Ligament Interface Research Articles

Deep-Learning-Based Segmentation of Individual Tooth and Bone With Periodontal Ligament Interface Details for Simulation Purposes

Deep-Learning-Based Segmentation of Individual Tooth and Bone With Periodontal Ligament Interface Details for Simulation Purposes

Numerical analysis of ligament instability and breakup in shear flow

In this study, we perform a numerical analysis of the instability of a ligament in a shear flow and investigate the effects of air–liquid shear on the growth rate of the ligament interface, breakup time, and droplet diameter formed by the breakup. The ligament is stretched in the flow direction by the shearing of airflow. Furthermore, as the influence of the shear flow increases, the ligament becomes deformed into a liquid sheet, and a perforation forms at the center of the liquid sheet. The liquid sheet breaks up due to the growth of the perforation and contracts under the influence of surface tension, forming two ligaments with diameters smaller than that of the original ligament. The shearing of the airflow causes the original ligament to elongate, and the cross section of the ligament becomes elliptical, which increases instability. As a result, the growth rate of the ligament exceeds the theoretical value and increases with increasing the wavenumber of the initial disturbance. Therefore, the diameter of the formed droplets in the shear flow decreases due to the increase in the wavenumber that governs the breakup of the ligament, and as the growth rate increases, the breakup time for the ligament decreases. As the velocity difference of the shear flow increases, constrictions of the ligament form earlier and the diameter of the satellite droplet increases. As the diameter of the satellite droplet increases and that of the main droplet decreases, the dispersion of the droplet diameter decreases, making the diameter uniform.

Fabrication of bioinspired grid-crimp micropatterns by melt electrospinning writing for bone–ligament interface study

Many strategies have been adopted to engineer bone–ligament interface, which is of great value to both the tissue regeneration and the mechanism understanding underlying interface regeneration. However, how to recapitulate the complexity and heterogeneity of the native bone–ligament interface including the structural, cellular and mechanical gradients is still challenging. In this work, a bioinspired grid-crimp micropattern fabricated by melt electrospinning writing (MEW) was proposed to mimic the native structure of bone–ligament interface. The printing strategy of crimped fiber micropattern was developed and the processing parameters were optimized, which were used to mimic the crimp structure of the collagen fibrils in ligament. The guidance effect of the crimp angle and fiber spacing on the orientation of fibroblasts was studied, and both of them showed different levels of cell alignment effect. MEW grid micropatterns with different fiber spacings were fabricated as bone region. Both the alkaline phosphatase activity and calcium mineralization results demonstrated the higher osteoinductive ability of the MEW grid structures, especially for that with smaller fiber spacing. The combined grid-crimp micropatterns were applied for the co-culture of fibroblasts and osteoblasts. The results showed that more cells were observed to migrate into the in-between interface region for the pattern with smaller fiber spacing, suggested the faster migration speed of cells. Finally, a cylindrical triphasic scaffold was successfully generated by rolling the grid-crimp micropatterns up, showing both structural and mechanical similarity to the native bone–ligament interface. In summary, the proposed strategy is reliable to fabricate grid-crimp triphasic micropatterns with controllable structural parameters to mimic the native bone-to-ligament structure, and the generated 3D scaffold shows great potential for the further bone–ligament interface tissue engineering.

Spatial Presentation of Tissue-Specific Extracellular Matrix Components along Electrospun Scaffolds for Tissue Engineering the Bone–Ligament Interface

The bone-ligament interface transitions from a highly organized type I collagen rich matrix to a nonmineralized fibrocartilage region and finally to a mineralized fibrocartilage region that interfaces with the bone. Therefore, engineering the bone-ligament interface requires a biomaterial substrate capable of maintaining or directing the spatially defined differentiation of multiple cell phenotypes. To date the appropriate combination of biophysical and biochemical factors that can be used to engineer such a biomaterial substrate remain unknown. Here we show that microfiber scaffolds functionalized with tissue-specific extracellular matrix (ECM) components can direct the differentiation of MSCs toward the phenotypes seen at the bone-ligament interface. Ligament-ECM (L-ECM) promoted the expression of the ligament-marker gene tenomodulin (TNMD) and higher levels of type I and III collagen expression compared to functionalization with commercially available type I collagen. Functionalization of microfiber scaffolds with cartilage-ECM (C-ECM) promoted chondrogenesis of MSCs, as evidenced by adoption of a round cell morphology and increased SRY-box 9 (SOX9) expression in the absence of exogenous growth factors. Next, we fabricated a multiphasic scaffold by controlling the spatial presentation of L-ECM and C-ECM along the length of a single electrospun microfiber construct, with the distal region of the C-ECM coated fibers additionally functionalized with an apatite layer (using simulated body fluid) to promote endochondral ossification. These ECM functionalized scaffolds promoted spatially defined differentiation of MSCs, with higher expression of TNMD observed in the region functionalized with L-ECM, and higher expression of type X collagen and osteopontin (markers of endochondral ossification) observed at the end of the scaffold functionalized with C-ECM and the apatite coating. Our results demonstrate the utility of tissue-specific ECM derived components as a cue for directing MSC differentiation when engineering complex multiphasic interfaces such as the bone-ligament enthesis.

