Interposition of acellular amniotic membrane at the tendon to bone interface would be better for healing than overlaying above the tendon to bone junction in the repair of rotator cuff injury

PURPOSE

The retear rate of rotator cuff (RC) after surgery is high, and the rapid and functional enthesis regeneration remains a challenge. Whether acellular amniotic membrane (AAM) helps to promote the healing of tendon to bone and which treatment is better are both unclear. The study aims to investigate the effect of AAM on the healing of RC and the best treatment for RC repair.

METHODS

Thirty-three Sprague Dawley rats underwent RC transection and repair using microsurgical techniques and were randomly divided into the suturing repair only (SRO) group (n = 11), the AAM overlaying (AOL) group (n = 11), and the AAM interposition (AIP) group (n = 11), respectively. Rats were sacrificed at 4 weeks, then examined by subsequent micro-CT, and evaluated by histologic and biomechanical tests. The statistical analyses of one-way ANOVA or Kruskal-Wallis test were performed using with SPSS 23.0. A p < 0.05 was considered a significant difference.

RESULTS

AAM being intervened between tendon and bone (AIP group) or overlaid over tendon to bone junction (AOL group) in a rat model, promoted enthesis regeneration, increased new bone and cartilage generation, and improved collagen arrangement and biomechanical properties in comparison with suturing repair only (SRO group) (AOL vs. SRO, p < 0.001, p = 0.004, p = 0.003; AIP vs. SRO, p < 0.001, p < 0.001, p < 0.001). Compared with the AOL group, the AIP group had better results in micro-CT evaluation, histological score, and biomechanical testing (p = 0 0.039, p = 0.011, p = 0.003, respectively).

CONCLUSION

In the RC repair model, AAM enhanced regeneration of the tendon to bone junction. This regeneration was more effective when the AAM was intervened at the tendon to bone interface than overlaid above the tendon to bone junction.

Kartogenin-loaded polyvinyl alcohol/nano-hydroxyapatite composite hydrogel promotes tendon-bone healing in rabbits after anterior cruciate ligament reconstruction

Accumulating evidence supports the role of cartilage tissue engineering in cartilage defect repair, but the biological function has yet to be fully explained. In this work, kartogenin (KGN), an emerging chondroinductive nonprotein small molecule, was incorporated into a composite hydrogel of polyvinyl alcohol/nano-hydroxyapatite (PVA/n-HA) to fabricate an appropriate microenvironment for tendon-bone healing after anterior cruciate ligament (ACL) reconstruction. KGN/PVA/n-HA composite hydrogel scaffolds were prepared by in situ synthesis and physical adsorption, followed by characterization under a scanning electron microscope. The scaffolds were transplanted into healthy New Zealand White (NZW) rabbits. It was confirmed that KGN/PVA/n-HA scaffolds were successfully prepared and exhibited good supporting properties and excellent biocompatibility. Unilateral ACL reconstruction was constructed with tendon autograft in NZW rabbits, and the morphology and diameter of collagen fiber were analyzed. The scaffolds were shown to promote ACL growth and collagen fiber formation. Furthermore, microcomputerized tomography analysis and bone formation histology were performed to detect new bone formation. KGN/PVA/n-HA scaffolds effectively alleviated cartilage damage and prevented the occurrence of osteoarthritis. Meanwhile, ligament-bone healing and bone formation were observed in the presence of KGN/PVA/n-HA scaffolds. In conclusion, these results suggest that the KGN/PVA/n-HA scaffolds can facilitate tendon-bone healing after ACL reconstruction and might be considered novel hydrogel biomaterials in cartilage tissue engineering.

Platelet-rich plasma in orthopedics: Bridging innovation and clinical applications for bone repair

In the burgeoning domain of orthopedic therapeutic research, Platelet-Rich Plasma (PRP) has firmly established its position, transforming paradigms ranging from tissue regeneration to the management of chondral lesions. This review delves into PRP's recent integrations with cutting-edge interventions such as 3D-printed scaffolds, its role in bone and cartilage defect management, and its enhanced efficacy when combined with molecules like Kartogenin (KGN) for fibrocartilage zone repair. Significant attention is paid to tissue engineering for meniscal interventions, where a combination of KGN, PRP, and bone marrow-derived mesenchymal stem cells are under exploration. Within the sphere of osteochondral regenerative therapy, the synergy of PRP with Bone Marrow Aspirate Concentrate (BMAC) represents a noteworthy leap towards cartilage regeneration. The innovative incorporation of PRP with biomaterials like hydroxyapatite and graphene oxide further underscores its versatility in supporting structural integrity and ensuring sustained growth factor release. However, while PRP's autologous and nontoxic nature makes it an inherently safe option, concerns arising from its preparation methods, particularly with bovine thrombin, necessitate caution. As of 2023, despite the burgeoning promise of PRP in bone healing, the quest for its standardization, optimization, and substantiation through rigorous clinical trials continues. This comprehensive review elucidates the contemporary applications, challenges, and future trajectories of PRP in orthopedics, aiming to spotlight areas primed for further research and exploration.

Simvastatin promotes rat Achilles tendon-bone interface healing by promoting osteogenesis and chondrogenic differentiation of stem cells

To investigate the effect and mechanism of simvastatin on cell components of tendon-bone healing interface. The tendon-bone healing model was established by inserting the end of the Achilles tendon into the tibial tunnel on 24 rats, and simvastatin was used locally at the tendon-bone interface. Healing was evaluated at 8 weeks by mechanical testing, micro-CT, and qualitative histology including H&E, Toluidine blue, and immunohistochemical staining. In vitro, bone marrow stromal cells (BMSCs) and tendon-derived mesenchymal stem cells (TDSCs) underwent osteogenic and chondrogenic differentiation respectively by plate co-culture. An analysis was performed on days 7 and 14 of cell differentiation. Biomechanical testing demonstrated a significant increase in maximum stiffness in the simvastatin-treated group. Micro-CT analysis showed that the bone tunnels in the simvastatin group were smaller in diameter and had higher bone density. H&E and Toluidine blue staining demonstrated that tendon-bone healing was significantly greater with better tissue arrangement and more extracellular matrix in the simvastatin-treated group than that in the control group, and immunohistochemical staining showed the expression of VEGF in simvastatin group was significantly higher. Histological staining and RT-PCR confirmed that simvastatin could promote the differentiation of co-cultured BMSCs and TDSCs into osteoblasts and chondroblasts, respectively. The effect of promoting osteogenic differentiation was more tremendous at 14 days, while its effect on promoting chondroblast differentiation was more evident on the 7th day of differentiation. In conclusion, local administration of simvastatin can promote the tendon-bone healing by enhancing neovascularization, chondrogenesis, and osteogenesis in different stages of the tendon-bone healing process.

