HPF1 regulates tendon stem/progenitor cell senescence and tendon repair via PARP1-mediated poly-ADP ribosylation of HuR.

BACKGROUND: Tendon stem/progenitor cells (TSPCs) play a vital role in tendon repair, regeneration and homeostasis. However, the specific mechanism of TSPCs aging is still unclear. OBJECTIVE: This study aims to explore the role and molecular mechanism of HPF1 in the aging of TSPCs. METHODS: Young and aged TSPCs (Y-TSPCs and A-TSPCs) were acquired from 3 to 4 and 24-26-month-old Sprague-Dawley male rats, TSPCs (Y-TSPCs and A-TSPCs) were subjected to senescence-associated ß-galactosidase (SA-ß-Gal))staining and telomerase activity detection, p16, p21, Scx, Tnmd, Col1, Col3HPF1 and PAPR1 expression levels were detected by Western blot or Reverse Transcription-quantitative Polymerase Chain Reaction (RT-qPCR), Reciprocal co-immunoprecipitation (co-IP) was used to explore the interaction between HPF1 and PARP1. Ribonucleoprotein immunoprecipitation (RNP-IP) was used to analyze the binding of HuR to the senescence marker gene mRNAs, IP was used to perform HPF1 to the PARylation of HuR, and the half-life of p16 and p21 were detected. Finally, we established an in vivo model, and the tendon tissue was used to perform hematoxylin and eosin (HE) and masson's trichrome staining, as well as the immunohistochemical analysis of Col I and TNMD. RESULTS: Compared with Y-TSPCs, A-TSPCs had significantly enhanced cell senescence and significantly reduced tendon differentiation ability, and significantly increased the expression of HPF1 and PARP1. In addition, HPF1 and PARP1 interacted and coordinated the senescence and differentiation of TSPCs, HPF1 could also regulate the expression of p21 and p21, the interaction of p16 or p21 with HuR, and the poly-ADP ribosylation of PARP1 to HuR. HPF1 overexpression and siHuR co-transfection significantly reduced the half-life of p16 and p21, and HPF1 and PARP1 regulated the mRNA levels of p16 and p21 through HuR. Finally, in vivo experiments have shown that HPF1 or PARP1 overexpression could both inhibit the ability of tendon differentiation and promote cell senescence. CONCLUSIONS: HPF1 promoted the senescence of TSPCs and inhibits the tendon differentiation of TSPCs through PARP1-mediated poly-ADP ribosylation of HuR.

Young TSPC-Derived Exosomal circPVT1 Ameliorates Aging-Impaired Cell Function via SIRT1/NF-κB.

Tendon stem/progenitor cell (TSPC) senescence is often associated with age-dependent tendon diseases and greatly reduces the capacities for tendon repair and replacement. Exosomes contain bioactive molecules and have been increasingly used in regenerative medicine. In the present study, we demonstrated the antiaging effects of young exosomes from circPVT1-overexpressing TSPCs at early passages (circPVT1-exo). These exosomes attenuated the phenotypes of aged TSPCs at late passages (L-TSPCs) by enhancing self-renewal and proliferation abilities, suppressing cell senescence, maintaining their tenogenic capacity, and weakening their osteogenic differentiation. Mechanistically, circPVT1-exo inhibited the NF-κB pathway and increased SIRT1 expression in L-TSPCs. Knockdown of SIRT1 reversed these effects as evidenced by increased senescence, decreased proliferation, and tenogenic differentiation. These results suggest that circPVT1-exo may ameliorate aging-impaired TSPC function by modulating the SIRT1/NF-κB pathway, suggesting that circPVT1-exo has therapeutic potential for age-related diseases.

Lentinan-loaded GelMA hydrogel accelerates diabetic wound healing through enhanced angiogenesis and immune microenvironment modulation.

Diabetic wound healing is a substantial clinical challenge, characterized by delayed angiogenesis and unresolved inflammation. Lentinan, a polysaccharide extracted from shiitake mushrooms, has the potential to regulate both macrophage polarization and angiogenesis, though this aspect remains inadequately explored. To facilitate lentinan's clinical utility, we have developed a GelMA hydrogel encapsulated with lentinan (10 µM), offering a controlled release mechanism for sustained lentinan delivery at the wound site. Application of the lentinan-encapsulated delivery system topically significantly expedites wound closure compared to control groups. Furthermore, histological examination demonstrates enhanced neovascularization and reduced inflammation in lentinan-treated wounds, as evidenced by increased M2 macrophage infiltration. Moreover, our results indicated that lentinan-induced AMPK activation promotes DAF16 expression, enhancing the resistance of macrophages and HUVECs to oxidative stress in high-glucose environments, thereby promoting M2 macrophage polarization and angiogenesis. All these findings underscore lentinan's capacity to modulate macrophage polarization and angiogenesis via the AMPK/DAF16 pathway, ultimately facilitating the healing of diabetic wounds.

[Mid-term effectiveness of arthroscopic anterior cruciate ligament reconstruction combined with meniscus allograft transplantation].

