Difference Between Stem Cells and Differentiated Cells

Main Difference – Stem Cells vs Differentiated Cells

Stem cells and differentiated cells are two types of cells that are involved in the cellular makeup of the body. Stem cells are continuously renewed throughout the lifetime of an organism. Due to the influence of transcription factors on stem cells, they are differentiated into morphologically and metabolically distinct cell types, specialized for a unique function. The main difference between stem cells and differentiated cells is that stem cells are the unspecialized cells which are capable of self-renewing and differentiating into mature cells while differentiated cells are specialized to perform a specified function in the body.

This article explains,

1. What are Stem Cells
      – Definition, Morphology, Types, Function, Examples
2. What are Differentiated Cells
      – Definition, Morphology, Types, Function, Examples
3. What is the difference between Stem Cells and Differentiated Cells

What are Stem Cells

Stem cells are the unspecialized cells found in the body, which are capable of self-renewing as well as differentiating into mature cells, specifying for specialized functions. In early embryo of humans, stem cells are found in the inner cell mass. Stem cells are also found in some tissues of the fetus, the placenta, and umbilical cord and in several adult organs of humans. More than one specialized cell types can be raised within a particular organ from the stem cells in adult organs. As an example, astrocytes, glial cells, and brain neurons are raised from neural stem cells. Some stem cells that differentiate into cells function in distinct places; this attribute is known as plasticity. On the other hand, multipotent stem cells are differentiated by forming multiple tissues.

Three types of stem cells can be identified during various development stages of organisms: embryonic stem cells, fetal stem cells, and adult stem cells. Stem cells, which are derived in the early stages of the embryo are referred to as embryonic stem cells (ESCs). The inner cell mass is composed of multipotent stem cells, which give rise to three germ layers: ectoderm, mesoderm, and endoderm. In the laboratory, this multipotent stem cells can be removed from the blastocyte in order to maintain their unspecialized stages as cell culture lines. These cell lines are used in medical therapies. The primitive cell types of the fetus are referred to as fetal stem cells, which are eventually developed into various unmatured organs like neural tube, heart, gut, liver, hormone-secreting glands, bones, face, skull and connective tissues. Hematopoietic stem cells are found in both fetal liver and blood as well as the placenta and umbilical cord. They give rise to multiple types of blood cells. Embryonic stem cells are shown in figure 1.

Figure 1: Embryonic stem cells

Undifferentiated cells, which can be found in differentiated tissues like bone marrow and brain in adults are referred to as adult stem cells. Adult stem cells self-renew throughout the lifespan of the adult by making identical copies of them. They are also capable of differentiating into specialized cells in the tissue. Other than bone marrow and brain, blood, liver, skin, dental pulp, eye, skeletal muscle, pancreas and gastrointestinal tract are the other sources of adult stem cells found in the body. Some adult cells are multipotent. Hemopoiesis, which is the process of differentiation of blood cells from the hematopoietic stem, cells is shown in figure 2.

Figure 2: Hemopoiesis

What are Differentiated Cells

Differentiated cells are specialized cells in order to perform a specified function in the body. These cells are morphologically distinct from their stem cells by size, shape and functionally distinct from metabolic activity, membrane potential, and responsiveness to signals. The mechanism of differentiation of stem cells is governed by the regulated gene expression. Each type of differentiated cells is defined by a particular array of transcription factors. During the early development of the embryo, the morula stage is developed into the blastocyte after 5-6 days to the fertilization. The blastocyte is separated of trophoblast, which is the outer cell layer and inner cell mass. The inner cell mass is composed of multipotent stem cells, which give rise to three germ layers: ectoderm, mesoderm, and endoderm. This process is called gastrulation. The differentiation of inner cell mass into three germ layers is considered as the first stage of differentiation. The three germ layers then differentiate into unmatured organs during the embryonic period.

