Semen rheology and its relation to male infertility

Abstract

Infertility affects 15% of couples of reproductive age worldwide. In spite of many advances in understanding and treating male infertility, there is still a number of issues that need further investigation and translation to the clinic. Here, we review the current knowledge and practice concerning semen rheology and its relation with pathological states affecting male infertility. Although it is well recognized that altered rheological properties of semen can impair normal sperm movement in the female reproductive tract, routine semen analysis is mostly focused on number, motility and morphology of spermatozoa, and includes only an approximate, operator-dependent measure of semen viscosity. The latter is based on the possible formation of a liquid thread from a pipette where a semen sample has been aspirated, a method that is sensitive not only to viscosity but also to elongational properties and surface tension of semen. The formation of a liquid thread is usually associated with a gel-like consistency of the sample and changes in spermatozoa motility in such a complex medium are still to be fully elucidated. The aim of this review is to point out that a more quantitative and reliable characterization of semen rheology is in order to improve the current methods of semen analysis and to develop additional tools for the diagnosis and treatment of male infertility.

A novel microfluidic device with parallel channels for sperm separation using spermatozoa intrinsic behaviors

“…Concerning the limitations of the proposed model, the present framework for predicting sperm cells’ rheotactic behavior did not consider the effects of background flow physics on sperm cells' motion. The fresh semen sample contains shear-thinning non-Newtonian fluid, which is less viscous in the regions exposed to high viscous-based tensions 44 . This is especially important from two aspects; the first aspect is that the flow will be less viscous due to the viscous-gradient effects near the microchannel walls, where most sperm cells tend to swim.…”

Metagenomics Reveals Specific Microbial Features in Males with Semen Alterations

“…The correct identification of the possible cause of male infertility, together with the female partner assessment, is crucial for proper couples’ evaluation and ensuring the best strategy to improve couples’ reproductive outcomes [ 6 ]. The semen analysis represents a routine step in assessing male infertility since it provides considerable information regarding macroscopic and microscopic features that can highlight underlying diseases [ 7 , 8 ]. Moreover, we have recently reported that semen sample parameters’ alterations correlate with urogenital infections and sperm DNA fragmentation, suggesting that an in-depth semen evaluation may improve male infertility management [ 9 ].…”

Editorial: theme issue on complex rheology in biological systems

“…For this theme issue, we gratefully received contributions from across the physics and life sciences with interests in biorheology ranging in length scale from the rheological properties of intracellular biomolecular networks [ 1 , 10 ] to the scale of the direct extracellular environment [ 3 , 7 , 10 , 12 , 13 , 16 ], tissues [ 3 – 5 ] and even entire organs that actively exert forces onto non-Newtonian fluids [ 6 ]. The mechanical properties at the cellular level are discussed in relationship to cancer [ 2 ], as well as in relationship to the transport of red blood cells in disordered porous environments, be it in vascular networks or in microfluidic devices.…”

“…The mechanical properties at the cellular level are discussed in relationship to cancer [ 2 ], as well as in relationship to the transport of red blood cells in disordered porous environments, be it in vascular networks or in microfluidic devices. The interaction of a cell with its environment, and in particular the consequence of these interactions to cell mobility, is discussed in the context of (i) blood flow in vascular networks [ 5 ], (ii) male infertility [ 7 ], (iii) the stability of biofilms [ 12 , 13 ] and (iv) new opportunities of using liquid crystals to impose controlled constraints to cell motion [ 16 ].…”

“…Vascular biology (e.g. haematology) is clearly a field where rheology is vital [ 5 ], but other key rheological control problems emerge in digestive [ 6 ] and reproductive biology [ 7 ]. Other biological flows contain rheologically induced structural or phase transitions, and the understanding of how biological fluids and soft solids flow and deform is a key scientific area within this collaboration of physical and life sciences (blood [ 8 ], the cytosol, silk protein solutions [ 9 ], saliva, mucus [ 10 ], synovial fluid, biofilms [ 11 – 13 ], tissue buckling [ 14 ], bacterial rheotaxis [ 15 ] and E. coli bacteria swimming in media with liquid crystalline order [ 16 ] are just some examples [ 17 ]).…”