Low Hematopoietic Stem Cells in Alzheimer's?

Tübingen, Germany -

The chemokine SDF-1 is known to attract hematopoietic stem cells and mesenchymal stem cells.  Under basal conditions it is produced by the bone marrow stromal cells, this is why hematopoietic stem cell transplants can be performed by intravenous administration and they find their way back to the bone marrow niche.  Under conditions of tissue injury, peaks of SDF-1 are found in the serum, apparently being responsible for mobilization of stem cells from the bone marrow compartment to the area of tissue injury. 

In a very interesting paper (Laske et al. Decreased CXCL12 (SDF-1) Plasma Levels in Early Alzheimer's Disease: A Contribution to a Deficient Hematopoietic Brain Support? J Alzheimers Dis. 2008 Sep;15(1):83-95) researchers found that patients with early Alzheimer's have decreased plasma SDF-1 as compared to healthy controls, and that a relationship exists between decreased SDF-1 and tau protein levels as well as cognitive decline. 

The authors are proposing that this reduction in SDF-1 may be associated with less bone marrow stem cells helping the brain of Alzheimer's patients to heal itself.

The same group previously published that decreased circulating CD34 cells in patients with Alzheimer's Disease compared to controls (Maler et al. Decreased circulating CD34+ stem cells in early Alzheimer's disease: Evidence for a deficient hematopoietic brain support? Mol Psychiatry 2006 Dec;11(12):1113-5), thus supporting the possibility that endogenous stem cells may have a role in controlling Alzheimer's.

Other diseases are associated with decreased stem cell numbers, for example, in Duchenne Muscular Dystrophy patients with a better prognosis have a higher number of circulating CD133 stem cells.