Replicating spine loading during functional and daily activities: An in vivo, in silico, in vitro research pipeline.

Lifestyle heavily influences intervertebral disc (IVD) loads, but measuring in vivo loads requires invasive methods, and the ability to apply these loads in vitro is limited. In vivo load data from instrumented vertebral body replacements is limited to patients that have had spinal fusion surgery, potentially resulting in different kinematics and loading patterns compared to a healthy population. Therefore, this study aimed to develop a pipeline for the non-invasive estimation of in vivo IVD loading, and the application of these loads in vitro. A full-body Opensim model was developed by adapting and combining two existing models. Kinetic data from healthy participants performing activities of daily living were used as inputs for simulations using static optimisation. After evaluating simulation results using in vivo data, the estimated six-axis physiological loads were applied to bovine tail specimens. The pipeline was then used to compare the kinematics resulting from the physiological load profiles (flexion, lateral bending, axial rotation) with a simplified pure moment protocol commonly used for in vitro studies. Comparing kinematics revealed that the in vitro physiological load protocol followed the same trends as the in silico and in vivo data. Furthermore, the physiological loads resulted in substantially different kinematics when compared to pure moment testing, particularly in flexion. Therefore, the use of the presented pipeline to estimate the complex loads of daily activities in different populations, and the application of those loads in vitro provides a novel capability to deepen our knowledge of spine biomechanics, IVD mechanobiology, and improve pre-clinical test methods.

The physiological, in-vitro simulation of daily activities in the intervertebral disc using a load Informed kinematic evaluation (LIKE) protocol.

Current spinal testing protocols generally adopt pure moments combined with axial compression. However, daily activities involve multi-axis loads, and multi-axis loading has been shown to impact intervertebral disc (IVD) cell viability. Therefore, integrating in-vivo load data with spine simulators is critical to understand how loading affects the IVD, but doing so is challenging due to load coupling and variable load rates. This study addresses these challenges through the Load Informed Kinematic Evaluation (LIKE) protocol, which was evaluated using the root mean squared error (RMSE) between desired and actual loads in each axis. Stage 1 involves obtaining the kinematics from six-axis load control tests replicating 20 Orthoload activities at a reduced test speed. Stage 2 applies these kinematics in five axes, with axial compression applied in load control, at the reduced speed and at the physiological test rate. Stage 3 enables long-term tests through six-axis kinematic control combined with diurnal height correction to account for the natural height fluctuations of the IVD. Stage 1 yielded RMSEs within twice the load cell noise floor. Low RMSEs were maintained during stage 2 at reduced speed (Tx:0.80 ± 0.30 N; Ty:0.77 ± 0.29 N; Tz:1.79 ± 0.50 N; Rx:0.02 ± 0.01Nm; Ry:0.02 ± 0.01Nm; and Rz:0.02 ± 0.01Nm) and at the physiological test rate (Tx:3.45 ± 1.81 N; Ty:3.82 ± 1.99 N; Tz:11.32 ± 8.69 N; Rx:0.13 ± 0.07Nm; Ry:0.16 ± 0.11Nm; and Rz:0.07 ± 0.04Nm). To address unwanted oscillations observed in longer tests (>2h), Stage 3 was introduced to enable the stable and consistent replication of activities at a physiological test rate. Despite higher RMSEs the axial error was 85.5 ± 24.27 N (equivalent to âˆ¼ 0.16 MPa), with shear RMSEs similar to other testing systems conducting pure moment tests at slower rates. The LIKE protocol enables the replication of physiological loads, providing opportunities for enhanced investigations of IVD mechanobiology, and the pre-clinical evaluation of IVD devices and therapies.

The importance of folate, zinc and antioxidants in the pathogenesis and prevention of subfertility.

