Direct bone-to-bone integration between recombinant human bone morphogenetic protein-2-injected tendon graft and tunnel wall in an anterior cruciate ligament reconstruction model

Influence of periostin on the development of fibrocartilage layers of anterior cruciate ligament insertion

BACKGROUND

Periostin (Postn) is thought to play a role in the formation of anterior cruciate ligament (ACL) insertion. However, the influence of Postn on the development of ACL insertion requires further understanding. This study aimed to clarify the influence of Postn on the development of fibrocartilage layers of ACL insertion.

HYPOTHESIS

We hypothesized that Postn would influence the development of fibrocartilage layers of ACL insertion.

MATERIALS AND METHODS

C57BL/6N wild-type (Postn+/+; n=54) and Postn knockout (Postn-/-; n=54) mice were used in this study. Six animals were euthanized at 1 d and 1, 2, 3, 4, 6, 8, 10, and 12 weeks of age in each group. The chondrocyte number, proliferation, apoptosis, safranin O-stained glycosaminoglycan (GAG) area, type II collagen staining area, tidemark length, and insertion width were evaluated.

RESULTS

Chondrocyte proliferation was high up to 2 weeks in Postn+/+, while low at age 1 d; it was, especially lower in Postn-/- than in Postn+/+ at age 1 d and 1 week. Chondrocyte apoptosis was high up to age 8 weeks in Postn+/+ and at 6 weeks in Postn-/-; it was especially higher in Postn-/- than in Postn+/+ at age 1 week. The GAG stained area was thickest for age 1 d to 4 weeks in Postn+/+ and for age 2 to 6 weeks in Postn-/-. The type II collagen staining area in Postn+/+ was thicker than that in Postn-/- at age 6 and 8 weeks. The tidemark length in Postn+/+ was longer than that in Postn-/- from age 8 to 12 weeks. The insertion width in Postn+/+ was longer than that in Postn-/- from age 1 to 3 weeks.

DISCUSSION

Postn decreased cell proliferation in the early postnatal phase and influenced the development of the fibrocartilage layer extracellular matrix of ACL insertion in mice. Postn may contribute to the development of methods for regeneration of the ACL insertion.

LEVEL OF EVIDENCE

V; controlled laboratory study.

The hydroxyapatite modified 3D printed poly L-lactic acid porous screw in reconstruction of anterior cruciate ligament of rabbit knee joint: a histological and biomechanical study

BACKGROUND

3D printing technology has become a research hotspot in the field of scientific research because of its personalized customization, maneuverability and the ability to achieve multiple material fabrications. The focus of this study is to use 3D printing technology to customize personalized poly L-lactic acid (PLLA) porous screws in orthopedic plants and to explore its effect on tendon-bone healing after anterior cruciate ligament (ACL) reconstruction.

METHODS

Preparation of PLLA porous screws with good orthogonal pore structure by 3D printer. The hydroxyapatite (HA) was adsorbed on porous screws by electrostatic layer-by-layer self-assembly (ELSA) technology, and PLLA-HA porous screws were prepared. The surface and spatial morphology of the modified screws were observed by scanning electron microscopy (SEM). The porosity of porous screw was measured by liquid displacement method. Thirty New Zealand male white rabbits were divided into two groups according to simple randomization. Autologous tendon was used for right ACL reconstruction, and porous screws were inserted into the femoral tunnel to fix the transplanted tendon. PLLA group was fixed with porous screws, PLLA-HA group was fixed with HA modified porous screws. At 6 weeks and 12 weeks after surgery, 5 animals in each group were sacrificed randomly for histological examination. The remaining 5 animals in each group underwent Micro-CT and biomechanical tests.

RESULTS

The pores of PLLA porous screws prepared by 3D printer were uniformly distributed and connected with each other, which meet the experimental requirements. HA was evenly distributed in the porous screw by ELSA technique. Histology showed that compared with PLLA group, mature bone trabeculae were integrated with grafted tendons in PLLA-HA group. Micro-CT showed that the bone formation index of PLLA-HA group was better than that of PLLA group. The new bone was uniformly distributed in the bone tunnel along the screw channel. Biomechanical experiments showed that the failure load and stiffness of PLLA-HA group were significantly higher than those of PLLA group.

