Browsing by Keyword "Sensory Systems"
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Item Acellular human corneal matrix sheets seeded with human adipose-derived mesenchymal stem cells integrate functionally in an experimental animal model(2015-03-01) Alio del Barrio, Jorge L.; Chiesa, Massimo; Garagorri, Nerea; Garcia-Urquia, Nerea; Fernandez-Delgado, Jorge; Bataille, Laurent; Rodriguez, Alejandra; Arnalich-Montiel, Francisco; Zarnowski, Tomasz; Álvarez de Toledo, Juan P.; Alio, Jorge L.; De Miguel, Maria P.; Tecnalia Research & Innovation; BiomaterialesPurpose: To evaluate the invivo biocompatibility of grafts composed of sheets of decellularized human corneal stroma with or without the recellularization of human adipose derived adult stem cells (h-ADASC) into the rabbit cornea. Methods: Sheets of human corneal stroma of 90μm thickness were decellularized, and their lack of cytotoxicity was assayed. The recellularization was achieved by the injection of 2×105 labeled h-ADASC in the graft followed by five days of cell culture. The grafts were implanted invivo into a stromal pocket at 50% depth. After a triple-masked three-month follow-up, the animals were euthanized and the biointegration of the graft, the viability of the stem cells and the expression of keratocan (human keratocyte-specific protein) were assessed. Results: The decellularized stromal sheets showed an intact extracellular matrix with a decellularization rate of 92.8% and an excellent recellularization capacity invitro with h-ADASC. A complete and stable graft transparency was observed during the full follow-up, with absence of any clinical sign of rejection. The postmortem analysis demonstrated the survival of the transplanted human stem cells inside the graft and their differentiation into functional keratocytes, as assessed by the expression of human keratocan. Conclusions: We report a new model of lamellar keratoplasty that requires only a simple and safe procedure of liposuction and a donor allogeneic cornea to provide an optically transparent autologous stromal graft with excellent biocompatibility and integration into the host tissue in a rabbit model.Item How Tilting the Head Interferes With Eye-Hand Coordination: The Role of Gravity in Visuo-Proprioceptive, Cross-Modal Sensory Transformations: The Role of Gravity in Visuo-Proprioceptive, Cross-Modal Sensory Transformations(2022-03-10) Bernard-Espina, Jules; Dal Canto, Daniele; Beraneck, Mathieu; McIntyre, Joseph; Tagliabue, Michele; Tecnalia Research & Innovation; Robótica MédicaTo correctly position the hand with respect to the spatial location and orientation of an object to be reached/grasped, visual information about the target and proprioceptive information from the hand must be compared. Since visual and proprioceptive sensory modalities are inherently encoded in a retinal and musculo-skeletal reference frame, respectively, this comparison requires cross-modal sensory transformations. Previous studies have shown that lateral tilts of the head interfere with the visuo-proprioceptive transformations. It is unclear, however, whether this phenomenon is related to the neck flexion or to the head-gravity misalignment. To answer to this question, we performed three virtual reality experiments in which we compared a grasping-like movement with lateral neck flexions executed in an upright seated position and while lying supine. In the main experiment, the task requires cross-modal transformations, because the target information is visually acquired, and the hand is sensed through proprioception only. In the other two control experiments, the task is unimodal, because both target and hand are sensed through one, and the same, sensory channel (vision and proprioception, respectively), and, hence, cross-modal processing is unnecessary. The results show that lateral neck flexions have considerably different effects in the seated and supine posture, but only for the cross-modal task. More precisely, the subjects’ response variability and the importance associated to the visual encoding of the information significantly increased when supine. We show that these findings are consistent with the idea that head-gravity misalignment interferes with the visuo-proprioceptive cross-modal processing. Indeed, the principle of statistical optimality in multisensory integration predicts the observed results if the noise associated to the visuo-proprioceptive transformations is assumed to be affected by gravitational signals, and not by neck proprioceptive signals per se. This finding is also consistent with the observation of otolithic projections in the posterior parietal cortex, which is involved in the visuo-proprioceptive processing. Altogether these findings represent a clear evidence of the theorized central role of gravity in spatial perception. More precisely, otolithic signals would contribute to reciprocally align the reference frames in which the available sensory information can be encoded.