Stem cells are foundational cells with the ability to develop into many different cell types in the body, making them a focus of medical research. The process of preserving these cells by freezing them at extremely low temperatures is known as cryopreservation. This technology allows for the long-term storage of stem cells, ensuring they are available for future medical treatments and research. Banking these cells separates the time of collection from the time of use, which has revolutionized aspects of medicine.
Understanding Stem Cell Cryopreservation
Cryopreservation is a process designed to store cells at ultra-low temperatures, around -196°C, while maintaining their viability. The primary biological hurdle in freezing any living cell is the formation of ice crystals. As water within the cells freezes, it expands, and the resulting ice crystals can rupture the cell membrane, leading to cell death. To counteract this, scientists use substances called cryoprotectants.
Cryoprotective agents like dimethyl sulfoxide (DMSO) and glycerol are used for cell preservation. They work by penetrating the cells and replacing some of the water. This lowers the freezing point and prevents the formation of large, damaging ice crystals, ensuring the internal structure of the stem cells remains intact.
Two primary techniques are used for freezing stem cells: controlled-rate slow freezing and vitrification. In controlled-rate freezing, the sample’s temperature is gradually lowered at a precise rate, often 1–2°C per minute. This slow reduction allows water to move out of the cells before it can freeze and cause damage, after which the sample is moved to long-term storage.
Vitrification is a method of ultra-rapid cooling. Stem cells are exposed to a higher concentration of cryoprotectants and then cooled so quickly that water molecules do not have time to form ice crystals. Instead, the sample solidifies into a glass-like, amorphous state. While vitrification can result in high cell survival rates, the high concentrations of cryoprotectants can sometimes be toxic to the cells.
Key Sources and Uses of Banked Stem Cells
Stem cells for cryopreservation can be harvested from several different sources. Umbilical cord blood, collected from the umbilical cord and placenta after birth, is a source of hematopoietic stem cells (HSCs). These cells, which form blood and immune cells, are less likely to be rejected by a recipient’s body because they are immunologically naive.
Bone marrow is another established source of HSCs and has been used in transplants for decades. Adipose, or fat, tissue has been identified as a source of mesenchymal stem cells (MSCs), which can differentiate into bone, cartilage, and fat cells. Researchers are also exploring other sources, such as dental pulp from baby teeth, as a way to obtain MSCs.
The therapeutic applications of banked stem cells are extensive. HSCs from cord blood and bone marrow are used in transplants to treat blood disorders like leukemias and lymphomas, as well as certain genetic and immune system diseases. These transplants can replenish a patient’s supply of healthy blood-forming cells after they have been destroyed by chemotherapy or radiation.
Beyond these established treatments, cryopreserved stem cells are used in regenerative medicine research. Scientists are investigating their potential to repair damaged tissues and organs. Promising areas of study include using MSCs to treat heart disease, developing new therapies for diabetes, and addressing neurological conditions like Parkinson’s disease and spinal cord injuries.
Navigating Stem Cell Banking Options
Stem cell banks are facilities responsible for the processing, testing, and long-term cryopreservation of stem cell units. When considering stem cell banking, individuals are faced with two primary models: public donation banks and private family banks. Each option serves a different purpose.
Public cord blood banks operate on an altruistic donation model. When a parent donates their baby’s cord blood to a public bank, the unit is made available to any matching patient in need of a stem cell transplant. There is no cost to the donor for this service, but the donated unit is not reserved for the donor’s family.
Private, or family, stem cell banks offer a service where families pay to store their baby’s cord blood or other stem cells for their own potential use. The primary advantage is that the stem cells are reserved exclusively for the donor or their close family members. The costs associated with private banking can be significant, involving an initial processing fee and an annual storage fee.
When selecting a private bank, it is important to consider several factors to ensure the quality and security of the stored cells.
- Accreditation from organizations like the AABB (Association for the Advancement of Blood & Biotherapies) or the Foundation for the Accreditation of Cellular Therapy (FACT), which indicates high standards.
- The bank’s specific processing and storage methods.
- The security of the storage facility.
- The company’s long-term financial stability.
Thawing and Utilizing Stored Stem Cells
When a cryopreserved stem cell unit is needed, it must undergo a controlled thawing process. The goal is to warm the cells rapidly to minimize the formation of ice crystals as the sample transitions from a solid to a liquid state. This is done in a water bath set to a specific temperature, often around 37°C. The timing is precise to prevent damage to the cells.
Once thawed, the stem cells undergo quality control tests to ensure they are viable and functional. These assessments include a cell count to determine the total number of cells and viability assays to measure the percentage of live cells. These tests confirm that the cells have survived the freeze-thaw cycle and are suitable for their intended purpose.
For therapeutic use, the thawed and verified stem cells are administered to the patient through an infusion, similar to a blood transfusion. The cells are introduced into the patient’s bloodstream, from where they can travel to the bone marrow or other target areas to begin regeneration. In a research setting, thawed stem cells are cultured in a laboratory to study their biological properties or to test new therapeutic applications.
The overall success rate for cell survival after thawing is high but can be influenced by several factors. These include the initial quality of the cells, the specific cryopreservation technique used, and adherence to strict protocols during both freezing and thawing.