New Kind of Endegenous Pluripotent Somatic Cell

I just stumbled upon an article where scientists from UCSF claim to have discovered endogenous pluripotent somatic cells comparable to hESC, said to be stable and mortal. They fit stemness as defined by most including Shinya Yamanaka’s, but however have different expressions, surface markers and other characteristics than those found with hESC. Isn’t being mortal for a cell forbidding it from fitting stemness?

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Read the Full Article Here

Dental Pulp Stem Cells – An Accessible Source

Dental pulp is the soft living tissue inside a tooth and, recently, mesenchymal type of stem cells (DPSCs), having for potential niche the perivascular region of the dental pulp, have been characterized to be self-renewing with an astonishing ability to regenerate a dentin-pulp like complex, with a mineralized matrix with tubules lines with ondontoblasts, and fibrous tissue containing blood vessels in an arrangement almost identical to that found in normal human teeth dental pulp. DPSCs are believed to be post-natal stem cells and are thought to originate from the cranial neural crest with the potential to differentiate into osteoblasts, chondrocytes, adipocytes, endothelial cells, and functionally active neurons in vitro, under defined conditions. Recent studies have identified three potential niches for the stem cells in the pulpal tissue as described in below figure (provided by Alastai et al.)

dental

DPSCs are the more interesting as they can be obtained without adverse health effects, i.e. naturally exfoliated deciduous and impacted adult wisdom teeth are not usually needed, and have the potential to be used to treat many diseases given their multipotent nature quality on top of the recent studies showing the feasibility of their use in the engineering of a whole tooth. Additionally, the interest in DPSCs keeps on growing as it is possible to obtain dental pulp stem cells from anyone of any age by a simple visit to the dentist in order to bank extracted dental stem cell. Many companies have started this process as the chances of rejection by the body are greatly reduced when using one’s own stem cells for therapy.

References:

  • Human dental pulp-derived stem cells promote locomotor recovery after complete transection of the rat spinal cord by multiple neuro-regenerative mechanisms.
  • Sakai K, Yamamoto A, Matsubara K, Nakamura S, Naruse M, Yamagata M, Sakamoto K, Tauchi R, Wakao N, Imagama S, Hibi H, Kadomatsu K, Ishiguro N, Ueda M., J Clin Invest. 2012 Jan 3;122(1):80-90. doi: 10.1172/JCI59251. Epub 2011 Dec 1.
  • Dental pulp stem cells: what, where, how?, Sloan AJ, Waddington RJ., Int J Paediatr Dent. 2009 Jan;19(1):61-70. Review.
  • Gronthos S, et al. Stem cell properties of human dental pulp stem cells. J Dent Res. 2002;81(8):531‚Äď535.
  • http://genecure.blogspot.com/2009/11/monkey-teeth-help-in-stimulation-of.html

Potential Stem-Cells Based Therapeutics

This is taken from a discussion I participated in regarding potential uses of stem cells to treat incurable diseases such as multiple scelerosis that I found particularly interesting:

Multiple sclerosis is an autoimmune disease of the central nervous system characterized by damaged myelin sheath. The myelin coating around axons of nerve cells allows for the nervous system to function properly. Damage to the myelin sheath is caused by attack from the body’s immune system. The cause of MS is unknown; it is thought that the disease could occur due to genetic mutation or from a viral infection.

damaged

Specific stem cells with regulatory properties of the immune system are thought to have a potential benefit for use in MS treatment. Stem cells, such as mesenchymal stem cells (MSCs), could help prevent the immune system to continue to attack the integrity of the myelin sheath of the CNS when used in therapy. This can assist in delaying disease progression. In this type of therapy, adult stem cells are harvested from the patient’s own body (bone marrow), human umbilical cord, and bone marrow. Both MSCs and T regulatory cells are embedded inside of the harvested tissue, and later isolated from fat tissues. 

Neural stem/precursor cells (NPCs), derived from the CNS, are also being used for therapeutic applications in MS treatments. These stem cells can serve to protect the myelin sheath from immune system attack.

