A novel nano-composite multi-layered biomaterial for treatment of osteochondral lesions: technique note and an early stability pilot clinical trial

Osteochondral regeneration with a tri-layered biomimetic resorbable scaffold: In vivo study in a sheep model up to 12 months of follow-up

The treatment of osteochondral joint lesions requires the regeneration of both articular cartilage and subchondral bone tissue. Scaffold-based strategies aimed at mimicking the native osteochondral structure have been explored with mixed results. The aim of this study was to evaluate the regenerative potential of a tri-layered osteochondral cell-free scaffold in a large animal model at both 6 and 12 months of follow-up. Bilateral critical-sized osteochondral defects were created in 22 sheep. One defect was filled with the scaffold, whereas the contralateral was left empty. The repair tissue quality was evaluated at 6 and 12 months of follow-up in terms of macroscopic appearance, histology, trabecular bone formation, and inflammation grade. The mean global ICRS II score in the scaffold and control groups was 41 ± 11 vs 30 ± 6 at 6 months (p = 0.004) and 54 ± 13 vs 37 ± 11 at 12 months (p = 0.002), respectively. A higher percentage of bone was found in the treatment group compared to controls both at 6 (BV/TV 48.8 ± 8.6 % vs 37.4 ± 9.5 %, respectively; p < 0.001) and 12 months (BV/TV 51.8 ± 8.8 % vs 42.1 ± 12.6 %, respectively; p = 0.023). No significant levels of inflammation were seen. These results demonstrated the scaffold safety and potential to regenerate both cartilage and subchondral tissues in a large animal model of knee osteochondral lesions.

Bioactive and Bioinductive Implants Are Increasingly Used in Orthopaedic Sports Medicine but Adequately Controlled Studies Are Needed: A Scoping Review

PURPOSE

To describe the currently available literature reporting clinical outcomes for bioactive and bioinductive implants in sports medicine.

METHODS

In accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic search of 4 databases was completed to identify eligible studies. Inclusion criteria were studies using bioactive or bioinductive implants in human clinical studies for sports medicine procedures. Data were extracted and reported in narrative form, along with study characteristics.

RESULTS

In total, 145 studies were included involving 6,043 patients. The majority of included studies were level IV evidence (65.5%), and only 36 included a control group (24.8%). Bioactive materials are defined as any materials that stimulate an advantageous response from the body upon implantation, whereas bioinductive materials provide a favorable environment for a biological response initiated by the host. Bioactivity can speed healing and improve clinical outcome by improving vascularization, osteointegration, osteoinduction, tendon healing, and soft-tissue regeneration or inducing immunosuppression or preventing infection. The most common implants reported were for knee (67.6%, primarily cartilage [most commonly osteochondral defects], anterior cruciate ligament, and meniscus), shoulder (16.6%, primarily rotator cuff), or ankle (11.7%, primarily Achilles repair). The most common type of implant was synthetic (44.1%), followed by autograft (30.3%), xenograft (16.6%), and allograft (9.0%). In total, 69% of implants were standalone treatments and 31% were augmentation.

CONCLUSIONS

The existing bioactive and bioinductive implant literature in sports medicine is largely composed of small, low-level-of-evidence studies lacking a control group.

CLINICAL RELEVANCE

Before bioactive implants can be adapted as a new standard of care, larger, comparative clinical outcome studies with long-term follow-up are essential.

In vitrodegradation of a chitosan-based osteochondral construct points to a transient effect on cellular viability

Bioresorbable chitosan scaffolds have shown potential for osteochondral repair applications. Thein vivodegradation of chitosan, mediated by lysozyme and releasing glucosamine, enables progressive replacement by ingrowing tissue. Here the degradation process of a chitosan-nHA based bioresorbable scaffold was investigated for mass loss, mechanical properties and degradation products released from the scaffold when subjected to clinically relevant enzyme concentrations. The scaffold showed accelerated mass loss during the early stages of degradation but without substantial reduction in mechanical strength or structure deterioration. Although not cytotoxic, the medium in which the scaffold was degraded for over 2 weeks showed a transient decrease in mesenchymal stem cell viability, and the main degradation product (glucosamine) demonstrated a possible adverse effect on viability when added at its peak concentration. This study has implications for the design and biomedical application of chitosan scaffolds, underlining the importance of modelling degradation products to determine suitability for clinical translation.

In situ cell condensation-based cartilage tissue engineering via immediately implantable high-density stem cell core and rapidly degradable shell microgels

Formation of chondromimetic human mesenchymal stem cells (hMSCs) condensations typically required in vitro culture in defined environments. In addition, extended in vitro culture in differentiation media over several weeks is usually necessary prior to implantation, which is costly, time consuming and delays clinical treatment. Here, this study reports on immediately implantable core/shell microgels with a high-density hMSC-laden core and rapidly degradable hydrogel shell. The hMSCs in the core formed cell condensates within 12 hours and the oxidized and methacrylated alginate (OMA) hydrogel shells were completely degraded within 3 days, enabling spontaneous and precipitous fusion of adjacent condensed aggregates. By delivering transforming growth factor-β1 (TGF-β1) within the core, the fused condensates were chondrogenically differentiated and formed cartilage microtissues. Importantly, these hMSC-laden core/shell microgels, fabricated without any in vitro culture, were subcutaneously implanted into mice and shown to form cartilage tissue via cellular condensations in the core after 3 weeks. This innovative approach to form cell condensations in situ without in vitro culture that can fuse together with each other and with host tissue and be matured into new tissue with incorporated bioactive signals, allows for immediate implantation and may be a platform strategy for cartilage regeneration and other tissue engineering applications.

