Stem cells are relatively ‘unspecialized’ cells that have the unique potential to develop into ‘specialized’ cell types in the body (for example, blood cells, muscle cells or nerve cells). They occur at all stages of human development, from embryo to adult, and in many tissues of the body. What are Stem Cells

General Properties of Stem cell Stem cells differ from other kinds of cells in the body. All stem cells (regardless of their source) have three general properties: They are capable of dividing and renewing themselves for long periods; They are unspecialized; They can give rise to specialized cell types.

Characteristics of Stem cells In some organs, such as the gut and bone marrow, stem cells regularly divide to repair and replace worn out or damaged tissues. In other organs, however, such as the pancreas and the heart, stem cells only divide under special conditions.

Where Are Stem Cells Found? Stem cells come from several sources in the body. The names of the cells below indicate the sources from which they are derived. Embryonic Stem Cells: These stem cells come from embryos in the early stages of development. They have the ability to differentiate into any type of cell in the initial stages of development and become slightly more specialized as they mature.

Fetal Stem Cells: These stem cells come from a fetus. At about nine weeks, a maturing embryo enters into the fetal stage of development. Fetal stem cells are found in fetal tissues, blood and bone marrow. They have the potential to develop into almost any type of cell.

Umbilical Cord Blood Stem Cells These stem cells are derived from umbilical cord blood. Umbilical cord stem cells are similar to those found in mature or adult stem cells. They are specialized cells that develop into specific types of cells.

Placental Stem Cells These stem cells are contained within the placenta. Like cord blood stem cells, these cells are specialized cells that develop into specific types of cells. Placentas however, contain several times more stem cells than do umbilical cords.

Adult Stem Cells These stem cells are present in mature body tissues in infants, children and adults. They may also be found in fetal and umbilical cord blood cells. Adult stem cells are specific to a particular tissue or organ and produce the cells within that particular tissue or organ. These stem cells help to maintain and repair organs and tissues throughout a person's life.

Hematopoietic stem cells: Hematopoietic stem cells (HSCs) are cells present in blood and bone marrow. They are capable of forming mature blood cells, such as red blood cells (the cells that carry oxygen), platelets (the cells that help stop bleeding) and white blood cells (the cells that fight infections). They give rise to the myeloid (monocytes and macrophages, neutrophils, basophils, eosinophils, erythroc ytes,megakaryocytes/platelets, dendritic cells), and lymphoid lineages (T-cells, B-cells, NK-cells).

Hematopoietic Stem Cell

Types of Stem Cell Totipotent Stem Cells These stem cells have the ability to differentiate into any type of cell in the body. Totipotent stem cells develop during sexual reproduction when male and female gametes fuse during fertilization to form a zygote. The zygote is totipotent because its cells can become any type of cell and they have limitless replicative abilities. As the zygote continues to divide and mature, its cells develop into more specialized cells called pluripotent stem cells.

Pluripotent Stem Cells These stem cells have the ability to differentiate into several different types of cells. Specialization in pluripotent stem cells is minimal and therefore they can develop into almost any type of cell. Embryonic stem cells and fetal stem cells are two types of pluripotent cells.

Multipotent Stem Cells  These stem cells have the ability to differentiate into a limited number of specialized cell types.  Multipotent stem cells typically develop into any cell of a particular group or type. For example, bone marrow stem cells can produce any type of blood cell. However, bone marrow cells don't produce heart cells.  Adult stem cells and umbilical cord stem cells are examples of multipotent cells.

Mesenchymal stem cells are multipotent cells of bone marrow that have the ability to differentiate into several types of specialized cells related to, but not including blood cells. These stem cells give rise to cells that form specialized connective tissues, as well as cells that support the formation of blood.

Oligopotent Stem Cells  These stem cells have the ability to differentiate into just a few types of cells.  A lymphoid stem cell is an example of a oligopotent stem cell. This type of stem cell can not develop into any type of blood cell as bone marrow stem cells can.  They only give rise to blood cells of the lymphatic system, such as T cells.

Unipotent Stem Cells – These stem cells have unlimited reproductive capabilities, but can only differentiate into a single type of cell or tissue. – Unipotent stem cells are derived from multipotent stem cells and formed in adult tissue. – Skin cells are one of the most prolific examples of unipotent stem cells. These cells must readily undergo cell division to replace damaged cells.

Stem cell and Diseases Stem-cell therapy is an intervention strategy that introduces new adult stem cells into damaged tissue in order to treat disease or injury.Stem cell research treats wider variety of diseases: – Cancer, – Type 1 diabetes mellitus – Parkinson's disease, – Spinal cord injuries, – Huntington's disease, – Multiple sclerosis, – Muscle damage, – Neurological disorders.

How stem cell treat various Diseases Tissue Repair Regenerate spinal cord, Heart tissue or any other major tissues in the body. Heart Disease Adult bone marrow stem cells injected into the heart arteries are believe to improve cardiac functions in victims of heart failure or heart attack. Haematopoitic stem cell treatment HPCs are used in the treatment of many malignant (e.g., leukemia, lymphoma) and non-malignant (e.g., sickle cell disease) diseases to replace or rebuild a patient's hematopoietic system. This type of treatment is called a bone marrow or stem cell transplant.

Overview of Stem cells to treat various disorders