Sleep Deprivation Decreases Stem Cell Activity


We have all been there: You are at your computer, working hard and then a yawn hits you. Alternatively, you are on the phone late at night and you start to nod. We all have our late nights burning the midnight oil, but we need our shut-eye.

Now it turns out that sleep deprivation might wreak havoc with your stem cells. New research in mice might (let me emphasize, might) have profound implications for patients undergoing bone marrow stem cell transplants.

This research was led by Dr. Asya Rolls, who formerly worked as a postdoctoral research fellow at Stanford University, but is now an assistant professor at the Israel Institute of Technology.

With regards to the clinical implications of this work, Dr. Rolls said, “Considering how little attention we typically pay to sleep in the hospital setting, this finding is troubling. We go to all this trouble to find a matching donor, but this research suggests that if the donor is not well-rested it can impact the outcome of the transplantation. However, it’s heartening to think that this is not an insurmountable obstacle; a short period of recovery sleep before transplant can restore the donor’s cells’ ability to function normally.”

Rolls and her colleagues used laboratory mice for this study and broke them into two different groups. One group of mice was physically handled by members of the research team for four hours in order prevent them from going to sleep. The other group of mice were not handled and slept soundly in their cages. Then Rolls and her collaborators isolated bone marrow stem cells from the sleepless and well-rested mice. These bone marrow stem cells were then used to them to help reconstitute the bone marrow of twelve different mice that had been given radiation treatments that wiped out their bone marrow stem cells. It is important to note that these donor mice had bone marrow stem cells that glowed when put under a fluorescent light.

The irradiated mice were then examined eight and 16 weeks after they had received the bone marrow stem cell transplants. By taking blood samples, Roll and others measured the production of blood cells by the transplanted bone marrow stem cells. Mind you, the irradiated mice also received some of their own bone marrow stem cells in combination with the bone marrow stem cells from the donor mice. This was to help determine the percentage of blood cells made by the stem cells from the donor mice. Surveys of the blood cells of the irradiated mice showed that donated stem cells from the mouse donors that had a good night’s sleep gave rise to about 26 percent of the examined blood cells. However, bone marrow stem cells from sleepless donor mice only produced approximately 12 percent of the surveyed blood cells.

Next, the Stanford team investigated the ability of the transplanted stem cells to find their way to the bone marrow of the recipient mice, twelve hours after transplantation. When the bone marrow of the donor mice was subjected to fluorescent light, the 3.3 percent of the bone marrow stem cells were from the well-rested donor mice. However, the same experiment in those recipient mice that had received mice had received bone marrow stem cells from the sleep-deprived mice showed that only 1.7 percent of the stem cells in the bone came from the donor mice. Thus the bone marrow stem cells from those mice that had a good night’s sleep were twice as likely to find their way to the bone marrow of the recipient.

When hematopoietic stem cells from the donor mice were tested in culture, stem cells from the sleepless mice showed a weak response to chemical cues found in bone marrow that activate migration to the bone marrow. Conversely, hematopoietic stem cells from the well-rested mice responded much more robustly to these same chemical cues and migrated appropriately.

Think of it; not sleeping for only four hours can decrease the activity of transplanted bone marrow stem cells by up to half. Remember that bone marrow stem cells contain the coveted hematopoietic stem cell population that produces all the blood cells coursing through our bloodstream. When transplanted into recipient animals (or patients), these stem cells must actively find their way to the bone marrow, take up residence there, and begin to produce all the blood cells necessary for the life and health of the recipient. Therefore even a small reduction in the health or activity of hematopoietic stem cells could drastically affect the success of the bone marrow transplant procedure.

Are the effects of sleeplessness permanent? Not at all, at least in mice. Rolls and her team showed that the decrease in bone marrow stem cell activity could be reversed by allowing the sleep-deprived mice to sleep. In fact, in the hands of Rolls and her co-workers, even letting mice get only two hours of recovery sleep effectively restored the activity of their bone marrow stem cells to properly reconstitute the bone marrow of a recipient in a bone marrow transplant procedure.

“Everyone has these stem cells, and they continuously replenish our blood and immune system,” said Rolls. “We still don’t know how sleep deprivation affects us all, not just bone marrow donors. The fact that recovery sleep is so helpful only emphasizes how important it is to pay attention to sleep.”