CONCLUSIONS

The 3D printed PLLA porous screw modified by HA can not only fix the grafted tendons, but also increase the inductivity of bone, promote bone growth in the bone tunnel and promote bone integration at the tendon-bone interface. The PLLA-HA porous screw is likely to be used in clinic in the future.

Biomaterials developed for facilitating healing outcome after anterior cruciate ligament reconstruction: Efficacy, surgical protocols, and assessments using preclinical animal models

Anterior cruciate ligament (ACL) reconstruction is the recommended treatment for ACL tear in the American Academy of Orthopaedic Surgeons (AAOS) guideline. However, not a small number of cases failed because of the tunnel bone resorption, unsatisfactory bone-tendon integration, and graft degeneration. The biomaterials developed and designed for improving ACL reconstruction have been investigated for decades. According to the Food and Drug Administration (FDA) and the International Organization for Standardization (ISO) regulations, animal studies should be performed to prove the safety and bioeffect of materials before clinical trials. In this review, we first evaluated available biomaterials that can enhance the healing outcome after ACL reconstruction in animals and then discussed the animal models and assessments for testing applied materials. Furthermore, we identified the relevance and knowledge gaps between animal experimental studies and clinical expectations. Critical analyses and suggestions for future research were also provided to design the animal study connecting basic research and requirements for future clinical translation.

Enhancement of tendon-bone interface healing and graft maturation with cylindrical titanium-web (TW) in a miniature swine anterior cruciate ligament reconstruction model: histological and collagen-based analysis

Background

Tendon-bone interface healing and ligamentization of the graft in anterior cruciate ligament (ACL) reconstruction with autografts are important factors affecting treatment outcome. This study aimed to investigate the effectiveness of a cylindrical titanium-web (TW) in tendon-bone interface healing and graft maturation in ACL reconstruction.

Methods

Fourteen mature female CLAWN miniature swine underwent bilateral ACL reconstructions with patellar tendon (PT) autografts. In one limb, the TW/tendon complex was placed into the proximal side of the tibial tunnel. Only the graft was transplanted into the tunnel in the control limb. The proximal side of the graft was sutured into the stump of the native ACL and the distal end was stapled to the tibia. The animals were euthanized at 4 and 15 weeks postoperatively, for histological and biochemical analyses.

Results

Microscopic images in TW limbs showed that ingrowth of tendon-like tissue and mineralized bone tissue into the TW connected the bone and the tendon directly. In contrast, fibrous tissue intervened between the bone and tendon in the control limbs. The total amount of collagen cross-links (which defines the strength of collagen fibers) and the maturation of collagen cross-links in TW tendons were significantly higher (p < 0.05) than those of control limbs. There was no significant difference in the ratio of dihydroxy-lysinonorleucine to hydroxy-lysinonorleucine (an indicator of tissue specific collagen maturation) between TW tendons and that of the native PT.

Conclusions

TW promoted the maturation and formation of collagen cross-links in the grafted tendon while maintaining the cross-links pattern of native tendon collagen, and enabled direct binding of tendon to bone.

Development of fibrocartilage layers in the anterior cruciate ligament insertion in rabbits

Background

A detailed evaluation focusing on the fibrocartilage layers in the anterior cruciate ligament (ACL) insertion is necessary to consider regeneration of the insertion. This study examined the development of the fibrocartilage layers in the ACL tibial insertion in rabbits by quantitative morphometric evaluations based on histological and immunohistochemical analyses.

Methods

Male Japanese white rabbits were used because of their history of use for histomorphometric analyses of the ACL insertion and to eliminate the influence of female hormones on the ACL. Six animals were euthanized at each age (1 day and 1, 2, 4, 6, 8, 12, and 24 weeks); in total, 48 animals were used. Proliferation rate, apoptosis rate, Sox9-positive rate, and chondrocyte number were evaluated. Safranin O-stained glycosaminoglycan (GAG) areas, tidemark length, ACL insertion width, and ACL length were also evaluated. All parameters were compared with those at age 24 weeks of age.

Results

High levels of chondrocyte proliferation and Sox9 expression continued until 4 and 8 weeks of age, respectively, and then gradually decreased. Chondrocyte apoptosis increased up to 8 weeks. The chondrocyte number, ACL insertion width, ACL length, safranin O-stained GAG areas, and tidemark length gradually increased up to 12 weeks.

