Evidence of nanobacterial-like structures found in human calcified arteries and cardiac valves

Evidence could indicate bacteria-like etiology of vascular calcification

Researchers at the Mayo Clinic found they could isolate and culture nanoparticles from filtered homogenates of diseased calcified human cardiovascular tissue. These cultured nano-sized particles were recognized by a DNA-specific dye, incorporated radiolabeled uridine, and after decalcification, appeared via electron microscopy to contain cell walls.

The research paper, entitled “Evidence of Nanobacterial-like Structures in Human Calcified Arteries and Cardiac Valves,” has been peer-reviewed and is scheduled for publication in the September 2004 issue of the American Journal of Physiology: Heart and Circulatory Physiology, published by the American Physiological Society. It is currently available online from APS as an Articles in PresS (see below for details).

Noting that the “biological nature of nanometer-sized particles remains controversial,” the researchers said their current study “provides anatomical evidence that calcified human arterial and valvular tissue contain nanometer-sized particles which share characteristics of nanoparticles recovered from geological specimens, mammalian blood, and human kidney stones, and observed by transmission electron microscopy in a calcified human mitral valve.”

Furthermore, they said they designed their study to systematically replicate earlier work conducted on nanoparticles isolated from human kidney stone using different, but rigorous techniques. They point out that what is recovered from diseased calcified tissue replicates in culture, but that they have not yet been able to identify or label what they have found as nanobacteria described by a unique DNA sequence.

However, they cite evidence that the cultured particles contain nucleic acids because compared to controls containing hydroxyapetite crystals they “incorporated radiolabeled uridine in a time-dependent manner of three days, providing evidence of ongoing nucleic acid synthesis.”

One interpretation of these results, especially given such potential parallels as H. pylori causing ulcers, could be that “objects hypothesized to be a type of bacteria (nanobacteria)” could be involved in “mechanisms mediating vascular calcification (which) remain incompletely understood.”

Researchers

“Evidence of Nanobacterial-like Structures in Human Calcified Arteries and Cardiac Valves,” was carried out by Virginia M. Miller (Mayo Clinic, Rochester, MN), George Rodgers (Heart Hospital, Austin, TX), Jon A. Charlesworth (Mayo), Brenda Kirkland (University of Texas, Austin), Sandra R. Severson (Mayo), Todd E. Rasmussen (Mayo), Marineh Yagubyan (Mayo), Jeri C. Rodgers (U. Texas), Ranklin R. Cockerill III (Mayo), Robert L. Folk (U. Texas), Vivek Kumar (Mayo), Gerard Farell-Baril (Mayo) and John C. Lieske (Mayo).