Hydrogel-based scaffolds to support intrathecal stem cell transplantation as a gateway to the spinal cord: clinical needs, biomaterials, and imaging technologies

The prospects for cell replacement in spinal cord diseases are impeded by inefficient stem cell delivery. The deep location of the spinal cord and complex surgical access, as well as densely packed vital structures, question the feasibility of the widespread use of multiple spinal cord punctures to inject stem cells. Disorders characterized by disseminated pathology are particularly appealing for the distribution of cells globally throughout the spinal cord in a minimally invasive fashion. The intrathecal space, with access to a relatively large surface area along the spinal cord, is an attractive route for global stem cell delivery, and, indeed, is highly promising, but the success of this approach relies on the ability of cells 1) to survive in the cerebrospinal fluid (CSF), 2) to adhere to the spinal cord surface, and 3) to migrate, ultimately, into the parenchyma. Intrathecal infusion of cell suspension, however, has been insufficient and we postulate that embedding transplanted cells within hydrogel scaffolds will facilitate reaching these goals. In this review, we focus on practical considerations that render the intrathecal approach clinically viable, and then discuss the characteristics of various biomaterials that are suitable to serve as scaffolds. We also propose strategies to modulate the local microenvironment with nanoparticle carriers to improve the functionality of cellular grafts. Finally, we provide an overview of imaging modalities for in vivo monitoring and characterization of biomaterials and stem cells. This comprehensive review should serve as a guide for those planning pre-clinical and clinical studies on intrathecal stem cell transplantation.Funds provided under the project NanoTech4ALS (ref. ENMed/0008/2015, 13/EuroNanoMed/2016), funded under the EU FP7 M-ERA.NET program, Strategmed 1/233209/12/NCBIR/2015, and NIH R01 NS091100. The FCT distinction attributed to J.M.O. under the Investigator FCT program (IF/01285/2015) is also gratefully acknowledgedinfo:eu-repo/semantics/publishedVersio

Detection of disfluencies in speech signal

During public presentations or interviews, speakers commonly and unconsciously abuse interjections or filled pauses that interfere with speech fluency and negatively affect listeners impression and speech perception. Types of disfluencies and methods of detection are reviewed. Authors carried out a survey which results indicated the most adverse elements for audience. The article presents an approach to automatic detection of the most common type of disfluencies - filled pauses. A base of patterns of filled pauses (prolongated I, prolongated e, mm, Im, xmm, using SAMPA notation) was collected from 72 minutes of recordings of public presentations and interviews of six speakers (3 male, 3 female). Statistical analysis of length and frequency of occurrence of such interjections in recordings are presented. Then, each pattern from training set was described with mean values of first and second formants (F1 and F2). Detection was performed on test set of recordings by recognizing the phonemes using the two formants with efficiency of recognition about 68%. The results of research on disfluencies in speech detection may be applied in a system that analyzes speech and provides feedback of imperfections that occurred during speech in order to help in oratorical skills training. A conceptual prototype of such an application is proposed. Moreover, a base of patterns of most common disfluencies can be used in speech recognition systems to avoid interjections during speech-to-text transcription

MR monitoring of minimally invasive delivery of mesenchymal stem cells into the porcine intervertebral disc.

Bone marrow stem cell therapy is a new, attractive therapeutic approach for treatment of intervertebral disc (IVD) degeneration; however, leakage and backflow of transplanted cells into the structures surrounding the disc may lead to the formation of undesirable osteophytes. The purpose of this study was to develop a technique for minimally invasive and accurate delivery of stem cells.Porcine mesenchymal stem cells (MSCs) were labeled with superparamagnetic iron oxide nanoparticles (SPIO, Molday ION rhodamine) and first injected into the explanted swine lumbar IVD, followed by ex vivo 3T MRI. After having determined sufficient sensitivity, IVD degeneration was then induced in swine (n=3) by laser-evaporation. 3 x 10(6) SPIO-labeled cells embedded within hydrogel were injected in 2 doses using a transcutaneous cannula and an epidural anesthesia catheter. T2-weighted MR images were obtained at 3T before and immediately after cell infusion. Two weeks after injection, histological examination was performed for detection of transplanted cells.MSCs were efficiently labeled with Molday ION rhodamine. Cells could be readily detected in the injected vertebral tissue explants as distinct hypointensities with sufficient sensitivity. MR monitoring indicated that the MSCs were successfully delivered into the IVD in vivo, which was confirmed by iron-positive Prussian Blue staining of the tissue within the IVD.We have developed a technique for non-invasive monitoring of minimally invasive stem delivery into the IVD at 3T. By using a large animal model mimicking the anatomy of IVD in humans, the present results indicate that this procedure may be clinically feasible

<i>Ex vivo</i> MR imaging of 1.0x10⁶ Molday ION-labeled MSCs injected in explanted spinal column.

<p>White arrow points to the hypointense region containing the cell deposit.</p

Prussian blue staining of disc tissue 2 weeks after injection of 3x10⁶ Molday ION-labeled MSCs.

<p>Iron positive blue precipitates are visible inside the transplanted MSCs.</p

Serial <i>in vivo</i> axial MR imaging of (A) the lumbar region of the spine before cell injection, (B) after the first injection of 1.5x10⁶ Molday ION-labeled MSCs, and (C) after the second injection of 1.5x10⁶ labeled cells.

<p>White arrowheads points to the areas where the cells were deposited.</p

Targeting of the intervertebral disc under C-arm fluoroscopy.

<p>An epidural anesthesia needle was advanced under fluoroscopic guidance until reaching the center of the nucleus pulposus. Injection of Omnipaque contrast confirmed its proper localization.</p

<i>In vitro</i> characterization of porcine MSCs.

<p>(A) Immunocytochemistry for CD90 antigen (<i>green</i>), Hoechst counterstain (<i>blue</i>). (B) Immunocytochemistry for CD45 (green), Hoechst counterstain (blue). (C) Fluorescent image of Molday ION-labeled MSCs (<i>red</i>); high power image shown in (D), confirming intracellular labeling.</p