HOW LONG CAN SPERM SURVIVE ONCE CRYOPRESERVED?

A common question I am often asked is, "How long can my cryopreserved sperm last?" Most experts would answer "indefinitely." However, like all great questions, the answer needs some explanation.

Cryopreservation, or the process of freezing sperm for future use (also known as sperm banking), has become a crucial option for men who wish to preserve their fertility due to various reasons, including medical treatments, advancing age, or lifestyle choices. Once cryopreserved, sperm can remain viable for many years. Viable births have been reported after 40 years of cryopreservation.  However, several factors can influence the longevity and quality of the sperm, impacting their potential use in assisted reproductive techniques (ART) such as in vitro fertilization (IVF) or intrauterine insemination (IUI). This article delves into the factors that affect the viability of cryopreserved sperm, including medications taken by the patient, period of abstinence before collection, underlying medical conditions, time in transport to the laboratory, whether a media was added to the specimen before transport, and the initial quality of the sperm sample.

The Cryopreservation Process

Cryopreservation involves freezing sperm at extremely low temperatures, typically around -196°C, using liquid nitrogen. This halts all biological processes, effectively "pausing" the sperm in time. The process usually involves mixing the sperm with a cryoprotectant, a substance that prevents ice crystals from forming, which could otherwise damage the sperm cells during freezing and thawing.

Once cryopreserved, sperm can theoretically last indefinitely. Studies have shown that sperm stored for over two decades can still result in successful pregnancies. However, the success of using cryopreserved sperm depends on the quality and viability of the sperm at the time of thawing.

Factors Affecting Sperm Viability During Cryopreservation

1. Medications Taken by the Patient

Medications taken by a man before providing a sperm sample can significantly impact the quality and viability of sperm, both before and after cryopreservation. Certain medications, such as chemotherapy drugs, can cause DNA damage in sperm cells, reducing their quality and potential for fertilization. Other medications, such as those used for treating infections, hormonal imbalances, or chronic illnesses, might also affect sperm count, motility, and morphology.

For instance, men who have undergone cancer treatment may experience reduced sperm quality, and this can be compounded if the sperm is cryopreserved after such treatments. Therefore, it's often recommended that sperm be collected and cryopreserved before starting any medical treatments that could impact fertility.

2. Period of Abstinence

The period of abstinence before collecting a sperm sample plays a crucial role in determining the quality of the sample. Abstaining from ejaculation for too short a period (less than 24 hours) might result in a lower sperm count, while abstaining for too long (over 10 days) can lead to an increase in sperm DNA fragmentation.

Studies have shown that an optimal period of abstinence for sperm collection is between 2 to 7 days. Sperm collected within this window tends to have better motility and a lower rate of DNA fragmentation, both of which are critical for successful fertilization, especially after cryopreservation.

3. Underlying Medical Conditions

Underlying medical conditions, such as diabetes, hypertension, varicocele, or infections, can negatively impact sperm quality. For example, diabetes can lead to oxidative stress, which damages sperm DNA and reduces motility. Varicocele, a condition characterized by enlarged veins in the scrotum, can also lead to poor sperm quality due to increased testicular temperature and oxidative stress.

These conditions can reduce the viability of sperm even before cryopreservation. As a result, sperm from men with these conditions may have a lower success rate when used in ART after thawing.

4. Time in Transport to the Laboratory

The time it takes to transport a sperm sample to the laboratory after collection is another critical factor in determining the viability of the sample. Sperm begin to lose motility shortly after ejaculation, and this decline can accelerate if the sample is not properly handled during transport.

Ideally, the sperm sample should reach the laboratory within an hour of collection. If a significant delay is expected, it's advisable to store the sample in a temperature-controlled environment. Some laboratories provide special transport kits that maintain the sample at an optimal temperature, helping to preserve sperm motility and viability until cryopreservation.

5. Addition of Media to the Specimen Before Transport

Adding a suitable culture medium to the sperm specimen immediately after collection can help protect the sperm cells during transport. These media are designed to provide nutrients and a stable pH environment, which can help maintain sperm motility and viability until the sample reaches the laboratory.

This step is particularly important if the sperm sample needs to be transported over a long distance or if there might be a delay before processing. The media act as a buffer against environmental fluctuations, such as changes in temperature or pH, that could otherwise harm the sperm.

6. Initial Specimen Quality

The initial quality of the sperm sample is perhaps the most significant factor in determining how well the sperm will survive the cryopreservation process. Sperm quality is typically assessed based on three main parameters: sperm count, motility, and morphology.

• Sperm Count: A higher sperm count increases the likelihood that a sufficient number of viable sperm will survive the freezing and thawing process.
• Motility: Sperm motility is crucial for successful fertilization, as sperm need to swim through the female reproductive tract to reach and penetrate the egg. Sperm with higher motility before freezing are more likely to retain their motility after thawing.
• Morphology: Sperm with normal morphology, meaning they have a typical shape and structure, are more likely to be capable of fertilization. Abnormal sperm are less likely to survive cryopreservation and may have reduced fertilization potential if they do.

If the initial quality of the sperm sample is poor, the chances of successfully using the sperm after cryopreservation are diminished. Therefore, men with known fertility issues may consider providing multiple samples for cryopreservation to increase the likelihood of success.

Conclusion

Cryopreservation is a highly effective method for preserving male fertility, allowing sperm to be stored for extended periods with minimal loss of viability. However, several factors can influence the success of cryopreservation and the eventual use of sperm in reproductive procedures.

Medications, period of abstinence, underlying medical conditions, time in transport, the addition of media, and the initial quality of the sperm all play vital roles in determining the longevity and viability of cryopreserved sperm. By understanding and optimizing these factors, men can improve their chances of successful fertilization and achieving a healthy pregnancy using their cryopreserved sperm.