Incorporating strontium enriched amorphous calcium phosphate granules in collagen/collagen-magnesium-hydroxyapatite osteochondral scaffolds improves subchondral bone repair

Osteochondral defect repair with a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold has demonstrated good clinical results. However, subchondral bone repair remained suboptimal, potentially leading to damage to the regenerated overlying neocartilage. This study aimed to improve the bone repair potential of this scaffold by incorporating newly developed strontium (Sr) ion enriched amorphous calcium phosphate (Sr-ACP) granules (100-150 μm). Sr concentration of Sr-ACP was determined with ICP-MS at 2.49 ± 0.04 wt%. Then 30 wt% ACP or Sr-ACP granules were integrated into the scaffold prototypes. The ACP or Sr-ACP granules were well embedded and distributed in the collagen matrix demonstrated by micro-CT and scanning electron microscopy/energy dispersive x-ray spectrometry. Good cytocompatibility of ACP/Sr-ACP granules and ACP/Sr-ACP enriched scaffolds was confirmed with in vitro cytotoxicity assays. An overall promising early tissue response and good biocompatibility of ACP and Sr-ACP enriched scaffolds were demonstrated in a subcutaneous mouse model. In a goat osteochondral defect model, significantly more bone was observed at 6 months with the treatment of Sr-ACP enriched scaffolds compared to scaffold-only, in particular in the weight-bearing femoral condyle subchondral bone defect. Overall, the incorporation of osteogenic Sr-ACP granules in Col/Col-Mg-HAp scaffolds showed to be a feasible and promising strategy to improve subchondral bone repair.

Bioinspired gradient scaffolds for osteochondral tissue engineering

Repairing articular osteochondral defects present considerable challenges in self-repair due to the complex tissue structure and low proliferation of chondrocytes. Conventional clinical therapies have not shown significant efficacy, including microfracture, autologous/allograft osteochondral transplantation, and cell-based techniques. Therefore, tissue engineering has been widely explored in repairing osteochondral defects by leveraging the natural regenerative potential of biomaterials to control cell functions. However, osteochondral tissue is a gradient structure with a smooth transition from the cartilage to subchondral bone, involving changes in chondrocyte morphologies and phenotypes, extracellular matrix components, collagen type and orientation, and cytokines. Bioinspired scaffolds have been developed by simulating gradient characteristics in heterogeneous tissues, such as the pores, components, and osteochondrogenesis-inducing factors, to satisfy the anisotropic features of osteochondral matrices. Bioinspired gradient scaffolds repair osteochondral defects by altering the microenvironments of cell growth to induce osteochondrogenesis and promote the formation of osteochondral interfaces compared with homogeneous scaffolds. This review outlines the meaningful strategies for repairing osteochondral defects by tissue engineering based on gradient scaffolds and predicts the pros and cons of prospective translation into clinical practice.

Effectiveness of BMP-2 and PDGF-BB Adsorption onto a Collagen/Collagen-Magnesium-Hydroxyapatite Scaffold in Weight-Bearing and Non-Weight-Bearing Osteochondral Defect Bone Repair: In Vitro, Ex Vivo and In Vivo Evaluation

Despite promising clinical results in osteochondral defect repair, a recently developed bi-layered collagen/collagen-magnesium-hydroxyapatite scaffold has demonstrated less optimal subchondral bone repair. This study aimed to improve the bone repair potential of this scaffold by adsorbing bone morphogenetic protein 2 (BMP-2) and/or platelet-derived growth factor-BB (PDGF-BB) onto said scaffold. The in vitro release kinetics of BMP-2/PDGF-BB demonstrated that PDGF-BB was burst released from the collagen-only layer, whereas BMP-2 was largely retained in both layers. Cell ingrowth was enhanced by BMP-2/PDFG-BB in a bovine osteochondral defect ex vivo model. In an in vivo semi-orthotopic athymic mouse model, adding BMP-2 or PDGF-BB increased tissue repair after four weeks. After eight weeks, most defects were filled with bone tissue. To further investigate the promising effect of BMP-2, a caprine bilateral stifle osteochondral defect model was used where defects were created in weight-bearing femoral condyle and non-weight-bearing trochlear groove locations. After six months, the adsorption of BMP-2 resulted in significantly less bone repair compared with scaffold-only in the femoral condyle defects and a trend to more bone repair in the trochlear groove. Overall, the adsorption of BMP-2 onto a Col/Col-Mg-HAp scaffold reduced bone formation in weight-bearing osteochondral defects, but not in non-weight-bearing osteochondral defects.

Development and in vitro assessment of a bi-layered chitosan-nano-hydroxyapatite osteochondral scaffold

An innovative approach was developed to engineer a multi-layered chitosan scaffold for osteochondral defect repair. A combination of freeze drying and porogen-leaching out methods produced a porous, bioresorbable scaffold with a distinct gradient of pore size (mean = 160-275 μm). Incorporation of 70 wt% nano-hydroxyapatite (nHA) provided additional strength to the bone-like layer. The scaffold showed instantaneous mechanical recovery under compressive loading and did not delaminate under tensile loading. The scaffold supported the attachment and proliferation of human mesenchymal stem cells (MSCs), with typical adherent cell morphology found on the bone layer compared to a rounded cell morphology on the chondrogenic layer. Osteogenic and chondrogenic differentiation of MSCs preferentially occurred in selected layers of the scaffold in vitro, driven by the distinct pore gradient and material composition. This scaffold is a suitable candidate for minimally invasive arthroscopic delivery in the clinic with potential to regenerate damaged cartilage and bone.

