Stem Cell Basics #1 – By Danielle L. King

Human Lungs isolated. X-Ray effectHannah Warren, a 2-year old girl born without a trachea made recent news for receiving a synthetic windpipe generated from her own stem cells. The stem cells were taken from Hannah’s bone marrow and placed onto an artificial scaffold, where the stem cells divided and replicated themselves into a new windpipe. Hannah survived 3 months with a normally functioning trachea succumbing to problems with other organs that could not be replaced. This is just one of many cases of the use of stem cells in modern medicine.

What are stem cells?

Stem cells are relatively unspecialized cells that have the ability to develop and differentiate into different cell types with a specific function. In other words, they are not devoted to a specific function, however they have the potential to differentiate into a specialized cell. Stem cells work to renew and restore cells in specific tissues and organs, by means of cell division. The division of a stem cell can result in an undifferentiated stem cell or a specialized cell. These specialized cells can be used towards further understanding of infections, cancer and many other diseases. In addition stem cells can aid in the study of new drugs and are the forefront in the future of tissue engineering and regenerative medicine, as displayed in the case of Hannah’s windpipe.

Types of Stem Cells:

There are two main sources of stem cells, which are embryonic stem cells and non-embryonic (also known as somatic, tissue, or adult stem cells). Embryonic stem cells are cells derived from an embryo that can differentiate into all specialized cells of the body. Non-embryonic stem cells are undifferentiated cells derived from a tissue or organ with the ability to differentiate into specialized cells for that specific tissue or organ. Owing to the fact embryonic stem cells can produce any type of cell in the body, they have a greater potency than adult stem cells. Thus, the potential for a stem cell to differentiate into a specialized cell varies. Therefore, stem cells are categorized into groups based on their capability to specialize, which is listed as follows: totipotent, pluripotent, multipotent, oligopotent and unipotent.

 

Stem Cell Sources:

Stem cells can be taken from specific sources in the body:

-Bone Marrow

-Peripheral Blood

-Umbilical Cord Blood and Tissue

-Tissue Stem Cells

-Teeth

-Adipose Tissue

-Testis

 

References:

1. Fitzgerald, Kelly. “Two-Year-Old Girl Born Without A Windpipe Receives Artificial

Trachea Grown From Stem Cells.” . N.p., 2 May 2013. Web. . <http://www.medicalnewstoday.com/articles/259942.php>.

2. Stöppler, Melissa. “Stem Cells.” . Medicine Net Inc., 13 July 2014. Web. .

<http://www.medicinenet.com/stem_cells/article.htm>.

3. “Stem Cell Information.” National Institutes of Health. National Institutes of Health, 04

Apr 2013. Web. <http://stemcells.nih.gov/Pages/Default.asp&xgt;.

4. “What are stem cells.” CHXA. CHXA, n.d. Web. <http://www.chxa.com/what-are-stem-

cells/>.

 

Threats to Male Fertility: Pesticides

farmer spraying pesticide in the rice fieldIf you have read our previous blogs, you know that some plastic chemicals and recreational drugs are threats to male fertility. These gonadotoxins either directly affect the testes or affect the hormones that produce sperm. Chemicals in pesticides have been shown to impact male fertility, though recent articles have suggested more research needs to be done in this area.

Effects of Pesticides

Since the early 2000s, the majority of studies linking male infertility to pesticides have reported that pesticide exposure leads to poor sperm quality and reduced sperm concentrations.1 Clear effects on sperm quality, for example, have been demonstrated for dibromochloropropane (DBCP) and ethylene dibromide, the active ingredients in some agricultural fumigants.2 Not all pesticides are so clear-cut, though. One article in particular notes that many of these studies are inconsistent, citing problems with sample populations, pesticide exposure, and study design.1

Research published as recently as 2011, however, strengthens the connection between pesticides and infertility. Scientists at the University of London tested 34 widely-used pesticides with high exposures through diet and found that 23 of them reduced fertility. The researchers recommend additional testing, but the study again points to the negative effect of pesticide exposure on fertility.3

Treatment

In many cases, gonadotoxic effects are reversible once exposure to the pesticide is eliminated, but because there are hundreds of pesticides, it can be difficult and even impossible to know exactly which one may be impacting your fertility. Still, there are some measures you can take to reduce exposure:

  • Thoroughly wash produce before eating, as many pesticides and fungicides used on agricultural crops contain gonadotoxins.
  • Limit exposure to wood preservatives and industrial chemical applications, if possible.

If you think pesticides might be the reason for your infertility, you should talk to your doctor about possible treatments.

References

  1. Roeleveld, N., & Bretveld, R. (2008, June). The impact of pesticides on male fertility. Curr Opin Obstet Gynecol, 20(3), 229–33. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/18460936
  2. Bretveld, R., Brouwers, M., Ebisch, I., & Roeleveld, N. (2007, February). Influence of pesticides on male fertility. Scand J Work Environ Health, 33(1), 13–28. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/17353961
  3. Tal, T. (2011, May 17). Widely used but just tested pesticides may contribute to infertility. Environmental Health News. Retrieved from http://www.environmentalhealthnews.org/ehs/newscience/test-show-current-pesticides-block-androgen-receptor-actions/

Threats to Male Fertility: Recreational Drugs

In a previous postDrugFreeZone, we talked about what gonadotoxins are and how chemicals found in everyday plastics can impact male fertility. But plastic chemicals aren’t the only toxins out there affecting sperm production. Drugs, such as nicotine, alcohol, marijuana, and steroids are common substances that can negatively impact fertility.

Recreational Drug Use

When you consider fertility, sperm count is not the only number that matters. Sperm quality, such as the size and shape of the sperm and the quality of the DNA they carry, are also factors that have been linked to male infertility. These recreational drugs may affect your fertility, especially if you are struggling with infertility. Here’s a list of common drugs and their known effects on fertility:

  • Tobacco smoke: Lowers sperm count among men who smoke and possibly men who breathe secondhand smoke.
  • Alcohol: Lowers testosterone levels, causes erectile dysfunction, and decreases sperm production. Liver disease caused by excessive drinking may lead to fertility problems as well.
  • Cocaine and marijuana: May temporarily reduce the number and quality of sperm.Long-term use of marijuana may result in low sperm count and abnormally-developed sperm.
  • Steroids: Anabolic steroids taken to stimulate muscle strength can cause the testicles to shrink and sperm production to significantly decrease.

Treatment

If you think recreational drug use might be the reason for your infertility, you should talk to your doctor about possible treatments. In many cases, gonadotoxic effects are reversible once exposure to the toxin is eliminated (in this case, once recreational drugs use has ceased). Your doctor may, however, recommend additional treatments, to help improve these and additional adverse effects of recreational drugs such as erectile dysfunction, or decreased testosterone, among others.