Spray-painted human fibronectin coating as an effective strategy to enhance graft ligamentization of a polyethylene terephthalate artificial ligament

Repair potential of self-assembling peptide hydrogel in a mouse model of anterior cruciate ligament reconstruction

Purpose

Establishing zonal tendon-to-bone attachment could accelerate the anterior cruciate ligament reconstruction (ACLR) rehabilitation schedule and facilitate an earlier return to sports. KI24RGDS is a self-assembling peptide hydrogel scaffold (SAPS) with the RGDS amino acid sequence. This study aimed to elucidate the therapeutic potential of KI24RGDS in facilitating zonal tendon-to-bone attachment after ACLR.

Methods

Sixty-four C57BL/6 mice were divided into the ACLR + SAPS and ACLR groups. ACLR was performed using the tail tendon. To assess the maturation of tendon-to-bone attachment, we quantified the area of mineralized fibrocartilage (MFC) in the tendon graft with demeclocycline. Immunofluorescence staining of α-smooth muscle actin (α-SMA) was performed to evaluate progenitor cell proliferation. The strength of tendon-to-bone attachment was evaluated using a pull-out test.

Results

The MFC and maximum failure load in the ACLR + SAPS group were remarkably higher than in the ACLR group on Day 14. However, no significant difference was observed between the two groups on Day 28. The number of α-SMA-positive cells in the tendon graft was highest on Day 7 after ACLR in both the groups and was significantly higher in the ACLR + SAPS group than in the ACLR group.

Conclusion

This study highlighted the latent healing potential of KI24RGDS in facilitating early-stage zonal attachment of tendon grafts and bone tunnels post-ACLR. These findings may expedite rehabilitation protocols and shorten the timeline for returning to sports.

Level of Evidence

Not applicable.

Biological Augmentation of ACL Repair and Reconstruction: Current Status and Future Perspective

Historically, anterior cruciate ligament (ACL) suture repair mostly resulted in failure because of intra-articular hypovascularity and poor intrinsic healing capacity of ACL. ACL reconstruction was therefore deemed the gold standard with a high success rate because of more evolved surgical technique. There are, however, clinical and subclinical disadvantages of reconstruction; low rate in full recovery to sports, donor harvest morbidity, tunnel enlargement, and incomplete microscopic healing of the graft. Recent experimental and clinical studies on biological augmentation of mesenchymal stem cells, platelet-rich plasma, or the other biologic agents with scaffold suggested potential feasibility of positive effects by such bio-therapies for both ACL repair and reconstruction. Biological augmentation of ACL surgery is still in the exploratory stages and more evidence from preclinical and clinical studies is required for implementation in clinical practice.

Analysis of early cellular responses of anterior cruciate ligament fibroblasts seeded on different molecular weight polycaprolactone films functionalized by a bioactive poly(sodium styrene sulfonate) polymer

With the growing number of anterior cruciate ligament (ACL) ruptures and the increased interest for regenerative medicine procedures, many studies are now concentrated on developing bioactive and biodegradable synthetic ligaments. For this application, the choice of raw materials with appropriate physicochemical characteristics and long-term degradation features is essential. Polycaprolactone (PCL) has the advantage of slow degradation that depends on its molecular weight. This study evaluates two PCL materials: a technical grade (PC60: 60 kDa) versus a medical grade (PC12: 80 kDa), both before and after functionalization with poly(sodium styrene sulfonate) (pNaSS). After determining the grafting process had little to no effect on the PCL physicochemical properties, sheep ACL fibroblast responses were investigated. The PC12 films induced a significantly lower expression of the tumor necrosis factor alpha inflammatory gene compared to the PC60 films. Both film types induced an overproduction of fibroblast growth factor-2 and transforming growth factor beta compared to the controls on day 5 and demonstrated collagen gene expression profiles similar to the controls on day 7. Upon protein adsorption, pNaSS grafting caused a rapid cell adhesion in the first 30 min and an increased adhesion strength (1.5-fold higher). Moreover, after 7 days, an increase in cell density and actin network development were noted on the grafted films.

Biological augmentation of graft healing in anterior cruciate ligament reconstruction: a systematic review

Aims

The success of anterior cruciate ligament reconstruction (ACLR) depends on osseointegration at the graft-tunnel interface and intra-articular ligamentization. Our aim was to conduct a systematic review of clinical and preclinical studies that evaluated biological augmentation of graft healing in ACLR.

Materials and Methods

In all, 1879 studies were identified across three databases. Following assessment against strict criteria, 112 studies were included (20 clinical studies; 92 animal studies).

