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categories: ["bodies"]categories: ["bodies"]tags: ["stem cells", "disease modelling", "brain organoids", "drug screening", "regenerative medicine", "bioethics"]tags: ["stem cells", "disease modelling", "brain organoids", "drug screening", "regenerative medicine", "bioethics"]summary: "Self-organizing tissue cultures grown from stem cells that reproduce some of the architecture and function of an organ, used mainly for disease modelling rather than transplantation."summary: "Self-organizing tissue cultures grown from stem cells that reproduce some of the architecture and function of an organ, used mainly for disease modelling rather than transplantation."updated: "2026-07-27"updated: "2026-10-29"humanEvidence: "Organoids grown from a patient's own biopsy are used in the Netherlands to predict that patient's response to cystic fibrosis drugs; organoid-derived cells have been transplanted only in early trials, and no organoid has replaced an organ."humanEvidence: "Organoids grown from a patient's own biopsy are used in the Netherlands to predict that patient's response to cystic fibrosis drugs; organoid-derived cells have been transplanted only in early trials, and no organoid has replaced an organ."access: "A laboratory product rather than a treatment: the culture reagents are sold commercially, and the only patient-facing uses are the Dutch cystic fibrosis drug-response assay and a few early transplantation trials."access: "A laboratory product rather than a treatment: the culture reagents are sold commercially, and the only patient-facing uses are the Dutch cystic fibrosis drug-response assay and a few early transplantation trials."reversibility: "difficult"reversibility: "difficult"lines 21–27 → 21–276 unchanged lines not shown
"rows": [ "rows": [ { "label": "First modern example", "value": "Intestinal organoid, 2009" }, { "label": "First modern example", "value": "Intestinal organoid, 2009" }, { "label": "Cell sources", "value": "Adult stem cells, iPSCs" }, { "label": "Cell sources", "value": "Adult stem cells, iPSCs" }, { "label": "Typical size", "value": "0.1–4 mm" }, { "label": "Typical size", "value": "0.1-4 mm" }, { "label": "Common matrix", "value": "Tumour-derived basement membrane gel" }, { "label": "Common matrix", "value": "Tumour-derived basement membrane gel" }, { "label": "Main use", "value": "Disease modelling, drug screening" }, { "label": "Main use", "value": "Disease modelling, drug screening" }, { "label": "Key limits", "value": "No vasculature, fetal maturity" }, { "label": "Key limits", "value": "No vasculature, fetal maturity" },lines 30–40 → 30–402 unchanged lines not shown
}}`````` **Organoids** are three-dimensional cell cultures, grown from stem cells, that self-organize into structures reproducing some of the cell types, spatial arrangement and function of a real organ. They are not miniature organs. A cerebral organoid has cortical layers and firing neurons but no blood supply, no immune cells, no thalamic input and no consistent body plan; an intestinal organoid has crypts and absorptive cells but no nerves and no microbiome. What makes them valuable is that they are human, three-dimensional, and generated in numbers large enough to screen against.**Organoids** are three-dimensional cell cultures, grown from stem cells, that self-organize into structures reproducing some of the cell types, spatial arrangement and function of a real organ. They are not miniature organs. A cerebral organoid has cortical layers and firing neurons but no blood supply, no immune cells, no thalamic input and no consistent body plan; an intestinal organoid has crypts and absorptive cells but no nerves and no microbiome. Their value is that they are human, three-dimensional, and can be generated in numbers large enough to screen against. ## How they are made## How they are made Two derivation routes dominate. The adult-stem-cell route takes tissue-resident stem cells — from an intestinal biopsy, say — and embeds them in a laminin-rich basement membrane gel with a defined cocktail of niche factors, typically including R-spondin, epidermal growth factor, and inhibitors of BMP and TGF-β signalling. The cells proliferate and spontaneously build crypt-villus architecture. These organoids are epithelial only, genetically stable, and can be passaged for years.Two derivation routes dominate. The adult-stem-cell route takes tissue-resident stem cells, from an intestinal biopsy for example, and embeds them in a laminin-rich basement membrane gel with a defined cocktail of niche factors, typically including R-spondin, epidermal growth factor, and inhibitors of BMP and TGF-β signalling. The cells proliferate and spontaneously build crypt-villus architecture. These organoids are epithelial only, genetically stable, and can be passaged for years. The pluripotent route starts from embryonic stem cells or from [[induced-pluripotent-stem-cells]] generated with the [[yamanaka-factors]], and applies a timed sequence of differentiation cues that mimics embryonic patterning: germ-layer induction, then regional specification, then self-organization. This route produces organoids containing multiple germ layers, including neurons and glia, but is slower, more variable, and yields tissue of fetal maturity.The pluripotent route starts from embryonic stem cells or from [[induced-pluripotent-stem-cells]] generated with the [[yamanaka-factors]], and applies a timed sequence of differentiation cues that mimics embryonic patterning: germ-layer induction, then regional specification, then self-organization. This route produces organoids containing multiple germ layers, including neurons and glia, but is slower, more variable, and yields tissue of fetal maturity. lines 87–101 → 87–10146 unchanged lines not shown
