The onset and progression of human inflammatory joint diseases are strongly controlled by the activation of resident synovium/infrapatellar fat pad (IFP) pro-inflammatory and pain-transmitting signaling. We recently reported that intra-articularly injected IFP-derived Mesenchymal Stem/Stromal Cells (IFP-MSC) acquire a potent immunomodulatory phenotype and actively degrade Substance P (SP) via neutral endopeptidase CD10 (neprilysin). Our hypothesis is that IFP-MSC robust immunomodulatory therapeutic ef-fects are largely exerted via their CD10-bound exosomal secretome (IFP-MSC EXOs) by attenuating synoviocyte pro-inflammatory activation and articular cartilage degradation. Herein, IFP-MSC EXOs were isolated from CD10High- and CD10Low-expressing IFP-MSC cultures and their exosomal miRNA cargo was assessed using multiplex methods. Functionally, we interrogated the effect of CD10High and CD10Low EXOs on stimulated by inflammatory/fibrotic cues synoviocytes monocultures and cocultures with IFP-MSC de-rived chondropellets. Finally, CD10High EXOs were tested in vivo for their therapeutic capacity in an animal model of acute synovitis/fat pad fibrosis. Our results showed that CD10High and CD10Low EXOs possess distinct miRNA profiles. Reactome analysis of miRNAs highly present in exosomes showed their involvement in the regulation of six gene groups, particularly the immune system. Stimulated synoviocytes exposed to IFP-MSC EXOs demonstrated significantly reduced proliferation and altered inflammation-related molecular profiles compared to control stimulated synoviocytes. Importantly, CD10High EXOs treatment of stimulated chondropellets/synoviocytes cocultures indicated a significant chondroprotective effects. Therapeutically, CD10High EXOs treatment resulted in robust chondroprotective effects by retaining articular cartilage structure/composition and PRG4 (lubricin)-expressing cartilage cells in the animal model of acute synovitis/IFP fibrosis. Our study suggests that CD10High EXOs possess immuno-modulatory miRNA attributes with strong chondroprotective/anabolic effects for articular cartilage in vivo. The results could serve as a foundation for EXOs-based therapeutics for the resolution of detrimental aspects of immune-mediated inflammatory joint changes associated with conditions such as osteoarthritis (OA).

Segmental bone defects caused by trauma, infection, tumor resection or osteoporotic fractures present significant surgical treatment challenges. Host bone autograft is considered the gold standard to restore function but comes with the cost of harvest site comorbidity. Allograft bone is a secondary option but has its own limitations in incorporation with host bone as well as cost. Therefore, developing new bone tissue engineering strategies to treat bone defects is critically needed. In the past three decades, the use of stem cells delivered with different scaffolds or growth factors for bone tissue engineering has made tremendous progress. Many varieties of stem cells have been isolated from different tissues for use in bone tissue engineering. This review summarizes the progress in using different postnatal stem cells including bone marrow mesenchymal stem cells, muscle-derived stem cells, adipose-derived stem cells, dental pulp stem cells/periodontal ligament stem cells, periosteum stem cells, umbilical cord-derived stem cells, peripheral blood stem cells and urine-derived stem cells for bone tissue engineering and repair. This review also summarizes the progress using exosomes or extracellular vesicles delivered with various scaffolds for bone repair. The advantages and disadvantages of each type of stem cell are also discussed and explained in detail. It is hopeful in the future that these preclinical results will translate into new therapies for bone defect repair.

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 organs in old sheep, a more translational model. Approximately 6-7 years old female sheep (N=6) were treated with 100mg/kg fisetin or vehicle two consecutive days a week for 8 weeks. All organs were harvested at the time of sacrifice. Histology, immunofluorescent staining, as well as Q-PCR was performed on different regions of brain tissues and organs. Our results indicated that Fisetin treatment at the current regimen did not affect general morphology of the brain. The presence of senescent cells in both cerebral brain cortex and cerebellum was detected by SA-β-Gal staining. More senescent cells were observed in the gray matter when compared to the white matter of the cerebral brain cortex. These senescent cells are mainly neurons in both gray and white matter of either cerebral brain cortex or cerebellum. Fisetin treatment showed a trend of decrease SA-β-Gal cells in gray matter of both cerebral brain cortex and cerebellum and significantly decreased in brain cortex white matter. Furthermore, fisetin treatment significantly decreased P16+ cells in brain cortex NEUN+ neurons, GFAP+ astrocytes, IBA+ microglia cells in both gray and white matter of cerebral brain cortex. Fisetin treatment also significantly decreased P16+ cells in microglia cells and a trend of decrease of P16+ cells in astrocytes in the non- (Cornu Ammonis) CA area of hippocampus. However, fisetin treatment did not change P16+ cells in the NEUN+ neurons in the CA1-4 area of the hippocampus. At the mRNA level, fisetin showed a decreased in GLB1 in heart ventricle muscle tissue and spleen tissues but not in other organs tested. Fisetin treatment also showed a decreased antioxidant gene SOD1 and increased CAT in spleen and bone marrow. Fisetin treatment showed variable effects in SASP and inflammasome genes in different organs. In conclusion, we found senescent cells are widely present in the cerebral brain cortex and cerebellum of old sheep. In addition, fisetin treatment decreased senescent cells as well as P16+ cells in the neurons in both gray and white matter of cerebral brain cortex and in astrocytes and microglia cells of cerebral brain cortex and non-CA area of hippocampus. Fisetin treatment represents a promising therapeutic strategy for age-related brain disease.