Hook Plate for Volar Rim Fractures of the Distal Radius: Review of the First 23 Cases and Focus on Dorsal Radiocarpal Dislocation.

Background Fragment-specific fixation of the distal radius is born to fix each articular fragment with limited surgical approach and low-profile devices. Over time, many devices with different designs and characteristics have been developed. However, many of them have showed the inability to securely fix marginal, small, and comminuted fragments as bony ligament avulsions and bony compression injuries. Purpose The purpose of this study was to evaluate the clinical and radiological outcome of a new device born to treat marginal articular fractures of the distal radius. Patients and Methods A retrospective review was conducted on 23 patients with a mean follow-up of 21 months including postoperative clinical evaluation, grip strength, computed tomography scan, and X-ray control. Results All fragments healed and maintained reduced until the final follow-up. The carpus was aligned with the distal radius in all patients presenting with a radiocarpal dislocation. Conclusion The volar rim fragment is an attachment site for the short radiolunate and the volar distal radioulnar ligament. Its unstable fixation can lead to articular incongruity, volar or dorsal subluxation of the carpus, and distal radioulnar instability. The involvement of this fragment on distal radius fractures is relatively common and many studies of the literature have been focused on its treatment. The Hook Plate stabilizes distal fragments at their bone-ligament interface. In addition to bony reduction, the device permits to stabilize the capsule and ligaments, as volar bony ligament avulsions, in a picture of dorsal radiocarpal dislocation. Level of Evidence This is a Level IV, case series.

Biofabrication of soft tissue templates for engineering the bone-ligament interface.

Regenerating damaged tissue interfaces remains a significant clinical challenge, requiring recapitulation of the structure, composition, and function of the native enthesis. In the ligament-to-bone interface, this region transitions from ligament to fibrocartilage, to calcified cartilage and then to bone. This gradation in tissue types facilitates the transfer of load between soft and hard structures while minimizing stress concentrations at the interface. Previous attempts to engineer the ligament-bone interface have utilized various scaffold materials with an array of various cell types and/or biological cues. The primary goal of this study was to engineer a multiphased construct mimicking the ligament-bone interface by driving differentiation of a single population of mesenchymal stem cells (MSCs), seeded within blended fibrin-alginate hydrogels, down an endochondral, fibrocartilaginous, or ligamentous pathway through spatial presentation of growth factors along the length of the construct within a custom-developed, dual-chamber culture system. MSCs within these engineered constructs demonstrated spatially distinct regions of differentiation, adopting either a cartilaginous or ligamentous phenotype depending on their local environment. Furthermore, there was also evidence of spatially defined progression toward an endochondral phenotype when chondrogenically primed MSCs within this construct were additionally exposed to hypertrophic cues. The study demonstrates the feasibility of engineering spatially complex soft tissues within a single MSC laden hydrogel through the defined presentation of biochemical cues. This novel approach represents a new strategy for engineering the ligament-bone interface. Biotechnol. Bioeng. 2017;114: 2400-2411. © 2017 Wiley Periodicals, Inc.

Multi-scale analysis of simulated capillary instability

This paper presents the 3-D multi-scale analysis of a cylindrical liquid ligament subjected to a capillary instability. This analysis aims to investigate the evolution of the ligament interface paying a specific attention to the physical mechanisms involved at small scales. The capillary instability behavior is obtained from direct numerical simulations. Calculations are performed for several wavenumbers of the initial sinusoidal perturbation. During the capillary instability, the scale space is divided in two regions: the small-scale region where a thinning mechanism is identified and the large-scale region where a thickening mechanism is observed. Although the characteristic scale dmax of the large-scale region displays a dynamics that agrees with the Rayleigh linear theory, this agreement is lost for the characteristic scale d1 of the small scale region showing that the non-linear effects mainly concentrate on the small scales. The dynamics of the characteristic scale d1 follows three successive regimes. The development of a simple model allows identifying the physical mechanisms related to these three regimes as well as their dependences with the wavenumber of the perturbation. Among other results it is found that the capillary contraction regime that develops when the breakup is approached is always preceded by an elongation mechanism whose effect is to increase the specific-surface-area of the ligament.

