title: Intercellular adhesion molecules (ICAMs) and spermatogenesis.
abstract: BACKGROUND
  During the seminiferous epithelial cycle, restructuring takes places at the Sertoli-Sertoli and Sertoli-germ cell interface to accommodate spermatogonia/spermatogonial stem cell renewal via mitosis, cell cycle progression and meiosis, spermiogenesis and spermiation since developing germ cells, in particular spermatids, move 'up and down' the seminiferous epithelium. Furthermore, preleptotene spermatocytes differentiated from type B spermatogonia residing at the basal compartment must traverse the blood-testis barrier (BTB) to enter the adluminal compartment to prepare for meiosis at Stage VIII of the epithelial cycle, a process also accompanied by the release of sperm at spermiation. These cellular events that take place at the opposite ends of the epithelium are co-ordinated by a functional axis designated the apical ectoplasmic specialization (ES)-BTB-basement membrane. However, the regulatory molecules that co-ordinate cellular events in this axis are not known.
  
  
  METHODS
  Literature was searched at http://www.pubmed.org and http://scholar.google.com to identify published findings regarding intercellular adhesion molecules (ICAMs) and the regulation of this axis.
  
  
  RESULTS
  Members of the ICAM family, namely ICAM-1 and ICAM-2, and the biologically active soluble ICAM-1 (sICAM-1) are the likely regulatory molecules that co-ordinate these events. sICAM-1 and ICAM-1 have antagonistic effects on the Sertoli cell tight junction-permeability barrier, involved in Sertoli cell BTB restructuring, whereas ICAM-2 is restricted to the apical ES, regulating spermatid adhesion during the epithelial cycle. Studies in other epithelia/endothelia on the role of the ICAM family in regulating cell movement are discussed and this information has been evaluated and integrated into studies of these proteins in the testis to create a hypothetical model, depicting how ICAMs regulate junction restructuring events during spermatogenesis.
  
  
  CONCLUSIONS
  ICAMs are crucial regulatory molecules of spermatogenesis. The proposed hypothetical model serves as a framework in designing functional experiments for future studies.
authors.affiliation: The Mary M. Wohlford Laboratory for Male Contraceptive Research,  Center for Biomedical Research, Population Council, 1230 York Avenue, New York, NY 10065,  USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Xiao
authors.forename: Dolores D
authors.initials: DD
authors.lastname: Mruk
authors.forename: C Yan
authors.initials: CY
authors.lastname: Cheng
mesh_terms: D001814:Blood-Testis Barrier / Q000378:metabolism / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000502:physiology*; D004848:Epithelium; D006801:Humans; D008297:Male; D012670:Seminiferous Epithelium / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D012708:Sertoli Cells / Q000166:cytology / Q000378:metabolism; D013087:Spermatids / Q000166:cytology; D013091:Spermatogenesis; D013094:Spermatozoa / Q000166:cytology; D013737:Testis / Q000166:cytology; D019108:Tight Junctions / Q000378:metabolism
chemical_list: D015815:Cell Adhesion Molecules