Alzheimer's Transmissible Via Stem Cell Transplantation?

 Studies in preclinical models hint that familial Alzheimer's disease (AD) may be transmissible via bone marrow transplant, but the researchers and outside experts caution against making the immediate leap to humans. 

The researchers observed that adoptive transplantation of donor bone marrow stem cells harboring a mutant human amyloid precursor protein (APP) transgene into both APP-deficient and healthy wild-type mice resulted in the rapid development of AD pathologic hallmarks. 

These pathologic features included compromised blood-brain barrier integrity, heightened cerebral vascular neoangiogenesis, elevated brain-associated beta-amyloid levels, and cognitive impairment.

In addition, symptoms of cognitive decline presented rapidly — 6 months after transplant in the APP-knockout mice and 9 months in the wild-type mice vs 12 months shown previously in AD transgenic mice.

"Contrary to prevailing beliefs regarding AD occurring solely in familial or sporadic forms, our study reveals an unexpected transplantable form of AD in a preclinical model, suggesting potential iatrogenic transmission in AD patients," the investigators, led by Wilfred Jefferies, BSc, DPhil, write. 

Although this is probably an "infrequent" occurrence, it's still "concerning," Jefferies told Medscape Medical News, and it suggests that "human donors of blood, tissue, organ, and stem cells should be screened to prevent its inadvertent transfer of disease during blood product transfusions and cellular therapies."

The study was published March 28 in Stem Cell Reports. 

Intriguing, but Limited Human Relevance

The researchers note the study also demonstrates that beta-amyloid accumulation originating outside of the central nervous system contributes to AD pathology, providing an opportunity for the development of new biomarkers for AD. 

Several experts weighed in on this research in a statement from the UK-based nonprofit and independent Science Media Centre (SMC).

David Curtis, MBBS, MD, PhD, with University College London's Genetics Institute, United Kingdom, noted that the study suggests that "theoretically there could be a risk of acquiring Alzheimer's disease if one received a stem cell transplant from somebody carrying the severe, familial form of the disease. However, this form is extremely rare so in practice the risk seems low and there are many safeguards around stem cell transplantation. I do not see that the risks extend to other areas such as organ transplantation or blood transfusion because these procedures do not involve large numbers of stem cells which can go on to form glial cells."

Paul Morgan, PhD, with UK Dementia Research Institute Cardiff, Cardiff University, said the study is "scientifically intriguing" in demonstrating in this "very specific experimental situation, that bone marrow cells are sufficient to transfer the gene and the disease. Relevance to human organ and cell transplant is limited."

Morgan cautioned against making the "gargantuan leap to propose that tissue, organ and cell transplantation, and even blood transfusion, carry a risk of transferring Alzheimer's disease and other neuropathologies in man."

Bart De Strooper, MD, PhD, with University College London, agreed. "There is not sufficient evidence here to suggest that anyone receiving a bone marrow transplant is at risk of developing Alzheimer's disease as a result of the procedure, and nobody should forgo a transplant for this reason," he said in the SMC release. 

The study had no specific funding. The authors hold equity in the start-up company, Cava Healthcare, which possesses intellectual property related to these findings. This had no role in the study design, data collection, analysis, or interpretation of data, or in the writing of the paper. Morgan, De Strooper, and Curtis have no relevant disclosures.

https://www.medscape.com/viewarticle/alzheimers-transmissible-stem-cell-transplantation-2024a10005x6