PTH/SDF-1α cotherapy induces CD90+CD34- stromal cells migration and promotes tissue regeneration in a rat periodontal defect model.

Stromal cell-derived factor-1α (SDF-1α) is a key stem cell homing factor that is crucial for recruitment of stem cells to many diseased organs. However, the therapeutic activity of SDF-1α is potentially limited by N-terminal cleavage at position-2 proline by a cell surface protein CD26/dipeptidyl peptidase-IV (DPP-IV). Parathyroid hormone (PTH) is a DPP-IV inhibitor and has been suggested as a promising agent for periodontal tissue repair. The purpose of this study was to explore the effects of a cell-free system comprising SDF-1α and scaffold plus PTH systemic application on periodontal tissue regeneration in vivo. The results showed that PTH/SDF-1α cotherapy improved the quantity of regenerated bone and resulted in better organization of ligament interface. We further investigated the possible mechanisms, and found that PTH/SDF-1α cotherapy enhanced CD90+CD34− stromal cells migration in vivo, increased the number of CXCR4 + cells in periodontal defects, induced early bone osteoclastogenesis and enhanced the expression of runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP) and collagen I (Col I) in newly formed bone tissue. In conclusion, this cell-free tissue engineering system with local administration of SDF-1α and systemic application of PTH could be employed to induce CD90+CD34− stromal cells recruitment and promote periodontal tissue regeneration.

Triphasic scaffolds for the regeneration of the bone–ligament interface

A triphasic scaffold (TPS) for the regeneration of the bone–ligament interface was fabricated combining a 3D fiber deposited polycaprolactone structure and a polylactic co-glycolic acid electrospun. The scaffold presented a gradient of physical and mechanical properties which elicited different biological responses from human mesenchymal stem cells. Biological test were performed on the whole TPS and on scaffolds comprised of each single part of the TPS, considered as the controls. The TPS showed an increase of the metabolic activity with culturing time that seemed to be an average of the controls at each time point. The importance of differentiation media for bone and ligament regeneration was further investigated. Metabolic activity analysis on the different areas of the TPS showed a similar trend after 7 days in both differentiation media. Total alkaline phosphatase (ALP) activity analysis showed a statistically higher activity of the TPS in mineralization medium compared to the controls. A different glycosaminoglycans amount between the TPS and its controls was detected, displaying a similar trend with respect to ALP activity. Results clearly indicated that the integration of electrospinning and additive manufacturing represents a promising approach for the fabrication of scaffolds for the regeneration of tissue interfaces, such as the bone-to-ligament one, because it allows mimicking the structural environment combining different biomaterials at different scales.

Spatiotemporally Controlled Microchannels of Periodontal Mimic Scaffolds

Physiologic bioengineering of the oral, dental, and craniofacial complex requires optimized geometric organizations of fibrous connective tissues. A computer-designed, fiber-guiding scaffold has been developed to promote tooth-supporting periodontal tissue regeneration and functional restoration despite limited printing resolution for the manufacture of submicron-scaled features. Here, we demonstrate the use of directional freeze-casting techniques to control pore directional angulations and create mimicked topographies to alveolar crest, horizontal, oblique, and apical fibers of natural periodontal ligaments. For the differing anatomic positions, the gelatin displayed varying patterns of ice growth, determined via internal pore architectures. Regardless of the freezing coordinates, the longitudinal pore arrangements resulted in submicron-scaled diameters (~50 µm), along with corresponding high biomaterial porosity (~90%). Furthermore, the horizontal + coronal () freezing orientation facilitated the creation of similar structures to major fibers in the periodontal ligament interface. This periodontal tissue-mimicking microenvironment is a potential tissue platform for the generation of naturally oriented ligamentous tissues consistent with periodontal ligament neogenesis.

