STEM CELL RESEARCH

Stem Cell Research

Outline

INTRODUCTION3

IDENTIFICATION AND APPLICATION4

STEM CELL MARKERS AND STEM CELL FUNCTION5

IDENTIFYING STEM CELLS IN A MIXED POPULATION OF CELLS6

APPLICATION OF OTHER STEM CELL PROPERTIES7

CONCLUSION8

Stem Cell Research

Introduction

Stem cells are unspecialized cells that possess properties such as self—renewal, high potential for proliferation, and the ability to become a variety of cell types in the body. Self—renewal is the process of generating more stem cells. Differentiation is the process of becoming different cell types. Embryonic stem cells are isolated from very early stage embryos that possess the ability to develop into all different cell types in an individual. Adult stem cells, in contrast, are isolated from specific tissues that can only differentiate into cell types in that specific tissue under normal conditions. However, in rare occasions, the adult stem cells can become cell types of other tissues—a phenomenon known as trans-differentiation (Shi, 2008, 55).

Markers of sternness are special properties and molecular signatures that distinguish stem cells from other differentiated cell types in the body. Many growth factors and signaling molecules in the body regulate the specific gene expression pattern. The molecular signature of stem cells is commonly identified by the gene microarray method to globally assess the gene expression pattern of stem cells and differentiated cells at different stages.

Identification and Application

Stem cell markers are gene expression products that are uniquely related to stem cells. They are typically proteins or carbohydrates that are specifically expressed in stem cells. These markers are relatively specific and are usually expressed at a low level or are not expressed at all in terminal differentiated cells. However, most of the stem cell markers are not expressed exclusively in stem cells: Some of the stem cell markers are also expressed on many other differentiated cells in various tissues, and in tumor stem cells at different levels.

So far, more than 100 stem cell markers have been identified in different tissues or at different stages of development, but the functional roles of most stem cell markers are not clear.

Stem cell markers play a very important role in scientific research. Antibodies to stem cell markers are the most commonly used tools for the initial identification of stem cells in the tissue. Antibodies to stem cells are generated by immunizing animals with proteins associated with stem cell markers. Fluorescence—labeled antibodies to stem cell markers are used to identify stem cells or localize the stem cell niche—an area enriched for stem cells. Several antibodies to stem cell markers can be used in combination to define different types of stem cells based on differential expression of these markers.

Stem Cell Markers and Stem Cell Function

The criteria used to define the stem cell markers and the functional roles of the identified stem cell markers are heavily debated issues in stem cell research. The stem cell functional assay is a more reliable method for testing whether or not isolated cells are stem cells. Stem cell functional assays include in vitro cell proliferation and differentiation assays, as well as an in vivo assay ...