Advances in the Clinical Application of Platelet-Rich Plasma in the Foot and Ankle: A Review

Autologous and recombinant biologic substances have been generated as a result of the research into the cellular features of the healing process. Orthobiologics are increasingly being used in sports medicine and musculoskeletal surgery. Nevertheless, clinical data are limited; consequently, further studies are required, particularly in foot and ankle pathologies. This review aims to provide evidence of the most recent literature results and ignite the interest of orthopedic specialists eager for an update about the most current discussion on platelet-rich plasma (PRP) clinical applications in the foot and ankle fields. Previous studies have shown that platelet-rich plasma can be beneficial in treating various conditions, such as chronic foot ulcers, osteoarthritis, Achilles tendinopathy, etc. Despite the positive effects of PRP on various musculoskeletal conditions, more prospective studies are needed to confirm its effectiveness at treating ankle and foot pathologies. In addition to clinical trials, other factors, such as the quality of the research and the procedures involved, must be considered before they can be used in patients. More long-term evaluations are needed to support or oppose its application in treating foot and ankle disorders. We present the most extensive review of PRP's clinical applications in the foot and ankle field.

Strategies for promoting tendon-bone healing: Current status and prospects

Tendon-bone insertion (TBI) injuries are common, primarily involving the rotator cuff (RC) and anterior cruciate ligament (ACL). At present, repair surgery and reconstructive surgery are the main treatments, and the main factor determining the curative effect of surgery is postoperative tendon-bone healing, which requires the stable combination of the transplanted tendon and the bone tunnel to ensure the stability of the joint. Fibrocartilage and bone formation are the main physiological processes in the bone marrow tract. Therefore, therapeutic measures conducive to these processes are likely to be applied clinically to promote tendon-bone healing. In recent years, biomaterials and compounds, stem cells, cell factors, platelet-rich plasma, exosomes, physical therapy, and other technologies have been widely used in the study of promoting tendon-bone healing. This review provides a comprehensive summary of strategies used to promote tendon-bone healing and analyses relevant preclinical and clinical studies. The potential application value of these strategies in promoting tendon-bone healing was also discussed.

Comparison of cortical versus cancellous bone fixation in tendon-to-bone healing with a rat trans-calcaneal suture model for Achilles tendon sleeve avulsion

BACKGROUND

Trans-calcaneal suture technique is an economical and effective method for repairing Achilles tendon sleeve avulsion. Whether cancellous bone fixation upon this technique could accelerate tendon-to-bone healing is unknown. The purpose of this study is to compare the effect of cortical versus cancellous bone fixation on tendon-bone healing with a novel rat trans-calcaneal suture model.

METHODS

Trans-calcaneal suture treatment was carried out on the right hindlimb in male Sprague-Dawley rats (N = 80). They were randomly divided into the cortical group (Achilles fixed to the calcaneal cortical bone, n = 40) and the cancellous group (Achilles fixed to the calcaneal cancellous bone, n = 40). Gait analysis and immunohistochemistry were performed 1, 4, 7, and 14 days after the operation. Gross observation, biomechanical analysis, micro-CT, and histological analysis were performed 4 and 8 weeks after surgery. Independent-samples t tests were used for comparison between groups.

RESULTS

At 1, 4, and 7 days, the swing time of the affected limb in the cancellous group decreased, while the duty cycle, the maximum contact area, the print area, and the mean intensity increased significantly. The cross-sectional area of the tendon-bone junction in the cancellous group was smaller, and the failure load and stiffness were higher 4 weeks after the operation. The cancellous group showed more proportion of new bone and a relatively well-organized and dense connective tissue interface with better fibrocartilage-like tissue at 4 weeks after the operation. The ratio of ED2 + macrophages in the cancellous group was significantly higher than in the cortical group on 1, 4, 7, and 14 days. There were no significant differences in gait at 2 weeks, in appearance, biomechanics, new bone formation, and histology at 8 weeks after surgery between the two groups.

CONCLUSION

In the new rat trans-calcaneal suture model, cancellous fixation can accelerate tendon-to-bone healing in the early stage, which perhaps is related to the abundant bone marrow tissue in the cancellous bone that modulates the inflammatory processes.

Platelet-rich plasma pretreatment protects anterior cruciate ligament fibroblasts correlated with PI3K-Akt-mTOR pathway under hypoxia condition

Background

/Objective: Biological factors such as platelet-rich plasma (PRP) combined with anterior cruciate ligament (ACL) primary repair technology are used to treat ACL injury. However, the protective mechanism of PRP for ACL fibroblasts under hypoxia condition is still unknown. The aim of this study was to investigate the protective effect of PRP on ACL fibroblasts under hypoxia condition and illustrate the mechanism of PRP regulating the ACL fibroblasts under hypoxia condition.

Methods

The cells were divided into three groups: control group, hypoxia group and PRP pretreatment group. Lethal dose (LD) 50 for hypoxia induction time and the maximum efficacy of PRP concentration were confirmed by CCK-8 assay. The ability of cell apoptosis, cell proliferation, and cell migration were tested by flow cytometry, scratch assay and transwell assay, respectively. Extracellular matrix (ECM) synthesis and hypoxia-inducible factor 1α (HIF-1α) were identified by immunofluorescence staining, Masson's staining and transmission electron microscope analysis. Inflammatory cell infiltration was assessed by hematoxylin and eosin staining as well as immunofluorescence staining. Western blot analysis and real-time PCR were performed to assess the associated gene and protein expression, respectively. The ratio of phosphorylated/total PI3K, Akt and mTOR were also assessed by western blot analysis.

Results

① LD 50 of hypoxia was 48 ​h and the maximum efficacy of PRP concentration was 600 ​× ​10⁹/L. ② ANNEXIN V-FITC/PI flow cytometry showed that the hypoxia condition significantly increased the apoptosis of cells (P ​< ​0.001) whereas PRP pretreatment significantly decreased the apoptosis of cells under hypoxia (P ​< ​0.001). The expressions of gene and protein of Bax, Bcl-2, cleaved-caspase 3 were consistent with the results of flow cytometric analysis. ③ Cell cycle analysis for flow cytometry showed the inhibitory effect of hypoxia and promotive effect of PRP pretreatment. ④ Immunofluorescence staining (HIF-1α, collagen I and III) showed the positive effect of hypoxia and negative effect of PRP on these parameters. Real-time PCR showed that type I and III collagen were 2.1 folds and 2.5 folds higher after 48 ​h hypoxia induction compared to the control group. PRP pretreatment significantly reduced the type I and III collagen mRNA expression of the hypoxia induced ACL fibroblasts to 78.5% and 77.7% at 48 ​h compared to hypoxia group (P ​< ​0.001), respectively.⑤ Cell migration assay showed that hypoxia condition significantly restrained cell migration compared with the control group. PRP could alleviate the inhibitory effect of hypoxia on fibroblasts. ⑥ Western blot analysis showed the ratio of phosphorylated/total PI3K, Akt and mTOR in hypoxia group increased to 31%, 20% and 44/% compared to control group, respectively. ⑦ The results of in vivo analysis was in accordance with the results of in vitro analysis.

