Extracellular matrix-derived hydrogels for dental stem cell delivery

Decellularized mammalian extracellular matrices (ECM) have been widely accepted as an ideal substrate for repair and remodelling of numerous tissues in clinical and pre-clinical studies. Recent studies have demonstrated the ability of ECM scaffolds derived from site-specific homologous tissues to direct cell differentiation. The present study investigated the suitability of hydrogels derived from different source tissues: bone, spinal cord and dentine, as suitable carriers to deliver human apical papilla derived mesenchymal stem cells (SCAP) for spinal cord regeneration. Bone, spinal cord, and dentine ECM hydrogels exhibited distinct structural, mechanical, and biological characteristics. All three hydrogels supported SCAP viability and proliferation. However, only spinal cord and bone derived hydrogels promoted the expression of neural lineage markers. The specific environment of ECM scaffolds significantly affected the differentiation of SCAP to a neural lineage, with stronger responses observed with spinal cord ECM hydrogels, suggesting that site-specific tissues are more likely to facilitate optimal stem cell behavior for constructive spinal cord regeneration

Stem cell treatment of degenerative eye disease

Stem cell therapies are being explored extensively as treatments for degenerative eye disease, either for replacing lost neurons, restoring neural circuits or, based on more recent evidence, as paracrine-mediated therapies in which stem cell-derived trophic factors protect compromised endogenous retinal neurons from death and induce the growth of new connections. Retinal progenitor phenotypes induced from embryonic stem cells/induced pluripotent stem cells (ESCs/iPSCs) and endogenous retinal stem cells may replace lost photoreceptors and retinal pigment epithelial (RPE) cells and restore vision in the diseased eye, whereas treatment of injured retinal ganglion cells (RGCs) has so far been reliant on mesenchymal stem cells (MSC). Here, we review the properties of non-retinal-derived adult stem cells, in particular neural stem cells (NSCs), MSC derived from bone marrow (BMSC), adipose tissues (ADSC) and dental pulp (DPSC), together with ESC/iPSC and discuss and compare their potential advantages as therapies designed to provide trophic support, repair and replacement of retinal neurons, RPE and glia in degenerative retinal diseases. We conclude that ESCs/iPSCs have the potential to replace lost retinal cells, whereas MSC may be a useful source of paracrine factors that protect RGC and stimulate regeneration of their axons in the optic nerve in degenerate eye disease. NSC may have potential as both a source of replacement cells and also as mediators of paracrine treatment

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

Translational considerations in injectable cell-based therapeutics for neurological applications: concepts, progress and challenges

Significant progress has been made during the past decade towards the clinical adoption of cell-based therapeutics. However, existing cell-delivery approaches have shown limited success, with numerous studies showing fewer than 5% of injected cells persisting at the site of injection within days of transplantation. Although consideration is being increasingly given to clinical trial design, little emphasis has been given to tools and protocols used to administer cells. The different behaviours of various cell types, dosing accuracy, precise delivery, and cell retention and viability post-injection are some of the obstacles facing clinical translation. For efficient injectable cell transplantation, accurate characterisation of cellular health post-injection and the development of standardised administration protocols are required. This review provides an overview of the challenges facing effective delivery of cell therapies, examines key studies that have been carried out to investigate injectable cell delivery, and outlines opportunities for translating these findings into more effective cell-therapy interventions

New Approaches to the Transplantation of Stem Cells and their Progeny for the Treatment of Retinal Degeneration

