Sperm DNA Fragmentation – The New Frontier of Fertility Testing

Worldwide male fertility has followed a disconcerting trend over the last 40 years. Since the 1970s, research shows sperm counts have plummeted by more than 50% in the United States, Europe, Australia, and New Zealand. Because the downward trajectory shows no sign of slowing or rebounding, being able to accurately assess male fertility and its impact on achieving a successful pregnancy has become more critical.

Overall, infertility affects between 10% and 15% of men in prime reproductive age. However, in as many as 15% of cases, conventional semen analysis, based on parameters established by the World Health Organization (WHO), does not identify sperm abnormalities that could cause decreased fertility (Box, below). While the WHO parameters, set in 2010, test volume, sperm count, and motility, they only provide information about sperm presence—not how effectively the sperm will fertilize an oocyte and foster a viable pregnancy.

That means men who fall within normal WHO ranges can still have significant sperm DNA damage. Consequently, there is a need for a technique that provides more detailed information about sperm quality. In the last decade, sperm DNA fragmentation (SDF) has emerged as a possible tool to highlight the level of molecular damage present in a man’s sperm. Several SDF tests are currently available, and the results can guide treatment option selections and fertility services. But reservations remain about how widely applicable and accepted SDF should be.

TESTING OPTIONS
SDF differs from raw semen analysis by examining the number of nicks and breaks present in the sperm’s DNA. Four main tests exist to identify a man’s DNA Fragmentation Index—the proportion of normal-to-damaged sperm—and each strategy is unique.

Sperm chromatin structure assay uses a chemical dye to stain broken sperm red and normal sperm green. Sperm chromatin dispersion treats sperm with acid denaturation after which normal sperm produce halos. Terminal deoxynucleotidyl transferase 2′-deoxyuridine 5′-triphosphates (dUTP) nick end labeling employs fluorescent dUTP to label single- and -double-strand breaks. And, SpermComet uses single-cell gel electrophoresis in which only -fragmented sperm travel through the gel.

Although the mechanisms are varied, these tests are valuable to couples who have not been able to identify the root of their infertility, said James Hotaling, MD, assistant professor of surgery and co-director of the Fertility Integrated Practice Unit at the University of Utah School of Medicine in Salt Lake City.

“SDF is the only test that allows us to look at anything other than bulk semen parameters,” he explained. “It lets us look at that quality of the DNA packaging critical for early embryo development.”

A PROMISING APPROACH
Every man has sperm DNA imperfections, said Mary Samplaski, MD, an assistant professor of urology at the University of Southern California Keck School of Medicine in Los Angeles, but levels are higher among sub-fertile and infertile men. High SDF, loosely defined as more than 30%, correlates with all reproductive outcomes, including lower success rates in natural pregnancy, intrauterine insemination, and in vitro fertilization (IVF), as well as higher miscarriage occurrences.

Several factors lead to this damage, said Ashok Agarwal, PhD, director of the Cleveland Clinic Clinical Andrology Lab and Sperm Bank. Oxidative stress, abortive apoptosis, and environmental factors, such as ultraviolet light and cellphone radiation, all can negatively impact DNA. Lifestyle factors, including obesity, diabetes, and sedentary occupations, also pose damage to sperm. Additionally, varicoceles—enlarged testicular veins that cause overheating and injure sperm—are present in approximately 40% of men with infertility.

With SDF test results in hand, reproductive specialists can recommend necessary lifestyle changes and guide patients toward the fertility treatment options that offer the best opportunities for success, he said.

“Rather than having a patient undergo and play Russian roulette with expensive technologies like IVF or [intracytoplasmic sperm injection] that can cost $10,000 to $15,000 per attempt with less than a 30% success rate,” he said, “we can avoid pricey and unnecessary treatments for couples with male factor infertility having repeated IVF failure or recurrent pregnancy loss by using SDF outcomes to reduce the DNA damage before undergoing assisted reproduction treatment.”

Samplaski agreed, noting that SDF offers vital information, pointing couples struggling with infertility down the right path as early as possible during their best reproductive years. That includes, she added, suggesting men take an antioxidant to counteract any oxidative stress damage.

SDF also supports clinical procedures that reduce DNA damage, according to Sheena Lewis, PhD, FRSB, emeritus professor at Queen’s University Belfast School of Medicine, Dentistry, and Biomedical Sciences in Northern Ireland. Removing sperm via testicular biopsy, before it picks up oxidative stress damage traveling along the epididymis (which she called the “war zone”), can yield healthier sperm for fertility procedures. Varicocele repair also offers similar improvement, she said. In fact, research shows men can experience a 3.4% damage reduction within 3 months via SDF retesting (Int Urol Nephrol 2015;47:1471–7).

WHAT IS HOLDING SDF BACK?
Despite providing a greater degree of actionable information, SDF still lags in the quest for widespread implementation. To a large degree, ease of access is a stumbling block, according to Amin S. Herati, MD, assistant -professor of urology and director of male infertility at the Brady Urological Institute at the Johns Hopkins School of Medicine in Baltimore. “For these tests, access for patients and providers is a big issue,” he said. “Only select labs offer it. Not everyone does it.”

Agarwal agreed, but he did not recommend every lab offer these tests as an in-house service. Instead, he said, they should identify a specialty lab, such as his own, already equipped with properly trained personnel, lab space, and equipment to process SDF tests to meet their needs.

Consistency and translatability have also been obstacles. Not only does each SDF test assess DNA fragmentation differently, each also has its own cut point to diagnose sperm quality levels. To make tests more easily accepted, procedures and results reporting must be standardized, Hotaling emphasized.

“There’s a lot of variability in how the test is run,” he said. “It’s not the same from one place to another, so it’s hard to compare results between labs.” Samplaski concurred, saying the level of existing differentiation makes reproductive specialists reticent to order SDF tests more frequently.

As with all other tests, though, until SDF methods are analyzed in larger clinical trials and submit reliable, reproducible results, providers will remain hesitant about suggesting the test for a wider patient population. Even as an initial SDF advocate, Herati acknowledged that the data to support the methods’ robust use has not appeared so far. However, these functional tests provide actionable information for a certain group of men struggling with infertility.

“I still use sperm DNA fragmentation, but its main role in my mind is for someone with normal semen parameters whose partner might have recurrent pregnancy loss,” Herati said. “We can decide where the sperm should come from for fertility services and what we can do to optimize that choice. That’s really where the utility of DNA fragmentation lies.”

Still, Agarwal said, SDF is one of the most important male fertility advancements in the last 60 years. Although it’s still in the early adoption phase, it offers hope for a successful pregnancy in cases when male-factor infertility was previously undiagnosed.

“Infertility is complicated, and sperm DNA fragmentation is an important part of testing in male patients, but it isn’t a silver bullet,” he emphasized. “It’s one way to examine, look for, and find hidden problems that aren’t told by semen analysis, and that’s a big thing. But, it’s not for every patient who has a problem with infertility.”

Sheena Lewis is the founder of Examen, producer of the SpermCOMET test and managing director of Lewis Fertility Testing, Ltd., a spin-out company of Queen’s University Belfast.
Whitney J. Palmer is a freelance journalist in Holly Springs, North Carolina. Email: whitneyljhowell@gmail.com

At the 71st AACC Annual Scientific Meeting & Clinical Lab Expo, scientific sessions cover a wide array of dynamic areas of clinical laboratory medicine. For sessions related to this and other cutting-edge laboratory methods visit https://2019aacc.org/conference-program.