Na⁺/H⁺ exchangers (NHEs) are a family of ion transporters that regulate the pH of various cell compartments across an array of cell types. In eukaryotes, NHEs are encoded by the SLC9 gene family comprising 13 genes. SLC9C2, which encodes the NHE11 protein, is the only one of the SLC9 genes that is essentially uncharacterized. Here, we show that SLC9C2 exhibits testis/sperm-restricted expression in rats and humans, akin to its paralog SLC9C1 (NHE10). Similar to NHE10, NHE11 is predicted to contain an NHE domain, a voltage sensing domain, and finally an intracellular cyclic nucleotide binding domain. An immunofluorescence analysis of testis sections reveals that NHE11 localizes with developing acrosomal granules in spermiogenic cells in both rat and human testes. Most interestingly, NHE11 localizes to the sperm head, likely the plasma membrane overlaying the acrosome, in mature sperm from rats and humans. Therefore, NHE11 is the only known NHE to localize to the acrosomal region of the head in mature sperm cells. The physiological role of NHE11 has yet to be demonstrated but its predicted functional domains and unique localization suggests that it could modulate intracellular pH of the sperm head in response to changes in membrane potential and cyclic nucleotide concentrations that are a result of sperm capacitation events. If NHE11 is shown to be important for male fertility, it will be an attractive target for male contraceptive drugs due to its exclusive testis/sperm-specific expression.

Na⁺/H⁺ exchangers (NHEs) are known to be important regulators of pH in multiple intracellular compartments of eukaryotic cells. Sperm function is especially dependent on changes in pH and thus it has been postulated that NHEs play important roles in regulating the intracellular pH of these cells. For example, in order to achieve fertilization, mature sperm must maintain a basal pH in the male reproductive tract and then alkalize in response to specific signals in the female reproductive tract during the capacitation process. Eight NHE isoforms are expressed in mammalian testis/sperm: NHE1, NHE3, NHE5, NHE8, NHA1, NHA2, NHE10, and NHE11. These NHE isoforms are expressed at varying times during spermatogenesis and localize to different subcellular structures in developing and mature sperm where they contribute to multiple aspects of sperm physiology and male fertility including proper sperm development/morphogenesis, motility, capacitation, and the acrosome reaction. Previous work has provided evidence for NHE3, NHE8, NHA1, NHA2, and NHE10 being critical for male fertility in mice and NHE10 has recently been shown to be essential for male fertility in humans. In this article we review what is known about each NHE isoform expressed in mammalian sperm and discuss the physiological significance of each NHE isoform with respect to male fertility.

This paper reports on the hybrid process we have used for producing hierarchical scaffolds made of poly(lactic-co-glycolic) acid (PLGA) and nanohydroxyapatite (nHA), analyzes their internal structures via scanning electron microscopy, and presents the results of our in vitro proliferation of MC3T3-E1 cells and alkaline phosphatase activity (ALP) for 0 and 21 days. These scaffolds were produced by combining additive manufacturing (AM) and thermally induced phase separation (TIPS) techniques. Slow cooling at a rate of 1.5 degrees C/min during the TIPS process was used to enable a uniform temperature throughout the scaffolds, and therefore, a relatively uniform pore size range. We produced ten different scaffold compositions and topologies in this study. These scaffolds had macrochannels with diameters of similar to 300 mu m, similar to 380 mu m, and similar to 460 mu m, generated by the extraction of embedded porous 3D-plotted polyethylene glycol (PEG) matrices. The other experimental factors included different TIPS temperatures (-20 degrees C, -10 degrees C, and 0 degrees C), as well as varying PLGA concentrations (8%, 10%, and 12% w/v) and nHA content (0%, 10%, and 20% w/w). Our results indicated that almost all these macro/microporous scaffolds supported cell growth over the period of 21 days. Nevertheless, significant differences were observed among some scaffolds in terms of their support of cell proliferation and differentiation. This paper presents the results of our in vitro cell culture for 0 and 21 days. Our optimal scaffold with a porosity of similar to 90%, a modulus of similar to 5.2 MPa, and a nHA content of 20% showed a cell adhesion of similar to 29% on day 0 and maintained cell proliferation and ALP activity over the 21-day in vitro culture. Hence, the use of additive manufacturing and designed experiments to optimize the scaffold fabrication parameters resulted in superior mechanical properties that most other studies using TIPS.

Utilizing high-resolution microscopy in conjunction with a new antibody highly specific for rat alpha4 Na,K-ATPase, we describe changes in alpha4 expression during spermatogenesis and in sperm incubated under capacitating and noncapacitating conditions. Immunohistochemical analyses showed alpha4 expression at low levels in spermatogonia and in pachytene spermatocytes. Alpha4 then becomes highly expressed on round spermatids and the midpiece of elongated spermatozoa within the seminiferous tubules. In noncapacitating conditions, alpha4 was confined mainly to the flagellum of mature sperm; however, under capacitating conditions, sperm acquired intense alpha4 staining along the acrosomal region of the sperm head. To visualize the precise localization of alpha4 in the sperm head, we performed an ultrastructural analysis using immuno-scanning electron microscopy. Under capacitating conditions, sperm exhibited alpha4 staining along the dorsal surface of the sperm head associated with the acrosome. In addition, after 4 h of incubation in motility buffer, we observed an increase in alpha4 protein in sperm that could be blocked with chloramphenicol, a mitochondrial-type ribosome inhibitor. These findings demonstrate that both the localization and expression level of alpha4 Na,K-ATPase are dynamic aspects of sperm maturation and suggest that sperm motility and capacitation may be supported by these changes to the location and amount of this protein.