title: DNA integrity is maintained after freeze-drying of human spermatozoa.
abstract: OBJECTIVE
  To evaluate the effects on human spermatozoa of freeze-drying, also known as lyophilization, and of cryopreservation in liquid nitrogen.
  
  
  METHODS
  Prospective experimental study.
  
  
  METHODS
  Reproductive medicine unit and a private IVF center.
  
  
  METHODS
  Thirty healthy male donors.
  
  
  METHODS
  Sperm samples from 30 donors divided as two aliquots, one to be lyophilized and the other to be cryopreserved in liquid nitrogen.
  
  
  METHODS
  Assessment of count, motility, morphology, viability, DNA integrity, chromosomal status, and birefringence properties of lyophilized and cryopreserved human spermatozoa compared with the same parameters in the fresh sample.
  
  
  RESULTS
  Although sperm viability and motility were totally compromised after freeze-drying, the sperm chromatin structure was not altered in comparison with fresh samples, which demonstrated that the procedure did not affect DNA integrity. The sperm-head inner protoplasmic structures were also preserved, which was estimated by assessing the corresponding birefringence characteristics. After cryopreservation with liquid nitrogen, the motility, viability, and DNA integrity of spermatozoa were statistically significantly reduced compared with the fresh samples; the proportion of sperm cells with abnormal head birefringence increased meaningfully.
  
  
  CONCLUSIONS
  The process of freeze-drying deeply damages cell membranes; however, unlike with liquid nitrogen preservation, it does not affect DNA integrity.
authors.affiliation: Società Italiana Studi Medicina della Riproduzione (S.I.S.Me.R.), Reproductive Medicine Unit, Bologna, Italy. luca.gianaroli@sismer.it
authors.forename: Luca
authors.initials: L
authors.lastname: Gianaroli
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Magli
authors.forename: Ilaria
authors.initials: I
authors.lastname: Stanghellini
authors.forename: Andor
authors.initials: A
authors.lastname: Crippa
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Crivello
authors.forename: Edoardo Stefano
authors.initials: ES
authors.lastname: Pescatori
authors.forename: Anna Pia
authors.initials: AP
authors.lastname: Ferraretti
mesh_terms: D000328:Adult; D000782:Aneuploidy; D001718:Birefringence; D002462:Cell Membrane / Q000473:pathology; D002470:Cell Survival; D042002:Chromatin Assembly and Disassembly; D015925:Cryopreservation / Q000379:methods*; D004249:DNA Damage; D005612:Freeze Drying; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D009584:Nitrogen / Q000009:adverse effects; D011446:Prospective Studies; D013076:Sperm Count; D013081:Sperm Motility; D013094:Spermatozoa / Q000473:pathology*
chemical_list: D009584:Nitrogen