Role of cathepsin K in the development of chronic subdural hematoma

Cathepsin K in Pathological Conditions and New Therapeutic and Diagnostic Perspectives

Cathepsin K (CatK) is a part of the family of cysteine proteases involved in many important processes, including the degradation activity of collagen 1 and elastin in bone resorption. Changes in levels of CatK are associated with various pathological conditions, primarily related to bone and cartilage degradation, such as pycnodysostosis (associated with CatK deficiency), osteoporosis, and osteoarthritis (associated with CatK overexpression). Recently, the increased secretion of CatK is being highly correlated to vascular inflammation, hypersensitivity pneumonitis, Wegener granulomatosis, berylliosis, tuberculosis, as well as with tumor progression. Due to the wide spectrum of diseases in which CatK is involved, the design and validation of active site-specific inhibitors has been a subject of keen interest in pharmaceutical companies in recent decades. In this review, we summarized the molecular background of CatK and its involvement in various diseases, as well as its clinical significance for diagnosis and therapy.

Serum Levels of MMP-8 and MMP-9 as Markers in Chronic Subdural Hematoma

Chronic subdural hematoma (CSDH) is a common neurological disease that involves the collection of blood products in the subdural space. The progression of CSDH is an angiogenic and inflammatory process, but the multifactorial mechanisms underlying CSDH are still not fully understood. We aimed to identify one or more factors that may play an important role in the development of CSDH. We enrolled 83 patients with CSDH, including 17 postoperative patients, and analyzed 20 markers in the hematoma fluid and peripheral blood of each patient. Overall differential gene expression was examined to identify the representative markers. The concentration of MMP-8 was significantly lower in the postoperative group than in the preoperative group. The concentration of MMP-9 was significantly higher in the postoperative group than in the preoperative group. These findings indicate that MMP-8 and MMP-9 may play important roles in the pathophysiology of CSDH. Understanding the pathways associated with CSDH may provide insights for improving disease outcomes.

Microvascular proliferation in the clots: The key finding of acute subdural hematoma transforming into chronic subdural hematoma?

Background:

Despite extensive investigations, the exact etiology of chronic subdural hematoma (CSDH) remains elusive. Organized CSDHs are a distinct but less-understood type of CSDH.

Case Description:

A 50-year-old hypertensive woman experienced headache without any previous head injury. At presentation, the patient showed no focal neurological deficits. Cranial computed tomography (CT) revealed a slightly compressive subdural hematoma that spontaneously regressed and no intracranial vascular lesions. Cerebral magnetic resonance imaging identified a non-enhancing nodular lesion in the subdural hematoma. After the patient presented disorientation and aphasia on post hospitalization day 14, CT showed a considerable enlargement of the subdural hematoma. Partial removal of the bi-layered hematoma was performed through a parietal craniotomy. Histological examination revealed microvascular proliferation in both the outer membrane and the nodular lesion. On postoperative day 35, CT demonstrated a remarkable resolution of the residual hematoma.

Conclusion:

Development of microvascular proliferation in the clots of an acute subdural hematoma may lead to its rapid enlargement as an organized CSDH. Organized CSDH can be managed by partial removal of the outer membrane and hematoma through a craniotomy.

Cathepsin K: The Action in and Beyond Bone

Cathepsin K (CatK) is one of the most potent proteases in lysosomal cysteine proteases family, of which main function is to mediate bone resorption. Currently, CatK is among the most attractive targets for anti-osteoporosis drug development. Although many pharmaceutical companies are working on the development of selective inhibitors for CatK, there is no FDA approved drug till now. Odanacatib (ODN) developed by Merck & Co. is the only CatK inhibitor candidate which demonstrated high therapeutic efficacy in patients with postmenopausal osteoporosis in Phase III clinical trials. Unfortunately, the development of ODN was finally terminated due to the cardio-cerebrovascular adverse effects. Therefore, it arouses concerns on the undesirable CatK inhibition in non-bone sites. It is known that CatK has far-reaching actions throughout various organs besides bone. Many studies have also demonstrated the involvement of CatK in various diseases beyond the musculoskeletal system. This review not only summarized the functional roles of CatK in bone and beyond bone, but also discussed the potential relevance of the CatK action beyond bone to the adverse effects of inhibiting CatK in non-bone sites.