Stem cells are a unique type of cell within the body, distinguished by their ability to both self-renew and differentiate into various specialized cell types. This characteristic makes them a significant area of focus in biological research and holds promise for numerous medical applications, from understanding disease mechanisms to developing regenerative therapies. Unlike mature cells that have a fixed role, stem cells maintain a degree of plasticity, allowing them to contribute to tissue repair, growth, and the replacement of damaged cells throughout an organism’s life.
Obtaining Adult Stem Cells
Adult stem cells, also known as somatic stem cells, are found in various tissues throughout the body and are multipotent, meaning they can differentiate into a limited range of cell types within their tissue of origin. Harvesting these cells from a living donor involves several common procedures. One established method is bone marrow aspiration, a minor surgical procedure often performed under general anesthesia. During this process, a hollow needle is inserted into the hip bone to extract a quantity of bone marrow, which is rich in hematopoietic stem cells. The procedure takes about 60 to 90 minutes.
Peripheral blood stem cell collection, also known as apheresis, is another frequently used approach. This non-surgical process involves mobilizing stem cells from the bone marrow into the bloodstream. Donors receive daily injections of growth factors for several days before the collection to increase the number of stem cells circulating in their peripheral blood. The apheresis procedure itself is similar to blood donation; blood is drawn from one arm, passed through a machine that separates and collects the stem cells, and the remaining blood components are returned to the donor through a vein in the other arm. This collection can take two to five hours per session and may require multiple sessions over several days to gather enough cells.
Stem cells can also be isolated from adipose (fat) tissue, obtained through liposuction. This tissue contains mesenchymal stem cells, which have the ability to differentiate into various cell types, including bone, cartilage, and fat cells. After liposuction, the adipose sample is washed, minced, and then digested with enzymes to release the stromal vascular fraction (SVF), a heterogeneous cell population that includes the stem cells. The SVF is then centrifuged to separate the stem cells from other components, and these cells can be further cultured in a laboratory.
Collecting Cord Blood Stem Cells
Umbilical cord blood and placental tissue offer a non-invasive source of hematopoietic stem cells. The collection process occurs immediately after birth, once the umbilical cord has been clamped and cut, ensuring no risk to either the mother or the baby. A trained healthcare professional inserts a needle into the umbilical vein, allowing the blood to drain by gravity into a specialized collection bag.
This procedure is quick, lasting about 5 to 10 minutes, and is painless for both the mother and the newborn. The collected cord blood is then prepared for transport to a specialized laboratory. There, it undergoes processing, which may involve separating the stem cells from other blood components, before being cryopreserved for long-term storage. This cryopreservation allows for the potential future use of these stem cells, for example, in treating certain diseases or for regenerative medicine applications.
Sourcing Embryonic Stem Cells
Embryonic stem cells (ESCs) are derived from the inner cell mass of an early-stage human embryo, specifically at the blastocyst stage. At this stage, the inner cell mass is the cluster of cells that will eventually give rise to all the tissues and organs of the developing fetus.
The process of obtaining ESCs involves isolating this inner cell mass from the blastocyst. This can be achieved through methods such as microsurgery or immunosurgery. Once isolated, these cells are then cultured in a laboratory setting on a layer of feeder cells and supplied with specific nutrients and growth factors to encourage their proliferation while maintaining their undifferentiated state. These embryos are those created for in vitro fertilization (IVF) that are not used for reproductive purposes, and their use for research requires donor consent.
Generating Induced Pluripotent Stem Cells
Induced pluripotent stem cells (iPSCs) represent a significant advancement in stem cell technology, as they are generated in the laboratory rather than directly harvested from the body or embryos. This process involves genetically reprogramming adult somatic cells to revert to an embryonic-like pluripotent state. Specific “reprogramming factors”—a set of transcription factors—were identified that could achieve this transformation.
These factors are introduced into the adult cells using various methods. Once inside the cell, these factors work to activate pluripotency-associated genes and suppress genes characteristic of the original somatic cell. The reprogramming process allows the adult cells to acquire the ability to self-renew and differentiate into any cell type in the body, similar to embryonic stem cells. This technology offers a source of patient-specific pluripotent cells, which can be used for disease modeling, drug discovery, and the development of personalized regenerative therapies without the ethical considerations associated with embryonic stem cells.