3D Bio-Printed Glioblastoma-Vascular Niche Models

Introduction Glioblastoma multiforme(GBM),a malignant brain tumor,is highly invasive and use brain microvessels to migrate and invade.Studying the perivascular invasion/migration of GBM may enable new possibilities in GBM therapy.However,the lack proper 3D study models that recapitulate GBM hallmarks restricts investigating cell-cell/cell-molecular interactions in tumor microenvironments.In this study,we created GBM-vascular niche models through 3D bioprinting [1-2] using patient-derived GBM cells with sternness(GSC:glioblastoma stem cells),vasculature endothelial cells(ECs),mural cells,and various hydrogels.Materials and methods Three GBM-vascular models were designed:Model A with large vessels and GBM spheroid;Model B with large-and micro-vessels,and GBM spheroid;Model C with large-and micro-vessels and scattered GBM cells.Large channels were created by sacrificial bioprinting.Microvessel network was formed through self-assembly of ECs(HUVEC or brain EC)and mural cells(fibroblast,pericytes,and/or astrocytes).Three GBM cell types were used in the study:SD02 and SD03 are GSCs;U87MG is a commercially-available GBM cell line.Collagen type I or fibrin hydrogel have been used as major scaffold materials.For drug treatment,Temozolomide in culture medium was perfused through large vasculatures in Model A.Results and discussion Three different GBM-vascular models were successfully fabricated and culture for 2-10.GSCs cultured in these models maintained sternness and heterogeneity during the long-term cultures.In Model A,GSCs actively invaded into the surrounding tissues(~Day26),initially regressed in response to the drug(~Day50),then developed therapeutic resistance and resumed aggressive invasion(~Day57).In Model B and C,three GBM types presented distinctive invasion patterns and EC-interactions.SD02 cells showed a spiky invasion pattern with elongated morphology.SD03 cells showed a more dispersed invasion pattern with many single cell migrations towards surrounding microvessels.U87MG cells showed a blunt invasion pattern,caused EC death in the spheroid form;however,the EC death was significantly reduced in the scattered single cell form.Conclusions In this study,we have created GBM-vascular niche models that can recapitulate various GBM characteristics such as cancer sternness,tumor type-specific invasion patterns,and drug responses with therapeutic resistance.Our models have a great potential in investigating patient-specific tumor behaviors under chemo-/radio-therapy conditions and consequentially helping to tailor personalized treatment strategy.The model platform is capable of modifying multiples variables including ECMs,cell types,vascular structures,and dynamic culture condition.Thus,it can be adapted to other biological systems and serve as a valuable tool for generating customized microenvironments.

Reshaping the chromatin landscape after spinal cord injury

The pathophysiology underlying spinal cord injury is complex. Mechanistic understanding of the adaptive responses to injury is critical for targeted therapy aimed at reestablishing lost connections between proximal and distal neurons. After injury, cell-type specific gene transcription programs govern distinct cellular behaviors, and chromatin regulators play a central role in shaping the chromatin landscape to adjust transcriptional profiles in a contextdependent manner. In this review, we summarize recent progress on the pleiotropic roles of chromatin regulators in mediating the diverse adaptive behaviors of neurons and glial cells after spinal cord injury, and wherever possible, discuss the underlying mechanisms and genomic targets. We specifically draw attention to the perspective that takes into consideration the impact of epigenetic modulation on axon growth potential, together with its effect on woundhealing properties of glial cells. Epigenetic modulation of chromatin state represents an emerging therapeutic direction to promote neural repair and axon regeneration after spinal cord injury.