Directed differentiation

Source: Wikipedia, the free encyclopedia.

Directed differentiation is a

cell fate decision, often provided by developmental biology.[2][4]

Conceptual frame

During differentiation,

developmental signaling pathways.[4]
It is thus possible to direct cell fate by controlling cell decisions through extracellular signaling, mimicking developmental signals.

Source material

Directed differentiation is primarily applied to

induced pluripotent stem (iPS) cells (2006), source material is potentially unlimited.[1][4][6]
Historically, embryonic carcinoma (EC) cells have also been used.[7] Fibroblasts or other differentiated cell types have been used for direct reprogramming strategies.[1]

Methods

Cell differentiation involves a transition from a proliferative mode toward differentiation mode. Directed differentiation consists in mimicking developmental (embryo's development) decisions in vitro using the stem cells as source material.

small molecules, controlling cell differentiation, is applied sequentially or in a combinatorial manner, at varying dosage and exposure time.[1] Proper differentiation of the cell type of interest is verified by analyzing cell type specific markers, gene expression profile, and functional assays.[1]

Early methods

  • co-culture with
    feeder cells
    , and on specific culture substrates:

support cells and matrices provide developmental-like environmental signals.[8]

  • 3D cell aggregate formation, termed embryoid bodies (EBs): the aggregate aim at mimicking early embryonic development and instructing the cell differentiation.[1][5][8]
  • culture in presence of fetal bovine serum, removal of pluripotency factors.

Current methodologies

Directed differentiation

This method consists in exposing the cells to specific signaling pathways modulators and manipulating cell culture conditions (environmental or exogenous) to mimick the natural sequence of developmental decisions to produce a given cell type/tissue.[1][8] A drawback of this approach is the necessity to have a good understanding of how the cell type of interest is formed.[1]

Direct reprogramming

This method, also known as transdifferentiation or direct conversion, consists in overexpressing one or several factors, usually transcription factors, introduced in the cells.[1] The starting material can be either pluripotent stem cells (PSCs), or either differentiated cell type such as fibroblasts. The principle was first demonstrated in 1987 with the myogenic factors MyoD.[9] A drawback of this approach is the introduction of foreign nucleic acid in the cells and the forced expression of transcription factors which effects are not fully understood.

Lineage/cell type-specific selection

This methods consists in selecting the cell type of interest, usually with

selection
.

Applications

Directed differentiation provides a potentially unlimited and manipulable source of cell and tissues. Some applications are impaired by the immature phenotype of the pluripotent stem cells (PSCs)-derived cell type, which limits the physiological and functional studies possible.[6] Several application domains emerged:

Model system for basic science

For

basic science, notably developmental biology and cell biology, PSC-derived cells allow to study at the molecular and cellular levels fundamental questions in vitro,[5] that would have been otherwise extremely difficult or impossible to study for technical and ethical reasons in vivo such as embryonic development of human. In particular, differentiating cells are amenable for quantitative and qualitative studies.[8]
More complex processes can also be studied in vitro and formation of organoids, including cerebroids, optic cup and kidney have been described.

Drug discovery and toxicology

Cell types differentiated from pluripotent stem cells (PSCs) are being evaluated as

Drug screen are performed on miniaturized cell culture in multiwell-plates or on a chip.[6]

Disease modeling

PSCs-derived cells from patients are used in vitro to recreate specific pathologies.

arrythmia. This can allow for a better understanding of the pathogenesis and the development of new treatments through drug discovery.[6] Immature PSC-derived cell types can be matured in vitro by various strategies, such as in vitro ageing
, to modelize age-related disease in vitro. Major diseases being modelized with PSCs-derived cells are
Type I diabetes.[6]

Regenerative medicine

The potentially unlimited source of cell and tissues may have direct application for tissue engineering, cell replacement and transplantation following acute injuries and reconstructive surgery.[2][5] These applications are limited to the cell types that can be differentiated efficiently and safely from human PSCs with the proper organogenesis.[1] Decellularized organs are also being used as tissue scaffold for organogenesis. Source material can be normal healthy cells from another donor (heterologous transplantation) or genetically corrected from the same patient (autologous). Concerns on patient safety have been raised due to the possibility of contaminating undifferentiated cells. The first clinical trial using hESC-derived cells was in 2011.[15] The first clinical trial using hiPSC-derived cells started in 2014 in Japan.[16]

See also

References

  1. ^
    S2CID 26358726
    .
  2. ^
    PMID 18295582
    .
  3. PMID 12176325
    .
  4. ^
    PMID 16919445
    .
  5. ^
    PMID 15905405
    . Retrieved 2014-11-06.
  6. ^
    S2CID 22976547
    .
  7. PMID 7107698
    .
  8. ^
    S2CID 205494131
    .
  9. S2CID 37741454
    .
  10. PMID 11973349
    .
  11. PMID 8690796
    .
  12. S2CID 13025470
    .
  13. S2CID 21241434. Closed access icon
  14. PMID 26404920.Closed access icon
  15. ^ "First test of human embryonic stem cell therapy in people discontinued - The Washington Post". washingtonpost.com. Retrieved 2014-11-06.
  16. ^ "Japanese team first to use iPS cells in bid to restore human sight | The Japan Times". japantimes.co.jp. Retrieved 2014-11-06.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Directed_differentiation&oldid=1217199099"