Conclusion

Chondrocytes that displayed chondrocyte proliferation and Sox9 expression increased until 12 weeks of age, in accordance with development of the ACL length and its insertion width. The GAG production and tidemark length also increased until 12 weeks of age. The development of fibrocartilage layers in the ACL insertion was complete at 12 weeks of age.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2614-0) contains supplementary material, which is available to authorized users.

Enhanced tendon-bone healing with acidic fibroblast growth factor delivered in collagen in a rabbit anterior cruciate ligament reconstruction model

Background

The objective of the present study was to investigate the effectiveness of acidic fibroblast growth factor delivered in collagen (aFGF/collagen) for promoting tendon–bone interface healing after anterior cruciate ligament (ACL) reconstruction in rabbits.

Methods

ACL reconstructions were performed in the right hind limbs of New Zealand rabbits. Each left long digital extensor tendon was harvested as an autograft, and collagen incorporating different concentrations of aFGF or same amount of collagen alone was applied at the tendon–bone interface after ACL reconstruction. The control group underwent ACL reconstruction only. There were high and low aFGF/collagen groups, collagen alone group, and control group (n = 21 rabbits per group). Histological and biomechanical analyses were performed at 4, 8, and 12 weeks postoperatively to evaluate the effect of aFGF/collagen on tendon–bone interface healing.

Results

Results of biomechanical tests showed that at both 8 and 12 weeks postoperatively, the elastic modulus and stiffness in both the high and low aFGF/collagen treatment groups were significantly higher than those in the control group and collagen alone group, with that in the high aFGF/collagen concentration group being the highest. Histological analysis showed that at 8 weeks, tightly organized Sharpey-like fibers were observed in both aFGF/collagen groups with new bone growth into the tendon in the high concentration group. At 12 weeks postoperatively, a fibrocartilage transition zone was observed in the bone tunnels in both aFGF/collagen groups, especially in the high aFGF/collagen group.

Conclusion

Application of the aFGF/collagen composite could enhance early healing at the tendon–bone interface after ACL reconstruction, especially with the use of a high aFGF/collagen concentration.

Incorporating BMP-2 and skeletal muscle to a semitendinosus autograft in an oversized tunnel yields robust bone tunnel ossification in rabbits: Toward single-step revision of failed anterior cruciate ligament reconstruction

BACKGROUND

Bone tunnel widening after anterior cruciate ligament (ACL) reconstruction is a known complication that can lead to graft failure. Subsequent revision surgery typically involves a two-stage procedure. The aim of this study was to test a novel autologous tendon graft retaining muscle tissue combined with Human Recombinant Bone Morphogenetic Protein-2 (rh-BMP-2) leading to rapid ossification of the muscle tissue, simultaneously replenishing bone stock and producing a mechanically stable bone-tendon insertion.

METHODS

In 12 skeletally mature New Zealand rabbits, the ACL was resected and oversized bone tunnels were drilled to model tunnel widening. The ipsilateral semitendinosus muscle-tendon graft was harvested and folded twice. Muscle tissue was removed in the middle third but retained at both distal ends. One side was wrapped in a collagen sponge loaded with rh-BMP-2 while the other end was used as its own control.

RESULTS

All animals were euthanized after six weeks. Micro-computed tomography (micro-CT) was used to analyze bone formation in 12 animals, with additional biomechanical testing to failure and histology performed for six animals each. Micro-CT showed that bone densities were higher by a factor of 2.4 in treated graft ends compared with their controls. Biomechanical testing showed a mean overall failure load of 37.5 N. Histology showed that the trabecular bone surrounding the implant was significantly (P = 0.0087) thicker on the treated (85.5 μm) compared with the control side (68.2 μm).

CONCLUSIONS

We conclude that a semitendinosus graft retaining the muscle tissue stimulated by recombinant Bone Morphogenetic Protein-2 (BMP-2) allows robust osseointegration of the graft within an oversized bone tunnel in an animal model.

