Name: reprogramming cells into stem cells
Uploaded: 2020-11-23T11:47:37.000Z
Duration: 1 min 13 s
Channel: JoVE

Induzierte pluripotente Stammzellen, iPSCs, sind reife, differenzierte Zellen wie Hautzellen, die im Labor umprogrammiert werden, um undifferenzierten embryonalen Stammzellen ähnlich zu sein.
 Das heißt, sie teilen sich und sind pluripotent, fähig, jeden Zelltyp im Körper zu produzieren.
 Zum Beispiel Netzhautzellen, mit denen beschädigtes Netzhautgewebe ersetzt werden kann.
 Um iPSCs zu erzeugen, werden reife Zellen wie Hautfibroblasten von einem Patienten entnommen und in Kulturen eingebracht.
 Dann werden typischerweise Gene für Transkriptionsfaktoren durch virale Vektoren in die Zellkerne geliefert, wo sie in das Genom eingebaut werden.
 Die Transkriptionsfaktoren schalten dann Gene ein, die von embryonalen Stammzellen exprimiert werden, die sie effektiv dedifferenzieren und in einen pluripotenten Zustand bringen.
 Die Zellen können sich nun teilen und idealerweise so ausgerichtet werden, dass sie einen bestimmten Zelltyp in der Kultur produzieren.
 Die neuen Zellen könnten dann wieder zurück in den Patienten transplantiert werden, um Schäden oder Krankheiten mit minimalem Abstoßungsrisiko zu behandeln, da sie aus den eigenen Zellen des Patienten stammen.

Hamazaki, Takashi, Nihal El Rouby, Natalie C. Fredette, Katherine E. Santostefano und Naohiro Terada. "Concise Review: Induced Pluripotent Stem Cell Research in the Era of Precision Medicine." Stem Cells (Dayton, Ohio) 35, Nr. 3 (März 2017): 545–50. [<a href="https://doi.org/10.1002/stem.2570" target="__blank">Quelle</a>].

induzierte pluripotente stammzellen

Induced Pluripotent Stem Cells

Stammzellen sind undifferenzierte Zellen, die sich teilen und unterschiedliche Zelltypen produzieren. Normalerweise befinden sich Zellen, die sich zu einem bestimmten Zelltyp differenziert haben, in einem post-mitotischen Zustand. Das bedeutet, dass sie sich nicht mehr teilen. Die Wissenschaftler haben jedoch einen Weg gefunden, diese reifen Zellen umzuprogrammieren, so dass sie sich wieder zurück differenzieren in einen nicht-spezialisierten, proliferativen Zustand. Diese Zellen sind wie embryonale Stammzellen ebenfalls pluripotent. Sie sind dazu in der Lage, alle Zelltypen zu produzieren und man nennt sie daher induzierte pluripotente Stammzellen (iPSCs).
 
 In der Medizin sind iPSCs theoretisch wertvoll, da ein Patient, der einen bestimmten Zelltyp benötigt. Zum Beispiel könnte ein Patient, der eine durch Makuladegeneration beschädigte Netzhaut hat, eine Transplantation der benötigten Zellen erhalten, welche von einem anderen Zelltyp aus seinem Körper entwickelt wurden. Dies wird autologe Transplantation genannt und reduziert das Risiko einer Transplantatabstoßung, welche bei der Transplantation von Gewebe zwischen Individuen auftreten kann.
 
 <h4>Der Prozess</h4>
 
 Um iPSCs zu erzeugen, werden reife Zellen wie Fibroblasten der Haut oder Blutzellen einer Person in einer Kultur gezüchtet. Dann werden Gene für mehrere Transkriptionsfaktoren mit Hilfe eines viralen Vektors in die Zellen eingeschleust. Die Transkriptionsfaktoren werden dann in der Zelle exprimiert. Die Transkriptionsfaktoren schalten dann viele andere Gene ein, die in embryonalen Stammzellen exprimiert werden. Dadurch kehren die Zellen in einen undifferenzierten, proliferativen und pluripotenten Zustand zurück.
 
 Es wird noch untersucht, ob iPSCs wirklich äquivalent zu embryonalen Stammzellen sind. Sie scheinen aber ähnlich zu sein und können Zellen aus allen drei Keimblättern des Körpers produzieren. Wie bei anderen Stammzelltypen lernen die Wissenschaftler, wie sie die Differenzierung bestimmter Zelltypen aus iPSCs effizient fördern können, so dass die benötigten Zelltypen in ausreichender Menge produziert werden können.
 
