Development of a Noninvasive, Laser-Assisted Experimental Model of Corneal Endothelial Cell Loss.

Nd:YAG lasers have been used to perform noninvasive intraocular surgery, such as capsulotomy for several decades now. The incisive effect relies on the optical breakdown at the laser focus. Acoustic shock waves and cavitation bubbles are generated, causing tissue rupture. Bubble sizes and pressure amplitudes vary with pulse energy and position of the focal point. In this study, enucleated porcine eyes were positioned in front of a commercially available Nd:YAG laser. Variable pulse energies as well as different positions of the focal spots posterior to the cornea were tested. Resulting lesions were evaluated by two-photon microscopy and histology to determine the best parameters for an exclusive detachment of corneal endothelial cells (CEC) with minimum collateral damage. The advantages of this method are the precise ablation of CEC, reduced collateral damage, and above all, the non-contact treatment.

Uptake of Ranibizumab but Not Bevacizumab into Uveal Melanoma Cells Correlates with a Sustained Decline in VEGF-A Levels and Metastatic Activities.

Despite the implication of vascular endothelial growth factor-A (VEGF-A) in the pathophysiology of uveal melanoma (UM), the anti-VEGF-A antibody bevacizumab yielded conflicting results on UM growth. Here, we evaluated whether bevacizumab and ranibizumab, a humanized Fab-fragment against VEGF-A, can enter UM cells and induce a sustained physiological response. The primary and metastatic UM cell lines Mel-270 and OMM-2.5 were exposed to bevacizumab or ranibizumab for one day and were maintained further in untreated medium for a total of three days. Both antibodies significantly reduced the levels of extracellular VEGF-A and the angiogenic potential of the conditioned medium after one day. These inhibitory effects of bevacizumab diminished by day three. Ranibizumab suppressed the metabolic activity, proliferation, and intracellular VEGF-A levels in a cell-type and concentration-dependent manner, whereas bevacizumab exerted no effect. Both drugs were detected inside early endosomes within the UM cells, with the stronger and sustained colocalization of ranibizumab. Our results therefore demonstrated the more potent and persistent suppressive activity of ranibizumab on the UM cells, possibly due to its higher level of uptake and prolonged intracellular retention. Further research on the endosome dynamics in UM cells might provide valuable insight into the response of these heterogenous tumors to therapeutic antibodies.

Drebrins and Connexins: A Biomedical Perspective.

In this chapter we summarize knowledge on the role of drebrin in cell-cell communications. Specifically, we follow drebrin-connexin-43 interactions and drebrin behavior at the cell-cell interface described earlier. Drebrin is a part of the actin cytoskeleton which is a target of numerous bacteria and viruses invading mammalian cells. Drebrin phosphorylation, self-inhibition and transition between filaments, particles, and podosomes underlie cellular mechanisms involved in diseases and cognitive disorders. Cytoskeletal rearrangements influence the state of gap junction contacts which regulate cell signaling and metabolic flow of information across cells in tissues. Taking into account that connexin-43 (Cx43) (together with Cx30) is heavily expressed in astrocytes and that drebrin supports cell-cell contacts, the understanding of details of how brain cells live and die reveals molecular pathology involved in neurodegeneration, Alzheimer's disease (AD), other cognitive disorders, and aging.Bidirectional connexin channels are permeable to Ca2+ ions, IP3, ATP, and cAMP. Connexin hemichannels are important for paracrine regulation and can release and exchange energy with other cells using ATP to transfer information and to support damaged cells. Connexin channels, hemichannels, and adhesion plaques are regulated by assembly and disassembly of the actin cytoskeleton. Drebrin degradation can alter gap junction communication, and drebrin level is decreased in the brain of AD patients. The diversity of drebrin functions in neurons, astrocytes, and non-neuronal cells still remains to be revealed. We believe that the knowledge on drebrin summarized here will contribute to key questions, "covering the gap" between cell-cell communications and the submembrane cytoskeleton.