The accelerated effect of recombinant human bone morphogenetic protein 2 delivered by β-tricalcium phosphate on tendon-to-bone repair process in rabbit models

BACKGROUND

Bone morphogenetic protein 2 (BMP-2) plays an important role in the tendon-to-bone repair process. However, there is no previous literature on acceleration of the tendon-to-bone repair process by BMP-2 delivered by β-tricalcium phosphate (β-TCP). The aim of this study was to investigate the accelerated effect of recombinant human BMP-2 (rhBMP-2) delivered by β-TCP on the tendon-to-bone repair process.

METHODS

The infraspinatus tendon of elderly female Japanese white rabbits was detached from its insertion site on the humerus. A bone tunnel (4.2 mm) was created at the original insertion site of the tendon, which was repaired using the McLaughlin procedure after filling in β-TCP (porosity 75%) without BMP-2 (control group) or with 10 µg rhBMP-2 (BMP group). The rabbits were sacrificed at the second, fourth, and eighth weeks after surgery for histologic analysis and biomechanical testing. We also evaluated the maturity of the tendon-to-bone junction using the tendon-to-bone maturity score.

RESULTS

Histologic analysis revealed no significant difference between the groups at 2 and 8 weeks but a more abundant organized fibrocartilage at the tendon-to-bone junction in the BMP group at 4 weeks. The tendon-to-bone maturity score improved sequentially. The interface of the BMP group at 4 weeks had significantly improved biomechanical properties than that of the control group.

CONCLUSION

The tendon-to-bone repair process was facilitated by the use of rhBMP-2 delivered by β-TCP at 4 weeks.

Effects of tendon-bone healing of anterior cruciate ligament reconstruction by osteoprotegerin combined with deproteinized bovine bone

Background

The healing of a tendon graft in a bone tunnel depends on bone ingrowth into the interface between tendon and bone, or that can enhance tendon-bone healing, which is important to reduce the failure rate after ACL reconstruction.

Methods

Sixty skeletally mature, New Zealand white rabbits underwent left ACL reconstruction. OPG/DBB compound (concentration ratio of 30%, 60%, 100%) was delivered to the tendon-bone interface with use of a DBB carrier, and nothing as control group. Twenty animals were killed at 4, 8 and 12 weeks after surgery. I-IV levels of semi-quantitative and Sharpey fibers at the healing tendon-bone interface were evaluated, and the biomechanical properties were tested.

Results

A significantly greater amount of Sharpey fibers at the healing tendon-bone interface in the concentration ratio of 100% OPG/DBB-treated group was found compared with the others at all time-points (P<0.05), and it is the same to the Grade Scores at 12 weeks (P<0.05). The femur-ACL-tibia complex of the concentration ratio of 100% OPG/DBB-treated group has significantly increased stiffness compared with the others at 12 weeks (P<0.05).

Conclusion

The concentration ratio of 100% OPG/DBB compound significantly improve bone formation around the grafted tendon and improve the stiffness at the healing tendon-bone junction in a rabbit model.

Capacity of muscle derived stem cells and pericytes to promote tendon graft integration and ligamentization following anterior cruciate ligament reconstruction

PURPOSE

The aim of this study is to examine the capacity of muscle tissue preserved on hamstring tendons forming candy-stripe grafts in order to improve tendon to bone ingrowth and ligamentization. We hypothesized that muscle tissue does possess a stem cell population that could enhance the healing process of the ACL graft when preserved on the tendons.

METHODS

Human samples from gracilis and semitendinosus muscles were collected during ACL surgery from ten patients and from these tissue samples human muscle-derived stem cells and tendon-derived stem cells were isolated and propagated. Both stem cell populations were in-vitro differentiated into osteogenic lineage. Alkaline phosphatase activity was determined at days zero and 14 of the osteogenic induction and von Kossa staining to assess mineralization of the cultures. Total RNA was collected from osteoblast cultures and real time quantitative PCR was performed. Western-blot for osteocalcin and collagen type I followed protein isolation. Immunofluorescence double labeling of pericytes in muscle and tendon tissue was performed.

