**1. Introduction**

Gamete cryobanking has been considerably incorporated in present assisted reproductive technology (ART). Preserving fertility through banking is an accessible and relatively reliable procedure that gives opportunity for men to parent their own biological child. Most of the clinics providing fertility treatment have their individual cryobanks and offer fertility preservation counseling. Network structures for gamete and tissue storage have also been developed. Some of the affirmed ones would be the Danish network (www.rigshospitalet.dk), *Ferti*PROTECT ® (www.fertiprotect.com), German-Austrian-Swiss centralized and decentralized network between the countries, Oncofertility® Concortium (www.oncofertility. northwestern.edu) for knowledge exchange in the field of fertility preservation [1]. The complexity of fertility preservation generates necessity for close interaction between the patients, reproductive specialist, reproductive biologist, urologist, oncologist, etc. In order to provide accurate and prompt counseling and treatment, each clinical case should be considered in full and timely.

Retrieving, freezing, storage and use of human oocytes, spermatozoa, embryos and ovarian and testicular tissue has been executively studied and explored in assisted reproduction (AR). Cryopreservation presents remarkable advance to men and women who have decided to postpone fertility. It turns out to be a safety plan for patient with subfertility and certain physiological or psychological conditions.

For patients with forthcoming cancer treatment it could be the only chance to have their own biological child.

Nowadays cryopreservation and cryobanking is inseparable branch to assisted reproduction and fertility preservation treatment.

#### **2. Historical preview of sperm cryopreservation**

First attempts to preserve human spermatozoa dates back to 1776 when Lazaro Spallanzani studied sperm cryopreservation by cooling it in snow. It was 1949 when Polge, Smith and Parkes discovered glycerol to be effective in protecting spermatozoa exposed to low temperatures [2]. This discovery, alongside with the first reports for achieving pregnancy by frozen and thawed spermatozoa in 1953 by Dr. Jerome K. Sherman [3], led to constant development and improvement of sperm freezing protocols and devices. In 1972 a slow freezing protocol, developed by D. Whittingham, S. Leibo, and P. Mazur, was introduced. Slow cooling with temperature drops in the range of 0.3 to 2 degrees Celsius per minute and consequent slow warming (4 to 25 degrees C° per minute) was performed. This protocol, applied to mouse embryos, resulted in 65% pregnancy rate and 40% full term pregnancy [4]. Recent challenge in cryobiology was freezing spermatozoa from strains of genetically engineered mice. A novel method using a cryoprotectant composed of 18% raffinose pentahydrate and 3% skim milk was presented [5, 6].

Not only protecting sperm cells at low temperatures, but preserving their structural (morphological), kinetic and functional characteristics is at aim when freezing semen samples. It is well known that cryopreservation has deleterious effect on sperm cells.

Although spermatozoa are relatively small in size and have large surface, cold shock and ice formation could damage different cell structures and organelles, as most affected structures are the plasmalema, acrosome and the tail [7]. Changes in membrane organization and permeability, formation of reactive oxygen species (ROS) and consequent DNA damage as a result to freezing hinders normal sperm activity and functions [8].

Semen cryopreservation strives high quality of the preserved samples. Thus, retaining sperm motility and viability, membrane integrity and intact DNA in thawed samples, has been formed as priority when developing freezing protocols. Cryoprotective medium, containing various additives – fatty acids, proteins, antioxidants, serum, essential oils derived from plants, nanoparticles and others, are also used in sperm freezing procedures.

#### **3. Conditions requiring sperm preservation**

Diversity of health conditions and personal or lifestyle circumstances could necessitate semen cryopreservation.

#### **3.1 Sperm freezing for cancer patients**

Five most common cancers diagnosed in men are prostate cancer, lung cancer, colorectal cancer, bladder cancer and melanoma. Testicular tumors, relatively rare condition on a per-population basis, are the most common malignancy in men aged 20 to 35 years [9, 10]. According to The National Cancer Institute one in two men will be diagnosed with cancer during their lifetime. Encouraging data for approximately

1.8% decrease in cancer death for male patients was recently published [11]. Modern medicine and constant scientific research in the field are the key to increasing the chances for long term survival (5 and above years). Quality of life after cancer treatment and when in remission is of great importance. Unfortunately, cancer by itself and chemo- and/or radiotherapy treatment, have adverse effect over the process of spermatogenesis. For most cured patients, after healing, sperm production recovers to a certain level in time. When bilateral orchiectomy was performed or high dosage of radiotherapy (24–25 Gy) was administrated permanent loss of fertility is inevitable [12]. Introducing cancer patients to fertility preservation before the treatment is required, especially for adolescents and young adults (aged 15–39 years) [13].