**Variability.** Batch-to-batch and line-to-line differences are substantial, particularly for the pluripotent route, where the same protocol can yield organoids of different regional identity. This limits statistical power and complicates use as a screening platform.**Variability.** Batch-to-batch and line-to-line differences are substantial, particularly for the pluripotent route, where the same protocol can yield organoids of different regional identity. This limits statistical power and complicates use as a screening platform. **Missing components.** Organoids typically lack resident immune cells, vasculature, innervation and mechanical loading. Assembloids, in which separately patterned organoids are fused, restore some of what is missing — cortical and subpallial spheroids fused together permit interneuron migration to be observed directly — but the reconstruction is partial.**Missing components.** Organoids typically lack resident immune cells, vasculature, innervation and mechanical loading. Assembloids, in which separately patterned organoids are fused, restore some of what is missing: cortical and subpallial spheroids fused together, for example, permit interneuron migration to be observed directly. The reconstruction is still partial. ## Brain organoids and the consciousness question## Brain organoids and the consciousness question Cerebral organoids generate spontaneous electrical activity, and cultured long enough they produce synchronized network oscillations. One widely discussed report compared the developmental trajectory of these oscillations to electroencephalographic features seen in preterm infants, a comparison the authors themselves qualified and that other researchers regarded as an artefact of the analysis rather than evidence of anything experiential.Cerebral organoids generate spontaneous electrical activity, and cultured long enough they produce synchronized network oscillations. One widely discussed report compared the developmental trajectory of these oscillations to electroencephalographic features seen in preterm infants, a comparison the authors themselves qualified and that other researchers regarded as an artefact of the analysis rather than evidence of anything experiential. The mainstream position is that current brain organoids are extremely unlikely to be conscious. They lack sensory input, lack the thalamocortical loops that most theories of consciousness treat as necessary, lack a body to act on, and are structurally disorganized compared to a real cortex. That said, the question is not empty, because there is no accepted test. Assessing organoid sentience runs into exactly the problem described in [[neural-correlates-of-consciousness]] and [[machine-consciousness]]: behavioural evidence is unavailable and theory-based indicators disagree with one another. Ethicists have argued for developing criteria in advance rather than after a disputed result — an application of the [[precautionary-principle]] to a research programme rather than to a deployed technology — and professional guidance so far treats organoid work as requiring standard rather than special oversight while flagging the issue as one to revisit.[^farahany2018] The situation differs from [[whole-brain-emulation]], where the object under discussion is a model of a specific existing brain; an organoid is an anonymous piece of developing tissue with no history and no prior mental content.The mainstream position is that current brain organoids are extremely unlikely to be conscious. They lack sensory input, lack the thalamocortical loops that most theories of consciousness treat as necessary, lack a body to act on, and are structurally disorganized compared to a real cortex. Even so, the question cannot be dismissed, because there is no accepted test. Assessing organoid sentience runs into exactly the problem described in [[neural-correlates-of-consciousness]] and [[machine-consciousness]]: behavioural evidence is unavailable and theory-based indicators disagree with one another. Ethicists have argued for developing criteria in advance rather than after a disputed result, which applies the [[precautionary-principle]] to a research programme rather than to a deployed technology; professional guidance so far treats organoid work as requiring standard rather than special oversight while flagging the issue as one to revisit.[^farahany2018] The situation differs from [[whole-brain-emulation]], where the object under discussion is a model of a specific existing brain; an organoid is an anonymous piece of developing tissue with no history and no prior mental content. Transplantation sharpens it. Human cortical organoids grafted into rat cortex have been shown to integrate into host circuits, respond to whisker stimulation, and drive learned behaviour, which raises questions about the moral status of the resulting chimeric animal rather than of the organoid alone.[^revah2022] Related questions attach to [[synthetic-embryos]], where the definitional problem is what counts as an embryo rather than what counts as a mind.Transplantation sharpens the question. Human cortical organoids grafted into rat cortex have been shown to integrate into host circuits, respond to whisker stimulation, and drive learned behaviour, which raises questions about the moral status of the resulting chimeric animal rather than of the organoid alone.[^revah2022] Related questions attach to [[synthetic-embryos]], where the definitional problem is what counts as an embryo rather than what counts as a mind. > [!note] Terminology> [!note] Terminology> "Organoid" is used loosely. It covers epithelial-only cultures with strict lineage fidelity, multi-lineage constructs from pluripotent cells, and assemblies fused from several pieces. Claims about what organoids can do rarely generalize across these categories. Cell collectives that self-organize into forms with no organ counterpart, such as the frog-cell constructs described in [[xenobots]], fall outside the term entirely.> "Organoid" is used loosely. It covers epithelial-only cultures with strict lineage fidelity, multi-lineage constructs from pluripotent cells, and assemblies fused from several pieces. Claims about what organoids can do rarely generalize across these categories. Cell collectives that self-organize into forms with no organ counterpart, such as the frog-cell constructs described in [[xenobots]], fall outside the term entirely.removed, struck through added, underlinedLine numbers count the serialised markdown of each revision, frontmatter included.
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