Stem Cells and Regenerative Medicine BACKGROUND For centuries, scientists have of missing parts known that certain animals can regenerate bodies humans are not capable of regenerating limbs, our their bodies. Although constantly regenerating blood, skin, and other tissues. The identity of these cells that allow us to do this was first discovered in the 1950s. These cells, called stem cells, bone come from our bone marrow, and their discovery led to the development of the regenerate marrow transplant. For the first time in medicine, it became possible to damaged tissue. to However, regeneration of body tissue is no easy task. For stem cells regenerate bone a tissue, they must be able to differentiate into the exact cell type needed. A5 similar cells marrow transplants became a huge success, scientists sought to identify within the embryo. Early studies had shown that cells of an embryo are capable of differentiating into any cell type in the human body, so scientists began extracting until embryotic stem cells from mice in the 1980s. They were met with little success 1998. A group of scientists from the University of Wisconsin-Madison became the first were able to group to successfully isolate human embryonic stem cells. These cells unspecialized for long periods of time all while maintaining the ability to transform into any type of cell: nerve, gut, muscle bone, etc. remain WHAT IS A STEM CELL? Although there are over 200 types of cells in the human body, each one of those cells can be tracked back to a fertilized egg, which becomes an embryo. An embryo has a whole arsenal of stem cells, which can specialize or differentiate to carry out a specific function of the body, which is how you were able to grow into the person you are today. Over the last two cells has immersed the decades, the study of stem scientific ability the differentiation process. This have gradually Scientists discovered community. to differentiate into the exact cell type needed has made the study of stem cells a talking point in the field of medicine. TYPES OF STEM CELLS Not all stem cells function equally. There are two main categories of stem cells: pluripotent stem cells (embryonic stem cells and induced pluripotent stem cells) and nonembryonic/somatic stem cells commonly called "adult" stem cells, Pluripotent describes the cell's ability to differentiate into cells from all three embryonic germ layers-mesoderm, endoderm, and ectoderm. All specialized cells are derived from one of these germ layers. Adult stem cells are not differentiated but are found in differentiated tissues. However, they are still self-renewing; they just don't have the potential to renew into a different cell type. Scientists were able to reprogram an adult ability to differentiate into any cell type. These reprogrammable adult cells are called an induced pluripotent stem cell (iPSC). IPSCs are formed by introducing transcription factors (Oct4, Sox2, KIf4, and CMyc) used in embryonic development into a mature adult somatic cell (non-reproductive cell). These transcription factors reprogram the somatic cell into a embryonic stem cell state by forcing the cell to express genes needed for maintaining embryonic stem cell cell with the characteristics. Endoderm Thymus Thyroid, parathyroid glands Larynx, trachea, lung Urinary bladder, vagina, urethra Gastrointestinal (GI) organs (liver, pancreas) Lining of the GI tract Lining of the respiratory tract Bone marrow (blood) Mesoderm Adrenal cortex Lymphatic tissue Skeletal, smooth, and cardiac muscle Connective tissues (bone, cartilage) Urogenital system Heart and blood vessels Skin Ectoderm Neural tissue Adrenal medulla Pituitary gland Connective tissue of the head and face Eyes, ears 71 stem Cells andPartners Regenative Mediche 11.o © university Lab 2022 STEM CELLS IN RESERCH Stem cells offer a whole new avenue for scientific research beyond regenerative medicine. Stem cells provide research tools to study human development, genetic mutation, environmental impact on cellular systems, disease modeling, and infectious cells In addition, stem cells play a large role in drug discovery. Normal from a extracted from a patient can only replicate a set number of times. iPSC derived patient can replicate indefinitely. Potential drug therapies can be applied to the diseases, patient's cells to determine an effective and efficacy drug strategy for cancer treatments, Stem Cells in the Lab MICROENVIRONMENT Stem cells are grown in an artificial, physiologically controlled environment through laboratory methods know as cell culturing. Unlike other cells lines that are isolated from tissue or are comprised of a single cell type, stem cells require to be grown in conditions that mimics the in vivo stem cell microenvironment. Initially, "feeder cells' (cells that cannot divide but provide growth factors, adhesion molecules, and extracellular matrix) were used to recreate the in vivo microenvironment. The most widely used feeder cells to support stem cells are mouse embryonic fibroblasts (MEFs) Today technology provides researchers the ability to grow stem cells without feeder cells. Stem cell media are now "complete media" containing the required growth factors needed to maintain the proper microenvironment. Growing stem cells in aggregates or "colonies" also recreates the vital cell-to-cell interactions, growth factors, cell to matrix interactions, and extracellular scaffolding needed to maintain their key characteristics of self-renewal and pluripotency. Stem cells on a feeder layer (MEF) Feeder free stem cells DIFFERENTIATION By changing the become chemical and physical environment, stem cells will begin to more specialized or in other words differentiate. When 3 cell differentiates, it undergoes major changes in its size, shape, metabolic activity, and overall function, Since all cells of DNA that Is of ell the only that each type DN4, same portions *reads" contaln will relevant to its own function. For a cell to differentiate into a specific cell type, it express specific genes and proteins while other genes are proteins remain silent. MORPHOLOGY Stem cells have a defined a defined morphology (cell appearance and shape). Healthy stem cells have bright dense, tightly packed shape with and a a defined, refractive boundary, high nucleus to cytoplasm ratio. Differentlated cells with have undefined boundaries, heterogenous centers, and loosely packed cells. Tightly packed shape Defined, refractive boundary High nucleus to cytoplasm ratio PASSAGING The stem cells microenvironment is maintained through daily media exchanges. Stem cells are ready to passage (removal from growth vessel) when the colonies are large, tightly packed, have large nucleus-to-cytoplasm ratio with minimal/no differentiation. Victronectin is a common glycoprotein found in extracellular matrix (materials between cells) and is usedto promote stem cell attachment and spreading.