Current treatments of subfertile couples are usually empiric, as the true cause of subfertility often remains unknown. Therefore, we outline the role of nutritional and biochemical factors in reproduction and subfertility. A literature search was performed using MEDLINE, Science Direct and bibliographies of published work with both positive and negative results. The studies showed that folate has a role in spermatogenesis. In female reproduction, folate is also important for oocyte quality and maturation, implantation, placentation, fetal growth and organ development. Zinc has also been implicated in testicular development, sperm maturation and testosterone synthesis. In females, zinc plays a role in sexual development, ovulation and the menstrual cycle. Both folate and zinc have antioxidant properties that counteract reactive oxygen species (ROS). Thiols, such as glutathione, balance the levels of ROS produced by spermatozoa and influence DNA compaction and the stability and motility of spermatozoa. Oocyte maturation, ovulation, luteolysis and follicle atresia are also affected by ROS. After fertilization, glutathione is important for sperm nucleus decondensation and pronucleus formation. Folate, zinc, ROS and thiols affect apoptosis, which is important for sperm release, regulation of follicle atresia, degeneration of the corpus luteum and endometrial shedding. Therefore, the concentrations of these nutrients may have substantial effects on reproduction. In conclusion, nutritional and biochemical factors affect biological processes in male and female reproduction. Further research should identify pathways that may lead to improvements in care and treatment of subfertility.

Homocysteine, glutathione and related thiols affect fertility parameters in the (sub)fertile couple.

BACKGROUND: Thiols are scavengers of reactive oxygen species (ROS). We aim to investigate associations between thiols in various fluids in (sub)fertile couples and fertility outcome parameters. METHODS: In 156 couples undergoing assisted reproduction techniques (ART), we measured the concentrations of glutathione (GSH), cysteine (Cys), homocysteine (Hcy) and cysteinylglycine (CGS) and fertility outcome parameters in the ejaculate, purified spermatozoa and follicular fluid. RESULTS: All thiols were detectable in most ejaculates, spermatozoa and follicular fluids, of which Cys concentrations were highest. Thiol concentrations in the ejaculate were similar in fertile and subfertile men. However, Hcy in follicular fluid was higher in women with endometriosis compared with women in the idiopathic subfertile group (P=0.04). The GSH, Cys, Hcy and CGS concentrations in spermatozoa of subfertile men were significantly higher compared with men in the idiopathic subfertile group and fertile men (P<0.001). Most notably, Hcy concentrations in both the ejaculate and follicular fluid were negatively associated with embryo quality on culture day 3 in the IVF/ICSI procedure. CONCLUSIONS: Spermatozoa of subfertile men contain significantly higher thiol concentrations as compared with those of fertile men. The detrimental effect on embryo quality of a high Hcy concentration in the ejaculate and in follicular fluid is intriguing and may suggest that Hcy is inversely associated with fertility outcome.

Does folic acid and zinc sulphate intervention affect endocrine parameters and sperm characteristics in men?

We evaluated pre- and post-intervention endocrine and semen parameters in a double-blind, placebo-controlled intervention study to investigate the underlying mechanism of increased sperm concentration after folic acid and zinc sulphate intervention. A total of 47 fertile and 40 subfertile males participated in a 26-week intervention study consisting of a daily treatment with folic acid (5 mg/day) and zinc sulphate (66 mg/day), or placebo. Pre- and post-intervention semen parameters, serum folate, zinc, follicle-stimulating hormone (FSH), testosterone and inhibin B concentrations were measured. The results indicated that intervention treatment significantly increased sperm concentration in subfertile males. Other semen and endocrine parameters were not affected by intervention treatment. At baseline, positive correlations were found between serum zinc and sperm concentration, motility and inhibin B. Serum zinc and FSH were inversely correlated. As (already) well known from previous research, inhibin B positively correlated with sperm concentration, motility and morphology, and was inversely correlated with FSH. The latter was positively correlated with testosterone. In addition, testosterone and inhibin B were inversely correlated. After intervention, the correlations with zinc disappeared. We conclude that the increase in sperm concentration after folic acid and zinc sulphate intervention is not the result of alterations in FSH, testosterone or inhibin B concentrations. Although zinc and folate have several effects on spermatogenesis, the underlying mechanisms involved are not clear.