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β-microseminoprotein in human spermatozoa and its potential role in male fertility

N Franchi, Laboratorio de Bioquimica y Biologia Reproductiva, Instituto de Ciencia y Tecnologia de Alimentos, Universidad Nacional de Cordoba, Cordoba, Argentina
C Avendaño, Laboratorio de Bioquimica y Biologia Reproductiva, Instituto de Ciencia y Tecnologia de Alimentos, Universidad Nacional de Cordoba, Cordoba, Argentina
R Molina, Laboratorio de Andrologia y Reproduccion (LAR), Cordoba, Argentina
A Tissera, Laboratorio de Andrologia y Reproduccion (LAR), Cordoba, Argentina
C Maldonado, Centro de Microscopa Electronica, Facultad de Ciencias Medicas, Universidad Nacional de Cordoba, Cordoba, Argentina
S Oehninger, Department of OB/GYN, The Jones Institute for Reproductive Medicine, Eastern Virgina Medical School, Norfolk, United States
C Coronel, Laboratorio de Bioquimica y Biologia Reproductiva, Instituto de Ciencia y Tecnologia de Alimentos, Universidad Nacional de Cordoba, Cordoba, Argentina

Correspondence: Nilda Franchi, Email: franchna{at}evms.edu

Abstract

Beta-microseminoprotein (MSMB) is one of the most abundant proteins in human seminal plasma. The objectives of this study were: (1) to purify MSMB from seminal plasma (SP) and generate antibodies against the pure protein; (2) to investigate the interaction of MSMB with ejaculated spermatozoa and its possible effect on the spontaneous acrosome reaction (AR) and (3) to quantify MSMB content in seminal plasma and examine its relationship with the clinical sperm parameters. MSMB was purified from SP and its presence on the sperm surface was examined by indirect immunofluorescence using a specific polyclonal antibody. The effect of MSMB on the AR was evaluated using guinea pig epididymal spermatozoa as model. MSMB quantification assay was performed with a two-site binding enzyme immunoassay (ELISA) using two polyclonal antibodies against MSMB. MSMB was assessed in semen samples from fertile donors (controls) and from subfertile patients according to WHO criteria. MSMB was detected on the sperm surface and mainly localized to the acrosomal region of the head and neck. A significant spontaneous acrosome reaction inhibition was observed when guinea pig epididymal spermatozoa were preincubated with MSMB. Finally, MSMB was significantly increased in subfertile patients when compared with fertile controls (p < 0.02). The association of MSMB to the sperm surface, the inhibitor effect on the spontaneous acrosome reaction and the increased MSMB levels found in seminal plasma in subfertile men suggests a relationship between this protein and semen quality and a possible role in the process of fertilization.