Do Now 11/18 Please copy the topics for Monday’s quiz, shown at right * Distinguish cilia, flagella, and pseudopodia, and identify their function. * Identify microtubules as the building materials of the cytoskeleton, cilia, flagella, and centrioles * Identify the function of the centrioles. * Distinguish animal, plant, fungi, and prokaryotic cells based on their cell wall structure. *Identify the two cell parts common to ALL cells *Identify the plant organelles vacuole, chloroplasts. * Define and apply stem-cell terms from today’s lesson.

Stem Cells Joseph G. Marx, PhD Baylor College of Medicine

Overview What is a cell? What is a stem cell? How do we get stem cells? What is the difference between embryonic and adult stem cells? Why are stem cells clinically important? Stem cells Photo: NIH Stem Cell Unit

What is a Cell? Cells are the fundamental, structural, and functional units of living organisms. All organisms except bacteria are made of cells in which the nucleus is surrounded by a membrane (eukaryotic cells). Eukaryotic cells contain DNA instructions for the entire organism. As cells specialize, only DNA related to the functions of a particular cell remains active. Cytoplasm DNA Nucleus

Cells: What Do They Really Look Like? Cells have dramatically different shapes and sizes. Muscle cells Kidney cell Nucleus

Genetic Flexibility Totipotent - a cell capable of giving rise to any of the cell types in the adult. In humans, the fertilized egg is totipotent until the eight-cell-stage. Pluripotent - a cell with the potential to generate cell types and tissues from the three primary germ layers of the body. Differentiation - cell specialization that occurs at the end of the developmental pathway. Plasticity - the ability of a cell of one tissue type to generate cells of another tissue type.

What is a Stem Cell? Unspecialized cells Able to self-renew without differentiating for extended periods of time Ability to differentiate into specialized cells Embryonic and adult stem cells are derived from different sources. TIME 2001 Human blastocyst showing inner cell mass and trophectoderm Photo: Mr. J. Conaghan

What is an Embryonic Stem Cell? Fusion of nuclei First cell division Only cells between the nuclei fusion and blastocyst stages are considered true stem cells. Blastocyst (~5-6 days old): a “pre-embryo” ball of cells which has not implanted in the uterus. Stem cells are harvested from the inner cell mass. By the latter stages of development in the fetus, cells already have “decided” which tissues they are to become. Placenta cell Stem cell

Embryonic Stem Cells are Derived from Blastocysts Fusion of nuclei First cell division Blastocyst (~5-6 days old) Stem cells are harvested from the inner cell mass. Undifferentiated stem cells are cultured (grown) in the laboratory. Placenta cell Stem cell

Adult Stem Cells Have two characteristics: They can make identical copies of themselves for the lifetime of the organism. They can give rise to differentiated mature cells with specific morphologies (shapes and functions). Adult stem cells are rare—and appear to help with homeostasis. Stem cells have been found in the brain and spinal cord, dental pulp, blood vessels, skeletal muscle, the digestive system, the cornea and retina, and the liver and pancreas.

Embryonic Stem Cells Can Become Any Tissue in the Body Blastocyst Cultured laboratory stem cells Scientific manipulations entice stem cells to become specialized tissues (blood, muscle, neuron, etc.). Blood cells Muscle cells Neuron (brain) cells Placenta cell Stem cell

What Diseases Could Be Impacted by Stem Cell Research? More than 100 million Americans suffer from diseases which might be alleviated by stem cell transplantation technologies. Examples include cardiovascular disease, autoimmune disease, diabetes, osteoporosis, cancer, Alzheimer’s disease and Parkinson’s disease. Stem cell treatment could potentially help patients with severe burns, spinal cord injuries, or birth defects. Types of Research Transplantation Therapeutic delivery systems Developmental studies Science (2000) 287:1423.