Local injection/induction of osteoclasts for the treatment of calcified tendinitis

Calcified tendinitis is characterized by calcification in the rotary cuff tendon of the shoulder. The rationale of therapeutic methods is mainly removal of the calcification. Osteoclasts are the principle cells capable of resorbing bone and calcified tissues. Therefore, we hypothesized local injection of cultured human osteoclasts or induction of osteoclasts by recombinant RANKL in vivo may be effective for the treatment of calcified tendonitis. Human osteoclasts cultured in vitro is technically feasible and the osteoclasts are capable of active bone resorption. Thus, injection of osteoclasts may help remove the calcified tendonitis. In addition, human RANKL is commercially available. Therefore, local RANKL injection can recruit peripheral monocytes and macrophages. In the presence of RANKL, these monocytes and macrophages can subsequently differentiate into osteoclasts that can directly resorb calcification via their bone resorbing machinery. Different from the other treatments, the advantage of this therapeutic method includes: (1) less invasive because only local injection/induction of osteoclasts into the calcified lesion is conducted; (2) more efficient by direct osteoclasts injection or using RANKL to recruit osteoclasts to efficiently resorb calcification. Therefore, we proposed local injection/induction of osteoclasts as a potential biological method for clinical treatment of calcified tendinitis.