The evaluation of a multiphasic 3D-bioplotted scaffold seeded with adipose derived stem cells to repair osteochondral defects in a porcine model

There is a need for the development of effective treatments for focal articular cartilage injuries. We previously developed a multiphasic 3D-bioplotted osteochondral scaffold design that can drive site-specific tissue formation when seeded with adipose-derived stem cells (ASC). The objective of this study was to evaluate this scaffold in a large animal model. Osteochondral defects were generated in the trochlear groove of Yucatan minipigs and repaired with scaffolds that either contained or lacked an electrospun tidemark and were either unseeded or seeded with ASC. Implants were monitored via computed tomography (CT) over the course of 4 months of in vivo implantation and compared to both open lesions and autologous explants. ICRS II evaluation indicated that defects with ASC-seeded scaffolds had healing that most closely resembled the aulogous explant. Scaffold-facilitated subchondral bone repair mimicked the structure of native bone tissue, but cartilage matrix staining was not apparent within the scaffold. The open lesions had the highest volumetric infill detected using CT analysis (p < 0.05), but the repair tissue was largely disorganized. The acellular scaffold without a tidemark had significantly more volumetric filling than either the acellular or ASC seeded groups containing a tidemark (p < 0.05), suggesting that the tidemark limited cell infiltration into the cartilage portion of the scaffold. Overall, scaffold groups repaired the defect more successfully than an open lesion but achieved limited repair in the cartilage region. With further optimization, this approach holds potential to treat focal cartilage lesions in a highly personalized manner using a human patient's own ASC cells.

Scaffold With Natural Calcified Cartilage Zone for Osteochondral Defect Repair in Minipigs

BACKGROUND

Long-term outcomes of current clinical interventions for osteochondral defect are less than satisfactory. One possible reason is an ignorance of the interface structure between cartilage and subchondral bone, the calcified cartilage zone (CCZ). However, the importance of natural CCZ in osteochondral defects has not been directly described.

PURPOSE

To explore the feasibility of fabricating trilayer scaffold containing natural CCZ for osteochondral defects and the role of CCZ in the repair process.

STUDY DESIGN

Controlled laboratory study.

METHODS

The scaffold was prepared by cross-linking lyophilized type II collagen sponge and acellular normal pig subchondral bone with or without natural CCZ. Autologous bone marrow stem cells (BMSCs) of minipig were mixed with type II collagen gel and injected into the cartilage layer of the scaffold before operation. Thirty minipigs were randomly divided into CCZ (n = 10), non-CCZ (n = 10), and blank control (n = 10) groups. An 8 mm-diameter full-thickness osteochondral defect was created on the trochlear surface, and scaffold containing BMSCs was transplanted into the defect according to grouping requirements. At 12 and 24 weeks postoperatively, specimens were assessed by macroscopic observation, magnetic resonance imaging examination, and histological observations (hematoxylin and eosin, Safranin O-fast green, type II collagen immunohistochemical, and Sirius red staining). Semiquantitative cartilage repair scoring was conducted using the MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) system and the O'Driscoll repaired cartilage value system.

RESULTS

The defects in the blank control and non-CCZ groups were filled with fibrous tissue, while the cartilage layer of the CCZ group was mainly repaired by hyaline cartilage at 24 weeks postoperatively. The superior repair outcome of the CCZ group was confirmed by MOCART and O'Driscoll score.

CONCLUSION

The trilayer scaffold containing natural CCZ obtained the best repair effect compared with the non-CCZ scaffold and the blank control, indicating the importance of the CCZ in osteochondral tissue engineering.

CLINICAL RELEVANCE

This study demonstrates the necessity to reconstruct CCZ in clinical osteochondral defect repair and provides a possible strategy for osteochondral tissue engineering.

Reliability of the MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) 2.0 knee score for different cartilage repair techniques-a retrospective observational study

OBJECTIVES

To evaluate the reliability of the MOCART 2.0 knee score in the radiological assessment of repair tissue after different cartilage repair procedures.

METHODS

A total of 114 patients (34 females) who underwent cartilage repair of a femoral cartilage lesion with at least one postoperative MRI examination were selected, and one random postoperative MRI examination was retrospectively included. Mean age was 32.5 ± 9.6 years at time of surgery. Overall, 66 chondral and 48 osteochondral lesions were included in the study. Forty-eight patients were treated with autologous chondrocyte implantation (ACI), 27 via osteochondral autologous transplantation, five using an osteochondral scaffold, and 34 underwent microfracture (MFX). The original MOCART and MOCART 2.0 knee scores were assessed by two independent readers. After a minimum 4-week interval, both readers performed a second reading of both scores. Inter- and intrarater reliabilities were assessed using intraclass correlation coefficients (ICCs).

