Recent advancements and future requirements in vascularization of cortical organoids - PubMed (original) (raw)
Recent advancements and future requirements in vascularization of cortical organoids
Erin LaMontagne et al. Front Bioeng Biotechnol. 2022.
Abstract
The fields of tissue engineering and disease modeling have become increasingly cognizant of the need to create complex and mature structures in vitro to adequately mimic the in vivo niche. Specifically for neural applications, human brain cortical organoids (COs) require highly stratified neurons and glial cells to generate synaptic functions, and to date, most efforts achieve only fetal functionality at best. Moreover, COs are usually avascular, inducing the development of necrotic cores, which can limit growth, development, and maturation. Recent efforts have attempted to vascularize cortical and other organoid types. In this review, we will outline the components of a fully vascularized CO as they relate to neocortical development in vivo. These components address challenges in recapitulating neurovascular tissue patterning, biomechanical properties, and functionality with the goal of mirroring the quality of organoid vascularization only achieved with an in vivo host. We will provide a comprehensive summary of the current progress made in each one of these categories, highlighting advances in vascularization technologies and areas still under investigation.
Keywords: brain organoid; microenvironment; organ-on-a-chip; tissue engineering; vasculature.
Copyright © 2022 LaMontagne, Muotri and Engler.
Conflict of interest statement
AM is a co-founder and has an equity interest in TISMOO, a company dedicated to genetic analysis and brain organoid modeling focusing on therapeutic applications customized for autism spectrum disorder and other neurological disorders with genetic origins. The terms of this arrangement have been reviewed and approved by the University of California San Diego in accordance with its conflict-of-interest policies. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Figures
FIGURE 1
Historic challenges in cortical organoid culture. Cortical organoids are generated from pluripotent stem cells harvested from an embryo or reprogrammed from somatic cells. Upon prolonged culture, cortical organoids commonly form necrotic cores due to insufficient distribution of oxygen and nutrients. They also exhibit delayed electrical maturation with spontaneous action potentials occurring only after months of culture with minimal improvement over time. Finally, cortical organoids have limited cell type specification and differentiation after prolonged culture.
FIGURE 2
Cortical organoid vascularization components and considerations. Cellular signalling between neural and vascular cells is essential for complex network architecture. Hemodynamic forces that exude pressure and shear stresses on vessel walls can be mimicked using microfluidics. The extracellular matrix provides support and aids in mechanotransduction. Cortical organoids may be implanted into animal hosts to connect with or be invaded by host vasculature.
FIGURE 3
Biological approaches to brain organoid vascularization. (A) Schematic of organoid vascularization by mixing pluripotent stem cells with endothelail cells. a.b. Vascularized brain organoids generated by mixing HUVECs with stem cells showing localized clusters of vessel-like structures and vascular cells interacting with neurites. Adapted from (Shi et al., 2020). (B) Schematic of a brain organoid fused to a vascular spheroid. c.d.e. Vessels from a vascular spheroid invading the neuroepithelium of a brain organoid. f.g.h. Vessels from a vascular spheroid interacting with neurons and astrocytes/radial glia. Adapted from (Wörsdörfer et al., 2019). (C) Schematic of brain organoid vascularization by the addition of soluble factors or genetic engineering of inducible transcription factor systems. i.j.k Co-differentiated vascularized brain organoid stained for neural cell, vasucular cell, and tight junction markers. Adapted from Ham et al. (2020). Vascular markers in control (hCO) versus vascularized cortical organoids (vhCO), which carry an inducible Ets variant transcription factor 2 (ETV2) genetic system. Adapted from (Cakir et al., 2019).
FIGURE 4
Microfluidics-based methods of vascularization. (A) Schematic of organoid vascularization using a microfluidic-generated vascular bed. a.b. Schematic showing the fabrication of a vascular bed. c.d.e. Introduction of lung tumor spheroids to the vascular bed. Adapted from (Paek et al., 2019). (B) Schematic of organoid vascularization by angiogenic sprouting towards a central brain organoid. g. Image of the organoid and angiogenic sprouts. h.i.j. Organoid and angiogenic sprouts fluorescently stained to show interaction between vessels and neurites. Adapted from (Salmon et al., 2022). (C) Schematic of tissue engineered vessel through a matrix containing organoids. k.l. A microfluidic device formed from a sacrificial ink in an embryoid body matrix. When a sacrificial ink is evacuated, the system is then perfusable. n. Images of brain organoids in the device after perfusion. Adapted from (Skylar-Scott et al., 2019).
FIGURE 5
Brain organoid vascularization by engraftment into animal hosts. (A) Schematic of unvascularized or pre-vascularized organoids being engrafted in living mice brains. a.b. An unvascularized GFP + brain organoid located in a mouse brain stains positive for a human-specific nuclear marker. c.d. Engrafted brain organoid exhibits invasive host vessels. e. Vessels located in the graft perfuse blood. Adapted from (Mansour et al., 2018). A vascularized brain organoid located in a mouse brain stains positive for a human-specific marker and interacts with host tissues. g. Computational rendering of vessels within the organoid graft. h. Vessels within the graft perfuse a labelled dextran injected into the host mouse. Adapted from (Shi et al., 2020).