Conclusion

PRP can protect ACL fibroblasts via decreasing apoptosis and increasing cell viability, cell migration and cell proliferation under hypoxia condition. And such PRP protective effect was correlated with PI3K/Akt/mTOR pathway.

The translational potential of this article

PRP can be used to treat patients with ACL tear by injection under arthroscopy or ultrasound guiding.

The effects of maturation and aging on the rotator cuff tendon-to-bone interface

Rotator cuff tendon injuries often occur at the tendon-to-bone interface (i.e., enthesis) area, with a high prevalence for the elderly population, but the underlying reason for this phenomenon is still unknown. The objective of this study is to identify the histological, molecular, and biomechanical alterations of the rotator cuff enthesis with maturation and aging in a mouse model. Four different age groups of mice (newborn, young, adult, and old) were studied. Striking variations of the entheses were observed between the newborn and other matured groups, with collagen content, proteoglycan deposition, collagen fiber dispersion was significantly higher in the newborn group. The compositional and histological features of young, adult, and old groups did not show significant differences, except having increased proteoglycan deposition and thinner collagen fibers at the insertion sites in the old group. Nanoindentation testing showed that the old group had a smaller compressive modulus at the insertion site when compared with other groups. However, tensile mechanical testing reported that the old group demonstrated a significantly higher failure stress when compared with the young and adult groups. The proteomics analysis detected dramatic differences in protein content between newborn and young groups but minor changes among young, adult, and old groups. These results demonstrated: (1) the significant alterations of the enthesis composition and structure occur from the newborn to the young time period; (2) the increased risk of rotator cuff tendon injuries in the elderly population is not solely because of old age alone in the rodent model.

Platelet HMGB1 in Platelet-Rich Plasma (PRP) promotes tendon wound healing

Platelet-rich plasma (PRP) is a widely used autologous treatment for tendon injuries in clinics. Platelets (PLTs) are a major source of high mobility group box1 (HMGB1) that is gaining attention as a chemoattractant that can recruit stem cells to the wound area to enhance healing of injured tissues; however, the contribution of PLT HMGB1 in wounded tendon healing remains unexplored. This study investigated the effect of PLT HMGB1 within PRP on tendon healing using PLT HMGB1 knockout (KO) and GFP mice. A window defect was created in the patellar tendons of both groups of mice, and wounds were treated with either saline, PRP isolated from PLT HMGB1-KO mice, or PRP isolated from GFP mice. Seven days post-treatment, animals were sacrificed and analyzed by gross inspection, histology, and immunostaining for characteristic signs of tendon healing and repair. Our results showed that in comparison to mice treated with PRP from PLT HMGB1-KO mice, wounds treated with PRP from GFP mice healed faster and exhibited a better organization in tendon structure. Mice treated with PRP from PLT HMGB1-KO mice produced tendon tissue with large premature wound areas and low cell densities. However, wounds of PLT HMGB1-KO mice showed better healing with PRP from HMGB1-KO mice compared to saline treatment. Moreover, wounds treated with PRP from GFP mice had increased extracellular HMGB1, decreased CD68, increased stem cell markers CD146 and CD73, and increased collagen III protein expression levels compared to those treated with PRP from PLT HMGB1-KO mice. Thus, PLT HMGB1 within PRP plays an important role in tendon wound healing by decreasing inflammation, increasing local HMGB1 levels, and recruiting stem cells to the wound area in the tendon. Our findings also suggest that the efficacy of PRP treatment for tendon injuries in clinics may depend on PLT HMGB1 within PRP preparations.

Alginate sulfate-based hydrogel/nanofiber composite scaffold with controlled Kartogenin delivery for tissue engineering

In this study, we fabricated two different arrangements of laminated composite scaffolds based on Alginate:Alginate sulfate hydrogel, PCL:Gelatin electrospun mat, and Kartogenin-PLGA nanoparticles (KGN-NPs). The optimized composite scaffold revealed a range of advantages such as improved mechanical features as well as less potential of damage (less dissipated energy), interconnected pores of hydrogel and fiber with adequate pore size, excellent swelling ratio, and controlled biodegradability. Furthermore, the synthesized KGN-NPs with spherical morphology were incorporated into the composite scaffold and exhibited a linear and sustained release of KGN within 30 days with desirable initial burst reduction (12% vs. 20%). Additionally, the cytotoxicity impact of the composite was evaluated. Resazurin assay and Live/Dead staining revealed that the optimized composite scaffold has no cytotoxic effect and could improve cell growth. Overall, according to the enhanced mechanical features, suitable environment for cellular growth, and sustained drug release, the optimized scaffold would be a good candidate for tissue regeneration.

Engineering multi-tissue units for regenerative Medicine: Bone-tendon-muscle units of the rotator cuff

Our body systems are comprised of numerous multi-tissue units. For the musculoskeletal system, one of the predominant functional units is comprised of bone, tendon/ligament, and muscle tissues working in tandem to facilitate locomotion. To successfully treat musculoskeletal injuries and diseases, critical consideration and thoughtful integration of clinical, biological, and engineering aspects are necessary to achieve translational bench-to-bedside research. In particular, identifying ideal biomaterial design specifications, understanding prior and recent tissue engineering advances, and judicious application of biomaterial and fabrication technologies will be crucial for addressing current clinical challenges in engineering multi-tissue units. Using rotator cuff tears as an example, insights relevant for engineering a bone-tendon-muscle multi-tissue unit are presented. This review highlights the tissue engineering strategies for musculoskeletal repair and regeneration with implications for other bone-tendon-muscle units, their derivatives, and analogous non-musculoskeletal tissue structures.

Fibrin Glue-Kartogenin Complex Promotes the Regeneration of the Tendon-Bone Interface in Rotator Cuff Injury

Objective

Rotator cuff injury healing is problematic because the tendon-bone junction often forms cicatricial tissues, rather than fibrocartilage, which leads to mechanical impairment and is prone to redamage. Kartogenin (KGN) is a newly discovered small molecule compound which can induce cartilage formation through chondrogenesis of endogenous mesenchymal stem cells.

