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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

Here, we present a protocol to engraft human brain organoids at multiple maturation stages into the chick chorioallantoic membrane (CAM). Brain organoids were grown following unguided standardized protocols.

Abstract

Engrafting organoids into vascularized tissues in model animals, such as the immunodeficient mouse or chick embryo chorioallantoic membrane (CAM), has proven efficient for neovascularization modeling. The CAM is a richly vascularized extraembryonic membrane, which shows limited immunoreactivity, thus becoming an excellent hosting model for human origin cell transplants.

This paper describes the strategy to engraft human brain organoids differentiated at multiple maturation stages into the CAM. The cellular composition of brain organoids changes with time, reflecting the milestones of human brain development. We grafted brain organoids at relevant maturation stages: neuroepithelial expansion (18 DIV), early neurogenesis (60 DIV), and early gliogenesis (180 DIV) into the CAM of embryonic day (E)7 chicken embryos. Engrafted brain organoids were harvested 5 days later and their histological features were analyzed.

No histological signs of neovascularization in the grafted organoids or abnormal blood vessels adjacent to the graftings were detected. Moreover, remarkable changes were observed in the cellular composition of the grafted organoids, namely, an increase in the number of glial fibrillary acidic protein-positive-reactive astrocytes. However, the cytoarchitectural changes were dependent on the organoid maturation stage. Altogether, these results suggest that brain organoids can grow in the CAM, and they show differences in the cytoarchitecture depending on their maturation stage at grafting.

Introduction

Human brain organoids are an emerging technique that allows us to recapitulate the early development of the human brain in vitro1,2,3. Nevertheless, one of the major limitations of this model is the lack of vascularization, which plays indispensable roles not only in brain homeostasis but also in brain development4. In addition to the delivery of oxygen and nutrients, accumulating evidence suggests that the vascular system of the brain regulates neural differentiation, migration, and synaptogenesis during development5

Protocol

The White Leghorn chicken (Gallus gallus) embryos were treated by following the Guide for the Care and Use of Laboratory Animals from the Institute of Laboratory Animals Resources, Commission of Life Sciences, National Research Council, USA, and the experiments were approved by the Council for Care and Use of Experimental Animals from the University of Barcelona.

1. Non-guided brain organoid preparation

  1. Maintain H9 human embryonic stem cells (hESCs) in mTE.......

Representative Results

Selecting the embryo maturation schedule for the transplant
The experiment begins at D0 when fertilized eggs are incubated at 38 °C and 60% relative humidity. The chorioallantoic membrane (CAM) is a highly vascularized extraembryonic membrane that develops after egg incubation. It is formed by the fusion of the allantois and chorion. At D1, after 24 h of incubation, the air chamber is punctured to prevent the CAM from attaching to the inner shell membrane. Puncturing the air chamber at D1 impr.......

Discussion

In this study, we describe a detailed protocol with numerous key steps that provide favorable growth and development of human brain organoids upon grafting without perturbing the survival of the chicken embryos. We recommended the use of sterile needles to puncture the air chamber of the egg after 24 h of incubation (day 1). Additionally, we also tried to make the puncture at day 4 (after checking through the eggshell by light to test the development of the vasculature to be sure that we were working only with healthy em.......

Acknowledgements

We thank Dr. Alcántara and Dr. Ortega from UB and the rest of the members in Dr. Acosta's lab for the insightful discussions. S.A. is Serra-Hunter fellow assistant professor from the Generalitat de Catalunya at Universitat de Barcelona.

....

Materials

NameCompanyCatalog NumberComments
Anti-TUBB3 [Tuj1], mouse BioLegend8012011:1,000
Anti-GFAP, rabbitGeneTexGTX1087111:500
Anti-rabbit AlexaFluor 488, goat.InvitrogenA-212061:1,000
Anti-mouse AlexaFluor 594, goatJackson ImmunoResearch715-585-1501:500
Fertilized White Leghorn chicken (Gallus gallus) eggsGranja Gibert (Cambrils, Spain)
DAPIInvitrogenD13061:10,000
DPXSigma100579xylene-based mounting medium 
Gentle Dissociation SolutionCreativeBiolabsITS-0622-YT187cell dissociation solution
MatrigelBD Biosciences356234
Mowiol 4-88 mounting mediaMerk81381
Paper towel, lab-gradeSigma-AldrichZ188956
ROCK inhibitor Y27632MilliporeSCM07510 nM
Sharp-Point Surgical ScissorsVWR470106-340
Superfrost Plus Adhesion Microscope SlidesEprediaJ1800AMNZ

References

  1. Camp, J. G., et al. Human cerebral organoids recapitulate gene expression programs of fetal neocortex development. Proc Natl Acad Sci U S A. 112 (51), 15672-15677 (2015).
  2. Lancaster, M. A., Knoblich, J. A.

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