Stem Cells Need Sleep, Too
Sleep is important for our body. With modest sleep deprivation it can be a struggle to function at our highest level and long term sleep deprivation, or disruption, can have significant health effects. It turns out that your sleep deprivation may also impact others…....if you are donating your hematopoietic stem cells.
Hematopoietic stem cells, also known as blood stem cells, are responsible for giving rise to the cells of our blood and immune system and are the key “ingredient” in bone marrow transplants, a cellular therapy that was pioneered over 50 years ago. The transplantation of bone marrow or hematopoietic stem cells is now routinely used to treat patients with blood cancers such as leukemia or lymphoma and disorders of the immune system. According to the American Society for Blood and Marrow Transplantation, approximately 24,000 patients world-wide are annually transplanted with donor blood stem cells.
There are many critical steps in a bone marrow or stem cell transplant between a donor and recipient (known as an allogenic transplant):
- Bone marrow or stem cells from an immunologically matched donor are harvested.
- The recipient’s immune system is “conditioned” to receive the donor cells.
- Transplanted donor stem cells migrate to the bone marrow - the vascular space inside the bone and home to hematopoietic stem cells.
- Donor stem cells engraft in the recipient bone marrow and begin to proliferate to generate the cells that enter the circulation and help restore the patient’s blood and immune system.
- Even a partial failure in one of these steps can threaten the success of the transplant.
It turns out that sleep may also be a critical factor in transplant success. A team of scientists from California and Israel used mice to test the effect of sleep on stem cell transplantation. When mice were sleep-deprived, the ability of their stem cells to restore the blood and immune system of a recipient mouse was dramatically decreased. Not only were there fewer transplanted cells found in the circulation, but there were also fewer donor cells in the bone marrow of transplanted mice.
How does sleep deprivation affect hematopoietic stem cell function? Part of the answer appears to be that the “sleepy cells” were functionally impaired (sound familiar?). Hematopoietic stem cells from the sleep-deprived mice were shown to have genetic changes that inhibited their migration. When these genetic changes were experimentally corrected, the “sleepy cells” were able to migrate normally thus demonstrating that the genetic changes were important for stem cell migration.
Growth hormone may be another part of the answer. Known to be regulated by sleep, growth hormone was linked to the same genetic changes seen in the “sleepy” stem cells thus suggesting that growth hormone was the link between the lack of sleep and the genetic changes.
We all know from our own experience that sleep is important, but how it affects cell function is a fundamental question and the subject of ongoing scientific inquiry. This research adds an important new and underappreciated dimension to stem cell research and their clinical use.