Methods

In this study, we used KGN with fibrin glue (FG) to repair the rotator cuff injury by promoting the formation of fibrocartilage at the tendon to bone interface. Firstly, we assessed the release rate of KGN from the FG-KGN complex and then created a rabbit rotator cuff tendon graft-bone tunnel model. The rabbits received saline, FG-KGN, or FG injections onto the tendon to bone interface after injury. Shoulder tissues were harvested at 6 and 12 weeks, and the sections were stained with HE and Safranin O/Fast green. The samples were assessed by histologic evaluation and biomechanical testing. Synovial mesenchymal stem cells derived from the synovial tissue around the rotator cuff were harvested for western blotting and qRT-PCR analysis.

Results

KGN was released rapidly from the FG-KGN complex during first 4 hrs and followed by a slow release until 7 days. The tendon graft-bone interface in the control (saline) group and the FG group was filled with scar tissue, rather than cartilage-like tissue, and only a small number of chondrocytes were found at the adjacent bone surface. In the FG-KGN group, the tendon to bone interface was fully integrated and populated by chondrocytes with proteoglycan deposition, indicating the formation of fibrocartilage-like tissues. At 12 weeks, the maximum tensile strength of the FG-KGN group was significantly higher than that of the FG and control groups (P < 0.01). The RNA expression levels of tendinous genes such as Tenascin C and the chondrogenic gene Sox-9 were substantially elevated in SMSCs treated with the FG-KGN complex compared to the other two groups.

Conclusion

These results indicated that fibrin glue is an effective carrier for KGN, allowing for the sustained release of KGN. The FG-KGN complex could effectively promote the regeneration and formation of fibrocartilage tissue of the tendon-bone interface in the rabbit rotator cuff tendon graft-bone tunnel model.

Exosomes from Kartogenin-Pretreated Infrapatellar Fat Pad Mesenchymal Stem Cells Enhance Chondrocyte Anabolism and Articular Cartilage Regeneration

Objective

To evaluate the effect of Kartogenin-pretreated exosomes derived from infrapatellar fat pad mesenchymal stem cells on chondrocyte in vitro and articular cartilage regeneration in vivo.

Methods

Infrapatellar fat pad mesenchymal stem cells (IPFP-MSCs) were isolated from rabbits to harvest exosomes. After identification of mesenchymal stem cells and exosomes, rabbit chondrocytes were divided into three groups for further treatment: the EXO group (chondrocytes treated with exosomes isolated from infrapatellar fat pad mesenchymal stem cells), KGN-EXO group (chondrocytes treated with exosomes isolated from infrapatellar fat pad mesenchymal stem cells pretreated with KGN), and control group. After processing and proliferation, phenotypic changes of chondrocytes were measured. In the in vivo study, 4 groups of rabbits with articular cartilage injury were treated with KGN-EXO, EXO, IPFP-MSCs, and control. Macroscopic evaluation and histological evaluation were made to figure out the different effects of the 4 groups on cartilage regeneration in vivo.

Results

The proliferation rate of chondrocytes in the EXO or KGN-EXO group was significantly higher than that in the control group (P < 0.05). The qRT-PCR results showed that the expression of Sox-9, Aggrecan, and Col II was the highest in the KGN-EXO group compared with the EXO group and the control group (P < 0.05). The results of Western blot were consistent with the results of qRT-PCR. In vivo, the cartilage defects in the KGN-EXO group showed better gross appearance and improved histological score than those in IPFP-MSC groups, EXO groups, and control groups (P < 0.05). At 12 weeks, the defect site in the KGN-EXO group was almost completely repaired with a flat and smooth surface, while a large amount of hyaline cartilage-like structures and no obvious cracks were observed.

Conclusion

Our study demonstrates that the exosomes isolated from infrapatellar fat pad mesenchymal stem cells pretreated with KGN have potent ability to induce chondrogenic differentiation of stem cells, effectively promoting the proliferation and the expression of chondrogenic proteins and genes of chondrocytes. The KGN-EXO can also promote the repair of articular cartilage defects more effectively, which can be used as a potential therapeutic method in the future.

Effect of kartogenin-loaded gelatin methacryloyl hydrogel scaffold with bone marrow stimulation for enthesis healing in rotator cuff repair

BACKGROUND

Strategies involving microfracture, biomaterials, growth factors, and chemical agents have been evaluated for improving enthesis healing. Kartogenin (KGN) promotes selective differentiation of bone marrow mesenchymal stem cells (BMSCs) into chondrocytes. Gelatin methacryloyl (GelMA) is a promising biomaterial for engineering scaffolds and drug carriers. Herein, we investigated KGN-loaded GelMA hydrogel scaffolds with a bone marrow-stimulating technique for the repair of rotator cuff tear.

METHODS

KGN-loaded GelMA hydrogel scaffolds were obtained by ultraviolet GelMA crosslinking and vacuum freeze-drying. Fifty-four New Zealand rabbits were randomly divided into (1) repair only (control), (2) microfracture + repair (BMS), and (3) microfracture + repair augmentation with a KGN-loaded GelMA hydrogel scaffold (combined) groups. Tendons were repaired by transosseous sutures. The structure, degradation, and in vitro KGN release of the scaffolds were characterized. Animals were euthanized 4, 8, and 12 weeks after repair. Enthesis healing was evaluated by macroscopy, microcomputed tomography, histology, and biomechanical tests.

RESULTS

The KGN-loaded GelMA hydrogel scaffolds are porous with a 60.4 ± 28.2-μm average pore size, and they degrade quickly in 2.5 units/mL collagenase solution. Nearly 81% of KGN was released into phosphate-buffered saline within 12 hours, whereas the remaining KGN was released in 7 days. Macroscopically, the repaired tendons were attached to the footprint. No differences were detected postoperatively in microcomputed tomography analysis among groups. Fibrous scar tissue was the main component at the tendon-to-bone interface in the control group. Disorderly arranged cartilage formation was observed at the tendon-to-bone interface in the BMS and combined groups 4 weeks after repair; the combined group exhibited relatively more cartilage. The combined group showed improved cartilage regeneration 8 and 12 weeks after repair. Similar results were found in tendon maturation scores. The ultimate load to failure and stiffness of the repaired tendon increased in all 3 groups. At 4 weeks after repair, the BMS and combined groups exhibited greater ultimate load to failure than the control group, although there was no difference in stiffness among groups. The BMS and combined groups exhibited greater ultimate load to failure and stiffness than the control group, and the combined group exhibited better values than the BMS group at 8 and 12 weeks after repair.

