title: Not all sperm are equal: functional mitochondria characterize a subpopulation of human sperm with better fertilization potential.
abstract: Human sperm samples are very heterogeneous and include a low amount of truly functional gametes. Distinct strategies have been developed to characterize and isolate this specific subpopulation. In this study we have used fluorescence microscopy and fluorescence-activated cell sorting to determine if mitochondrial function, as assessed using mitochondrial-sensitive probes, could be employed as a criterion to obtain more functional sperm from a given ejaculate. We first determined that mitochondrial activity correlated with the quality of distinct human samples, from healthy donors to patients with decreased semen quality. Furthermore, using fluorescence-activated cell sorting to separate sperm with active and inactive mitochondria we found that this was also true within samples. Indeed, sperm with active mitochondria defined a more functional subpopulation, which contained more capacitated and acrosome intact cells, sperm with lower chromatin damage, and, crucially, sperm more able to decondense and participate in early development using both chemical induction and injection into mature bovine oocytes. Furthermore, cell sorting using mitochondrial activity produced a more functional sperm subpopulation than classic swim-up, both in terms of improvement in a variety of functional sperm parameters and in statistical significance. In conclusion, whatever the true biological role of sperm mitochondria in fertilization, mitochondrial activity is a clear hallmark of human sperm functionality.
authors: Department of Life Sciences, Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
authors: Ana Paula
authors: AP
authors: Sousa
authors: Alexandra
authors: A
authors: Amaral
authors: Marta
authors: M
authors: Baptista
authors: Renata
authors: R
authors: Tavares
authors: Pedro
authors: P
authors: Caballero Campo
authors: Pedro
authors: P
authors: Caballero Peregrín
authors: Albertina
authors: A
authors: Freitas
authors: Artur
authors: A
authors: Paiva
authors: Teresa
authors: T
authors: Almeida-Santos
authors: João
authors: J
authors: Ramalho-Santos
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002458:Cell Fractionation; D002469:Cell Separation; D002843:Chromatin / Q000378:metabolism; D005306:Fertilization / Q000502:physiology*; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D008677:Metaphase; D008928:Mitochondria / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D013081:Sperm Motility / Q000502:physiology; D013094:Spermatozoa / Q000378:metabolism*; D013194:Staining and Labeling
chemical_list: D000447:Aldehydes; D002843:Chromatin; C111472:mitotracker green FM