RESULTS

The MOCART 2.0 knee score showed higher interrater reliability than the original MOCART score with an ICC of 0.875 versus 0.759, ranging from 0.863 in the MFX group to 0.878 in the ACI group. Intrarater reliability was good with an overall ICC of 0.860 and 0.866, respectively. Overall, interrater reliability was higher for osteochondral lesions than for chondral lesions, with ICCs of 0.906 versus 0.786.

CONCLUSIONS

The MOCART 2.0 knee score enables the assessment of cartilage repair tissue after different cartilage repair techniques (ACI, osteochondral repair techniques, MFX), as well as for different lesion types with good intra- and interrater reliability.

KEY POINTS

• The MOCART 2.0 knee score provides improved intra- and interrater reliability when compared to the original MOCART score. • The MOCART 2.0 knee score enables the assessment of cartilage repair tissue after different cartilage repair techniques (ACI, osteochondral repair techniques, MFX) with similarly good intra- and interrater reliability. • The assessment of osteochondral lesions demonstrated better intra- and interrater reliability than the assessment of chondral lesions in this study.

Ex Vivo Systems to Study Chondrogenic Differentiation and Cartilage Integration

Articular cartilage injury and repair is an issue of growing importance. Although common, defects of articular cartilage present a unique clinical challenge due to its poor self-healing capacity, which is largely due to its avascular nature. There is a critical need to better study and understand cellular healing mechanisms to achieve more effective therapies for cartilage regeneration. This article aims to describe the key features of cartilage which is being modelled using tissue engineered cartilage constructs and ex vivo systems. These models have been used to investigate chondrogenic differentiation and to study the mechanisms of cartilage integration into the surrounding tissue. The review highlights the key regeneration principles of articular cartilage repair in healthy and diseased joints. Using co-culture models and novel bioreactor designs, the basis of regeneration is aligned with recent efforts for optimal therapeutic interventions.

Hierarchical and heterogeneous hydrogel system as a promising strategy for diversified interfacial tissue regeneration

A state-of-the-art review on the design and preparation of hierarchical and heterogeneous hydrogel systems for interfacial tissue regeneration.

AMIC for Focal Osteochondral Defect of the Talar Shoulder

BACKGROUND

The management of a focal osteochondral lesion of the talus (OLT) is challenging. Evidence concerning the role of the autologous matrix-induced chondrogenesis (AMIC) procedure in patients with focal OLT is promising. The purpose of the present study was to investigate clinical outcomes and radiographic findings of the AMIC technique for focal unipolar OLT.

MATERIAL AND METHODS

The present study was performed according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. Twenty-four patients who underwent AMIC for focal OLT were prospectively recruited at our institution. All the surgeries were performed by two experienced surgeons through malleolar osteotomy and autologous cancellous bone grafting. The outcomes of interest were the American orthopedic foot and ankle score (AOFAS), the foot-function index (FFI), and the magnetic resonance observation of cartilage repair tissue (MOCART). Surgical duration, hospitalization length, and complications were also collected.

RESULTS

24 patients were included in the present study. The mean follow-up was 25.17 ± 13.1 months. The mean age of the patients at surgery was 46.75 ± 15.2 years, the mean BMI 26.92 ± 5.7 kg/m², and 50% (12 of 24) of patients were female. The right ankle was involved in 62.5% (15 of 24) of patients. The mean defect size was 6.95 ± 2.9 mm². The mean surgical duration was 112 ± 20 min while the mean hospitalization 5.58 ± 1.7 days. At last follow-up, the AOFAS increased by 27.8 points (p < 0.0001), while the FFI reduced by 25.3 points (p < 0.0001) and the MOCART score increased by 28.33 points (p < 0.0001). No complications were observed.

CONCLUSION

The AMIC procedure for focal osteochondral defects of the talar shoulder is feasible and reliable at midterm follow-up.

FGF2: a key regulator augmenting tendon-to-bone healing and cartilage repair

Ligament/tendon and cartilage injuries are clinically common diseases that perplex most clinicians. Because of the lack of blood vessels and nerves, their self-repairing abilities are rather poor. Therefore, surgeries are necessary and also widely used to treat ligament/tendon or cartilage injuries. However, after surgery, there are still many problems that affect healing. In recent years, it has been found that exogenous FGF2 plays an important role in the repair of ligament/tendon and cartilage injuries and exerts a synergistic effect with endogenous FGF2. Therefore, FGF2 can be used as a new type of biomolecule to accelerate tendon-to-bone healing and cartilage repair after injury.

Evolution of hydrogels for cartilage tissue engineering of the knee: A systematic review and meta-analysis of clinical studies

INTRODUCTION

In recent years, studies have boosted our knowledge about the biology and disorders of articular cartilage. In this regard, the design of hydrogel-based scaffolds has advanced to improve cartilage repair. However, the efficacy of knee cartilage repair using hydrogels remains unclear. The aim of systematic review and meta-analysis was to scrutinize the efficiency of hydrogel-based therapy in correcting cartilage defects of knee (femoral condyle, patella, tibia plateau and trochlea).

METHODS

The search was conducted in PubMed to gather articles published from 2004/1/1 to 2019/10/01, addressing the effects of implant of hydrogel on knee joint cartilage regeneration. The Cochrane Collaboration's tool for estimating the risk of bias was applied to check the quality of articles. The clinical data for meta-analysis was recorded using the visual analog scale (VAS), Lysholm score, WOMAC, and IKDC. The guidelines of Cochrane Handbook for Systematic Reviews of Interventions were utilized to conduct the review and meta-analysis in the RevMan 5.3 software.

