BST-CarGel: In Situ ChondroInduction for Cartilage Repair

The repair of articular cartilage has posed a longstanding orthopedic challenge. The concept of marrow stimulation is basically the intentional injury of a subchondral bone below a cartilage lesion to elicit a wound repair response. However, the desire to fill the lesion with a blood clot is at odds with platelet-driven clot retraction, which results in clot shrinkage and detachment. Therefore, BST-CarGel was developed to produce a physically stabilized blood clot that is more voluminous and adherent within a debrided cartilage lesion having access to bone marrow, thus improving existing bone marrow-stimulation procedures. BST-CarGel is a soluble polymer scaffold containing the polysaccharide chitosan, which is dispersed throughout uncoagulated whole blood, and then delivered to a surgically prepared lesion. BST-CarGel allows normal clot formation, reinforces the clot, impedes retraction, increases adhesivity, and ensures prolonged residency of both the clot and critical tissue repair factors from blood. In animals, BST-CarGel was shown to increase the volume and hyaline character of repair tissue, with increased GAG and collagen content, compared with microfracture controls. A patient cohort received BST-CarGel treatment, which encompassed the spectrum of traumatic to degenerative lesions, along with other joint pathologies. Anecdotal evidence demonstrated the potential of BST-CarGel for treating focal cartilage lesions of variable etiology through both mini-open and arthroscopic approaches. Because it requires only a single minimally invasive intervention, BST-CarGel and its unique characteristics are novel in orthopedics. In addition, its use with marrow stimulation provides familiarity with well-recognized surgical techniques, bringing a simple-yet-versatile treatment modality that applies scaffold-guided regenerative medicine to a potentially wide-ranging group of indications.