Depending on the ability to proliferate, differentiated cells can be divided into three groups. Most of the differentiated cells in adults stay resting at G₀ phase. As a result of cell death due to various reasons like injuries, differentiated cells only resume proliferation. As an example, epithelial cells, skin fibroblasts, endothelial cells lining the blood vessels and smooth muscle cells are capable of proliferating after undergoing a tissue injury. In a wound, skin fibroblasts undergo rapid proliferation I order to repair the damage. The second group of differentiated cells usually divide rarely. As an example, liver cells are only stimulated to divide in order to replace the missing tissue after undergoing a huge loss of the cell number. The entire liver can be regenerated after the removal of two-thirds of the liver within a few weeks of time. Some nerve cells in the brain are also capable of proliferating. The third group of differentiated cells is incapable of proliferating. Differentiated cells like human cardiac muscle cells are developed and differentiated during embryonic period and retained throughout the life. Cardiac muscle cells are unable of being replaced either during the death of cardiac muscle cells or a heart attack. A differentiated neuron cell is shown in figure 3.    

Figure 3: A neuron cell

Difference Between Stem Cells and Differentiated Cells

Definition

Stem Cells: Stem cells are the unspecialized cells which are capable of self-renewing and differentiating into mature cells.

Differentiated Cells: Differentiated cells are specialized to perform a specified function in the body.

Proliferation

Stem Cells: Stem cells continuously proliferate throughout the lifetime of the organism.

Differentiated Cells: Some differentiated cells are capable of proliferating in a high rate, some are at a low rate and others are unable to proliferate.

Morphology

Stem Cells: Most stem cells are round in shape and small in size.

Differentiated Cells: Differentiated cells are morphologically distinct from their stem cells by size, shape, metabolic activity, membrane potential and responsiveness to signals.

Place of Action

Stem Cells: Stem cells grow and self-renew in the same place of the body, where they were derived.

Differentiated Cells: Some differentiated cells function in the same place they were differentiated and others function in a distinct location.

Examples

Stem Cells: Hematopoietic stem cells and the cells in bone marrow, brain, blood, liver, skin, dental pulp, the eye, skeletal muscle, pancreas and gastrointestinal tract are examples of stem cells.

Differentiated Cells: Epithelial cells, skin fibroblasts, endothelial cells lining the blood vessels and smooth muscle cells, liver cells, nerve cells and human cardiac muscle cells are examples of differentiated cells.

Conclusion

Stem cells and differentiated cells are found in the body of both plants and animals and play a vital role in both building and functioning of the body. Stem cells are the early-deriving cells of the embryo. The inner cell mass is differentiated into three germ layers, which are responsible for creating organs and tissues of the boy. Three types of stem cells can be found in different developmental stages of the body. They are embryonic stem cell, fetal stem cells, and adult stem cells. Some stem cells exhibit plasticity and some are capable of generating multiple types of differentiated cells. Differentiated cells are morphologically and metabolically distinct from their stem cells. Some differentiated cells also give up the ability to proliferate. Hence, the main difference between stem cells and differentiated cells is their morphology and functions in the body.

Image Courtesy:
1.”Human embryonic stem cell colony phase” By Id711 at English Wikipedia – Transferred from en.wikipedia to Commons by Sreejithk2000 using CommonsHelper. (Public Domain) via Commons Wikimedia
2. “1902 Hemopoiesis” By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
3. “415 Neuron” By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia

Reference:
1. National Research Council (US) and Institute of Medicine (US) Committee on the Biological and Biomedical Applications of Stem Cell Research. “Project Overview and Definitions.” Stem Cells and the Future of Regenerative Medicine. U.S. National Library of Medicine, 01 Jan. 1970. Web. 28 Mar. 2017.
2. Cooper, Geoffrey M. “Cell Proliferation in Development and Differentiation.” The Cell: A Molecular Approach. 2nd edition. U.S. National Library of Medicine, 01 Jan. 1970. Web. 28 Mar. 2017.