Activated protein C mediates a healing phenotype in cultured tenocytes

Tendon injuries cause considerable morbidity in the general adult population. The tenocytes within the tendon have the full capacity to heal the tendon intrinsically. Activated protein C (APC) plays an important role in coagulation and inflammation and more recently has been shown to promote cutaneous wound healing. In this study we examined whether APC can induce a wound healing phenotype in tenocytes. Sheep tenocytes were treated with APC, endothelial protein C receptor (EPCR) blocking antibody (RCR252) and/or EPCR small interfering (si)RNA. Cell proliferation and migration were measured by crystal violet assay and a scratch wounding assay, respectively. The expression of EPCR, matrix metalloproteinase (MMP)-2, type I collagen and MAP kinase activity were detected by real time PCR, zymography, immunofluorescence, immunohistochemistry and Western blotting. APC stimulated proliferation, MMP-2 activity and type I collagen deposition in a dose-dependent manner and promoted migration of cultured tenocytes. APC dose-dependently stimulated phosphorylated (P)-ERK2 and inhibited P-p38. Interestingly, tenocytes expressed EPCR protein, which was up-regulated by APC. When tenocytes were pre-treated with RCR252 or EPCR siRNA the effect of APC on proliferation, MMP-2 and type 1 collagen synthesis and MAP kinases was blocked. APC promotes the growth, MMP-2 activity, type I collagen deposition and migration of tenocytes. Furthermore, EPCR is expressed by tenocytes and mediates the actions of APC, at least partly by signalling through selective MAP kinases. These data implicate APC as a potential healing agent for injured tendons.     

Biosensors for real-time monitoring of physiological processes in the musculoskeletal system: A systematic review

Biosensors are composed of (bio)receptors, transducers, and detection systems and are able to convert the biological stimulus into a measurable signal. This systematic review evaluates the current state of the art of innovation and research in this field, identifying the biosensors that in vitro monitor the musculoskeletal system cellular processes. Two databases found 20 in vitro studies, from January 1, 2008 to December 31, 2017, dealing with musculoskeletal system cells. The biosensors were divided into two groups based on the transduction mechanism: optical or electrochemical. The first group evaluated osteoblasts or mesenchymal stem cell (MSC) biocompatibility, viability, differentiation, alkaline phosphatase, enzyme, and protein detection. The second group detected cell impedance, ATP release, and superoxide concentration in tenocytes, osteoblasts, MSCs, and myoblasts. This review highlighted that the in vitro scenario is still at an early phase and limited for what concerns both the type of bioanalyte and for the type of system detector used.     

Continuous cultivation of human hamstring tenocytes on microcarriers in a spinner flask bioreactor system

Tendon healing is a time consuming process leading to the formation of a functionally altered reparative tissue. Tissue engineering‐based tendon reconstruction is attracting more and more interest. The aim of this study was to establish tenocyte expansion on microcarriers in continuous bioreactor cultures and to study tenocyte behavior during this new approach. Human hamstring tendon‐derived tenocytes were expanded in monolayer culture before being seeded at two different seeding densities (2.00 and 4.00 × 10⁶ cells/1000 cm² surface) on Cytodex? type 3 microcarriers. Tenocytes' vitality, growth kinetics and glucose/lactic acid metabolism were determined dependent on the seeding densities and stirring velocities (20 or 40 rpm) in a spinner flask bioreactor over a period of 2 weeks. Gene expression profiles of tendon extracellular matrix (ECM) markers (type I/III collagen, decorin, cartilage oligomeric protein [COMP], aggrecan) and the tendon marker scleraxis were analyzed using real time detection polymerase chain reaction (RTD‐PCR). Type I collagen and decorin deposition was demonstrated applying immunolabeling. Tenocytes adhered on the carriers, remained vital, proliferated and revealed an increasing glucose consumption and lactic acid formation under all culture conditions. “Bead‐to‐bead” transfer of cells from one microcarrier to another, a prerequisite for continuous tenocyte expansion, was demonstrated by scanning electron microscopy. Type I and type III collagen gene expression was mainly unaffected, whereas aggrecan and partly also decorin and COMP expression was significantly downregulated compared to monolayer cultures. Scleraxis gene expression revealed no significant regulation on the carriers. In conclusion, tenocytes could be successfully expanded on microcarriers. Therefore, bioreactors are promising tools for continuous tenocyte expansion. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 30:142–151, 2014