 <h4>Frühe klinische Studien</h4>
 
 Die erste klinische Studie erforschte die Transplantation von Netzhautzellen die aus iPSCs hergestellt wurden in Patienten mit altersbedingter Makuladegeneration. Seitdem wurden mehrere klinische Studien für die Behandlung von Parkinson, Herzkrankheiten und Rückenmarksverletzungen mit iPSCs zugelassen. Zellen, die von Patienten entnommen und in iPSCs umgewandelt wurden, werden auch zur Untersuchung ihrer Krankheiten im Labor verwendet. Im Allgemeinen stellen iPSCs eine weitere Quelle von Stammzellen für die wissenschaftliche Forschung dar.

Induzierte pluripotente Stammzellen

Stammzellen sind undifferenzierte Zellen, die sich teilen und verschiedene Zelltypen produzieren. Normalerweise werden Zellen, die sich zu einer bestimmten Zelle ...

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JoVE Core

Molecular Biology

Molekularbiologie

Unit 1

Einheit 1

Gene Expression

Genexpression

KEY TERMS AND CONCEPTS

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reprogramming cells into stem cells

Induced pluripotent stem cells are created by reprogramming mature cells back into a stem-cell state. This process shows that specialized cells can be changed into cells with broader developmental potential. The topic is important in biology because it links cell identity, gene control, and stem cell research.

These cells begin as ordinary body cells and are pushed to de-differentiate, or lose their specialized features. After reprogramming, they behave like pluripotent stem cells, which means they can give rise to many different cell types. That ability makes them useful for studying how cells develop and how cell fate can be changed.

The transcript focuses on induced pluripotent stem cells as a key example of reprogramming rather than on a single tissue source. It highlights how scientists can generate stem-cell-like cells from mature cells in the lab. For high school biology, this topic connects cell specialization with the idea that gene activity can be reset.

Reprogramming Cells into Stem Cells

cell specific gene expression

How Cells Switch Genes On and Off

Cells switch genes on and off to make different proteins for different jobs. In multicellular organisms, many cell types are built from the same DNA, but they do not use the same genes in the same way. This difference in gene expression helps explain why cells can look and act so differently. Liver cells are a clear example. They help detoxify blood, make bile to help digest fats, and produce proteins needed for metabolism. To do these jobs, liver cells must express a specific set of genes.

regulation of expression occurs at multiple steps

regulation-of-expression-occurs-at-multiple-steps

How Cells Control Gene Expression

Cells control gene expression at several points between DNA and protein. The most common control point is transcription. At this stage, proteins bind to short regulatory DNA sequences and can either increase or reduce transcription of the linked gene. After transcription, a precursor mRNA is made. This pre-mRNA contains exons, which code for protein, and introns, which do not. It must be processed before translation, and splicing removes the introns and joins the exons. Cells can also regulate...

cis-regulatory sequences

How Cis-Regulatory DNA Controls Transcription

Cis-regulatory sequences are short, non-coding DNA segments that control gene transcription. They sit on the same chromosome as the genes they regulate and act as binding sites for transcriptional regulators. In eukaryotes, these proteins help control gene expression patterns in different cell types. These DNA sequences can be close to a gene or thousands of bases away. When they are far from the gene in the DNA sequence, they are often brought close together in space because chromosomes are...

cooperative binding of transcription regulators

cooperative-binding-of-transcription-regulators

How Transcription Factors Bind DNA

Transcriptional regulators bind to cis-regulatory DNA sequences to control gene transcription. These DNA sequences are very short, usually fewer than ten nucleotide pairs long. Because they are so short, the same sequence can appear by chance in many places across the genome. Some regulators can also bind to groups of similar sequences. That raises the chance of random binding even more. To lower this risk, transcription regulators often form dimers, which are pairs of proteins that bind a DNA...

prokaryotic transcriptional activators and repressors

prokaryotic-transcriptional-activators-and-repressors

Operon Control by Activators and Repressors

Operon control in prokaryotes depends on activators and repressors. Prokaryotic genes are often arranged in groups, not one by one like in eukaryotes. Genes that help carry out the same biochemical process are placed together with their regulatory elements. This group is called an operon, and it is transcribed into a single polycistronic mRNA strand. Activators and repressors are DNA-binding proteins that control transcription in an operon. Activators bind near the promoter, which is the site...

operons

Operons in Bacterial Gene Control

Operons help bacteria control groups of genes at the same time. An operon is a set of genes that are regulated together and can be turned on or off as a unit. This shared control helps bacteria respond quickly to changes in their environment. In many operons, a promoter gives RNA polymerase a place to bind and start transcription. The operon also includes a regulatory region that helps control whether the genes are expressed. When conditions change, the cell can use this setup to manage gene...