RESULTS

The search resulted in 50 clinical trials that included 2846 patients, 986 of whom received cell-based hydrogel implants while 1860 patients used hydrogel without cell. There were significant differences comparing the pain scores based on the VAS (MD: -2.97; 95% CI: -3.15 to -2.79, P<0.00001) and WOMAC (MD: -25.22; 95% CI: -31.22 to -19.22, P<0.00001) between pre- and post-treatment with hydrogels. Furthermore, there were significant improvements in the functional scores based on the IKDC total score (MD: 30.67; P<0.00001) and the Lysholm knee scale (MD: 29.26; 95% CI: 26.74 to 31.78, P<0.00001). According to the Lysholm and IKDC score and after cumulative functional analysis, there was a significant improvement in this parameter (MD: 29.25; 95% CI: 27.26 to 31.25, P<0.00001).

CONCLUSIONS

This meta-analysis indicated clinically and statistically significant improvements in the pain score (VAS and WOMAC) and the functional score (IKDC and Lysholm) after the administration of hydrogel compared to pretreatment status. So, the current evidence shows the efficiency of hydrogel-based therapy in correcting and repairing knee cartilage defects.

The five year outcome of a clinical feasibility study using a biphasic construct with minced autologous cartilage to repair osteochondral defects in the knee

PURPOSE

Autologous minced cartilage has been used to repair cartilage defects. We have developed a biphasic cylindrical osteochondral construct for such use in human knees, and report the five year post-operative outcomes.

METHODS

Ten patients with symptomatic osteochondral lesion at femoral condyles were treated by replacing pathological tissue with the osteochondral composites, each consisted a _DL-poly-lactide-co-glycolide chondral phase and a _DL-poly-lactide-co-glycolide/β-tricalcium phosphate osseous phase. A flat chamber between the two phases served as a reservoir to house double-minced (mechanical pulverization and enzymatical dissociation) autologous cartilage graft. The osteochondral lesion was drill-fashioned a pit of identical dimensions as the construct. Graft-laden construct was press fit to the pit. Post-operative outcome was evaluated using Knee Injury and Osteoarthritis Outcome Score (KOOS) up to five years. Regenerated tissue was sampled with arthroscopic needle biopsy for histology at one year, and imaged with magnetic resonance at one, three, and five years to evaluate the neocartilage with MOCART chart. Subchondral bone integration was evaluated with computed tomography at three and five years.

RESULTS

Nine patients completed the five-year follow-up. Post-operative mean KOOS, except that of the "symptom" subscale, had been significantly higher than pre-operation from one year and maintained to five years. The change of MOCRAT scores of the regenerated cartilage paralleled the change of KOOS. The osseous phase remained mineralized during the five-year period, yet did not fully integrate with the host bone.

CONCLUSIONS

This novel construct for chondrocyte implantation yielded promising mid-term outcome. It repaired the osteochondral lesion with hyaline-like cartilage durable for at least five years.

Hypoxia Inducible Factor-1α in Osteochondral Tissue Engineering

Damage to osteochondral (OC) tissues can lead to pain, loss of motility, and progress to osteoarthritis. Tissue engineering approaches offer the possibility of replacing damaged tissues and restoring joint function; however, replicating the spatial and functional heterogeneity of native OC tissue remains a pressing challenge. Chondrocytes in healthy cartilage exist in relatively low-oxygen conditions, while osteoblasts in the underlying bone experience higher oxygen pressures. Such oxygen gradients also exist in the limb bud, where they influence OC tissue development. The cellular response to these spatial variations in oxygen pressure, which is mediated by the hypoxia inducible factor (HIF) pathway, plays a central role in regulating osteo- and chondrogenesis by directing progenitor cell differentiation and promoting and maintaining appropriate extracellular matrix production. Understanding the role of the HIF pathway in OC tissue development may enable new approaches to engineer OC tissue. In this review, we discuss strategies to spatially and temporarily regulate the HIF pathway in progenitor cells to create functional OC tissue for regenerative therapies. Impact statement Strategies to engineer osteochondral (OC) tissue are limited by the complex and varying microenvironmental conditions in native bone and cartilage. Indeed, native cartilage experiences low-oxygen conditions, while the underlying bone is relatively normoxic. The cellular response to these low-oxygen conditions, which is mediated through the hypoxia inducible factor (HIF) pathway, is known to promote and maintain the chondrocyte phenotype. By using tissue engineering scaffolds to spatially and temporally harness the HIF pathway, it may be possible to improve OC tissue engineering strategies for the regeneration of damaged cartilage and its underlying subchondral bone.

A 3D porous microsphere with multistage structure and component based on bacterial cellulose and collagen for bone tissue engineering

Collagen (COL) and bacterial cellulose (BC) were chemically recombined by Malaprade and Schiff-base reactions. A three-dimensional (3D) porous microsphere of COL/BC/Bone morphogenetic protein 2 (BMP-2) with multistage structure and components were prepared by the template method combined with reverse-phase suspension regeneration. The microspheres were full of pores and had a rough surface. The particle size ranged from 8 to 12 microns, the specific surface area (S_BET) was 123.4 m²/g, the pore volume (V_Pore) was 0.59 cm³/g, and the average pore diameter (D_BJH) was 198.5 nm. The adsorption isotherm of the microspheres on the N₂ molecule belongs to that of mesoporous materials. The microspheres showed good biocompatibility, and the 3D porous microspheres with multiple structures and components effectively promoted the adhesion, proliferation, and osteogenic differentiation of mice MC3T3-E1 cells. The study can provide a theoretical basis for the application of COL/BC porous microspheres in the field of bone tissue engineering.