Rac-Null Leukocytes Are Associated with Increased Inflammation-Mediated Alveolar Bone Loss

Periodontitis is characterized by altered host-biofilm interactions that result in irreversible inflammation-mediated alveolar bone loss. Genetic and epigenetic factors that predispose to ineffective control of biofilm composition and maintenance of tissue homeostasis are not fully understood. We elucidated how leukocytes affect the course of periodontitis in Rac-null mice. Mouse models of acute gingivitis and periodontitis were used to assess the early inflammatory response and patterns of chronicity leading to loss of alveolar bone due to inflammation in Rac-null mice. Leukocyte margination was differentially impaired in these mice during attachment in conditional Rac1-null (granulocyte/monocyte lineage) mice and during rolling and attachment in Rac2-null (all blood cells) mice. Inflammatory responses to subgingival ligatures, assessed by changes in peripheral blood differential leukocyte numbers, were altered in Rac-null compared with wild-type mice. In response to persistent subgingival ligature-mediated challenge, Rac-null mice had increased loss of alveolar bone with patterns of resorption characteristic of aggressive forms of periodontitis. These findings were partially explained by higher osteoclastic coverage of the bone-periodontal ligament interface in Rac-null compared with wild-type mice. In conclusion, this study demonstrates that leukocyte defects, such asdecreased endothelial margination and tissue recruitment, are rate-limiting steps in the periodontal inflammatory process that lead to more aggressive forms of periodontitis.

Preparation and Characterization of Alveolar Bone and Periodontal Ligament Interface Scaffolds

To mimic the alveolar bone and periodontal ligament interface, a chitosan(CS for short) composite polysaccharide scaffold was fabricated which was cross-linked with sodium alginate(SA for short). The conditions of physical crosslinking in the scaffolds were discussed. By characterization after biomineralization, it turns out that pH=5.0 and 40min crosslinking time can make for crosslinking. Better crosslinking makes the material more antiswelling and give more compressive strength. In the other hand, the biomineralization can improve the physical properties of the material. We hope that after further research it can come to a scaffold material with good properties.

Anterior cruciate ligament reconstruction in a rabbit model using canine small intestinal submucosa and autologous platelet-rich plasma

BackgroundThe bone–ligament interface is the main point of failure after anterior cruciate ligament reconstruction. Synthetic ligament materials have problems such as a greater failure rate of the bone–ligament insertion than autografts. Small intestinal submucosa (SIS) is a biologic scaffold that has been used to repair musculoskeletal tissue and has been shown to promote cell migration and enhance collagen fiber regeneration. Autologous platelet-rich plasma (PRP) has also been investigated as a potential promoter of tendon healing. We investigated SIS and PRP as biomaterials that might strengthen the bone–tunnel interface and improve tendon structure formation. MethodsAnterior cruciate ligament grafts were formed of braid-twist canine SIS. These canine SIS ligament grafts were used for anterior cruciate ligament reconstruction in 20 New Zealand white rabbits. The rabbits were divided into 2 treatment groups. In 1 group (SIS group; n = 10), we only implanted the canine SIS grafts. In the second group (PRP group; n = 10), we applied autologous PRP to the surgical area after implantation of canine SIS grafts. We determined the cytokine level of the autologous PRP using a transforming growth factor-β1 enzyme-linked immunosorbent assay kit. At 1 and 4 wk after surgery, magnetic resonance imaging was performed to evaluate the grafts. The femur–graft–tibia complex was assessed histologically and biomechanically at 8 wk after surgery. ResultsAt 1 wk after surgery, the magnetic resonance imaging scans of the PRP group showed high signal-intensity lesions. In biomechanical tests, the SIS group had a significantly greater maximum load, maximum stress, and ultimate load and strain than the PRP group. The histologic findings of the PRP group revealed a greater cellular response, fibrotic tissue regeneration around the graft, broad chondrocyte cell infiltration, and collagen fibers that were loosely attached to the bone. ConclusionsThe PRP group had significantly lower tension load values than the SIS group, and there was greater cellular response in a broad area around the grafts of the rabbits in the PRP group compared with those in the SIS group. The early inflammatory responses around the canine SIS grafts in the PRP group and the altered cytokine or growth factor concentration in the intra-articular capsule of the rabbits in PRP group might explain their relatively low tensile strength results.

