2The Stem Cell ConceptA stem cell is an undifferentiated, dividing cell that gives rise to a daughter cell like itself and a daughter cell that becomes a specialized cell type.
3What Is a Stem Cell? Unspecialized cells Give rise to more than 225 specialized cells in the bodyServe as the body’s repair systemRenew itselfReplenish other cells
4In Summary: Two Major Types of SC Mature Stem CellsEarly Stem Cellsa.k.a. Adult (includes umbilical cord & placenta)a.k.a. Embryonic; blastocysticCells obtained from specific mature body tissues, umbilical cord, placentaCells obtained from inner cell mass of a blastocystMultipotent — Give rise to multiple but limited cell typesPluripotent — Flexible, give rise to any cell type in the body
5What Are the Sources of Mature Stem Cells? Mature Body Tissues
6Stem Cells are Found in the Adult, but the Most Promising Types of Stem Cells for Therapy are Embryonic Stem Cells
7Where Are Early Stem Cells Found? Who did it first?In 1998, U. Wisconsin research team isolates stem cells from IVF-blastocysts5 days ofdevelopment
8The Inner Cell Mass is the Source of Embryonic Stem Cells The embryo is destroyed by separating it into individual cells for the collection of ICM cells.
13Additional Potential Dilemmas – Therapeutic Cloning to Obtain Matched Embryonic Stem Cells Cultured mouse embryonic stem cells.Cells from any source other than you or an identical twin present the problem of rejection.If so, how can matched embryonic stem cells be obtained?A cloned embryo of a person can be made, and embryonic stem cells harvested from these clones.
14Some Thorny Ethical Questions Are these masses of cells a human?Is it ethical to harvest embryonic stem cells from the “extra” embryos created during in vitro fertilization?
17Somatic Cell Nuclear Transfer (SCNT) Sometimes referred to as“therapeutic cloning”
18SCNT: Asexual Reproduction No sperm involvedTransfers nucleus from a mature cell into a donor eggRequires electric or chemical stimulus to begin dividingFunctionally different from regular fertilized egg
19What Should You Know About SCNT? Purpose:Find cures and therapies for diseasesAwaken the natural capacity for self-repair that resides in our genesPotential Results:Patients will receive own stem cells to treat diseaseNo need for donor matchLike transplantation, but without rejection
21What Should You Know About SCNT? No reputable scientist wants to clone human beingsSCNT stem cells are alive in a Petri dishUnless implanted in uterus, you can not generate a fetusEvidence suggests that SCNT stem cells may never develop into a human even when implanted
22The Biotechnology of Reproductive Cloning Even under the best of circumstances, the current technology of cloning is very inefficient.Cloning provides the most direct demonstration that all cells of an individual share a common genetic blueprint.
23Therapeutic CloningIs there any ethical difference between therapeutic and reproductive cloning?
24The Next Step? Highly unlikely. Attempts at human cloning are viewed very unfavorably in the scientific community.
26Both Kinds of SCR are Needed Mature Stem CellsEarly Stem CellsFirst isolated in 1960sFirst isolated in 199850+ years of research9 years of researchFederal Funding = >$2.7 Billion (FY02-06)Federal Funding = $132 Million (FY02-06)Results: 50+ human therapiesResults: Only in animal trials; No human trials