Investigation of multiphasic 3D-bioplotted scaffolds for site-specific chondrogenic and osteogenic differentiation of human adipose-derived stem cells for osteochondral tissue engineering applications

Osteoarthritis is a degenerative joint disease that limits mobility of the affected joint due to the degradation of articular cartilage and subchondral bone. The limited regenerative capacity of cartilage presents significant challenges when attempting to repair or reverse the effects of cartilage degradation. Tissue engineered medical products are a promising alternative to treat osteochondral degeneration due to their potential to integrate into the patient's existing tissue. The goal of this study was to create a scaffold that would induce site-specific osteogenic and chondrogenic differentiation of human adipose-derived stem cells (hASC) to generate a full osteochondral implant. Scaffolds were fabricated using 3D-bioplotting of biodegradable polycraprolactone (PCL) with either β-tricalcium phosphate (TCP) or decellularized bovine cartilage extracellular matrix (dECM) to drive site-specific hASC osteogenesis and chondrogenesis, respectively. PCL-dECM scaffolds demonstrated elevated matrix deposition and organization in scaffolds seeded with hASC as well as a reduction in collagen I gene expression. 3D-bioplotted PCL scaffolds with 20% TCP demonstrated elevated calcium deposition, endogenous alkaline phosphatase activity, and osteopontin gene expression. Osteochondral scaffolds comprised of hASC-seeded 3D-bioplotted PCL-TCP, electrospun PCL, and 3D-bioplotted PCL-dECM phases were evaluated and demonstrated site-specific osteochondral tissue characteristics. This technique holds great promise as cartilage morbidity is minimized since autologous cartilage harvest is not required, tissue rejection is minimized via use of an abundant and accessible source of autologous stem cells, and biofabrication techniques allow for a precise, customizable methodology to rapidly produce the scaffold.

Use of nanoparticles in skeletal tissue regeneration and engineering

Bone and osteochondral defects represent one of the major causes of disabilities in the world. Derived from traumas and degenerative pathologies, these lesions cause severe pain, joint deformity, and loss of joint motion. The standard treatments in clinical practice present several limitations. By producing functional substitutes for damaged tissues, tissue engineering has emerged as an alternative in the treatment of defects in the skeletal system. Despite promising preliminary clinical outcomes, several limitations remain. Nanotechnologies could offer new solutions to overcome those limitations, generating materials more closely mimicking the structures present in naturally occurring systems. Nanostructures comparable in size to those appearing in natural bone and cartilage have thus become relevant in skeletal tissue engineering. In particular, nanoparticles allow for a unique combination of approaches (e.g. cell labelling, scaffold modification or drug and gene delivery) inside single integrated systems for optimized tissue regeneration. In the present review, the main types of nanoparticles and the current strategies for their application to skeletal tissue engineering are described. The collection of studies herein considered confirms that advanced nanomaterials will be determinant in the design of regenerative therapeutic protocols for skeletal lesions in the future.

Cell-Free Biomimetic Osteochondral Scaffold: Implantation Technique

This 1-stage cell-free scaffold-based technique is indicated for the treatment of full-thickness chondral and osteochondral lesions in the knee, regardless of the lesion size. The aim of the procedure is restoration of the osteochondral unit while avoiding the issues of donor site morbidity and those related to cell management.

Description

The surgical technique is simple and can be performed as a 1-stage procedure. The lesion site is visualized through a standard knee medial or lateral parapatellar arthrotomy. The defect is prepared by excision of the injured cartilage and subchondral bone to ensure adequate bone-marrow blood flow and to create a squared, regularly shaped lodging for the device. The scaffold is then shaped and sized according to the dimensions of the prepared lesion site and implanted by press-fitting or with addition of fibrin glue. Finally, the complete range of motion is tested to assess the stability of the implant before and after releasing the tourniquet.

Alternatives

Nonsurgical alternatives have been reported to include nonpharmacological modalities, such as dietary supplements, and pharmacological therapies as well as physical therapies and novel biological procedures involving injections of various substances¹. There are several surgical alternatives, including among others microfracture, mosaicplasty, osteochondral allograft, and total knee arthroplasty, depending primarily on the disease stage and etiology as well as the specific patient conditions^2,3.

Rationale

This cell-free device is engineered in 3 layers to mimic the structure and composition of the osteochondral unit in order to guide resident cells toward an ordered regeneration of both bone and cartilage layers, providing a better quality of regenerated articular surface. The treatment approach offers a useful alternative to current procedures in the field of osteochondral lesions, in particular for young and middle-aged patients affected by symptomatic defects in which subchondral bone is likely involved. The advantages of this scaffold include the ability to perform a 1-stage surgical procedure, off-the-shelf availability, a straightforward surgical technique, and lower costs compared with cell-based regenerative options. Furthermore, in contrast to some more traditional treatments, it can be used for large lesions.

