Fisetin has been shown to be beneficial for brain injury and age-related brain disease via different mechanisms. The purpose of this study was to determine the presence of senescent cells and the effects of fisetin on cellular senescence in the brain and other vital organs in old sheep, a more translational model. Female sheep 6–7 years old (N = 6) were treated with 100 mg/kg fisetin or vehicle alone on two consecutive days a week for 8 weeks. All vital organs were harvested at the time of sacrifice. Histology, immunofluorescence staining, and RT-Q-PCR were performed on different regions of brain tissues and other organs. Our results indicated that fisetin treatment at the current regimen did not affect the general morphology of the brain. The presence of senescent cells in both the cerebral brain cortex and cerebellum and non-Cornu Ammonis (CA) area of the hippocampus was detected by senescent-associated β-galactosidase (SA-β-Gal) staining and GL13 (lipofuscin) staining. The senescent cells detected were mainly neurons in both gray and white matter of either the cerebral brain cortex, cerebellum, or non-CA area of the hippocampus. Very few senescent cells were detected in the neurons of the CA1-4 area of the hippocampus, as revealed by GL13 staining and GLB1 colocalization with NEUN. Fisetin treatment significantly decreased the number of SA-β-Gal⁺ cells in brain cortex white matter and GL13⁺ cells in the non-CA area of the hippocampus, and showed a decreasing trend of SA-β-Gal⁺ cells in the gray matter of both the cerebral brain cortex and cerebellum. Furthermore, fisetin treatment significantly decreased P16⁺ and GLB1⁺ cells in neuronal nuclear protein (NEUN)⁺ neurons, glial fibrillary acidic protein (GFAP)⁺ astrocytes, and ionized calcium binding adaptor molecule 1 (IBA1)⁺ microglia cells in both gray and white matter of cerebral brain cortex. Fisetin treatment significantly decreased GLB1⁺ cells in microglia cells, astrocytes, and NEUN⁺ neurons in the non-CA area of the hippocampus. Fisetin treatment significantly decreased plasma S100B. At the mRNA level, fisetin significantly downregulated GLB1 in the liver, showed a decreasing trend in GLB1 in the lung, heart, and spleen tissues, and significantly decreased P21 expression in the liver and lung. Fisetin treatment significantly decreased TREM2 in the lung tissues and showed a trend of downregulation in the liver, spleen, and heart. A significant decrease in NRLP3 in the liver was observed after fisetin treatment. Finally, fisetin treatment significantly downregulated SOD1 in the liver and spleen while upregulating CAT in the spleen. In conclusion, we found that senescent cells were widely present in the cerebral brain cortex and cerebellum and non-CA area of the hippocampus of old sheep. Fisetin treatment significantly decreased senescent neurons, astrocytes, and microglia in both gray and white matter of the cerebral brain cortex and non-CA area of the hippocampus. In addition, fisetin treatment decreased senescent gene expressions and inflammasomes in other organs, such as the lung and the liver. Fisetin treatment represents a promising therapeutic strategy for age-related diseases.

The interventricular septum contributes to the pumping function of both ventricles. However, unlike the ventricular wall, its mechanical behavior remains largely unknown. To fill the knowledge gap, this study aims to characterize the biaxial and transmural variation of the mechanical properties of the septum and compare it to the free walls of the left and right ventricles (LV/RV). Fresh hearts were obtained from healthy, adult sheep. The septal wall was sliced along the mid-line into two septal sides and compared to the epicardial layers of the LV- and RV-free walls. Biaxial tensile mechanical tests and constitutive modeling were performed to obtain the passive mechanical properties of the LV- and RV-side of the septum and ventricular walls. We found that both sides of the septum were significantly softer than the respective ventricular walls, and that the septum presented significantly less collagen than the ventricular walls. At low strains, we observed the symmetric distribution of the fiber orientations and a similar anisotropic behavior between the LV-side and RV-side of the septum, with a stiffer material property in the longitudinal direction, rather than the circumferential direction. At high strains, both sides showed isotropic behavior. Both septal sides had similar intrinsic elasticity, as evidenced by experimental data and constitutive modeling. These new findings offer important knowledge of the biomechanics of the septum wall, which may deepen the understanding of heart physiology.