CONCLUSION

Compared with the bone marrow-stimulating technique, the KGN-loaded GelMA hydrogel scaffold with bone marrow stimulation improved enthesis healing by promoting fibrocartilage formation and improving the mechanical properties.

Biologic therapies for foot and ankle injuries

Introduction: The use of orthobiologics as supplemental treatment for foot and ankle pathologies have increased in the past decades. They have been used to improve the healing of bone and soft tissue injuries. There have been several studies that examined the use of biologics for knee and hip pathologies but the foot and ankle construct has unique features that must be considered.Areas covered: The biologics for foot and ankle injuries that are covered in this review are platelet-rich plasma (PRP), stem cells, growth factors, hyaluronic acid, bone grafts, bone substitutes, and scaffolds. These modalities are used in the treatment of pathologies related to tendon and soft tissue as well as cartilage.Expert opinion: The utilization of biological adjuncts for improved repair and regeneration of ankle injuries represents a promising future in our efforts to address difficult clinical problems. The application of concentrated bone marrow and PRP each represents the most widely studied and commonly used injection therapies with early clinical studies demonstrating promising results, research is also being done using other potential therapies such as stem cells and growth factors; further investigation and outcome data are still needed.

FGF-2-Induced Human Amniotic Mesenchymal Stem Cells Seeded on a Human Acellular Amniotic Membrane Scaffold Accelerated Tendon-to-Bone Healing in a Rabbit Extra-Articular Model

Background

FGF-2 (basic fibroblast growth factor) has a positive effect on the proliferation and differentiation of many kinds of MSCs. Therefore, it represents an ideal molecule to facilitate tendon-to-bone healing. Nonetheless, no studies have investigated the application of FGF-2-induced human amniotic mesenchymal stem cells (hAMSCs) to accelerate tendon-to-bone healing in vivo.

Objective

The purpose of this study was to explore the effect of FGF-2 on chondrogenic differentiation of hAMSCs in vitro and the effect of FGF-2-induced hAMSCs combined with a human acellular amniotic membrane (HAAM) scaffold on tendon-to-bone healing in vivo.

Methods

In vitro, hAMSCs were transfected with a lentivirus carrying the FGF-2 gene, and the potential for chondrogenic differentiation of hAMSCs induced by the FGF-2 gene was assessed using immunofluorescence and toluidine blue (TB) staining. HAAM scaffold was prepared, and hematoxylin and eosin (HE) staining and scanning electron microscopy (SEM) were used to observe the microstructure of the HAAM scaffold. hAMSCs transfected with and without FGF-2 were seeded on the HAAM scaffold at a density of 3 × 10⁵ cells/well. Immunofluorescence staining of vimentin and phalloidin staining were used to confirm cell adherence and growth on the HAAM scaffold. In vivo, the rabbit extra-articular tendon-to-bone healing model was created using the right hind limb of 40 New Zealand White rabbits. Grafts mimicking tendon-to-bone interface (TBI) injury were created and subjected to treatment with the HAAM scaffold loaded with FGF-2-induced hAMSCs, HAAM scaffold loaded with hAMSCs only, HAAM scaffold, and no special treatment. Macroscopic observation, imageological analysis, histological assessment, and biomechanical analysis were conducted to evaluate tendon-to-bone healing after 3 months.

Results

In vitro, cartilage-specific marker staining was positive for the FGF-2 overexpression group. The HAAM scaffold displayed a netted structure and mass extracellular matrix structure. hAMSCs or hAMSCs transfected with FGF-2 survived on the HAAM scaffold and grew well. In vivo, the group treated with HAAM scaffold loaded with FGF-2-induced hAMSCs had the narrowest bone tunnel after three months as compared with other groups. In addition, macroscopic and histological scores were higher for this group than for the other groups, along with the best mechanical strength.

Conclusion

hAMSCs transfected with FGF-2 combined with the HAAM scaffold could accelerate tendon-to-bone healing in a rabbit extra-articular model.

Functionalization of Novel Theranostic Hydrogels with Kartogenin-Grafted USPIO Nanoparticles To Enhance Cartilage Regeneration

Here, kartogenin (KGN), an emerging stable nonprotein compound with the ability to promote differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) into chondrocytes, was grafted onto the surface of modified ultrasmall superparamagnetic iron-oxide (USPIO) and then integrated into cellulose nanocrystal/dextran hydrogels. The hydrogels served as a carrier for the USPIO-KGN and a matrix for cartilage repair. We carried out in vitro and in vivo studies, the results of which demonstrated that KGN undergoes long-term stable sustained release, recruits endogenous host cells, and induces BMSCs to differentiate into chondrocytes, thus enabling in situ cartilage regeneration. Meanwhile, the USPIO-incorporated theranostic hydrogels exhibited a distinct magnetic resonance contrast enhancement and maintained a stable relaxation rate, with almost no loss, both in vivo and in vitro. According to noninvasive in vivo observation results and immunohistochemistry analyses, the regenerated cartilage tissue was very similar to natural hyaline cartilage. This innovative diagnosis and treatment system increases the convenience and effectiveness of chondrogenesis.

A novel kartogenin-platelet-rich plasma gel enhances chondrogenesis of bone marrow mesenchymal stem cells in vitro and promotes wounded meniscus healing in vivo

Background

The meniscus tear is one of the most common knee injuries particularly seen in athletes and aging populations. Subchondral bone sclerosis, irreparable joint damage, and the early onset of osteoarthritis make the injured meniscus heal difficultly.

Methods

The study was performed by in vitro and in vivo experiments. The in vitro experiments were carried out using the bone marrow stem cells (BMSCs) isolated from the rabbits, and the stemness of the BMSCs was tested by immunostaining. The BMSCs positively expressed stem cell markers were cultured with various concentrations of kartogenin (KGN) for 2 weeks. The chondrogenesis of BMSCs induced by KGN was examined by histochemical staining and quantitative RT-PCR. The in vivo experiments were completed by a rabbit model. Three holes were created in each meniscus by a biopsy punch. The rabbits were treated with four different conditions in each group. Group 1 was treated with 20 μl of saline (saline); group 2 was treated with 5 μl of 100 μM KGN and 15 μl saline (KGN); group 3 was treated with 5 μl of 100 μM KGN, 5 μl of 10,000 U/ ml thrombin, and 10 μl of PRP (KGN+PRP); group 4 was treated with 10,000 BMSCs in 10 μl of PRP, 5 μl of saline solution, and 5 μl of 10,000 U/ml thrombin (PRP+BMSC); group 5 was treated with 10,000 BMSCs in 10 μl of PRP, 5 μl of 100 μM KGN, and 5 μl of 10,000 U/ml thrombin (KGN+PRP+BMSC). The menisci were collected at day 90 post-surgery for gross inspection and histochemical analysis.