RESULTS

Mesenchymal stem cells from muscle and tendon tissue were isolated and expanded in cell culture. More time was needed to grow the tendon derived culture compared to muscle derived culture. Muscle derived stem cells exhibited more alkaline phosphatase actvity compared to tendon derived stem cells, whereas tendon derived stem cells formed more mineralized nodules after 14 days of osteoinduction. Muscle derived stem cells exhibited higher expression levels of bone sialoprotein, and tendon derived stem cells showed higher expression of dental-matrix-protein 1 and osteocalcin. Immunofluorescent staining against pericytes indicated that they are more abundant in muscle tissue.

CONCLUSIONS

These results indicate that muscle tissue is a better source of stem cells than tendon tissue. Achievement of this study is proof that there is vast innate capacity of muscle tissue for enhancement of bone-tendon integration and ligamentization of ACL hamstring grafts and consequently muscle tissue should not be treated as waste after harvesting.

Time-Dependent Effects of Arthroscopic Conditions on Human Articular Cartilage: An In Vivo Study

PURPOSE

To assess time-dependent effects of arthroscopic conditions on human articular cartilage in vivo.

METHODS

From each of 10 patients undergoing multiligament reconstruction of the knee under our routine arthroscopic conditions (gravity irrigation of 0.9% normal saline solution at room temperature with 150 cm H₂O [110 mm Hg] pressure and pneumatic tourniquet under 270 mm Hg pressure), cartilage specimens were harvested from the lateral edge of the femoral notch at the beginning of the operation (baseline) and at 15-, 30-, 45-, and 60-minute time points during the operation. H&E staining and safranin O staining were used to evaluate the tissue structure, chondrocytes, and extracellular matrix (ECM) of the articular cartilage. Chondrocyte viability was evaluated, and a biochemical examination of the ECM was performed to detect changes in glycosaminoglycan and collagen content. The expression levels of genes associated with proinflammatory cytokines, ECM metabolism, and chondrocyte apoptosis of the articular cartilage were evaluated.

RESULTS

At the 45- and 60-minute time points, an obvious impairment of tissue structure, a significant decrease in glycosaminoglycan content, and a significantly lower percentage chondrocyte viability were observed, as compared with baseline (P < .05). Regarding the tissue collagen content, no significant change was detected at any time point (P > .05). The gene expression examination at the 45- and 60-minute time points detected significant upregulation of interleukin 1β and tumor necrosis factor α (P < .05), indicating an inflammatory response by the chondrocytes, and significant upregulation of aggrecanase 1 (P < .05), which indicates catabolism or the disturbance of aggrecan metabolism.

CONCLUSIONS

Under current arthroscopic conditions, an operative duration of 45 minutes or longer can cause detrimental structural, biochemical, and metabolic effects on human articular cartilage.

CLINICAL RELEVANCE

Arthroscopic skills should always be improved to reduce operation time and thus minimize the potential detrimental effects of arthroscopic conditions on articular cartilage.

Does a different dose of gamma irradiation have the same effect on five different types of tendon allografts? - a biomechanical study

INTRODUCTION

The goals of our study were to evaluate the biomechanical differences between five tendons and the changes in biomechanical properties caused by irradiation.

METHODS

Achilles, quadriceps, semitendinosus + gracilis (STG), tibialis anterior (TA) and the peroneus longus (PL) were harvested from 30 donors. Group A contained 50 tendons without gamma irradiation. The groups were irradiated with a dose of 21 kGy (group B 50 tendons) and with a dose of 42 kGy (group C 50 tendons). The grafts were soaked in a radio-protectant solution and frozen at -80 °C. Cyclic loading tests were performed followed by load to failure tests. Young modulus of elasticity, maximum force, strain at tensile strength and strain at rupture were calculated.

RESULTS

The Achilles tendons had significantly lower Young modulus than the TA (p = 0.0036) in group A. The Achilles showed significantly lower than PL (p = 0.000042) and TA (p = 0.00142) in group B and C. The quadriceps and the ST (p = 0.0037) provided poorer values than the TA (p = 0.0432) in group C. We found no difference in maximum loads among the tendons in group A. The maximum load of the Achilles and quadriceps showed better results than the PL (p = 0.0016), (p = 0.0018) and the STG (p = 0.0066), (p = 0.0019) in group C. The TA had similar results like the Achilles and quadriceps.

DISCUSSION AND CONCLUSIONS

The vulnerability of gamma irradiation of TA was less than Achilles and quadriceps tendons.