Intervertebral disc degeneration is highly prevalent within the elderly population and is a leading cause of chronic back pain and disability. Due to the link between disc degeneration and senescence, we explored the ability of the Dasatinib and Quercetin drug combination (D + Q) to prevent an age-dependent progression of disc degeneration in mice. We treated C57BL/6 mice beginning at 6, 14, and 18 months of age, and analyzed them at 23 months of age. Interestingly, 6- and 14-month D + Q cohorts show lower incidences of degeneration, and the treatment results in a significant decrease in senescence markers p16INK4a, p19ARF, and SASP molecules IL-6 and MMP13. Treatment also preserves cell viability, phenotype, and matrix content. Although transcriptomic analysis shows disc compartment-specific effects of the treatment, cell death and cytokine response pathways are commonly modulated across tissue types. Results suggest that senolytics may provide an attractive strategy to mitigating age-dependent disc degeneration.

The coupling between solvent fluctuations and the electronic states of solutes is critically important in charge transfer and other chemical reactions. This has piqued enormous interest in solvation dynamicsthe study of how solvent motions relax changes in a solute's charge distribution. In nearly every computer simulation of solvation dynamics, the system is modeled by an atomic or molecular solute whose charge (or higher multipole moment) is suddenly changed, and the motions of the solvent molecules that relax the new charge distribution are monitored. Almost none of this work, however, accounts for the fact that most reacting solutes also undergo significant changes in size and shape as well as charge distribution. For the excited states of dye molecules typically used as probes in solvation experiments or for the atoms and molecules that change oxidation state in charge transfer reactions, we expect changes in reactant size on the order of 5−20%. In this paper, we use computer simulation to explore the differences between dielectric solvation, due to changes in charge distribution, and mechanical solvation, due to changes in size and shape, for a Lennard-Jones sphere in flexible water. The solvation energy for the size changes expected in typical reactions is on the same order as that for the appearance of a fundamental unit of charge, indicating that dielectric and mechanical solvation dynamics should participate at comparable levels. For dielectric solvation, solvent librations dominate the influence spectrum, but we also find a significant contribution from the water bending motion as well as low-frequency translations. The influence spectrum for mechanical solvation, on the other hand, consists solely of low-frequency intermolecular translational motions, leading to mechanical solvation dynamics that are significantly slower than their dielectric counterparts. The spectrum of couplings for various mechanical perturbations (size, shape, or polarizability) depends somewhat on the magnitude of the change, but all types of mechanical relaxation dynamics appear qualitatively similar. This is due to the steepness of the solute−solvent interaction potential, which dictates that the majority of the solvation energy for mechanical changes comes from the translational motion of the closest one or two solvent molecules. Finally, we explore the solvation dynamics for combined changes in both size and charge and find that the resulting dynamics depend sensitively on the sign and magnitude of both the size and charge changes. For some size/charge combinations, the translational and rotational motions that lead to relaxation work cooperatively, producing rapid solvation. For other combinations, the key translational and rotational solvent motions for relaxation are antagonistic, leading to a situation where mechanical solvation becomes rate limiting:  solvent rotational motions are “frustrated” until after translational relaxation has occurred. All the results are compared with previous experimental and theoretical stu...

Intervertebral disc degeneration presents a wide spectrum of clinically degenerative disc phenotypes; however, the contribution of genetic background to the degenerative outcomes has not been established. We characterized the spinal phenotype of 3 mouse strains with varying cartilage‐regenerative potential at 6 and 23 months: C57BL/6, LG/J and SM/J. All strains showed different aging phenotypes. Importantly, LG/J mice showed an increased prevalence of dystrophic disc calcification in caudal discs with aging. Quantitative‐histological analyses of LG/J and SM/J caudal discs evidenced accelerated degeneration compared to BL6, with cellular disorganization and cell loss together with fibrosis of the NP, respectively. Along with the higher grades of disc degeneration, SM/J, at 6M, also differed the most in terms of NP gene expression compared to other strains. Moreover, although we found common DEGs between BL6 and LG/J aging, most of them were divergent between the strains. Noteworthy, the common DEGs altered in both LG/J and BL6 aging were associated with inflammatory processes, response to stress, cell differentiation, cell metabolism and cell division. Results suggested that disc calcification in LG/J resulted from a dystrophic calcification process likely aggravated by cell death, matrix remodelling, changes in calcium/phosphate homeostasis and cell transformation. Lastly, we report 7 distinct phenotypes of human disc degeneration based on transcriptomic profiles, that presented similar pathways and DEGs found in aging mouse strains. Together, our results suggest that disc aging and degeneration depends on the genetic background and involves changes in various molecular pathways, which might help to explain the diverse phenotypes seen during disc disease.

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Design of rapid, selective, and sensitive DNA and ribonucleic acid (RNA) biosensors capable of minimizing false positives from nuclease degradation is crucial for translational research and clinical diagnostics. We present proof-of-principle studies of an innovative micro-ribonucleic acid (miRNA) reporter-probe biosensor that displaces a self-complementary reporter, while target miRNA binds to the probe. The freed reporter folds into a hairpin structure to induce a decrease in the fluorescent signal. The self-complementarity of the reporter facilitates the reduction of false positives from nuclease degradation. Nanomolar limits of detection and quantitation were capable with this proof-of-principle design. Detection of miRNA occurs within 10 min and does not require any additional hybridization, labeling, or rinsing steps. The potential for medical applications of the reporter-probe biosensor is demonstrated by selective detection of a cancer regulating microRNA, Lethal-7 (Let-7a). Mechanisms for transporting the biosensor across the cell membrane will be the focus of future work.