Organoid

An organoid (from the Greek ὄργανον órganon: organ, tool and εἶδος eidos: type, form, shape) is a few millimeters in size, organ-like microstructure that can be artificially created using cell culture methods . Under suitable culture conditions, organoids can be grown from one or a few tissue cells, embryonic stem cells or induced pluripotent stem cells . If no mesenchymal stem cells were used, organoids have no stroma and no vessels; they nevertheless show physiologically relevant, organ-like properties.

Intestinal organoid differentiated from Lgr5 + stem cells

requirements

Pluripotent stem cells are required as starting material to produce organoids . Such cells are in a state from which they are able to differentiate and structure themselves together. The self-organization results in tissue-like associations made up of differentiated cells that differ in shape and function. The structure of organoids is at least partially similar to human or animal organs.

Organoids usually do not arise on an agar layer ; they need a liquid nutrient medium that offers the possibility of spatial growth in a 3D cell culture . The production of organoids requires a sterile cell culture laboratory in order to carry out the demanding, constructive tissue engineering . In this field of work and research in biotechnology , genetic engineering processes may also be used, especially the CRISPR / Cas method .

The product range includes tiny models of internal organs (heart, stomach, intestines, kidneys). Amazing advances have been made in the complex structures of the brain. Such cerebral organoids model the cerebral cortex , hippocampus , midbrain , hypothalamus , cerebellum , anterior pituitary and ocular retina in humans, mammals, and more rarely other vertebrates. There are protocols for their cultivation that cause regions of the brain to develop.

Cerebral organoids

Cerebrum models

For complex structures it is necessary to merge partial results. A composite with a dorsoventral axis was created from the dorsal and ventral organoids of the cerebrum . Fluorescent reporter molecules represented interneurons that migrated from the ventral to the dorsal cerebral unit.

Cerebellum models

The culture of human embryonic stem cells was gradually offered growth factors. Cell associations that resembled the embryonic neural tube emerged through self-organization . They had dorsoventral polarity and an anterior-posterior alignment. The layered structures repeated the formation of the cerebellum. And the induced Purkinje cells showed specifically human characteristics.

More organoids

Heart models

Two-dimensional colonies of induced pluripotent human stem cells (hiPSC) were transferred to three-dimensional cultures. In this way, tiny chambers of the heart emerged, again in self-organization. The following link shows a video of a beating ventricular organoid.

Gastrointestinal models

Human gastric organoids have been sequentially produced in vitro by mimicking the spatial and temporal cell signals of natural gastric development . Studies on intestinal and lung tissues served as models. The stomach models are suitable for studying the interaction of cells that do not belong to an epithelial type, but are endothelial , neuronal or mesenchymal . The purpose of such studies is genetic modeling, drug testing and, in the future, transplantation .

Kidney models

According to a nephron protocol, precursor cells for subunits of the human kidney could be differentiated. Suitable biomarkers were used to detect podocytes , proximal kidney tubules , Henle loops and distal tubules. The structural sequence was equivalent to a nephron in vivo . A review article reports on the proof of function in proximal renal tubules that ingested dextran through endocytosis . Congenital kidney diseases could be simulated with organoids in whose human pluripotent stem cells pathogenic mutations were introduced using CRISPR. In this way, (unknown) genes can be tracked down that cause kidney diseases.

Research goals

• Testing of drugs, which can reduce the number of animal testing.
• Represent the gene cascades for differentiation and self-organization.
• Identify gene mutations that are responsible for structural defects in the organs or their functional disorders.
• Develop organ donations and cell donations obtained from the patient's body through the induction of stem cells. Such stem cell therapies replace perfectly fitting sick cells with healthy ones; they are a hope of personalized medicine .

literature

• Madeline A Lancaster, Juergen A. Knoblich : Organogenesis in a dish: modeling development and disease using organoid technologies. In: Science , 345 (6194), 2014, p. 1247125. doi: 10.1126 / science.1247125. → In principle, pluripotent stem cells can produce all cell types. This ability is used to model the development of organs or their diseases.
• Jürgen A Knoblich: Mini-brains from the laboratory . In: Spectrum of Science . 12/2017, pp. 30–37.
• Ulrich Bahnsen: This is where brains grow . In: Die Zeit , No. 17/2018, pp. 35–36.
• A Lavazza, M Massimini: Cerebral organoids: ethical issues and consciousness assessment. In: J Med Ethics , February 2018. doi: 10.1136 / medethics-2017-104555 ; under pressure.

Individual evidence

1. ↑ Gretel Nusspaumer, Sumit Jaiswal, Andrea Barbero, Robert Reinhardt, Dana Ishay Ronen, Alexander Haumer, Thomas Lufkin, Ivan Martin, Rolf Zeller: Ontogenic identification and analysis of mesenchymal stromal cell populations during mouse limb and long bone development. In: Stem Cell Reports , 9, 2017, pp. 1124–1138.
2. ↑ Elizabeth Di Lullo, Arnold R Kriegstein: The use of brain organoids to investigate neural development and disease. In: Nat Rev Neurosci 18 (10), 2017, pp. 573-584, PMC 5667942 (free full text).
3. ↑ Joshua A Bagley, Daniel Reumann, Juergen A Knoblich: Detailed cerebral organoid fusion method. In: Protocol Exchange , 2017, doi: 10.1038 / protex.2017.064 .
4. ↑ Joshua A Bagley, Daniel Reumann, Shan Bian, Julie Lévi-Strauss, Juergen A Knoblich: Fused dorsal-ventral cerebral organoids model complex interactions between diverse brain regions. In: Nature Methods , 14 (7), 2017, pp. 743-751, PMC 5540177 (free full text).
5. ↑ Keiko Muguruma, Ayaka Nishiyama, Hideshi Kawakami, Kouichi Hashimoto, Yazici Sasai: Self-organization of polarized cerebellar tissue in 3D culture of human pluripotent stem cells. In: Cell Rep 10 (4), 2015, pp. 537-550. cell.com (PDF).
6. ↑ Plansky Hoang, Jason Wang, Bruce R Conklin, Kevin E Healy, Zhen Ma: Generation of spatial-patterned early-developing cardiac organoids using human pluripotent stem cells. In: Nature Protocols , 13 (4), 2018, pp. 723-737. At the end of the link: Video of a beating heart chamber model, 600 μm diameter .
7. ↑ Alexandra K Eicher, H Matthew Berns, James M Wells: Translating developmental principles to generate human gastric organoids. In: Cell Mol Gastroenterol Hepatol , 5 (3), 2018, pp. 353-363, PMC 5852324 (free full text).
8. ↑ Ryuji Morizane, Albert Q Lam, Benjamin S Freedman, Seiji Kishi, M Todd Valerius, Joseph V Bonventre: Nephron organoids derived from human pluripotent stem cells model kidney development and injury. In: Nat Biotechnol , 33 (11), 2015, pp. 1193-1200, PMC 4747858 (free full text).
9. ↑ Elena Garreta, Nuria Montserrat, Juan Carlos Izpisua Belmonte: Kidney organoids for disease modeling. In: Oncotarget 9 (16), 2018, pp. 12552-12553.