MS currently has no cure, and treatments serve to delay progression of the disease, but none consistently so. Some scientists believe that the use of stem cells in MS treatment has the most potential for discovering a cure or reliable treatment to effectively alleviate suffering from patients and increase quality of life.  

Recent research has suggested stem cells from the brain carrying the CD140 protein, a protein that makes up¬†oligodendrocytes, which often form myelin, are the most superior candidates for MS treatment with stem cells. This would allow the restoration of damaged myelin throughout the CNS. A doctor from Rochester Medical Center, currently involved in research in this area, stated: ‚ÄúThese cells are our best candidates right now for someday helping patients with M.S., or children with fatal hereditary myelin disorders‚ĶThese cells migrate more efficiently throughout the brain, and they¬†myelinate¬†other cells more quickly and more efficiently than any other cells assessed thus far. Now we finally have a cell type that we think is safe and¬†effectivie¬†enough to propose clinical trials‚ÄĚ( 4).¬†

¬†Jennifer Gutierrez Rodriguez”

References:

(1) MS Research Australia, http://www.msra.org.au/living-ms

(2) PubMedHealth, USNLB, Multiple Scelrosis, http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001747/

(3) Baron Van Evercooren A, Franklin R, Kerr D, Martino G, Stem cell transplantation in multiple sclerosis: current status and future prospects, Nature Reviews Neurology 6, 247-255, May 2010http://www.nature.com/nrneurol/journal/v6/n5/abs/nrneurol.2010.35.html

(4) News Medical, Brain stem cell treatment for multiple sclerosis, http://www.news-medical.net/news/20111015/Brain-stem-cell-treatment-for-multiple-sclerosis.aspx

Induced Pluripotent Stem Cells

In order to avoid the ethical issues of using embryonic stem cells, an alternative method was found and involves using induced pluripotent stem cells (iPSCs).  iPSCs are derived from adult somatic cells that have already differentiated by reprogramming them back genetically to an undifferentiated embryonic stem cell-like state.  This is accomplished by inducing the expression of factors and genes that characterize the properties of natural pluripotent stem cells.  The expression of 4 transcription factors, Oct4, Sox2, Klf4, and cMyc, have been found to be sufficient to revert somatic cells like fibroblasts in mice back to pluripotent stem cells.
This method is relatively recent, with the first iPSCs from mice being reported in 2006 and from human cells in late 2007.  While the generation of iPSCs as a stem cell research tool is very promising in terms of getting around the ethical issues surrounding the use of embryos, there are various challenges and issues with iPSCs as well.  I will briefly describe a couple of pros and cons:
Advantages
– iPSCs have the capability to divide in an umlimited fashion in culture and also to maintain the potential to differentiate into many cell types by giving arise of any of the three germ layers.
– iPSCs can be derived from a patient’s own cells, making them a valuable tool for developing therapies for various diseases as well as modeling human diseases.
Disadvantages
– The use of viral vectors is used to deliver the reprogramming factors to the adult cells which presents some problems such as insertional mutagenesis leading to developmental abnormalities in the cells.
– Elevated mutation rate induced by the stress incurred from reprograming the cells.
РStudies with iPSCs so far showed yields of iPSCs from somatic cells that are as low as 0.1% with higher yields being only around 1-3%.  This low efficiency presents some challenges for clinical applications of iPSCs.
– Unknown differences between iPSCs and natural pluripotent stem cells
Ling Phoun  (edited by Y. S. Hassan)

References:
1.  Weinacht et al.  The role of induced pluripotent stem cells in research and therapy of primary immunodeficiencies.  Current opinion in immunology. Epub ahead of print, published online 25 July 2012.
2.  Lei et al.  Directed differentiation of induced pluripotent stem cells towards T lymphocytes. J Vis Exp. 2012 May 14;(63):e3986. doi: 10.3791/3986.
3.  Park et al. Generation of human-induced pluripotent stem cells. (2008) Nat Protoc. 3(7):1180-6.
4. Ji J et al. Elevated coding mutation rate during the reprogramming of human somatic cells into induced pluripotent stem cells. Stem Cells. 2012 Mar;30(3):435-40. doi: 10.1002/stem.1011.

