Stem cells are the body’s fundamental, unspecialized cells. They have the ability to self-renew, dividing almost indefinitely to create more cells like themselves. They can also differentiate, or mature, into many different types of specialized cells, such as nerve, blood, or bone cells. This dual capability makes them the subject of regenerative medicine, a field focused on replacing or repairing damaged tissues and organs. Stem cell injections deliver these restorative cells directly to an injury site to encourage the body’s natural healing processes.
Autologous Versus Allogeneic Sources
A primary distinction in stem cell therapy is the source of the cells relative to the patient. Autologous stem cells are harvested directly from the patient’s own body, processed, and then returned to the same individual. The main advantage is the complete absence of immune rejection, eliminating the need for immune-suppressing drugs. However, this approach requires a separate harvesting procedure, and cell quality may be compromised in older or ill patients.
Conversely, allogeneic stem cells are sourced from a donor, which can be a related or unrelated healthy person. This approach allows for “off-the-shelf” availability because the cells can be harvested, banked, and prepared in large quantities for multiple patients. Allogeneic therapy is necessary when a patient’s own cells are unhealthy, such as in cancer, or when a readily available source is needed for urgent treatment. The main drawback is the risk of immune rejection, requiring careful tissue matching and sometimes immunosuppressive therapy.
Harvesting Stem Cells from Adult Tissues
Adult stem cells are primarily obtained from two tissues for use in autologous procedures. Bone Marrow Aspirate (BMA) is a common source, typically harvested from the posterior iliac crest (the hip or pelvic bone) using a specialized needle. This aspirate contains a mix of cells, including Hematopoietic Stem Cells (HSCs) that form blood cells, and Mesenchymal Stem Cells (MSCs) that can differentiate into bone, cartilage, and fat cells. BMA has a long history of clinical use supporting its application in regenerative therapies.
Adipose tissue, commonly known as body fat, is the other major adult source for autologous stem cells. This material is collected through a minimally invasive liposuction procedure, often from the abdomen or lower back. Adipose tissue is recognized for its high concentration of Mesenchymal Stem Cells, often being more abundant here than in bone marrow. The cells derived from fat are often considered younger and healthier because they reside in a less metabolically active environment.
A third, less common method involves drawing stem cells from the peripheral blood, a process that usually targets HSCs. To increase the number of circulating stem cells, a donor is first injected with a growth factor, such as granulocyte-colony stimulating factor (G-CSF). Once mobilized from the bone marrow into the blood, the cells are collected using apheresis. This procedure filters the blood through a machine that separates the stem cells before returning the remaining components to the patient.
Perinatal Sources and Their Unique Advantages
Perinatal tissues, collected at the time of birth, offer a potent and non-invasive source of allogeneic stem cells. These tissues include the umbilical cord blood and tissue, the placenta, and the amniotic fluid. Collection occurs after the baby is born, meaning they are typically considered medical waste and pose no risk to the mother or newborn.
Umbilical cord blood is rich in young Hematopoietic Stem Cells, which have been used for decades to treat blood disorders. The umbilical cord tissue, particularly the Wharton’s jelly, is a dense source of Mesenchymal Stem Cells. These young cells have a high degree of multipotency and are less likely to provoke an immune response in a recipient compared to adult-derived allogeneic cells.
Amniotic fluid and the placenta also contain various types of stem cells, sharing characteristics of both embryonic and adult cells. The use of these tissues provides a consistent supply of youthful cells that are less exposed to environmental factors and disease, making them a valuable resource for allogeneic banking and therapy. These sources bypass the need for an invasive collection procedure on the patient, offering a ready-to-use option for physicians.
Processing and Preparing Cells for Injection
Once the stem cell material is harvested, it must undergo several laboratory steps before injection. The first step is cell isolation, which separates the desired stem cells from the surrounding tissue, such as blood cells, fat, or bone marrow components. For tissues like fat, this often involves using enzymes to digest the structural connective fibers, leaving the cells in a fluid mixture.
The next step is concentration, where the isolated cells are processed using a centrifuge, which spins the mixture at high speeds. This process separates components by density, creating a concentrated layer of stem cells that can be isolated to achieve a therapeutic dosage. This ensures that a sufficient number of cells are present in the final injection volume to maximize the regenerative effect.
Before final preparation, quality testing is performed to ensure the product is safe and viable. This testing includes assessing the cell count, viability, and purity of the stem cell population, along with screening for infectious agents. The final step involves suspending the concentrated, tested cells in a sterile solution, such as saline or platelet-rich plasma, to create the final injectable product for administration.