Tissue engineering bone-ligament complexes using fiber-guiding scaffolds

Regeneration of bone-ligament complexes destroyed due to disease or injury is a clinical challenge due to complex topologies and tissue integration required for functional restoration. Attempts to reconstruct soft-hard tissue interfaces have met with limited clinical success. In this investigation, we manufactured biomimetic fiber-guiding scaffolds using solid free-form fabrication methods that custom fit complex anatomical defects to guide functionally-oriented ligamentous fibers in vivo. Compared to traditional, amorphous or random-porous polymeric scaffolds, the use of perpendicularly oriented micro-channels provides better guidance for cellular processes anchoring ligaments between two distinct mineralized structures. These structures withstood biomechanical loading to restore large osseous defects. Cell transplantation using hybrid scaffolding constructs with guidance channels resulted in predictable oriented fiber architecture, greater control of tissue infiltration, and better organization of ligament interface than random scaffold architectures. These findings demonstrate that fiber-guiding scaffolds drive neogenesis of triphasic bone-ligament integration for a variety of clinical scenarios.

Factors affecting the longevity and strength in an in vitro model of the bone-ligament interface.

The interfaces between musculoskeletal tissues with contrasting moduli are morphologically and biochemically adapted to allow the transmission of force with minimal injury. Current methods of tissue engineering ligaments and tendons do not include the interface and this may limit the future clinical success of engineered musculoskeletal tissues. This study aimed to use solid brushite cement anchors to engineer intact ligaments from bone-to-bone, creating a functional musculoskeletal interface in vitro. We show here that modifying anchor shape and cement composition can alter both the longevity and the strength of an in vitro model of the bone–ligament interface: with values reaching 23 days and 21.6 kPa, respectively. These results validate the use of brushite bone cement to engineer the bone–ligament interface in vitro and raise the potential for future use in ligament replacement surgery.

The 2.5 mm PushLock suture anchor system versus a traditional suture anchor for ulnar collateral ligament injuries of the thumb: a biomechanical study

We compared the biomechanical strength of the 2.5 mm PushLock suture anchor with a traditional Bio-SutureTak suture anchor in repair of ulnar collateral ligament injuries. Iatrogenic ulnar collateral ligament injuries in 18 cadaveric thumbs were repaired and used to test for load to failure and cyclic loading. The average force required to generate a 2 mm gap was 7.7 N for the 2.5 mm PushLock and 6.3 N for the Bio-SutureTak (p = 0.04). The ultimate load to failure was 28.0 N for the 2.5 mm PushLock and 18.8 N for the Bio-SutureTak (p = 0.16). There were no statistical differences between the two suture anchors under cyclic loading. The 2.5 mm PushLock suture anchor provides significantly stronger resistance to 2 mm gap formation at the repair site and is less likely to fail at the suture-ligament interface. However, there was no difference in the load to failure between the two suture anchors.

Engineering the Bone–Ligament Interface Using Polyethylene Glycol Diacrylate Incorporated with Hydroxyapatite

Ligaments and tendons have previously been tissue engineered. However, without the bone attachment, implantation of a tissue-engineered ligament would require it to be sutured to the remnant of the injured native tissue. Due to slow repair and remodeling, this would result in a chronically weak tissue that may never return to preinjury function. In contrast, orthopaedic autograft reconstruction of the ligament often uses a bone-to-bone technique for optimal repair. Since bone-to-bone repairs heal better than other methods, implantation of an artificial ligament should also occur from bone-to-bone. The aim of this study was to investigate the use of a poly(ethylene glycol) diacrylate (PEGDA) hydrogel incorporated with hydroxyapatite (HA) and the cell-adhesion peptide RGD (Arg-Gly-Asp) as a material for creating an in vitro tissue interface to engineer intact ligaments (i.e., bone-ligament-bone). Incorporation of HA into PEG hydrogels reduced the swelling ratio but increased mechanical strength and stiffness of the hydrogels. Further, HA addition increased the capacity for cell growth and interface formation. RGD incorporation increased the swelling ratio but decreased mechanical strength and stiffness of the material. Optimum levels of cell attachment were met using a combination of both HA and RGD, but this material had no better mechanical properties than PEG alone. Although adherence of the hydrogels containing HA was achieved, failure occurs at about 4 days with 5% HA. Increasing the proportion of HA improved interface formation; however, with high levels of HA, the PEG HA composite became brittle. This data suggests that HA, by itself or with other materials, might be well suited for engineering the ligament-bone interface.