Inflammasomes

The nucleotide-binding oligomerization domain-like receptor (NLR) family of proteins has a key role in the regulation of innate immunity responses by sensing pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) in the cytosol, and, for some NLRs, by inducing the assembly of inflammasomes.

Inflammasomes are multiprotein oligomers that coordinate the interaction of signaling molecules in order to induce the efficient and rapid activation of inflammatory processes. They are expressed in myeloid cells and are components of the innate immune system. The composition of inflammasomes depends on the type of the activator which triggered the assembly of the particular inflammasome. For example, the most studied inflammasome, NLRP3, is triggered in macrophages by a multitude of PAMPs in the presence of ATP (i.e. liposaccharide, peptidoglycan, and bacterial nucleic acids) and also crystallized endogenous molecules. Other inflammasomes, such as NLRP1, NLRC4 and AIM2 are activated by numerous signals such as muramyl dipeptide (MDP) and anthrax lethal toxin, flagellin, and dsDNA respectively (see below figure for full pathway provided by invivogen).

Inflammasome_pathways_small

Inflammasomes are composed of caspase 1, PYCARD, NALP and sometimes caspase 5 (also called caspase 11 or ICH-3), and, once activated, promotes the cleavage of pro-IL-1beta and pro-IL-18 to form active IL-1 beta and IL-18 in order to be secreted by the cell as an inflammatory response, crucial for host defense to pathogens (see below figure for general composition of inflammasomes provided by invivogen).

inflammasome_complex

Furthermore, it has been shown that inflammasomes induce pyroptosis, a programmed cell death different from apoptosis that is regarded as a host response to remove the niche of the bacteria and to hasten their demise [3], as well as many other effect, such as vascular endothelium and lymphocytes activation as well as pyrogen effects (increasing body’s temperature).

References:

  • [1] Immunological Receptors: Innate, Dr. Meredith Safford.
  • [2] Inflammasomes Review, 2012,¬†www.invivogen.com
  • [3] Caspase-1: is IL-1 just the tip of the ICEberg?, Denes A, Lopez-Castejon G, Brough D., Cell Death Dis. 2012 Jul 5;3:e338. doi: 10.1038/cddis.2012.86.

Embryo Screening

This is taken from a discussion I took part in concerning preimplantation genetic diagnosis, a very touchy subject from an ethical point of view, and also from a technical point of view:

“….¬†There have been many issues with genetic testing of the embryos for hereditary diseases such as Huntington Disease for many reasons. First, of course, during pregnancy women can have a genetic test performed on the fetus in order to find out if their infants will be affected by a known disease or not. However, many centers refuse to perform this test as it divulges information about the parents as well and usually leads to pregnancy termination. The test in itself cannot predict the time of onset of course. However, more interestingly in my opinion, this opens the door to a whole new approach to birth, in vitro fertilization with pre-implantation genetic diagnosis (PGD). This procedure is also known as embryo screening and it allows couples at risk of transmitting a genetic disease to ensure their descendants to be unaffected by the genetic disorder through artificially combining many sperm cells from a man with many egg cells from a woman to create many embryos. Then, cell samples are taken from all of the embryos and the DNA analyzed for the defective genes. The non-disease carrier embryos are selected and artificially implanted into the mother‚Äôs uterus. This allows the parent to ensure a ‚Äúdisease free‚ÄĚ child and avoid having to go through the painful termination process, in case the pre-natal test is positive (see below link to video for Comprehensive Chromosome Screening technic, a novel approach to embryo screening). This method, while very appealing, is an ethical nightmare, as it opens the door to the quest for a ‚Äúperfect baby‚ÄĚ …”

Y.S.H.

  

References:

  • Embryo Screening and the Ethics of Human Genetic Engineering, By: Leslie A. Pray, Ph.D. ¬© 2008 Nature Education
  • [Ethics and medical genetics], Lacombe D., J Int Bioethique. 2012 Jun;23(2):95-102, 178-9. French.
  • Preimplantation genetic screening: “established” and ready for prime time?, Gleicher N, Weghofer A, Barad D.,Fertil Steril. 2008 Apr;89(4):780-8. Epub 2008 Mar 18. Review.