Current trends in Nanotechnology applications in surgical specialties and orthopedic surgery

Nanotechnology is manipulation of matter on atomic, molecular and supramolecular scale. It has extensive range of applications in various branches of science including molecular biology, Health and medicine, materials, electronics, transportation, drugs and drug delivery, chemical sensing, space exploration, energy, environment, sensors, diagnostics, microfabrication, organic chemistry and biomaterials. Nanotechnology involves innovations in drug delivery,fabric design, reactivity and strength of material and molecular manufacturing. Nanotechnology applications are spread over almost all surgical specialties and have revolutionized treatment of various medical and surgical conditions. Clinically relevant applications of nanotechnology in surgical specialties include development of surgical instruments, suture materials, imaging, targeted drug therapy, visualization methods and wound healing techniques. Management of burn wounds and scar is an important application of nanotechnology.Prevention, diagnosis, and treatment of various orthopedic conditions are crucial aspects of technology for functional recovery of patients. Improvement in standard of patient care,clinical trials, research, and development of medical equipments for safe use are improved with nanotechnology. They have a potential for long-term good results in a variety of surgical specialties including orthopedic surgery in the years to come.

Scaffolding Strategies for Tissue Engineering and Regenerative Medicine Applications

During the past two decades, tissue engineering and the regenerative medicine field have invested in the regeneration and reconstruction of pathologically altered tissues, such as cartilage, bone, skin, heart valves, nerves and tendons, and many others. The 3D structured scaffolds and hydrogels alone or combined with bioactive molecules or genes and cells are able to guide the development of functional engineered tissues, and provide mechanical support during in vivo implantation. Naturally derived and synthetic polymers, bioresorbable inorganic materials, and respective hybrids, and decellularized tissue have been considered as scaffolding biomaterials, owing to their boosted structural, mechanical, and biological properties. A diversity of biomaterials, current treatment strategies, and emergent technologies used for 3D scaffolds and hydrogel processing, and the tissue-specific considerations for scaffolding for Tissue engineering (TE) purposes are herein highlighted and discussed in depth. The newest procedures focusing on the 3D behavior and multi-cellular interactions of native tissues for further use for in vitro model processing are also outlined. Completed and ongoing preclinical research trials for TE applications using scaffolds and hydrogels, challenges, and future prospects of research in the regenerative medicine field are also presented.

Neither significant osteoarthritic changes nor deteriorating subjective outcomes occur after hybrid fixation of osteochondritis dissecans in the young adult

PURPOSE

The goal of the fixation of painful osteochondritis dissecans of the femoral condyles in adults is to integrate the osteochondral fragment and thus achieve a normal hyaline cartilaginous coverage. The addition of a biological process to primary fixation may result in improved fragment integration (hybrid fixation). Osteochondral plugs may fulfil this role. The aim of this study was to evaluate long-term clinical and radiological results after hybrid fixation of unstable osteochondritis dissecans. The hypothesis was that the rate of secondary osteoarthritis would be low.

METHODS

Nine patients treated by hybrid fixation were retrospectively reviewed at a median follow-up of 10.1 years (range 7-14). The median age at surgery was 21 (range 17-28). Six of them were evaluated as ICRS grade II and three, as ICRS grade III. The mean surface of the lesion was 4.5 cm². All patients were followed up clinically (IKDC, KOOS, Lysholm) and radiologically [Kellgren-Lawrence score (KL)].

RESULTS

During arthroscopic assessment at the time of screw removal (3 months after surgery), the fragments were stable, and autograft plugs were all well integrated. At the most recent follow-up visit, the median IKDC score was 85.8 (range 51.72-100), the KOOS score was 87.7 (52.4-100), and the Lysholm scale score was 89.8 (77-100). In 7 out of 9 patients, radiographs showed a joint space KL grade of 0 or 1.

CONCLUSION

Hybrid fixation for treating osteochondritis dissecans lesions of the femoral condyles using mechanical and biological fixation provides healing of the osteochondral fragments with good long-term outcomes. No significant osteoarthritic change was seen with this technique at a mid-term follow-up.

LEVEL OF EVIDENCE

IV-case series.

Novel radiomics evaluation of bone formation utilizing multimodal (SPECT/X-ray CT) in vivo imaging

Although an extensive research is being undertaken, the ideal bone graft and evaluation method of the bone formation draw still a warranted attention. The purpose of this study was to develop a novel multimodal radiomics evaluation method, utilizing X-ray computed tomography (CT) and single photon emission computed tomography (SPECT) with Tc-99m-Methyl diphosphonate (Tc-99m-MDP) tracer. These modalities are intended to provide quantitative data concerning the mineral bone density (after evaluation it is referred to as opacity) and the osteoblast activity, at the same time. The properties of bone formation process within poly (methyl methacrylate)-based bone cement graft (PMMA) was compared to that of albumin coated, sterilized, antigen-extracted freeze-dried human bone grafts (HLBC), in caudal vertebrae (C5) of rats. The animals were scanned at 3 and 8 weeks after surgery. In both groups, the mean opacity increased, while the mean Tc-99m-MDP activity decreased. The later parameter was significant (n = 4, p = 0.002) only in HLBC group. The linear regression analysis of PMMA-treated group variables (mean opacity increase; mean Tc-99m-MDP activity decrease), revealed a negative correlation with the medium strength (r = 0.395, p = 0.605). Whereas, it showed strong positive correlation when HLBC group variables were analyzed (r = 0.772, p = 0.012). These results indicate that using HLBC grafts is advantageous in terms of the osteoblast activity and bone vascularization over PMMA cement. Using this regression analysis method, we were able to distinguish characteristics that otherwise could not be distinguished by a regular data analysis. Hence, we propose utilizing this novel method in preclinical tests, and in clinical monitoring of bone healing, in order to improve diagnosis of bone-related diseases.

