Inhibition of the P53/P21 Pathway Attenuates the Effects of Senescent Nucleus Pulposus Cell-Derived Exosomes on the Senescence of Nucleus Pulposus Cells.

OBJECTIVE: The purpose of this paper is to investigate the effects of senescent nucleus pulposus cell (NPC)-derived exosomes (SNPC-Exo) and the roles of the P53/P21 pathway on the senescence of NPC. METHODS: The senescent phenotypes of NPC were induced by interleukin-1ß treatment. SNPC-Exo was extracted from the culture medium of senescent NPC and purified by differential centrifugation. The structure of SNPC-Exo was identified by transmission electron microscopy and western blot analysis was used to determine the exosomal marker proteins CD63 and Tsg101. Western blot analysis was performed to determine the relative expression levels of P16, P21, and P53 in NPC. Senescence-associated ß-galactosidase (SA-ß-gal) staining was used to stain the senescent NPC and a phase contrast microscope was used to observe and count the SA-ß-gal staining of NPC. The proliferation of SNPC-Exo-treated NPC was assessed using growth curve analysis and the colony formation assay. The cell cycle of SNPC-Exo-treated NPC was determined by flow cytometry. NPC were transfected with siRNA to knock down P53 and P21 expression. RESULTS: Interleukin-1ß-treated NPC had a higher percentage of SA-ß-gal positive cells (45%) than the control group (20%) and showed an increase in the relative expression of P16, P21, and P53 (P < 0.05). SNPC-Exo were positive for exosomal marker protein CD63 and Tsg 101 and negative for calnexin, and successfully internalized as previously described. SNPC-Exo-treated NPC showed an increase in the relative expression of P21 and P53 (P < 0.05). Compared with the control group, the SNPC-Exo-treated NPC showed a lower growth rate (3 times lower on the 5th day and 2 times lower on the 7th day), fewer colony-forming units (12.0%), and a higher percentage of SA-ß-gal-positive NPC (50.0%). The SNPC-Exo-treated NPC contained more G1 phase cells (68.0%) and fewer S phase (15.5%) cells than the control group (53.0% in G1 phase, 33.5% in S phase). The expression of P21 and P53 significantly decreased in SNPC-exo-treated NPC after siRNA transfection (P < 0.05), followed by a higher growth rate (2 times higher on the 5th day and 1.5 times higher on the 7th day) and lower percentage of SA-ß-gal-positive NPC (22.5%). Moreover, the inhibition of the P53/P21 pathway promoted the SNPC-Exo-treated NPC to enter the S phase (from 15.5% to 25.3%). CONCLUSION: The inhibition of the P53/P21 pathway attenuated the senescence of NPC induced by SNPC-Exo.

[Reconstruction of medial patellofemoral ligament with transposition of great adductor muscular tendon for the treatment of teenagers' recurrent patellar dislocation].

OBJECTIVE: To investigate surgical method and clinical curative effects of medial patellofemoral ligament (MPFL) reconstruction with great adductor muscular tendon in treating teenagers' recurrent patellar dislocation. METHODS: From May 2012 to September 2014, 19 patients with recurrent dislocation of patellar, including 6 males and 13 females with an average of 16 years old (ranged from 13 to 17 years), the courses of disease ranged from 3 to 18 months(averaged 6 months). All patients were underwent great adductor muscular tendon transposition to reconstruct medial patellofemoral ligament. The curative effects were evaluated by preoperative and postoperative with Lysholm scores and Patellofemoral angle and Q angle. RESULTS: All patients were followed up from 12 to 18 months with an average of 16.5 months. Primary healing was achieved at stage I. No pain, swelling and patellar dislocation or subluxation occurred. Patellofemoral angle increased from preoperative (-3.8±4.9)° to (10.3±4.1)° postoperatively. Q angle decreased from preoperative(16.4±3.1)° to(10.5±1.2)° postoperatively; Lysholm scores were improved from preoperative (68.6±8.5) to (93.7±6.5) final follow-up (P<0.01), and 15 cases got excellent results, 3 good, and 1 fair. CONCLUSIONS: Reconstruction of medial patellofemoral ligament with transposition of great adductor muscular tendon could obviously recover stability of patellar, and it is one of the effective methods for the treatment of teenagers' recurrent patellar dislocation.