In vivo quantification of the 3D kinematics and coupling of the thumb base joints.

Full thumb mobility is required to execute tasks of daily living and results from the combined motions of the thumb joints. In this study, we focus on the coupling between the proximal joints of the thumb, the radioscaphoid (RS), scaphotrapezial (ST) and trapeziometacarpal (TMC) joints. We quantified the 3D kinematics of these joints during maximal thumb extension and abduction in a group of healthy volunteers using an image-based technique. Semi-dynamic CT scans of the dominant hand of 36 healthy subjects with the thumb in different standardized positions were used. The maximal range of motion of each joint in the different planes was calculated using a markerless bone registration method. Inter-joint coupling was assessed by performing a regression analysis between the range of motion of the joints during both thumb movements. Strong inter-joint coupling was found between the RS and ST joints during thumb extension and abduction, whereas coupling between the other joints was moderate to weak. This study provides valuable information on the in vivo 3D kinematics of the RS, ST and TMC joints during thumb movement. This can be used as input for modeling studies, where the coupling between the joints can decrease the degrees of freedom of the model. Moreover, these baseline data of a healthy cohort can be used for comparison with the kinematics of patients with TMC osteoarthritis or other pathologies and aid our understanding of motion deficits resulting from these joint disorders.

PD1/PD-L1 immune checkpoint as a potential target for preventing brain tumor progression.

Programmed death-1 (PD-1) is a cell surface receptor that functions as a T cell checkpoint and plays a central role in regulating T cell collapse. The binding of PD-1 to its ligand programmed death-ligand 1 (PD-L1) activates downstream signaling pathways and inhibits T cell activation in the perspective of immune system mechanism and regulation in tumor progression. It is well reported that tumors adopt certain immune-checkpoint pathways as a mechanism of resistance against immune cells such as T cells that are specific for tumor antigens. Indeed, the PD-1/PD-L1 pathway controls the induction and maintenance of immune tolerance within the tumor microenvironment. Thus, the PD-1/PD-L1 checkpoint regulation appears to be of extreme importance as well as the immunotherapy targeting that via and the using of PD-1/PD-L1 inhibitors that have changed the scenario of brain cancer treatment and survival. Here, we review the mechanism of action of PD-1 and PD-L1, the PD/PDL-1 signaling pathway involved in the progression of brain tumors, and its application as cancer immunotherapy counteracting tumor escape in central nervous system.