Bone marrow transplants are used to treat patients with blood cancers, immune system disorders or others types of conditions. Each year, many thousands of bone marrow transplant procedures are performed. Therefore refining the bone marrow stem cell transplant procedure is essential to helping patients who need such a procedure.

This study was published in Nature Communications, with Asya Rolls as the lead author, who did her work in the laboratory of Irving Weissman, the director of the Stanford Institute of Stem Cell Biology and Regenerative Medicine.

Five-Year Follow-up of REPAIR-AMI Clinical Trial


The REPAIR-AMI clinical trial was a double-blind placebo-controlled trial in which 204 recent heart attach patients received either an infusion of bone marrow stem cells or a placebo. The results of this clinical trial have been published in three different papers (Schächinger, et al., N Engl J Med 2006 355: 1210-1221; Schächinger, et al., Eur Heart Journal 2006 27: 2775-2783; Schächinger, et al., Nat Clin Pract Cardvasc Med 2006 3(Suppl 1): 523-528).

This clinical trial showed that the bone marrow-treated group showed significant functional improvements over the placebo group. However, a long-term follow-up of these patients was required to demonstrate that the benefits conferred by the stem cell treatments were long-lasting and not merely transient.

Upon 5-year examination, the stem cell-treated group showed lower rates of a second heart attack, hospitalization, strokes, cancer, surgical interventions to open blocked vessels and death. Thus, the stem cell-treated group fared better in almost all the major categories.

There was, however, an additional experiment that gave a truly remarkable result. After each patient had their bone marrow extracted, the stem cells were subjected to individual tests, one of which were mobility tests. When this research group examined the stem cell motility data and correlated it to the five-year follow-up, they discovered a very tight association between the motility of the bone marrow stem cells and the absence of cardiac events. More active bone marrow cells provided greater recovery and fewer post-procedural events.

These data show that the quality of the bone marrow is a significant factor in the success of the stem cell treatment.

This also brings up another question: Can be beef up the quality of the bone marrow some how? Culturing stem cells can expand them, but it can also significantly change them. Therefore, this remains a fertile field for research and development, and the bone marrow quality may also explain why bone marrow transplants into the heart work so well or some patients and not at all for others.

Stem Cells Build “Biobridges” to Aid Brain Repair


University of South Florida (USF) scientists have suggested a new strategy for stem cell-mediated brain repair following trauma.

In several preclinical experiments, the USF group found that transplanted stem cells build a “biobridge” that links an injured site in the brain to a site where neural stem cells form.

Principal investigator, Cesar Borlongan, professor and director of the USF Center for Aging and Brain Repair, said: “The transplanted stem cells serve as migratory cues for the brain’s own neurogenic cells, guiding the exodus of these formed host cells from their neurogenic niche towards the injured brain.”

Cesar Borlongan
Cesar Borlongan

On the strength of these preclinial studies in laboratory animals, the US Food and Drug Administration recently approved a limited clinical trial to transplant SanBio Inc.’s SB632 cells into patients with traumatic brain injuries. SB632 cells are a proprietary product of SanBio, Inc., and SB632 cells are derived from mesenchymal stem cells but they have been genetically engineered to express the intracellular domain of the Notch protein (NICD; see C. Tate, et al., Cell Transplantation, Vol. 19, pp. 973–984, 2010). If the Notch protein, which functions as a signaling protein and normally sits in the cell membrane, has its outer piece removed, the protein is constitutively activated. This full-time activation of the Notch protein and its downstream targets drive SB632 cells to form neural cells; something that mesenchymal stem cells typically do not readily make.

