title: Spermatogonial stem cell preservation and transplantation: from research to clinic.
abstract: OBJECTIVE
  What issues remain to be solved before fertility preservation and transplantation can be offered to prepubertal boys?
  
  
  CONCLUSIONS
  The main issues that need further investigation are malignant cell decontamination, improvement of in vivo fertility restoration and in vitro maturation.
  
  
  BACKGROUND
  Prepubertal boys who need gonadotoxic treatment might render sterile for the rest of their life. As these boys do not yet produce sperm cells, they cannot benefit from sperm banking. Spermatogonial stem cell (SSC) banking followed by autologous transplantation has been proposed as a fertility preservation strategy. But before this technique can be applied in the clinic, some important issues have to be resolved.
  
  
  METHODS
  Original articles as well as review articles published in English were included in a search of the literature.
  
  
  METHODS
  Relevant studies were selected by an extensive Medline search. Search terms were fertility preservation, cryopreservation, prepubertal, SSC, testis tissue, transplantation, grafting and in vitro spermatogenesis. The final number of studies selected for this review was 102.
  
  
  RESULTS
  Cryopreservation protocols for testicular tissue have been developed and are already being used in the clinic. Since the efficiency and safety of SSC transplantation have been reported in mice, transplantation methods are now being adapted to the human testes. Very recently, a few publications reported on in vitro spermatogenesis in mice, but this technique is still far from being applied in a clinical setting.
  
  
  CONCLUSIONS
  Using tissue from cancer patients holds a potential risk for contamination of the collected testicular tissue. Therefore, it is of immense importance to separate malignant cells from the cell suspension before transplantation. Because biopsies obtained from young boys are small and contain only few SSCs, propagation of these cells in vitro will be necessary.
  
  
  CONCLUSIONS
  The ultimate use of the banked tissue will depend on the patient's disease. If the patient was suffering from a non-malignant disease, tissue grafting might be offered. In cancer patients, decontaminated cell suspensions will be injected in the testis. For patients with Klinefelter syndrome, the only option would be in vitro spermatogenesis. However, at present, restoring fertility in cancer and Klinefelter patients is not yet possible.
  
  
  BACKGROUND
  Research Foundation, Flanders (G.0385.08 to H.T.), the Institute for the Agency for Innovation, Belgium (IWT/SB/111245 to E.G.), the Flemish League against Cancer (to E.G.), Kom op tegen kanker (G.0547.11 to H.T.) and the Fund Willy Gepts (to HT). E.G. is a Postdoctoral Fellow of the FWO, Research Foundation, Flanders. There are no conflicts of interest.
authors: Biology of the testis, Department for Embryology and Genetics, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels 1090, Belgium. ellen.goossens@uzbrussel.be
authors: E
authors: E
authors: Goossens
authors: D
authors: D
authors: Van Saen
authors: H
authors: H
authors: Tournaye
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects; D015925:Cryopreservation; D059247:Fertility Preservation / Q000379:methods*; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D051379:Mice; D009369:Neoplasms / Q000188:drug therapy / Q000532:radiotherapy; D011627:Puberty; D011878:Radiotherapy / Q000009:adverse effects; D051381:Rats; D013093:Spermatogonia / Q000166:cytology / Q000637:transplantation*; D033581:Stem Cell Transplantation / Q000379:methods*; D014182:Transplantation, Autologous
chemical_list: D000970:Antineoplastic Agents