Results

The histochemical staining showed that KGN induced chondrogenesis of BMSCs in a concentration-dependent manner. The RT-PCR results indicated that chondrocyte-related genes were also increased in the BMSCs cultured with KGN in a dose-dependent manner. The in vivo results showed that large unhealed wound areas were still found in the wounds treated with saline and KGN groups. The wounds treated with BMSCs-containing PRP gel healed much faster than the wounds treated without BMSCs. Furthermore, the wounds treated with BMSCs-containing KGN-PRP gel have healed completely and formed more cartilage-like tissues than the wounds treated with BMSCs-containing PRP gel.

Conclusions

BMSCs could be differentiated into chondrocytes when they were cultured with KGN-PRP gel in vitro and formed more cartilage-like tissues in the wounded rabbit meniscus when the wounds were treated with BMSCs-containing KGN-PRP gel. The results indicated that the BMSCs-containing KGN-PRP gel is a good substitute for injured meniscus repair and regeneration.

Autologous Freeze-Dried, Platelet-Rich Plasma Carrying Icariin Enhances Bone-Tendon Healing in a Rabbit Model

BACKGROUND

Tendon-bone interface (TBI) injuries are common in sports activities. Owing to the limited regenerative ability of the TBI, its functional healing remains a difficulty in clinical practice. Icariin (ICA) provides strong stimulation for osteogenesis. Platelet-rich plasma (PRP) can be used as a carrier for bioactive molecules, although its ability to provide sustained release for such molecules needs improvement.

HYPOTHESIS

Freeze-dried PRP (FD-PRP) as a carrier for ICA can provide sustained release of ICA into the tendon-bone (T-B) healing site, thus accelerating T-B healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 84 New Zealand rabbits with partial patellectomy in the hindlimb were randomly allocated into 3 different treatments: ICA incorporated with FD-PRP (ICA/FD-PRP), FD-PRP alone (FD-PRP), or saline control (CTL). The rabbit patella-patellar tendon (PP) interfaces were postoperatively harvested at postoperative week 8 or 16 for gross, radiological, histological, and mechanical evaluations.

RESULTS

Our results showed that FD-PRP can act as a carrier for sustained release of ICA into the T-B healing site. Macroscopically, no signs of infection or osteoarthritis were shown in the regenerated PP interfaces, and the area of cartilaginous metaplasia in the FD-PRP and ICA/FD-PRP groups at postoperative week 16 was significantly larger than that of the CTL group (P < .05 for all). Radiologically, micro-computed tomography showed that new bone which formed at the healing site in the ICA/FD-PRP group was significantly increased, remodeled, and mineralized in comparison with the CTL group (P < .05 for all). Histologically, the ICA/FD-PRP group exhibited a significant native PP interface, as shown by the enlargement and remodeling of new bone, well-organized collagen fibers, and robust production of proteoglycans in the regenerated fibrocartilage. The mechanical strength of the regenerated PP interface was significantly improved in the ICA/FD-PRP group. Significantly higher failure load and stiffness were shown in the ICA/FD-PRP group compared with the CTL and FD-PRP groups, respectively (P < .05 for all).

CONCLUSION

FD-PRP is a suitable sustained-release carrier for ICA, and ICA/FD-PRP can provide sustained release of ICA into the T-B healing site, thus effectively accelerating T-B healing.

CLINICAL RELEVANCE

Findings of this study demonstrate the feasibility of using FD-PRP as a carrier for ICA to improve T-B healing and provide a foundation for future clinical application.

Enhancement of rotator cuff tendon-bone healing using combined aligned electrospun fibrous membranes and kartogenin

Rotator cuff tear (RCT) is a major challenging shoulder disease because the fibrocartilage zone is hard to regenerate in the enthesis. Electrospun membranes with aligned nanofibers can guide the ordered tissue regeneration and kartogenin (KGN) is able to stimulate chondrocyte differentiation of mesenchymal stem cells. In this study, we fabricated a functional engineered scaffold for regenerating tendon-bone enthesis in RCTs by taking advantage of both the structural guiding ability of aligned nanofibers and the biology effects of KGN. Polycaprolactone (PCL) fibrous membranes with aligned nanofibers loaded with or without KGN were fabricated using electrospinning and characterized using scanning electron microscopy (SEM). The release of KGN from PCL membranes and the effects of KGN on differentiation of mesenchymal stem cells were investigated. Results indicated that 100 μM KGN-loaded PCL (KGN-PCL) membranes significantly stimulated chondrogenic and tenogenic differentiation of rat bone marrow stromal cells. In addition, after PCL and 100 μM KGN-PCL membranes were applied to an acute rat RCT model, KGN-PCL membranes promoted fibrocartilage formation and collagen organization as well as increased cross-sectional area and load failure. In conclusion, PCL electrospun fibrous membranes with aligned nanofibers and KGN could be an effective tissue engineering scaffold to enhance tendon-bone healing in RCTs.

Effect of Autologous Platelet-Rich Plasma and Gelatin Sponge for Tendon-to-Bone Healing After Rabbit Anterior Cruciate Ligament Reconstruction

PURPOSE

To investigate platelet-rich plasma (PRP) combined with gelatin sponge (GS) to improve tendon-bone interface healing and structure formation.

METHODS

Characterization of the GS scaffold was performed with a scanning electron microscope, and the release curve after loading with PRP was evaluated. A real-time reverse transcription quantitative polymerase chain reaction assay was performed to test the levels of tendon-to-bone healing-related gene expression. Finally, 18 New Zealand white rabbits were randomly divided into 3 groups and underwent semitendinosus autograft anterior cruciate ligament reconstruction: autograft group without PRP, PRP group, and PRP-GS group. All rabbits were killed 8 weeks after the operation. Magnetic resonance imaging scans, biomechanical testing, and histologic evaluation were performed.

RESULTS

An enzyme-linked immunosorbent assay and cell counting kit-8 assay showed that the GS could control the release of PRP and prolong its bioactivity time, as well as promote bone marrow mesenchymal stem cell proliferation. In the PRP-GS group, the levels of related genes were upregulated compared with the PRP group (P < .05). Lower signal in the magnetic resonance images indicated fibrocartilage formation in the 2 groups with PRP. In addition, histologic staining showed that the tendon-bone connection had a greater fibrocartilaginous transition region in the PRP-GS group, and the histologic scores were higher (vs the PRP group, P = .039). The maximum failure load and stiffness were higher in the PRP-GS group than in the other 2 groups.