Induction of osteopenia during experimental tooth movement in the rat: alveolar bone remodelling and the mechanostat theory

Increases in bone strains above a certain threshold have a positive effect on bone mass, whereas reductions in strain magnitude lead to bone loss and osteopenia; the term 'mechanostat' has been introduced to describe this tissue-level negative feedback mechanism. The mechanobiology of bone and particularly alveolar bone is poorly understood, and whether the mechanostat theory has any relevance to explaining the osseous changes that occur during orthodontic tooth movement remains unclear. To investigate the relationship further, an expansile force of 0.2 N was applied to the maxillary molars of 36, 6-week-old Wistar rats by helical coil springs. The animals were sacrificed at 1, 2, 4, and 8 days and the tissue response analyzed by histological, biochemical, and finite element (FE) methods. Differences between groups were determined by Student's t-test (two-tailed). The appliance produced an increase in the intermolar width averaging 0.5 mm after 8 days. Tetracycline uptake in the control rats suggested a rapid turnover of bone in both the interradicular domain and the bone-periodontal ligament interface. In the experimental group, however, incorporation of tetracycline into the interradicular domain was reduced and conventional histology revealed evidence of bone loss and osteopenia, in both the experimental and a group of sham-treated positive controls (with inactive, annealed springs). Serum alkaline phosphatase declined significantly in both experimental and sham-treated groups over the 8-day time course, indicating decreased bone formation. Serum acid phosphatase also declined, suggesting a concomitant decrease in bone resorption. Three-dimensional FE analysis of the stresses generated in the bone following occlusal (2 N) and orthodontic loading showed that the orthodontic force created a constant loading condition shielding some areas of bone from mechanical stress. Areas of low mechanical stimulation were coincident with sites of bone loss observed histologically, while bone mass was preserved in areas with higher levels of loading. These findings suggest that (1) the osteopenia resulted from stress shielding of the interradicular bone by the appliance, and a consequent reduction in occlusal loading below the critical threshold required for maintaining normal osseous architecture and (2) the mechanostat model can be employed to explain, at least in part, the response of the bone to orthodontic loading.

Integrin mediated attachment of periodontal ligament to titanium surfaces

Objective Reducing the force between the implant and the bone by recapitulating a similar matrix has the potential to reduce implant failure. To begin to pursue the goal of creating a periodontal ligament interface between a dental implant and bone, the mechanism of cellular attachment to dental implant surfaces must be characterized. Methods In this study we examined the role of integrin receptors in the attachment of periodontal ligament fibroblasts to titanium surfaces utilized on dental implants; those surfaces included smooth polished titanium, acid pickled titanium, ground titanium, sandblasted and acid etched titanium, non-oxidized titanium that has been sandblasted and acid etched, hydroxyapatite coated titanium, titanium plasma sprayed or uncoated titanium. For these studies integrin mediated fibroblast attachment was blocked by the integrin blocking peptide GRGDSP or anti-integrin β1 antibody or a combination of the two. Quantitation of periodontal ligament fibroblast attachment was completed by counting cells on the various implant surfaces after culturing in vitro for 24 h with and without the integrin receptor blockers. Results Antibody and peptide treatment significantly reduced the number of fibroblasts cells attached to the various implant surfaces but this effect varied significantly depending on the surface. Moreover, increased levels of peptide further decreased fibroblasts attachment in a dose dependent manner. Significance Blocking studies suggest first, that integrin receptors function in periodontal ligament attachment to titanium surfaces and second, that different integrin subunits are important in attachment to a particular surface.

Ligament regeneration using a knitted silk scaffold combined with collagen matrix

This study was aimed to develop a new practical ligament scaffold by synergistic incorporation of silk fibers, a knitted structure, and a collagen matrix. The efficacy for ligament tissue engineering was investigated in vitro and in animal models. Cells cultured on a collagen substrate expressed ligament matrix genes at higher levels than those on a silk substrate. The silk scaffold elicited little inflammatory reaction and degraded slowly after subcutaneous implantation in a mouse model. In the rabbit MCL defect model, MCLs treated with a silk + collagen scaffold deposited more collagen, had better mechanical properties, and showed more native microstructure with larger diameter collagen fibrils and stronger scaffold–ligament interface healing than untreated MCLs and those treated with silk scaffolds. These results demonstrated that the knitted silk + collagen sponge scaffold improves structural and functional ligament repair by regulating ligament matrix gene expression and collagen fibril assembly. The findings are the first to highlight the important roles of biomaterials in ligament regeneration biology. Also, the concept of an “internal-space-preservation” scaffold is proposed for the tissue repair under physical loading.