Part 4/10:
Dr. Hariri discusses the phenomenon of "stem cell exhaustion," which occurs as we age. From the abundance of stem cells present at birth, their numbers drop significantly over a lifetime. For instance, in bone marrow, about 1 in 20,000 cells is a stem cell in infants, while that ratio declines to about 1 in 20 million in older adults. This depletion is a critical factor in the aging process and has led researchers to investigate ways to replenish stem cell supply.