CONCLUSIONS

GS loading with PRP could prolong the bioactivity time of PRP and promote bone marrow mesenchymal stem cell proliferation and osteogenic gene expression in vitro. It also promoted the early healing process at the tendon-bone junction in a rabbit anterior cruciate ligament reconstruction model.

CLINICAL RELEVANCE

GS is a natural material and offers satisfactory biocompatibility. Using GS as a scaffold to control the release of bioactive factors in bone tunnels may be useful, but additional studies in human subjects will be necessary to evaluate its clinical prospects.

Kartogenin and Its Application in Regenerative Medicine

Regenerative medicine refers to the possibility of replacing aged/damaged cells with genetically similar young and functional cells to restore or establish normal function. Kartogenin (KGN), a small heterocyclic, drug-like compound was discovered in 2012, which is strongly associated with regenerative medicine. KGN has been applied in many regenerative fields, including cartilage regeneration and protection, tendon-bone healing, wound healing, and limb development. KGN could facilitate cartilage repair, promote formation of cartilage-like transition zone in tendon-bone junctions, stimulate collagen synthesis for wound healing, and regulate limb development in a coordinated manner. Considering the related mechanism, filamin A/CBFβ/RUNX1, Ihh, and TGFβ/Smad pathways have been reported to involve KGN. Therefore, KGN is proven a promising agent in regenerative medicine; however, studies conducted on the effect of KGN are limited to date and not convictive for long-term use. Further studies are recommended to explore the long-term effect and potential molecular mechanisms of KGN. Our investigations may motivate researchers to expand its applications in different forms and fields.

Simvastatin With PRP Promotes Chondrogenesis of Bone Marrow Stem Cells In Vitro and Wounded Rat Achilles Tendon-Bone Interface Healing In Vivo

BACKGROUND

Tendons and ligaments are joined to bone in a specialized interface that transmits force from muscle to bone and permits body movement. Tendon/ligament injuries always occur in the interface areas, and injured tendons/ligaments have a limited healing response because the insertion site is composed of a fibrocartilaginous zone.

PURPOSE

To study the effect of simvastatin with platelet-rich plasma (PRP) on chondrogenesis of rat bone marrow stem cells (BMSCs) in vitro and wounded rat Achilles tendon-bone interface healing in vivo.

STUDY DESIGN

Controlled laboratory study.

METHODS

The in vitro model was performed by the culture of rat BMSCs with various concentrations of simvastatin (0, 10, 50, 100 nM) for 2 weeks. The effect of simvastatin on the chondrogenic differentiation of the BMSCs was examined by histochemical analysis and real-time quantitative reverse transcription polymerase chain reaction. The in vivo model was carried out by testing the healing effect of simvastatin with PRP on 12 wounded rat Achilles tendon-bone interfaces.

RESULTS

Simvastatin induced chondrogenic differentiation of rat BMSCs in a concentration-dependent manner as evidenced by histological staining and real-time quantitative reverse transcription polymerase chain reaction. The wounds treated with simvastatin alone or with simvastatin-containing PRP gel healed much faster than the wounds treated with saline alone or PRP alone. Histological analysis showed that higher percentages of healed tissues were positively stained with safranin O and fast green in wounds treated with simvastatin-containing PRP gel than in the other 3 groups. Immunohistochemical analysis further demonstrated these findings, as evidenced by more positively stained healed tissues with collagen I and II antibodies in the wound areas treated with simvastatin-containing PRP gel than the other 3 groups.

CONCLUSION

The combination of simvastatin with PRP induced chondrogenesis of BMSCs in vitro and enhanced fibrocartilage formation in vivo. The simvastatin-PRP gel treatment promotes wounded tendon-bone interface healing in clinical treatment.

CLINICAL RELEVANCE

The combination of simvastatin with PRP may be a good clinical treatment for wounded tendon/ligament junction healing, especially for acute sports-related tendon/ligament injuries.

Editorial Commentary: Kartogenin Promotes Wounded Enthesis Regeneration

Entheses are the insertion sites where tendons and ligaments attach to bone. Commonly, entheses are subject to overuse injuries, and tendon-to-bone healing is poor because the healing has occurred between 2 different tissues: hard tissue (bone) and soft tissue (tendon). It is necessary to form the zonal arrangement of the enthesis region in vivo after repair.

Kartogenin Enhances Collagen Organization and Mechanical Strength of the Repaired Enthesis in a Murine Model of Rotator Cuff Repair

PURPOSE

To investigate the use of kartogenin (KGN) in augmenting healing of the repaired enthesis after rotator cuff repair in a murine model.

METHODS

Seventy-two C57BL/6 wild-type mice underwent unilateral detachment and transosseous repair of the supraspinatus tendon augmented with either fibrin sealant (control group; n = 36) or fibrin sealant containing 100 μmol/L of KGN (experimental group; n = 36) applied at the repair site. Postoperatively, mice were allowed free cage activity without immobilization. Mice were humanely killed at 2 and 4 weeks postoperatively. Repair site integrity was evaluated histologically through fibrocartilage formation and collagen fiber organization and biomechanically through load-to-failure testing of the supraspinatus tendon-bone construct.

RESULTS

At 2 weeks, no differences were noted in percent area of fibrocartilage, collagen organization, or ultimate strength between groups. At 4 weeks, superior collagen fiber organization (based on collagen birefringence [17.3 ± 2.0 vs 7.0 ± 6.5 integrated density/μm²; P < .01]) and higher ultimate failure loads (3.5 ± 0.6 N vs 2.3 ± 1.1 N; P = .04) were seen in the KGN group. The percent area of fibrocartilage (13.2 ± 8.4% vs 4.4 ± 5.4%; P = .04) was higher in the control group compared with the KGN group.

CONCLUSIONS

Rotator cuff repair augmentation with KGN improved the collagen fiber organization and biomechanical strength of the tendon-bone interface at 4 weeks in a murine model.

CLINICAL RELEVANCE

These findings have implications for improving the structural integrity of the repaired enthesis and potentially reducing the retear rate after rotator cuff repair, which can ultimately lead to improvements in clinical outcomes.