Cellular transplantation for photoreceptor replacement in retinal disease is limited by poor distribution, survival and integration of cells in vivo after standard delivery in saline vehicle. We were interested in addressing each of these barriers in order to improve transplant efficacy. To this end, we designed the first injectable biomaterial-based cell delivery vehicle to transplant adult stem cell progeny into the subretinal space of adult retina. A minimally-invasive and bio-resorbable blend of hyaluronan and methylcellulose (HAMC) was found to overcome cellular aggregation and non-contiguous distribution. The ability to direct stem cell differentiation toward a particular retinal lineage is another challenge facing clinical application. We showed that prospectively and clonally isolated multipotent mouse and human retinal stem cells (RSCs) could be directed toward a mature rod photoreceptor fate with the highest efficiency reported to date (>90%). Combinations of taurine and retinoic acid directed rod differentiation similar to rod development in vivo. RSC-derived rods exhibited morphology, protein and gene expression consistent with primary cultures of rods in vitro. When combined with the HAMC delivery vehicle, greater cell survival and improved integration of post-mitotic RSC-derived rods was observed in vivo compared to saline delivery. Improved donor rod survival was ascribed to the CD44 receptor – HAMC interaction in vitro and in vivo. Combined with HAMC delivery, disruption of the glial limiting membrane improved cell integration and resulted in the highest levels of integration of adult stem cell-derived rod photoreceptors relative to previous reports in the literature. Mature rod-lineage committed cells demonstrated higher integration potential compared to immature rods in this context. The integrated cells expressed Rhodopsin and elaborated outer segments. In the absence of the glial limiting membrane, rod integration depended on pro-survival signals from the environment. This work demonstrates that adult RSCs show promise for regenerative medicine strategies in the adult retina.Ph

Beyond Sector Retinitis Pigmentosa: Expanding the Phenotype and Natural History of the Rhodopsin Gene Codon 106 Mutation (Gly-to-Arg) in Autosomal Dominant Retinitis Pigmentosa

Sector and pericentral are two rare, regional forms of retinitis pigmentosa (RP). While usually defined as stable or only very slowly progressing, the available literature to support this claim is limited. Additionally, few studies have analyzed the spectrum of disease within a particular genotype. We identified all cases (9 patients) with an autosomal dominant Rhodopsin variant previously associated with sector RP (RHO c.316G > A, p.Gly106Arg) at our institution. Clinical histories were reviewed, and testing included visual fields, multimodal imaging, and electroretinography. Patients demonstrated a broad phenotypic spectrum that spanned regional phenotypes from sector-like to pericentral RP, as well as generalized disease. We also present evidence of significant intrafamilial variability in regional phenotypes. Finally, we present the longest-reported follow-up for a patient with RHO-associated sector-like RP, showing progression from sectoral to pericentral disease over three decades. In the absence of comorbid macular disease, the long-term prognosis for central visual acuity is good. However, we found that significant progression of RHO p.Gly106Arg disease can occur over protracted periods, with impact on peripheral vision. Longitudinal widefield imaging and periodic ERG reassessment are likely to aid in monitoring disease progression

Challenges Facing Physician Scientist Trainees: a Survey of Trainees in Canada’s Largest Undergraduate and Postgraduate Programs in a Single Centre

Purpose: A number of indicators suggest that the physician scientist career track is threatened. As such, it is an opportune time to evaluate current training models. Perspectives on physician scientist education and career path were surveyed in trainees at the University of Toronto, home to Canada’s longest standing physician scientist training programs. Methods: Trainees from the Clinician Investigator Program (CIP) and MD/PhD Program at the University of Toronto were surveyed. Liekert-style closed-ended questions were used to assess future career goals, present and future perspectives and concerns about and beliefs on training. Demographic information was collected regarding year of study, graduate degree program and focus of clinical and health research. Statistical analysis included non-parametric tests for sub-group comparisons. Results: Both groups of trainees were motivated to pursue a career as a physician scientist. While confident in their decision to begin and complete physician scientist training, they expressed concerns about the level of integration between clinical and research training in the current programs. They also expressed concerns about career outlook, including the ability to find stable and sustainable careers in academic medicine. Trainees highlighted a number of factors, including career mentorship, as essential for career success. Conclusion: These findings indicate that while trainees at different stages consistently express career motivation, they identified concerns that are program- and training stage-specific. These concerns mirror those highlighted in the medical education literature regarding threats to the physician scientist career path. Understanding these different and changing perspectives and exploring those differences could form an important basis for trainee program improvements both nationally and internationally

Heterochromia and ocular ischemia resulting from Neurofibromatosis I-related optic pathway glioma

NF1-OPG are typically benign optic nerve tumors arising in childhood which may be associated with visual loss from optic neuropathy, impaired extraocular motility, and proptosis. While optic disc edema, pallor, or choroidal folds are commonly observed, iris and retinal vascular sequelae arising from NF1-OPG are exceedingly rare (1-4)