the eukaryotic promoter region

Eukaryotic Promoter Motifs and Gene Control

The eukaryotic promoter region is a stretch of DNA located upstream of a gene. It includes an RNA polymerase binding site, a transcription start site, and several cis-regulatory sequences. These DNA signals help control when transcription begins. The promoter can be divided into proximal and distal regions. The proximal promoter lies close to the gene and includes cis-regulatory sequences and the core promoter. The core promoter is the RNA polymerase binding site, and it is usually found...

co-activators and co-repressors

Chromatin Control in Gene Transcription

Chromatin control plays a major role in gene transcription in eukaryotes. Gene expression is regulated by several proteins that work together at a gene regulatory site. Some of these proteins bind directly to specific DNA sequences, while co-regulators attach to those regulators but do not bind DNA on their own. Co-regulators can act as co-activators or co-repressors, depending on the complex they join. One co-regulator may even switch roles in different settings. For example, the...

eukaryotic transcription activators

How Transcription Activators Turn Genes On

Transcription activators are proteins that help turn genes on by promoting transcription from DNA to RNA. They often have two parts. One part binds to DNA, and the other part activates transcription. In some proteins, such as the glucocorticoid receptor and MyoD, one domain can do both jobs. The DNA-binding part recognizes specific regulatory sequences on the DNA. These binding domains are grouped into families based on their structure. Common examples include the leucine zipper, zinc finger,...

eukaryotic transcription inhibitors

How Eukaryotic Gene Repressors Work

Eukaryotic gene repressors help turn specific genes off when the cell needs to control growth, development, or other biochemical processes. These DNA-binding proteins regulate gene expression in eukaryotes. Their presence at the right time and place can be triggered by hormones and signals from other cells. Most transcription inhibitors have two main parts. One part binds DNA, and the other is a repressor domain, which helps shut down transcription. Repressor domains can connect with basal...

combinatorial gene control

Gene Expression by Transcription Factor Combinations

Gene expression can depend on combinations of transcription factors working together. In combinatorial gene control, several transcription factors act in a coordinated way to regulate a single gene. If one or more of these factors are missing, the level of gene expression or repression can change a lot. This kind of control helps explain how a relatively small number of transcription factors can regulate a very large number of genes. More than 30,000 genes are controlled by about 2,000 to...

induced pluripotent stem cells

Induced pluripotent stem cells are created by reprogramming mature cells back into a stem-cell state. This process shows that specialized cells can be changed into cells with broader developmental potential. The topic is important in biology because it links cell identity, gene control, and stem cell research. These cells begin as ordinary body cells and are pushed to de-differentiate, or lose their specialized features. After reprogramming, they behave like pluripotent stem cells, which means...

master transcription regulators

MEF2C and Gene Control Cascades

MEF2C is a master transcription regulator that controls gene expression in coordinated cascades. These regulators are proteins that manage the activity of multiple genes that often work together to produce a complex outcome. When a master transcription regulator is activated, it can start a chain of transcriptional activation that supports that outcome. Master transcription regulators can act in two main ways. They may bind directly to the regulatory sequences of several genes involved in a...

epigenetic regulation

DNA Methylation and Histone Changes

Epigenetic regulation controls gene activity without changing the DNA sequence. It helps determine when genes are turned on or off in a cell. Two major epigenetic mechanisms are DNA methylation and histone modification. DNA methylation adds chemical groups to DNA, while histone changes affect how tightly DNA is packed around histone proteins. These changes can make genes easier or harder to use. In high school biology, epigenetic regulation is important for understanding how cells with the...

genomic imprinting and inheritance

Genomic Imprinting in Human Disease

Genomic imprinting affects how some inherited genes are turned on or off in human cells. Diploid organisms inherit chromosomes from both parents, and each gene usually has two alleles. In most cases, both alleles are expressed. If one allele is missing or mutated, the other can often compensate, but some genes do not work that way. In genomic imprinting, a gene or its regulatory sequence carries chemical tags, such as methyl groups, on the copy inherited from only one parent. These tags are...

key terms and concepts

Learn how mature cells can be reprogrammed into induced pluripotent stem cells and why de-differentiation matters in stem cell biology.

Reprogramming Cells into Stem Cells | JoVE K12

molecular biology

JoVE Core Molecular Biology veranschaulicht die molekularen Prozesse der Zelle in prägnanten animierten Video-Lektionen. In Videos von Wissenschaftlern in Aktion wird die Anwendung dieser Konzepte zusätzlich durch reale Experimente in modernen Laboren demonstriert.

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Reprogramming Cells into Stem Cells

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