Background context: While the clinical effectiveness of recombinant human Platelet Derived Growth Factor‐B chain homodimer combined with collagen and β‐tricalcium phosphate (rhPDGF‐BB + collagen/β‐TCP) treatment for indications involving hindfoot and ankle is well‐established, it is not approved for use in spinal interbody fusion, and the use of autograft remains the gold standard.Purpose: The purpose of this study was to compare the effects of rhPDGF‐BB + collagen/β‐TCP treatment on lumbar spine interbody fusion in an ovine model to those of autograft bone and collagen/β‐TCP treatments using biomechanical, radiographic, and histological assessment techniques.Study design: Thirty‐two skeletally mature Columbian Rambouillet sheep were used to evaluate the safety and effectiveness of rhPDGF‐BB + collagen/β‐TCP matrix in a lumbar spinal fusion model. Interbody polyetheretherketone (PEEK) cages contained either autograft, rhPDGF‐BB + collagen/β‐TCP, collagen/β‐TCP matrix, or left empty.Methods: Animals were sacrificed 8‐ or 16‐weeks post‐surgery. Spinal fusion was evaluated via post‐sacrifice biomechanical, micro‐computed tomography (μCT), and histological analysis. Outcomes were statistically compared using a two‐way analysis of variance (ANOVA) with an alpha value of 0.05 and a Tukey post‐hoc test.Results: There were no statistically significant differences between groups within treatment timepoints for flexion‐extension, lateral bending, or axial rotation range of motion, neutral zone, neutral zone stiffness, or elastic zone stiffness. μCT bone volume fraction was significantly greater between treatment groups independent of timepoint where Autograft and rhPDGF‐BB + collagen/β‐TCP treatments demonstrated significantly greater bone volume fraction as compared to collagen/β‐TCP (P = .026 and P = .038, respectively) and Empty cage treatments (P = .002 and P = .003, respectively). μCT mean bone density fraction was most improved in rhPDGF‐BB + collagen/β‐TCP specimens at the 8 week and 16‐week timepoints as compared to all other treatment groups. There were no statistically significant differences in histomorphometric measurements of bone, soft tissue, or empty space between rhPDGF‐BB + collagen/β‐TCP and autograft treatments.Conclusions: The results of this study indicate that the use of rhPDGF‐BB combined with collagen/β‐TCP promotes spinal fusion comparable to that of autograft bone.Clinical significance: The data indicate that rhPDGF‐BB combined with collagen/β‐TCP promotes spinal fusion comparably to autograft bone treatment and may offer a viable alternative in large animal spinal fusion. Future prospective clinical studies are necessary to fully understand the role of rhPDGF‐BB combined with collagen/β‐TCP in human spinal fusion healing.

Background: Untreated rotator cuff tears lead to irreversible tendon degeneration, resulting in unacceptable repair prognosis. The inability of current animal models of degenerated rotator cuff tendons to more fully emulate the manifestation and degree of pathology seen in humans with a previously torn rotator cuff tendon (s) significantly impairs the development of novel therapeutics. Therefore, the objective of this study was to develop a large-animal translational model of enthesis damage to the rotator cuff tendons to mimic the chronic degenerative changes that occur in patients that demonstrate clinical manifestations of tendinopathy. Methods: A partial enthesis tear model (i.e., sharp transection) in adult sheep was created by cutting the tendon fibers perpendicularly through the enthesis midpoint, while leaving the other portion of the tendon in-tact. To assess tendon integrity, non-destructive biomechanical tests were performed, followed by histopathological, histomorphological, and gene expression analysis. Samples of degenerated human rotator cuff tendons obtained from patients undergoing reverse total shoulder arthroplasty to use for comparative pathological analysis. Results: In the sheep model, transected tendons at all timepoints had significantly decreased mechanical properties. Histopathologic evaluation and Bonar scoring revealed that the tendons in sheep underwent degenerative changes similar in magnitude and manifestation as the degenerated human tendon samples. Furthermore, similar levels of collagen disorganization were noted between the 6 and 12-week ovine samples and the degenerated human samples. Conclusions: These findings indicate that the new sheep model of rotator cuff injury reliably recapitulates the structural and cellular changes that occur clinically in humans with chronic rotator cuff tendon injuries and suggest that this new model is well suited to evaluation of new therapeutic interventions.