Stem cells are self-renewing, unspecialized cells that can give rise to all of the 210 specialized cells in the body. Cells in the first two weeks of life in the newly-formed baby, at a developmental stage before the time that implantation would normally occur in the mother's uterus, are called embryonic stem cells. Differentiation is the process by which stem cells divide and form specialized cells that can perform special functions, such as blood stem cell formation or nerve cell transmission.

Stem cells may be totipotent, pluripotent, or multipotent. The fertilized egg or zygote and the first division into the two-cell blastomere are totipotent, meaning that its potential is total, each capable of growing into a human being. In fact, identical twins develop when the zygote or blastomere separate and form two individual, genetically identical human beings.

A few days after fertilization, a hollow sphere called a blastocyst is formed, the outer cells of which are called the trophoblast and form the placenta, and the inner cluster of cells are called the inner cell mass. The inner cell mass are known as the pluripotent stem cells, and these form the embryo. While they can form all 210 types of cells of the human body, they are unable to form a human being, because they lack the trophoblast which attaches to the uterus and forms the placenta.

The pluripotent stem cells undergo further specialization into stem cells that are committed to give rise to cells that have a particular function, such as nerve stem cells, or blood stem cells which produce red blood cells, white blood cells, and platelets. These more specialized stem cells are called multipotent.

Adult stem cells have been identified in many organs and tissues, including bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, dental pulp, brain and heart. Adult stem cells are multipotent and have the ability to self-renew, for they can make identical copies of themselves. They also can further differentiate into specialized cells. Bone marrow contains at least two kinds of stem cells: hematopoietic stem cells, which form all types of blood cells in the body, and mesenchymal stem cells, which form the stroma or supporting tissue for bone marrow, such as bone, fat, and cartilage (see image).

An allogeneic bone marrow stem cell transplant, where a donor who is genetically similar to the patient such as a brother or sister, is now employed to treat refractory cancers such as chronic lymphocytic leukemia unresponsive to standard chemotherapy. Hematopoietic stem cells and Mesenchymal stem cells from umbilical cord blood and bone marrow are promising new areas of stem cell research.

Adult Bone Marrow Hematopoietic and Mesenchymal Stem Cells, adapted from T Winslow and L Kibiuk,


The ethical concern in Stem Cell Research is the source of stem-cells. The use of stem-cells from newborn placental or umbilical cord blood or adult bone-marrows without loss of natural life is ethical.

The moral viewpoint is opposed to the creation of embryos by in-vitro fertilization or somatic cell nuclear transfer and then harvesting stem cells and destroying the lives of the most vulnerable human beings for the benefit of those already living. To command the death of others so that one's own life may be enhanced or prolonged is completely opposed to human rights. In effect, it is a form of cannibalism - killing a human being for the survival of another.

In the Gospel of Matthew 19:17-18 in the New Testament of the Bible, Jesus Christ himself said: "If you wish to enter into life, keep the commandments." When asked which ones, he referred to the Law of Moses (Exodus 20:13), "Thou shalt not kill." These ethical principles have practical significance, such as the production of vaccines, particularly with the world-wide distribution of the coronavirus Covid-19 vaccine.

The Vatican Congregation for the Doctrine of the Faith issued a statement on December 21, 2020 noting it is "morally acceptable" for Catholics to take vaccines against COVID-19. "The morality of vaccination depends not only on the duty to protect one's own health, but also on the duty to pursue the common good." The Pfizer and Moderna Covid-19 vaccines rely only on messenger ribonucleic acid (mRNA) from the virus itself and are deemed acceptable from a Catholic moral perspective. However, the Astra-Zeneca vaccine is clearly objectionable, for it is derived from embryonic cells from aborted tissue. The U. S. Conference of Catholic Bishops, as well as the Archdiocese of New Orleans, also expressed moral concern in a statement released March 2, 2021, urging people to seek alternatives to the newly-released coronavirus vaccine produced by Janssen Pharmaceuticals, because of its connection to aborted fetal cells. "If one can choose among equally safe and effective COVID-19 vaccines, the vaccine with the least connection to abortion-derived cell lines should be chosen. Therefore, if one has the ability to choose a vaccine, the Pfizer or Moderna vaccines should be chosen."

Furthermore, three scientific articles from Norway, Germany, and England published in the New England Journal of Medicine from April to June 2021 noted that the Astra-Zeneca vaccine employed in Europe is associated with the rare complication of life-threatening and even fatal blood clots. The most recent article from England documented 7 deaths in 23 patients. These reports have caused the vaccine to be suspended in several European countries.

As Pope John Paul II expressed in The Splendor of Truth, "it is never lawful, even for the gravest reasons, to do evil that good may come of it (Romans 3:8) — in other words, to intend directly something which of its very nature contradicts the moral order (the natural law), and which must therefore be judged unworthy of man."

The end never justifies the means!


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3 Coleman M (Ed). "Understanding Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma," Lymphoma Research Foundation, New York, October 2014.
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5 New American Bible, Revised Edition. Catholic Book Publishing, New Jersey, 2011.
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8 Pope John Paul II. The Splendor of Truth, the encyclical Veritatis Splendor, 80. Pauline Books & Media, Boston, 1993.
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10 Vatican News Agency: "Vatican Congregation for the Doctrine of the Faith says use of anti-Covid vaccines “morally acceptable," December 21, 2020 -
11 US Conference of Catholic Bishops. "Pfizer and Moderna Vaccines Ethically Preferable," Angelus News, March 2, 2021.
12 Andreas Greinacher MD and Others. "Thrombotic Thrombocytopenia after ChAdOx1 nCov-19 Vaccination," New England Journal of Medicine DOI: 10.1056/NEJMoa2104840, 384 (14) 2092-2101, June 3, 2021.
13 Nina Schultz and Others. "Thrombosis and Thrombocytopenia after ChAdOx1 nCoV-19 Vaccination," New England Journal of Medicine DOI: 10.1056/NEJMoa2104882, 384 (14) 2124-2130, June 3, 2021.
14 Marie Scully and Others. "Pathologic Antibodies to Platelet Factor 4 after ChAdOx1 nCoV-19 Vaccination," New England Journal of Medicine 384 (15), DOI: 10.1056/NEJMoa2105385, April 16, 2021.

Principles of Medical Ethics

Life Begins at Conception