Exosomes could lead to less costly, less intrusive, more accurate diagnosis
July 11, 2012
Researchers at the Translational Genomics Research Institute
(TGen) have developed a method of isolating biospecimens that could
lead to a less costly, less invasive and more accurate way of
diagnosing chronic kidney disease, or CKD.
CKD is a major complication of diabetes, high blood pressure and a
form of kidney disease known as glomerulonephritis, which is
characterized by a progressive deterioration of the kidney's
ability to filter waste from the blood.
TGen's customized procedure produced high amounts of protein-rich
urinary exosomes, which are microscopic vesicles that could help
scientists discover biomarkers leading to better diagnosis and
treatment of CKD.
TGen's findings were published today in the journal Kidney
International, part of the Nature Publishing Group.
"Our method of extracting exosomes from urine is simple, fast and
easily adapted to clinical research, so we can ultimately help
physicians provide better therapies for their patients," said Dr.
Johanna DiStefano, Director of TGen's Diabetes, Cardiovascular and
Metabolic Diseases Division, and the study's senior author.
The goal of the study was to identify the best exosome isolation
methods for both proteomic analysis and RNA profiling of urinary
exosomes as a first step for biomarker discovery.
"Unlike a kidney biopsy - an invasive and expensive procedure that
provides only a small sample from one of two kidneys - urinary
exosomes provide a full representation of the entire urinary
system," said Dr. Lucrecia Alvarez, a post-doctoral fellow at TGen
and the study's lead author.
TGen researchers evaluated six different methods of isolating
exosomes, which can carry genetic material that, when profiled, can
lead to biomarkers that could help identify patients with kidney
disease.
One of the six methods in the study tested was based on a
commercially available exosome precipitation reagent called
ExoQuick-TC, which by itself did not yield high quantities or pure
preparations of protein and RNA. However, the TGen modification of
the protocol led to the highest yields of miRNA and mRNA, which can
subsequently be used in downstream genetic profiling
experiments.
CKD typically is diagnosed by detecting increased levels of
urinary albumin, a protein that is filtered out of urine in healthy
kidneys, or of serum creatinine, a breakdown product of creatine,
which is an important part of muscle. Neither measurement, however,
can accurately indicate the type of kidney injury or disease.
Significant kidney disease can be present with minimal or even no
change in levels of albumin or creatinine.
Biomarkers can serve as indicators of normal biological processes,
disease development or response to therapeutic drugs.
"In contrast to renal biopsy, urine is an ideal source of
biomarkers, particularly for diseases of the kidney and urinary
tract because it can be conveniently collected in large amounts
without risk to the patient," said Dr. DiStefano.
TGen's method of isolating exosomes in urine is an improvement
over the use of today's mostly commonly used centrifuge processes.
The current method is time-consuming, requires expensive equipment,
can only process low volumes, and only a few samples of urine at a
time, which makes it unsuitable for clinical use.
Another current method is ultrafiltration, which tends to retain
unwanted proteins that interfere with the isolation of exosomal
proteins.
"Faster and more efficient methods of isolating exosomes are
needed," Dr. Alvarez said. "The method we developed provides strong
potential for identifying and characterizing exosomal biomarkers
from urine, which presents favorable implications for the diagnosis
and treatment of chronic kidney disorders."
The Roney Family Foundation funded this study: "Comparison of
protein, microRNA, and mRNA yields using different methods of
urinary exosome isolation for the discovery of kidney disease
biomarkers."
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About TGen
The Translational Genomics Research Institute (TGen) is a
Phoenix-based non-profit organization dedicated to conducting
groundbreaking research with life changing results. Research at
TGen is focused on helping patients with diseases such as cancer,
neurological disorders and diabetes. TGen is on the cutting edge of
translational research where investigators are able to unravel the
genetic components of common and complex diseases. Working with
collaborators in the scientific and medical communities, TGen
believes it can make a substantial contribution to the efficiency
and effectiveness of the translational process. For more
information, visit: www.tgen.org.
Press Contact:
Steve Yozwiak
TGen Senior Science Writer
602-343-8704
[email protected]