The Notch pathway. Notch is synthesised as a precursor protein that is processed by a furin-like convertase (S1 cleavage) in the Golgi before being transported to the cell surface, where it resides as a heterodimer. Interaction of Notch receptors with Notch ligands, such as Delta-like or Jagged, between two bordering cells leads to a cascade of proteolytic cleavages. The first cleavage (S2 cleavage) is mediated by ADAM-family metalloproteases such as ADAM10 or TNF-alpha-converting enzyme (TACE, also known as ADAM17), generating a substrate for S3 cleavage by the gamma-secretase complex. This cleavage releases the Notch intracellular domain (NICD) from the cell membrane. NICD then translocates to the nucleus, where it interacts with the DNA-binding protein RBP-Jkappa (also known as CBF1) and cooperates with Mastermind to displace corepressor proteins, thus activating the transcription of Notch target genes. The basic helix-loop-helix proteins hairy/enhancer of split (such as Hes1, 5 and 7) and Hes-related proteins (Hey1, 2 and L) and EphrinB2 are the best characterised downstream targets. Blockade of Notch signalling has been achieved by using different strategies, including (A) anti-DLL4 monoclonal antibodies, (B) gamma-secretase inhibitors such as DBZ and DAPT, (C) soluble DLL4-Fc, (D) anti-Notch1 neutralising antibodies, and (E) Notch1-trap.
The Notch pathway. Notch is synthesised as a precursor protein that is processed by a furin-like convertase (S1 cleavage) in the Golgi before being transported to the cell surface, where it resides as a heterodimer. Interaction of Notch receptors with Notch ligands, such as Delta-like or Jagged, between two bordering cells leads to a cascade of proteolytic cleavages. The first cleavage (S2 cleavage) is mediated by ADAM-family metalloproteases such as ADAM10 or TNF-alpha-converting enzyme (TACE, also known as ADAM17), generating a substrate for S3 cleavage by the gamma-secretase complex. This cleavage releases the Notch intracellular domain (NICD) from the cell membrane. NICD then translocates to the nucleus, where it interacts with the DNA-binding protein RBP-Jkappa (also known as CBF1) and cooperates with Mastermind to displace corepressor proteins, thus activating the transcription of Notch target genes. The basic helix-loop-helix proteins hairy/enhancer of split (such as Hes1, 5 and 7) and Hes-related proteins (Hey1, 2 and L) and EphrinB2 are the best characterised downstream targets. Blockade of Notch signalling has been achieved by using different strategies, including (A) anti-DLL4 monoclonal antibodies, (B) gamma-secretase inhibitors such as DBZ and DAPT, (C) soluble DLL4-Fc, (D) anti-Notch1 neutralising antibodies, and (E) Notch1-trap.

While this over-simplifies the field to some extent, there are two views on how stem cells heal brain damage caused by injury or neurodegenerative disorders. One view postulates that stem cells implanted into the brain directly replace dead or dying cells by differentiating into neurons and glial cells. The other view is that transplanted stem cells secrete growth factors that indirectly rescue the injured tissue. This present USF study argues for a third view, namely that implanted stem cells for a causeway in the brain between damaged areas and those anatomical structures that give birth to neural stem cells.

In this USF study, Borlongan and his group randomly assigned rats with traumatic brain injury and confirmed neurological impairment to one of two groups. The first group received transplants of SB632 cells into the region of the brain affected by traumatic injury. The second group received a sham procedure in which solution alone was infused into the brain with no implantation of stem cells.

At one and three months post-TBI (traumatic brain injury), the rats that had received SB632 transplants showed significantly better motor and neurological function and reduced brain tissue damage when compared to rats that had received no stem cells. These robust improvements despite the fact that the transplanted stem cells showed fair to poor survival that diminished over time.

Next, Borlongan’s laboratory workers examined the brain tissue of these rats. At three months post-TBI, the brains of transplanted rats showed massive cell proliferation and differentiation of stem cells into neuron-like cells in the area of injury. This was accompanied by a solid stream of stem cells that had migrated from the brain’s uninjured subventricular zone (where many new stem cells are formed) to the brain’s site of injury.

In contrast, those rats that had received solution alone showed limited proliferation and neural-commitment of stem cells, and only showed scattered migration to the site of brain injury and almost no expression of newly formed cells in the subventricular zone. Thus, without the addition of transplanted stem cells, the brain’s self-repair process appeared insufficient to mount a defense against the cascade of TBI-induced cell death.

Borlongan concluded that the transplanted stem cells create a neurovascular matrix that bridges the gap between the region in the brain where host neural stem cells arise and the site of injury. This pathway, or “biobridge,” ferries the newly emerging host cells to the specific place in the brain in need of repair, and helps them to promote functional recovery from traumatic brain injury.