BY: ISLAM OSMAN

Definition: stem cell is the mother of all cells , it’s a blank

unspecialized immature cell that has the capacity of self-renewal and differentiated cells regeneration .Unique Features:

stem cell has some properties that make it different from other cells Self-renewal : stem cells are capable of dividing and renewing themselves for long periodsDifferentiation: stem cells are blank cells that can be transformed to other types of cells.Plasticity: the ability of stem cells from one tissue to generate specialized cell type of another tissue, for example hemopoietic cells may give rise to skeletal, myocardial and hepatic cells.Potency: it’s the differentiation potential of the stem cells and according to potency stem cells can be classified.

Classification of stem cells

Stem cells

According to potency

Totipotent: stem cells produced from fusion of an egg and sperm. Cells produced by the first few divisions of the fertilized egg are also totipotent. These cells can be differentiated into embryonic and extra embryonic cell types (e.g. placenta) Pluripotent: stem cells derived from inner cell mass of the blastocyst and can differentiate into cells derived from any of the three germ layers excluding the placenta.Multipotent: stem cells that can produce only cells of closely related family of cells for example hematopoietic stem cells can differentiate into red blood cells. White blood cells, platelets, etc.. . Oligopotent: stem cells that can differentiate to only few cells, for example lymphoid stem cells.Bipotent: dual differentiation, for example oval cells can differentiate into hepatic and biliary epithelium.Unipotent: stem cells that can produce only one cell type …

Stem cells

Stem cells

Stem cells

According to their Origin

Embryonic stem cells: isolated from the inner cell mass of the blastocyst of the discarded embryos after IVF( in vitro fertilization) or from aborted embryos ,which has an ethical debate in different thoughts and religions as embryos are destroyed when inner cell mass is taken.

Fetal stem cells: obtained from aborted fetal gonadal tissue.

Cord blood stem cells: obtained from the remaining blood in the umbilical cord after delivery, these cells contain a big deal of hemopoietic stem cells.

Adult stem cells: are multipotent stem cells present in few numbers in many sites(bone marrow and niches) of human body.

Stem cells

Embryonic VS Adult stem cells Embryonic Stem Cells Adult Stem Cells

Pluripotent can be differentiated to any cell

Multipotentmany but not any

Unlimited self-renewal capacity Limited self- renewal

Easier to getIVF , Reproductive clonoing

Difficult to be obtained

Tumorigenic (teratomes)

Not

Immunogenic (rejection)

Not

Ethical problemsblastocyst is destroyed

Accepted

Stem cells

Are there other sources of stem cells ?

The answer was negative till the emergence of the last few years , science have exceeded the classic limit of stem cells knowledge by the appearance of two miracles

Induced pluripotent stem

cellsIPSC

Stimulus-triggered

Acquisition of pluripotency

STAP

Stem cells

Induced pluripotent stem cells

In the year of 2007 , professor Shinya Yamanaka and his research team said that aduld defferenitated cells can be transformed into pluripotent cells , and they published their results of transforming adult human fibroblasts into pluripotent cells by defined factors.

Stem cells

Stem cells

Shinya Yamanaka was given Nobel Prize in physiology for the year 2012 in grateful to his promising work .

The evidence of success of the trial is the ability of the induced cells to develop tumors (teratoma) which is a sure sign of their pluripotency by the capacity to develop into ectodermal,mesenchymal,endodermal derived structures.

Stem cells

Stimulus –Triggered Acquisition of pluripotency

(STAP)The newest breakthrough in the

field of stem cell research was declared by the beginning of this year (2014) by the valuable research of Haruko Obokata . simply , adult cells like lymphocytes were exposed to strong external stimulus like transient low PH resulting in plruipotency.

Stem cells

After doing the resarch using lymphoctes , Obokata did it on other cells of the bdoy and the same results were obtained.

Ethical Debate

Stem cells

Stem cells

some people are in favor of the stem cell and they have their own motives …embryonic stem cells will decrease human suffering.embryonic stem cells are taken from excess IVF that will be discarded anyway ..so it’s better to use them.

the other face of the debate is against stem cells research entirely and specially against embryonic stem cells ..also they have their own thoughts about that..taking the cells from the blastocyst destroys it ..that’s murder..embryonic stem cells research will open the door to reproductive cloning ..and that will replace the role of God ..

Stem cells

Stem cells

The solution the emergence of the great

discovery of Shinya Yamanaka and the STAP technique will put an end for this debate for sure ..there will no need to destroy embryos anymore ..as adult own cells will be transformed into pluripotency by usage of some transcription genes or some stressor factors..we can save embryos .

Stem cells

Applications of stem cells - Basic research

Stem cell theory of cancerRole of signals in gene transcription and differentiation of stem cells.-Biotechnology:specific cell lines to test new drugs and decrease animal testing.Development effictive antitumor drugs -cell based therapy:regerative therapy for many diseases like Parkinsonism , Alzhimer’s ,spinal cord injury , stroke , burns , heart diseases , diabetes …

Stem cells

Stem cells

CVS

Stem cells are injected into the circulation or directly into the injured heart tissue appear to improve cardiac function and/or induce the formation of new capillaries.

Stem cells

Stem cells

DM

Researchers in California report that they have reversed the equivalent of type 1 diabetes in mice through transplants of stem cells. Their experiments have replaced cells in the pancreas damaged by the disease that are unable to make insulin.

Stem cells

Skin burns

Stem cells may have a promising role in the treatment of extenxive burns and lrge ulcer through providing suffiecent numbers of epidermal and epithelial cell lines that can be used in replacing damged tissues.

Stem cells

Parkinsonism Studies confirmed

significant effects of pluripotent stem cell grafting in 6-OHDA and MPTP animal models of motor parkinsonism.Pluripotent stem cells can nestle in affected organs and can differentiate into a variety of cells, including neural (dopamine producing) cells. (Pub-med, Jan 2014)

Stem cells

Stem cells