From Humors to Stem Cells

Posted by: Laurie Fish on July 25, 2011 at 12:11AM
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The Humors of Hippocrates

If you lived any time between 370BC and the late 19th century much of your medical treatment would have been influenced by the writings of Hippocrates. Hippocrates believed there were four humors that would cause dis-ease when out of balance. The idea that four humors - blood, black bile, yellow bile and phlegm caused all matter of maladies was born in Ancient Egypt. The Greeks refined the theory that would dominate medical treatment until 1868 when a brilliant German doctor named Rudolf Virchow published his theories of cellular pathology. As Hippocrates holds the title of 'father of modern medicine', Virchow has the honor of being considered the 'father of modern pathology.

The Birth of Microscopy Reveals a New Life Science

It was a lens grinder named Sacharias Janssen however, who has been credited for inventing the microscope which in turn allowed Virchow, and many others, to formulate and advance their theories. Invented in 1590, it was not until 1644 that the use of a microscope brought living tissue into focus. For the first time physicians could catch a glimpse of the inner workings of the human body. This shift in perspective provided fertile ground for new ideas and exploration. Though rudimentary and primitive, early microscopes gave way to a host of discoveries.

Fast Forward

Over time the microscope was refined. We discovered the root cause of many diseases and developed new diagnostic tools. We began to understand enough about the immune system to create vaccines and fight pathogenic bacteria and viruses. We learned more about our cellular composition. The human body was no longer a divine mystery but rather an extraordinary set of organic processes all leading to the smallest of all components - the cell.

Cells From Which all Others Stem

Which brings us to a Russian histologist by the name of Alexander Maksimow; a renowned scientist who, in 1908, first coined the term – stem cells. Maximow provided evidence proving that lymphocytes of the blood and lymph nodes are undifferentiated cells. Sixty years and two Canadian scientists later, we discovered self-renewing cells in the bone marrow of mice (James Till and Ernest McCulloch). Further advancement led to isolating haematopoietic stem cells (stem cells that produce blood cells) in human cord cells and eventually, in 1998, James Thomas and his team at the University of Wisconsin – Madison, derived human embryonic stem cells. It’s a brave new world.

Human Stem Cell Research

Human stem cell research holds the promise of less invasive medical treatments. In the most basic terms, stem cells are undifferentiated cells with the potential to divide endlessly. Primitive stem cells, those derived from human embryos, are considered plurapotent, and can differentiate into any of the several hundred cell types in the human body. The Rosetta stone of human cells, embryonic stem cells can be manipulated with biological building materials turning them into specific differentiated cells. Scientists are attempting to expand their use to repair damaged organs, fight disease and generate healthy tissues to grow replacement organs and cure cancer. Over 70 disorders have been identified as candidates for stem cell therapy.

Embryonic Stem Cells

At 3-5 days after fertilization, the entire embryo consists of 100-150 cells. Cell lines are derived from these. Stem cell lines are families of self regenerating cells grown from a single parent group. Once a stem cell line is established it is essentially immortal. The researcher will not have to go through the rigorous process necessary to isolate stem cells again. A cell line can be grown in the laboratory indefinitely and may be frozen for storage or distribution to other research labs. The most flexible are harvested from human embryos. Processing embryonic stems cells is more difficult than other stem cells. They also have the annoying tendency to cause tumor formations. For this reason, they cannot be used for transplantation. But this is not the only source of stem cells. Stem cells derived from umbilical cord blood hold a great deal of promise as do the use of adult stem cells. Though not as versatile as the embryonic stem cell, these alternatives eliminate the controversy around the destruction of embryos.

Adult Stem Cells

Adult stem cells are rare and hard to isolate. You have probably read about adult stem cells found in bone marrow. Though limited, they can replace cells that die because of injury or disease. Only an estimated 1 in 10,000 cells in bone marrow is a hematopoietic, or a blood forming stem cell. These are called HSCs. The primary role of HSCs is to replace blood cells. HSCs are constantly being generated in the bone marrow where they differentiate into mature types of blood cells. No one knows the origin of adult stem cells. Some speculate that stem cells are somehow set aside during fetal development and restrained from differentiating. The list of adult tissues reported to contain stem cells is growing and includes bone marrow, peripheral blood, brain, spinal cord, dental pulp, blood vessels, skeletal muscle, epithelial of the skin and digestive system, cornea, retina, liver, and pancreas. Adult stem cells are useful as autotransplants. For example, tissue donated to oneself after a heart attack or cancer treatment.

Banking on Stem Cells

Today, parents can bank their infant's umbilical cord blood. The umbilical cord and placenta are a rich source of stem cells. Heather Brown of the Cord Blood Registry was interviewed by Questional a few months back. She explains the process: "Typically, an OB physician would collect the cord blood within five or ten minutes after birth using a specialized collection kit ... On average, about 60 or 70 milliliters or about a half a cup of blood is collected at birth." These stem cells provide a rich resource for many illnesses that may occur in the individual's lifetime. Stem cells harvested from cord blood was first introduced as a therapy in 1983. They have been playing an important and growing role in the treatment of life-threatening blood diseases. Cord blood preservation may become as common as setting up that college fund or buying those government bonds.

Refining Stem Cell Treatments

It's hard to keep pace with the research. A team at Harvard successfully created embryonic stem cell-like cells from adult stem cells. Returning adult stem cells to an embryonic state unlocks the possibility of using an individual's own undifferentiated stem cells for tissue or organ growth. Given that the donor is the patient himself, there would be no threat of rejection. Presently stem cell therapy is used in the treatment of Juvenile Macular Dystrophy, blood disorders, Diabetes, immunodeficiency syndromes, congenital disorders of metabolism, ALS to name a few.

Wired magazine featured an article outlining an advancement in reconstructive surgery. The article by Sharon Begley entitled '100% Natural – Who needs implants?' discusses the use of stem cells in breast reconstruction. Surgeons are using stem cells derived from fat cells to rebuild breast tissue. In pediatric research, Dr. Deepak Srivastava, a pediatric cardiologist, is working on building healthy heart valves. On a biodegradable scaffold a structure of a valve is created and seeded with stem cells. These valves will be used to replace defective valves in infants. It seems there's nothing these little guys can't do.

I'll admit I want my kids to have the advantage of tapping into their stem cell super repair kit to extend their lives. I want to be able to grow a new set of lungs if mine give out. But I can't help but wonder what the dark side of this research looks like. Lines are easily crossed to pursue cures. This is big business. When billions of dollars can be made, ethical boundaries are tested. Review the freakish side of 20th century medical research.