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Extracellular environment contribution to astrogliosis-lessons learned from a tissue engineered 3D model of the glial scar.

ABSTRACT: Glial scars are widely seen as a (bio)mechanical barrier to central nervous system regeneration. Due to the lack of a screening platform, which could allow in-vitro testing of several variables simultaneously, up to now no comprehensive study has addressed and clarified how different lesion microenvironment properties affect astrogliosis. Using astrocytes cultured in alginate gels and meningeal fibroblast conditioned medium, we have built a simple and reproducible 3D culture system of astrogliosis mimicking many features of the glial scar. Cells in this 3D culture model behave similarly to scar astrocytes, showing changes in gene expression (e.g., GFAP) and increased extra-cellular matrix production (chondroitin 4 sulfate and collagen), inhibiting neuronal outgrowth. This behavior being influenced by the hydrogel network properties. Astrocytic reactivity was found to be dependent on RhoA activity, and targeting RhoA using shRNA-mediated lentivirus reduced astrocytic reactivity. Further, we have shown that chemical inhibition of RhoA with ibuprofen or indirectly targeting RhoA by the induction of extracellular matrix composition modification with chondroitinase ABC, can diminish astrogliosis. Besides presenting the extracellular matrix as a key modulator of astrogliosis, this simple, controlled and reproducible 3D culture system constitutes a good scar-like system and offers great potential in future neurodegenerative mechanism studies, as well as in drug screenings envisaging the development of new therapeutic approaches to minimize the effects of the glial scar in the context of central nervous system disease.

SUBMITTER: Rocha DN

PROVIDER: S-EPMC4586948 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Mesenchymal stem cell (MSC) derived extracellular vesicles (EVs) in their naïve and engineered forms have emerged as potential alternatives to stem cell therapy. While they have a defined therapeutic potential, the spatial and temporal control of their activity in vivo remains a challenge. The objective of this study was to devise a methodology to encapsulate EVs in 3D hydrogels for prolonged delivery. To achieve this, we have leveraged the MSC EV interactions with ECM proteins and their derivative peptides. Using osteoinductive functionally engineered EVs (FEEs) derived from MSCs, we show that FEEs bind to mimetic peptides from collagen (DGEA, GFPGER) and fibronectin (RGD). In in vitro experiments, photocrosslinkable alginate hydrogels containing RGD were able to encapsulate, tether and retain the FEEs over a period of 7 days while maintaining the structural integrity and osteoinductive functionality of the EVs. When employed in a calvarial defect model in vivo, alginate-RGD hydrogels containing the FEEs enhanced bone regeneration by a factor of 4 compared to controls lacking FEEs and by a factor of 2 compared to controls lacking the tethering peptide. These results show that EVs can be tethered to biomaterials to promote bone repair and the importance of prolonged delivery in vivo. Results also provide a prelude to the possible use of this technology for controlled delivery of EVs for other regenerative medicine applications. STATEMENT OF SIGNIFICANCE: The beneficial effects of human MSC (HMSC) therapy are attributable to paracrine effects of the HMSC derived EVs. While EV engineering has the potential to impact several fields of regenerative medicine, targeted delivery of the engineered EVs with spatial and temporal control is necessary to prevent off-target effects and enhance tissue specificity. Here, we have leveraged the interactions of MSC EVs with ECM proteins to develop a tethering system that can be utilized to prolong EV delivery in vivo while maintaining the structural and functional integrity of the EVs. Our work has provided a tunable platform for EV delivery that we envision can be formulated as an injectable material or a bulk hydrogel suitable for regenerative medicine applications.

Project description:BackgroundThe purpose of the National Health and Medical Research Council Centre of Research Excellence in Pulmonary Fibrosis (CRE-PF) is to improve and extend the lives of patients living with pulmonary fibrosis through the development of a comprehensive and integrated program of basic and clinical research and education across Australia. A key objective of the CRE-PF was establishment of a unique national training scheme, CREATE, for early-career researchers (ECRs) in respiratory research. CREATE ECRs are broadly drawn from two main fields of researchers: clinicians and scientists, where clinicians tend to be involved in part-time translational research and scientists are involved in broad scientific research including laboratory or genetic research, health economics or population research.MethodsWe describe the CREATE Program which, with limited budget and the assistance of key organisations, has provided funding opportunities (scholarships, fellowships, prizes, travel and collaboration grants), professional development (mentoring program, symposia, presentation opportunities and on-line training) and fostered a connected, supportive research community for respiratory ECRs.ResultsThe CREATE program has successfully fostered the development of the supported researchers, contributing substantially to the future of pulmonary fibrosis research in Australia. During the life of the program the CRE-PF has offered 10 PhD scholarships and five postdoctoral fellowships, awarded 13 travel grants and three grants to promote collaboration between ECRs from different institutes. A mentoring program has been established and CREATE Symposia have been held in association with key meetings. During COVID-19 restrictions, a series of virtual research meetings has offered 12 CREATE ECRs from seven universities the opportunity to present their research to a national audience. CREATE research-related achievements are impressive, including over 80 first-author publications by ECRs, and many conference presentations. Contributions to the research community, measured by committee membership, is also strong.ConclusionsIn spite of a very limited budget, wide geographic distribution of participants and the multi-disciplinary nature of the cohort, we have succeeded in providing a unique, supportive academic development environment for CREATE ECRs. Lessons learned in the process of developing this program include the importance of leveraging funding, being flexible, building networks and seeking and responding to ECR input.

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Extracellular environment contribution to astrogliosis-lessons learned from a tissue engineered 3D model of the glial scar.

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