Results

Seven categories of biological interventions were identified: growth factors, biomaterials, stem cells, gene therapy, autologous tissue, biophysical/environmental, and pharmaceuticals. The methodological quality of animal studies was moderate in 97%, but only 10% used clinically relevant outcome measures. The most interventions in clinical trials target the graft-tunnel interface and are applied intraoperatively. Platelet-rich plasma is the most studied intervention, but the clinical outcomes are mixed, and the methodological quality of studies was suboptimal. Other biological therapies investigated in clinical trials include: remnant-augmented ACLR; bone substitutes; calcium phosphate-hybridized grafts; extracorporeal shockwave therapy; and adult autologus non-cultivated stem cells.

Conclusion

There is extensive preclinical research supporting the use of biological therapies to augment ACLR. Further clinical studies that meet the minimum standards of reporting are required to determine whether emerging biological strategies will provide tangible benefits in patients undergoing ACLR. Cite this article: Bone Joint J 2018;100-B:271-84.

Silk fibroin and hydroxyapatite segmented coating enhances graft ligamentization and osseointegration processes of the polyethylene terephthalate artificial ligament in vitro and in vivo

A silk fibroin and hydroxyapatite segmented coating ligament is fabricated to enhances graft ligamentization and osseointegration processes successfully.

The inferior medial genicular artery and its vascularization of the pes anserinus superficialis: A cadaveric study

BACKGROUND

A common method for reconstruction of the anterior cruciate ligament (ACL) is it's replacement by a free avascular graft, using the gracilis and/or semitendinosus tendons. These grafts pass a vulnerable phase in the ligamentization-process during the 1^st year after reconstruction. The aims of this study were first to evaluate the vascularization of the pes anserinus superficialis (PAS) by the inferior medial genicular artery (IMGA) and second to develop a pedunculated surgical technique for ACL reconstruction, to preserve a maximal amount of natural vascularization of the tendons inserting at the PAS.

MATERIALS AND METHODS

First, the vascularization of the PAS was assessed in 12 fresh-frozen lower extremities. The IMGA was identified at its origin at the popliteal artery and perfused with a methylene blue solution. Second, a pedunculated ACL reconstruction was performed in 5 fresh-frozen lower extremities under maintenance of the distal tendon insertion at PAS.

RESULTS

The PAS is a highly vascularized structure. Vessels originate from the IMGA, running along the three tendons of the PAS in the paratendinous tissue. Histologically intratendinous vessels exist; however, perfusion of the inserting tendons through intratendinous vessels was not proven macroscopically. The pedunculated grafts could be positioned and fixed successfully into the bone tunnels in all knees.

CONCLUSION

Although intratendinous vascularization of the tendons of the PAS via the IMGA was not proven, this study indicates a new possibility of ACL reconstruction. The described operation technique can be conducive to shorten the vulnerable phase of the graft-ligamentization after ACL reconstruction.

Effects of graphene modification on the bioactivation of polyethylene-terephthalate-based artificial ligaments

The objective of this study was to investigate whether surface coating with graphene could enhance the surface bioactivation of PET-based artificial ligaments to accelerate graft-to-bone healing after anterior cruciate ligament reconstruction. In an in vitro study, the proliferation of MC3T3-E1 cells and their differentiation on the scaffolds were quantified via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and real-time polymerase chain reaction assays. The significantly higher optical-density values and transcription levels of osteoblast-specific genes indicated that graphene modification could promote the proliferation of MC3T3-E1 cells and accelerate their specific differentiation into osteogenic lineages on scaffolds. In an in vivo test, rabbits were used to establish an extra-articular graft-to-bone healing model. At 4, 8, and 12 weeks after surgery, biomechanical tests, microcomputed tomography analysis, and histological observations were performed. The final results demonstrated that the microstructural parameters, the average mineral apposition rate of the bone, and the biomechanical properties of the graphene-coated polyethylene terephthalate (PET)-based artificial ligament (G-PET-AL) group were significantly higher than those of the PET-AL graft group (P < 0.05). The results of Van Gieson staining indicated that in the G-PET-AL group, there was more newly formed bone than there was in the group in which nongraphene-coated PET-ALs were used. In conclusion, graphene exhibits considerable potential for enhancing the surface bioactivation of materials.

Biomedical coatings on polyethylene terephthalate artificial ligaments

This review comprehensively covers research conducted to enhance polyethylene terephthalate (PET) artificial ligament osseointegration in the bone tunnel. These strategies, using biocompatible or bioactive coatings, had a positive effect in promoting PET ligament osseointegration by increasing bone formation and decreasing fibrous scar tissue at the ligament-to-bone interface. The improved osseointegration can be translated into a significant increase in the biomechanical pull-out loads. However, the load-to-failure of coated ligament is far lower than that of native ACL. Coatings to promote intra-articular ligamentization are also discussed in this study. Collectively, our investigations may arouse further study of the biological coating of PET artificial ligaments in order to effectively enhance ligament osseointegration and promote artificial ligament ligamentization.