A potential role for Dkk-1 in the pathogenesis of osteosarcoma predicts novel diagnostic and treatment strategies.

Canonical Wnt signaling is an osteo-inductive signal that promotes bone repair through acceleration of osteogenic differentiation by progenitors. Dkk-1 is a secreted inhibitor of canonical Wnt signaling and thus inhibits osteogenesis. To examine a potential osteo-inhibitory role of Dkk-1 in osteosarcoma (OS), we measured serum Dkk-1 in pediatric patients with OS (median age, 13.4 years) and found it to be significantly elevated. We also found that Dkk-1 was maximally expressed by the OS cells at the tumor periphery and _in vitro_ Dkk-1 and RANKL are co-expressed by rapidly proliferating OS cells. Both Dkk-1 and conditioned media from OS cells reduces osteogenesis by human mesenchymal cells and by immuno-depletion of Dkk-1, or by adding a GSK3[beta] inhibitor, the effects of Dkk-1 were attenuated. In mice, we found that the expression of Dkk-1 from implanted tumors was similar to the human tumor biopsies in that human Dkk-1 was present in the serum of recipient animals. These data demonstrate that systemic levels of Dkk-1 are elevated in osteosarcoma. Furthermore, the expression of Dkk-1 by the OS cells at the periphery of the tumor probably contributes to its expansion by inhibiting repair of the surrounding bone. These data demonstrate that Dkk-1 may serve as a prognostic or diagnostic marker for evaluation of OS and furthermore, immuno-depletion of Dkk-1 or administration of GSK3[beta] inhibitors could represent an adjunct therapy for this disease

Utilization of Thromboelastogram and Inflammatory Markers in the Management of Hypercoagulable State in Patients with COVID-19 Requiring ECMO Support

The role of extracorporeal membrane oxygenation (ECMO) in the management of critically ill patients with COVID-19 is evolving. Extracorporeal support independently confers an increased predilection for thrombosis, which can be exacerbated by COVID-19-associated coagulopathy. We present the successful management of a hypercoagulable state in two patients who required venovenous ECMO for the treatment of COVID-19. This included monitoring inflammatory markers (D-dimer and fibrinogen), performing a series of therapeutic plasma exchange procedures, and administering high-intensity anticoagulation therapy and thromboelastography- (TEG-) guided antiplatelet therapy. TPE was performed to achieve goal D-dimer less than 3000 ng/mL D-dimer units (N≤232 ng/mL D-dimer units) and goal fibrinogen less than 600 mg/dL (N=200-400 mg/dL). These therapies resulted in improved TEG parameters and normalized inflammatory markers. Patients were decannulated after 37 days and 21 days, respectively. Post-ECMO duplex ultrasound of the upper and lower extremities and cannulation sites revealed a nonsignificant deep venous thrombosis at the site of femoral cannulation in patient 2 and no deep venous thrombosis in patient 1. The results of this case report show successful management of a hypercoagulable state among COVID-19 patients requiring ECMO support by utilization of inflammatory markers and TEG

How Wnt signaling affects bone repair by mesenchymal stem cells from the bone marrow

Human mesenchymal stem cells (hMSCs) from bone marrow are a source of osteoblast progenitors in vivo, and under appropriate conditions they differentiate into osteoblasts ex vivo. The cells provide a convenient cell culture model for the study of osteogenic tissue repair in an experimentally accessible system. Recent advances in the field of skeletal development and osteogenesis have demonstrated that signaling through the canonical wingless (Wnt) pathway is critical for the differentiation of progenitor cell lines into osteoblasts. Inhibition of such signals can predispose hMSCs to cell cycle entry and prevent osteogenesis. Our investigation of the role of Wnt signaling in osteogenesis by hMSCs ex vivo has demonstrated that osteogenesis proceeds in response to bone morphogenic protein 2 stimulation and is sustained by Wnt signaling. In the presence of Dkk-1, an inhibitor of Wnt signaling, the cascade is disrupted, resulting in inhibition of osteogenesis. Peptide mapping studies have provided peptide Dkk-1 agonists and the opportunity for the production of blocking antibodies. Anti-Dkk-1 strategies are clinically relevant since high serum levels of Dkk-1 are thought to contribute to osteolytic lesion formation in multiple myeloma and possibly some forms of osteosarcoma. Specific inhibitors of glycogen synthetase kinase 3beta (GSK3beta), which mimic Wnt signaling, may also have a therapeutic benefit by enhancing in vitro osteogenesis despite the presence of Dkk-1. Antibodies that block Dkk-1 and GSK3beta inhibitors may provide novel opportunities for the enhancement of bone repair in a variety of human diseases such as multiple myeloma and osteosarcoma

Proteinous components of Neutrophil extracellular traps are arrested by the cell wall proteins of Candida albicans during fungal infection, and can be used in the host invasion

One of defense mechanisms of the human immune system to counteract infection by the opportunistic fungal pathogen Candida albicans is the recruitment of neutrophils to the site of invasion, and the subsequent production of neutrophil extracellular traps (NETs) that efficiently capture and kill the invader cells. In the current study, we demonstrate that within these structures composed of chromatin and proteins, the latter play a pivotal role in the entrapment of the fungal pathogen. The proteinous components of NETs, such as the granular enzymes elastase, myeloperoxidase and lactotransferrin, as well as histones and cathelicidin-derived peptide LL-37, are involved in contact with the surface of C. albicans cells. The fungal partners in these interactions are a typical adhesin of the agglutinin-like sequence protein family Als3, and several atypical surface-exposed proteins of cytoplasmic origin, including enolase, triosephosphate isomerase and phosphoglycerate mutase. Importantly, the adhesion of both the elastase itself and the mixture of proteins originating from NETs on the C. albicans cell surface considerably increased the pathogen potency of human epithelial cell destruction compared with fungal cells without human proteins attached. Such an implementation of adsorbed NET-derived proteins by invading C. albicans cells might alter the effectiveness of the fungal pathogen entrapment and affect the further host colonization