Recent advances in kartogenin for cartilage regeneration

Either osteoarthritis or sports-related injuries can lead to cartilage defects, whereas both chondrocyte self-renewal and conventional treatments face limitations. In cartilage regenerative medicine, growth factors are commonly used to induce chondrogenic differentiation of stem cells. However, application of growth factors is confined by some drawbacks. Emerging small molecules are regarded as an alternative for cartilage regeneration. A recently discovered small-molecule compound, kartogenin (KGN), has been proven to be a chondrogenic and chondroprotective agent and is more effective in inducing cartilage regeneration when compared with growth factors. KGN has been processed and applied in many forms, such as in intra-articular injection, in collaboration with growth factors, in incorporation in drug delivery systems, and in combination with scaffolds. Fortunately, progress has been achieved in KGN applications. The current review discusses the recent advances in KGN for cartilage regeneration and thus presents new concepts in cartilage repair in clinical settings.

Comparison of Bone Tunnel and Cortical Surface Tendon-to-Bone Healing in a Rabbit Model of Biceps Tenodesis

BACKGROUND

Many orthopaedic surgical procedures involve reattachment of a single tendon to bone. Whether tendon-to-bone healing is better facilitated by tendon fixation within a bone tunnel or on a cortical surface is unknown. The purpose of this study was to evaluate tendon-healing within a bone tunnel compared with that on the cortical surface in a rabbit model of biceps tenodesis.

METHODS

Thirty-two rabbits (24 weeks of age) underwent unilateral proximal biceps tenodesis with tendon fixation within a bone tunnel (BT group) or on the cortical surface (SA [surface attachment] group). Postoperatively, rabbits were allowed free-cage activity without immobilization. All rabbits were killed 8 weeks after surgery. Healing was assessed by biomechanical testing, microcomputed tomography (micro-CT), and histomorphometric analysis.

RESULTS

Biomechanical testing demonstrated no significant difference between the groups in mean failure loads (BT: 56.8 ± 28.8 N, SA: 55.8 ± 14.9 N; p = 0.92) or stiffness (BT: 26.3 ± 16.6 N/mm, SA: 32.3 ± 9.6 N/mm; p = 0.34). Micro-CT analysis demonstrated no significant difference between the groups in mean volume of newly formed bone (BT: 69.3 ± 13.9 mm, SA: 65.5 ± 21.9 mm; p = 0.70) or tissue mineral density of newly formed bone (BT: 721.4 ± 10.9 mg/cm, SA: 698.6 ± 26.2 mg/cm; p = 0.07). On average, newly formed bone within the tunnel represented only 5% of the total new bone formed in the BT specimens. Histological analysis demonstrated tendon-bone interdigitation and early fibrocartilaginous zone formation on the outer cortical surface in both groups. In contrast, minimal tendon-bone bonding was observed within the tunnel in the BT specimens.

CONCLUSIONS

Tendon fixation in a bone tunnel and on the cortical surface resulted in similar healing profiles. For tendons placed within a bone tunnel, intratunnel healing was minimal compared with the healing outside the tunnel on the cortical surface.

CLINICAL RELEVANCE

The creation of large bone tunnels, which can lead to stress risers and increase the risk of fracture, may not be necessary for biceps tenodesis procedures.

Influence of Kartogenin on Chondrogenic Differentiation of Human Bone Marrow-Derived MSCs in 2D Culture and in Co-Cultivation with OA Osteochondral Explant

Articular cartilage has limited capacity for natural regeneration and repair. In the present study, we evaluated kartogenin (KGN), a bioactive small heterocyclic molecule, for its effect on in vitro proliferation and chondrogenic differentiation of human bone marrow-derived mesenchymal stromal cells (hBMSCs) in monolayer culture and in co-culture models in vitro. OA osteochondral cylinders and hBMSCs were collected during total knee replacement. The effect of KGN on hBMSCs during 21 days of culture was monitored by real-time proliferation assay, immunofluorescence staining, histological assay, scanning electron microscopy (SEM) (imaging and multiplex enzyme-linked immunosorbent assay) ELISA assay. The rate of proliferation of hBMSCs was significantly increased by treatment with 10 µM KGN during nine days of culture. Histological and SEM analyses showed the ability of hBMSCs in the presence of KGN to colonize the surface of OA cartilage and to produce glycosaminoglycans and proteoglycans after 21 days of co-culture. KGN treated hBMSCs secreted higher concentrations of TIMPs and the secretion of pro-inflammatory molecules (MMP 13, TNF-α) were significantly suppressed in comparison with control without hBMSCs. Our preliminary results support the concept that 10 µM KGN enhances proliferation and chondrogenic differentiation of hBMSCs and suggest that KGN is a potential promoter for cell-based therapeutic application for cartilage regeneration.

The combined use of kartogenin and platelet-rich plasma promotes fibrocartilage formation in the wounded rat Achilles tendon entheses

Objectives

After an injury, the biological reattachment of tendon to bone is a challenge because healing takes place between a soft (tendon) and a hard (bone) tissue. Even after healing, the transition zone in the enthesis is not completely regenerated, making it susceptible to re-injury. In this study, we aimed to regenerate Achilles tendon entheses (ATEs) in wounded rats using a combination of kartogenin (KGN) and platelet-rich plasma (PRP).

Methods

Wounds created in rat ATEs were given three different treatments: kartogenin platelet-rich plasma (KGN-PRP); PRP; or saline (control), followed by histological and immunochemical analyses, and mechanical testing of the rat ATEs after three months of healing.

Results

Histological analysis showed well organised arrangement of collagen fibres and proteoglycan formation in the wounded ATEs in the KGN-PRP group. Furthermore, immunohistochemical analysis revealed fibrocartilage formation in the KGN-PRP-treated ATEs, evidenced by the presence of both collagen I and II in the healed ATE. Larger positively stained collagen III areas were found in both PRP and saline groups than those in the KGN-PRP group. Chondrocyte-related genes, SOX9 and collagen II, and tenocyte-related genes, collagen I and scleraxis (SCX), were also upregulated by KGN-PRP. Moreover, mechanical testing results showed higher ultimate tensile strength in the KGN-PRP group than in the saline control group. In contrast, PRP treatment appeared to have healed the injured ATE but induced no apparent formation of fibrocartilage. The saline-treated group showed poor healing without fibrocartilage tissue formation in the ATEs.

Conclusions

Our results show that injection of KGN-PRP induces fibrocartilage formation in the wounded rat ATEs. Hence, KGN-PRP may be a clinically relevant, biological approach to regenerate injured enthesis effectively.

Cite this article: J. Zhang, T. Yuan, N. Zheng, Y. Zhou, M. V. Hogan, J. H-C. Wang. The combined use of kartogenin and platelet-rich plasma promotes fibrocartilage formation in the wounded rat Achilles tendon entheses. Bone Joint Res 2017;6:231–244. DOI: 10.1302/2046-3758.64.BJR-2017-0268.R1.