Umbilical cord blood, collected at birth, is a rich source of hematopoietic stem cells (HSCs) that can be cryopreserved for potential future medical use. This resource is often banked to provide a treatment option for the child or a family member if a life-threatening disease arises decades later. The question of what happens to the cord blood after 18 years centers on the science of long-term storage. Scientific consensus demonstrates that cord blood units, when processed and stored correctly, retain their full therapeutic potential well into a person’s adulthood.
The Blood’s Journey Halted
The stem cells within a stored cord blood unit enter a state of suspended animation through cryopreservation. This method involves freezing the cells to ultra-low temperatures, typically around negative 180 degrees Celsius or colder, using vapor-phase liquid nitrogen. At this temperature, all metabolic and biological activity ceases, halting the cellular aging process. Studies have demonstrated that cord blood stem cells remain viable and potent after more than two decades of storage, with some tests showing stability even after 27 to 29 years.
This state contrasts profoundly with the dynamic, constantly renewed blood circulating within the 18-year-old individual. The adult hematopoietic system, primarily in the bone marrow, replaces billions of blood cells daily. For example, red blood cells circulate for about 120 days, and platelets have a lifespan of only 9 to 12 days. The body’s circulating blood is in a continuous state of turnover, while the banked cord blood unit remains exactly as it was the day it was collected.
Blood’s Main Functions and the Circulatory System
The stored cord blood contains a concentration of hematopoietic stem cells (HSCs), the building blocks of the entire blood and immune system. These specialized cells differentiate into every type of mature blood cell, including red blood cells, white blood cells, and platelets. The primary function of the cryopreserved unit is to act as a therapeutic resource for a stem cell transplant. This procedure treats over 80 conditions, such as leukemias, lymphomas, and inherited disorders of the blood and immune system.
If the 18-year-old requires the unit, the transplanted HSCs migrate to the bone marrow to repopulate the body with a new, healthy blood and immune system. The circulatory system transports oxygen, nutrients, and immune cells throughout the body. The power of the stored stem cells lies in their capacity to repair or replace a damaged or diseased hematopoietic system. Restoring the function of the circulatory system’s cellular components relies entirely on the long-term viability of the cryopreserved cells.
The Science of Aging in Circulating Blood
While the banked cells are preserved, the circulating blood of the 18-year-old has undergone significant biological changes over nearly two decades. As the individual ages, the composition of plasma proteins gradually changes, which can be linked to the onset of age-related conditions. The body’s constant renewal process is imperfect, and the cumulative effects of environmental factors and cell division begin to appear.
Red blood cells circulating in the adult body experience metabolic shifts as they age, such as alterations in the arginine pathway that influence nitric oxide production and blood flow. These changes create a molecular signature of aging detectable even in a healthy person’s blood. The hematopoietic stem cells in the adult bone marrow are also subject to the wear and tear of time and replication. This contrast highlights the value of the banked unit as a source of “biologically young” cells.
Telomeres and the Aging Process – A Comparative Look
A direct comparison between the adult’s circulating blood and the banked cord blood is the length of telomeres, the protective caps on the ends of chromosomes. Telomeres in newborn cord blood are at their longest, and they shorten with every cell division, acting as a biological clock. The cryopreserved stem cells retain this original, maximum telomere length because cell division is suspended during freezing.
In the 18-year-old’s body, leukocytes (white blood cells) have experienced significant telomere attrition since birth. The most rapid shortening occurs in the first few years of life, but it continues throughout adulthood at an estimated rate of 26 to 43 base pairs per year. Therefore, the banked cord blood unit represents a source of stem cells with telomeres eighteen years longer than those currently circulating in the adult’s body. This “youthful” genetic material is an advantage for a future transplant, offering a fresh start for the patient’s new blood and immune system.