OBJECTIVE: To summarize the mid-term effectiveness of arthroscopic anterior cruciate ligament (ACL) reconstruction combined with meniscus allograft transplantation. METHODS: A clinical data of 21 patients treated with arthroscopic ACL reconstruction and meniscus allograft transplantation and followed up more than 5 years between February 2007 and December 2014 was retrospectively analyzed. There were 12 males and 9 females, aged from 18 to 45 years, with an average age of 23.5 years. The cause of injury was sport sprain in 15 cases, falling in 4 cases, and traffic accident in 2 cases. The time from injury to operation ranged from 2 to 36 months, with an average of 12 months. Among them, 15 patients underwent previous meniscectomy, with an average interval of 1.6 years (range, 3 months to 6.5 years). All patients were primary ACL reconstruction. Preoperative anterior drawer test, Lachman test, and pivot shift test were positive. Lysholm score was 43.6±10.2. International Knee Documentation Committee (IKDC) score was 60.50±14.06. Of the 21 patients, 10 were gradeⅠ-Ⅱcartilage injuries and 11 were grade Ⅲ cartilage injuries according to MRI. RESULTS: All patients were followed up 5.1-7.8 years, with an average of 5.5 years. There were 2 cases of numbness of lower extremity, 3 cases of slight exudation of incision, 2 cases of articular movement bounce, 5 cases of mild joint swelling and pain after exercise. At last follow-up, Lachman tests were negative in 18 cases and positive in 3 cases; anterior drawer tests were negative in 19 cases and positive in 2 cases; pivot shift tests were negative in all cases. Lysholm score was 84.5±16.5 and IKDC score was 85.25±4.60, which were significantly higher than those before operation ( P<0.01). The flexion and extension of the affected knee joint were (128±13) and (3±7)°, respectively, which were smaller than those of the healthy knee joint [(133±15), (0±5)°] ( P<0.01). The results of KT-1000 test showed that when knee flexion was 30 and 90°, tibial anterior displacement of affected side [(2.35±1.20), (1.60±1.15) mm] were not significantly different from those of healthy side [(1.20±1.10), (1.10±1.03) mm] ( P>0.01). MRI showed that the ACL graft was in normal position and meniscus survived well. Cartilage injuries were gradeⅠ-Ⅱ in 18 cases and grade Ⅲ in 3 cases. CONCLUSION: For patients with severe meniscus injury and ACL rupture, ACL reconstruction combined with meniscus allograft transplantation can restore the stability of the joint, recover the meniscus function which is conducive to the protection of articular cartilage and obtain satisfactory mid-term effectiveness.

Arthroscopic techniques and instruments for meniscal allograft transplantation using the bone bridge in trough method.

The aim of the current study was to investigate the construction of the bone bridge and tibial plateau under arthroscopy during meniscal allograft transplantation, in order to simplify and enhance the accuracy of bone bridge fixation intraoperatively. A traction line passed through the attachment of the anterior and posterior horns of the superior meniscus to the bone bridge was used to pull the bone bridge into the knee joint cavity and fix the anteroposterior horns of the meniscus. At the junction of the body of the meniscus and the posterior and anterior horns of the meniscus, a traction line was created at the anterior and posterior 1/3 of the meniscus to pull and fix the meniscus. Under the arthroscope, the aiming device was placed on the tibial plateau. The direction and width of the guide plate were identical to those of the bone trough of the tibial plateau. The bone tunnel was made using the guide needle and a 9-mm hollow drill, the piston rod was inserted, and the arch-shaped bone knife was inserted along with the piston rod to construct the 9-mm bone trough of the tibial plateau. The periphery of the meniscus was sutured to the joint capsule. These surgical techniques and instruments could standardize meniscal graft transplantation and avoid the incidence of surgical errors caused by mismatched size and shape of the bone bridge and bone trough. This would make the surgery more convenient, safe and accurate. The four-point fixation of the tibial plateau contributed to preventing the reversal of the meniscus during transplantation, and partially reconstructed the coronary ligament of the meniscal tibia, which probably enhanced the stability of the meniscus and minimized the risk of extrusion of the meniscal allograft. The bone bridge and bone trough of the tibial plateau were properly constructed under arthroscopy. Dynamic monitoring of surgical indications, explicit preoperative preparation and standardized surgical procedures could achieve high efficacy and excellent fixation effect during meniscal graft transplantation. The four-point fixation of the tibial plateau maintains and enhances the stability of the meniscal allograft, reduces the risk of meniscal extrusion and ensures the postoperative recovery of meniscal function.

[Effects of meniscectomy and transplantation of human knee on stress of tibiofemoral articular surface].

OBJECTIVE: To investigate the effects of meniscectomy and transplantation repair ot the knee on the stress area and average pressure of the tibiofemoral articular surface so as to provide a reference for the relevant basic and clinical researches. METHODS: Seven qualified right knee joints from adult men cadavers were selected. Required structure was retained after careful dissection. The pressure-sensitive paper was clipped to the proper size in accordance with the measured size of the tibial platform to reserve. The experiment was divided into 4 groups: normal knee group (group A), knee meniscus injury group (group B), knee meniscectomy group (group C), and knee meniscus transplantation group (group D). A horizontal incision above the meniscus was made in the position of knee joint capsule, and the pressure-sensitive paper was placed into the medial and lateral space of the knee joint, then the proximal tibia and distal femur were fixed stably and finally a universal mechanical machine was used for testing in appropriate environmental conditions (the knee joints were given longitudinal 700 N pressure at 00 extension and 30, 60, 90, and 1200 flexion for continuous 120 seconds) until the full color reaction. The knee models were prepared, and then the universal mechanical machine was used to perform a test according to the method stated above respectively. The pressure-sensitive paper was removed, and the color negative films were separated and marked. Colorful image analysis system was used to calculate and analyze the stress area and average pressure after the scanner being used to collect image information. RESULTS: The stress area was gradually reduced and the average pressure was gradually increased with increasing flexion angle of the knee. There was significant difference in the stress area and the average pressure between various flexion angles in 4 groups (P < 0.05). Group C had significantly lower stress area and significantly higher average pressure than the other 3 groups (P < 0.05), but no significant difference was found among groups A, B, and D (P > 0.05). CONCLUSION: The stress of the tibiofemoral articular surface significantly increases after knee meniscus injury or resection, and the average pressure significantly increases. The stress of the tibiofemoral articular surface can be restored to almost normal after meniscus transplantation. Therefore, the injured meniscus should also be retained or repaired in the static state.