significant amount of basic studies should be conducted to optimize the preparation procedure and the platelet concentration of the PRP. In this work, a 3-chamber co-culture device was developed for the PRP study in order to reduce the usage of primary cells and to avoid the PRP gelation effect. The device was a culture, well partitioning into 3 sub-chambers. Tenocytes and PRP could be respectively loaded into the sub-chambers and co-cultured under the interlinked medium. The results showed that a higher platelet number in the PRP could diffuse higher concentration of the growth factors in the medium and induce higher tenocyte proliferation. The 3-chamber co-culture device provides a simple and practical tool for the PRP study. It is potentially applied for optimizing the preparation procedure and platelet concentration of the PRP therapy.

Hamstring tendon is one of the best graft choices for anterior cruciate ligament reconstruction. The upper age limit of reconstruction is not determined because tenocytes from old individuals have less proliferative ability than young ones. Dexamethasone is commonly used to deal with musculoskeletal disorder with dose-dependent cytotoxicity toward tenocytes. Ascorbic acid is essential for tenocytes culture and collagen secretion and can alleviate the cytotoxicity of dexamethasone. In the current study, a microfluidic platform was used to screen the best dexamethasone and ascorbic acid combination treatment for tenocytes from young and old donors because it has been proven to provide a high throughput analysis platform. Comparison of their proliferation under three concentrations of ascorbic acid and dexamethasone was performed. Tenocytes proliferation among young and old donors was also measured when exposed to nine combinations of ascorbic acid and dexamethasone. The result confirmed the differences in cells proliferation when hamstring tenocytes from different ages of donors are exposed to different concentrations of dexamethasone and ascorbic acid. Tenocytes from old donors are not always more susceptible to dexamethasone and ascorbic acid. An optimal dose of ascorbic acid in decreasing the cytotoxic effect of dexamethasone can be screened by a high throughput microfluidic platform.