Bosentan, a non-specific endothelin antagonist, stimulates fracture healing

It is assumed that bosentan, a non-selective ET-1 receptor antagonist, will enhance fracture healing. The aim of this prospective randomized controlled study was to investigate the effects of transcutaneous bosentan administration into diaphyseal bone fractures using radiology, histology, prostaglandin E ₂ (PGE₂) and leukotrien C₄ (LTC₄) activity measurements. A closed diaphyseal fracture was created in the hind limbs following intramedullary rod fixation of Guinea pigs. Bosentan was administred by repetitive weekly 0.1 μg transcutaneous injections into the fracture site. The effects of bosentan were evaluated by radiology and histology on weeks 1, 2 and 4, whereas prostaglandin E₂ (PGE₂)-like and leukotrien C₄ (LTC₄)-like activity was assessed on weeks 1 and 2. The radiological degree of union (p = 0.001) at the fracture site and cortex-callus ratio (p = 0.02) was significantly better in the bosentan administered site at week 1 when compared to the control. Histology presented an initial stimulation of bone formation on weeks 1 and 2 in the experimental group. PGE₂-like activity was significantly higher (p = 0.002) on week 1 and 2 in the bosentan-administered side. LTC₄-like activity remained constant on week one and decreased on week two. Transcutaneous repetitive bosentan administration into the fracture site initially stimulated periosteal bone healing that resulted with extracellular matrix mineralization. The inflammatory mediators PGE₂/LTC₄ played a significant role in this process.