Implant strategy affects scaffold stability and integrity in cartilage treatment

PURPOSE

To identify the most appropriate implantation strategy for a novel chondral scaffold in a model simulating the early post-operative phase, in order to optimize the implant procedure and reduce the risk of early failure.

METHODS

Eight human cadaveric limbs were strapped to a continuous passive motion device and exposed to extension-flexion cycles (0°-90°). Chondral lesions (1.8 cm diameter) were prepared on condyles, patella and trochlea for the implant of a bi-layer collagen-hydroxyapatite scaffold. The first set-up compared four fixation techniques: press-fit (PF) vs. fibrin glue (FG) vs. pins vs. sutures; the second compared circular and square implants; the third investigated stability in a weight-bearing simulation. The scaffolds were evaluated using semi-quantitative Drobnic and modified Bekkers scores.

RESULTS

FG presented higher total Drobnic and Bekkers scores compared to PF (both p = 0.002), pins (p = 0.013 and 0.001) and sutures (p = 0.001 and < 0.0005). Pins offered better total Drobnic and Bekkers scores than PF in the anterior femoral condyles (p = 0.007 and 0.065), similar to FG. The comparison of round and square implants applied by FG showed worst results for square lesions (Drobnic score p = 0.049, Bekkers score p = 0.037). Finally, load caused worst overall results (Drobnic p = 0.018).

CONCLUSIONS

FG improves the fixation of this collagen-HA scaffold regardless of lesion location, improving implant stability while preserving its integrity. Pins represent a suitable option only for lesions of the anterior condyles. Square scaffolds present weak corners, therefore, round implants should be preferred. Finally, partial weight-bearing simulation significantly affected the scaffold. These findings may be useful to improve surgical technique and post-operative management of patients, to optimize the outcome of chondral scaffold implantation.

Orthopaedic regenerative tissue engineering en route to the holy grail: disequilibrium between the demand and the supply in the operating room

Orthopaedic disorders are very frequent, globally found and often partially unresolved despite the substantial advances in science and medicine. Their surgical intervention is multifarious and the most favourable treatment is chosen by the orthopaedic surgeon on a case-by-case basis depending on a number of factors related with the patient and the lesion. Numerous regenerative tissue engineering strategies have been developed and studied extensively in laboratory through in vitro experiments and preclinical in vivo trials with various established animal models, while a small proportion of them reached the operating room. However, based on the available literature, the current strategies have not yet achieved to fully solve the clinical problems. Thus, the gold standards, if existing, remain unchanged in the clinics, notwithstanding the known limitations and drawbacks. Herein, the involvement of regenerative tissue engineering in the clinical orthopaedics is reviewed. The current challenges are indicated and discussed in order to describe the current disequilibrium between the needs and solutions made available in the operating room. Regenerative tissue engineering is a very dynamic field that has a high growth rate and a great openness and ability to incorporate new technologies with passion to edge towards the Holy Grail that is functional tissue regeneration. Thus, the future of clinical solutions making use of regenerative tissue engineering principles for the management of orthopaedic disorders is firmly supported by the clinical need.

Enhancing Biological and Biomechanical Fixation of Osteochondral Scaffold: A Grand Challenge

Osteoarthritis (OA) is a degenerative joint disease, typified by degradation of cartilage and changes in the subchondral bone, resulting in pain, stiffness and reduced mobility. Current surgical treatments often fail to regenerate hyaline cartilage and result in the formation of fibrocartilage. Tissue engineering approaches have emerged for the repair of cartilage defects and damages to the subchondral bones in the early stage of OA and have shown potential in restoring the joint's function. In this approach, the use of three-dimensional scaffolds (with or without cells) provides support for tissue growth. Commercially available osteochondral (OC) scaffolds have been studied in OA patients for repair and regeneration of OC defects. However, some controversial results are often reported from both clinical trials and animal studies. The objective of this chapter is to report the scaffolds clinical requirements and performance of the currently available OC scaffolds that have been investigated both in animal studies and in clinical trials. The findings have demonstrated the importance of biological and biomechanical fixation of the OC scaffolds in achieving good cartilage fill and improved hyaline cartilage formation. It is concluded that improving cartilage fill, enhancing its integration with host tissues and achieving a strong and stable subchondral bone support for overlying cartilage are still grand challenges for the early treatment of OA.

Good clinical results but moderate osseointegration and defect filling of a cell-free multi-layered nano-composite scaffold for treatment of osteochondral lesions of the knee

PURPOSE

The aim of this retrospective study was to evaluate the clinical and radiological results of a nano-composite multi-layered three-dimensional biomaterial scaffold for treatment of osteochondral lesions (OCL) of the knee. It was a particular radiological interest to analyse the osseointegration, filling of the defects and the bone tracer uptake (BTU), and it was hypothesised that this scaffold, which was created to mimic the entire osteo-cartilaginous unit, is integrated within the bone 12 months postoperatively and comes along with improved patients symptoms and function.

METHODS

Fourteen patients (male:female = 11:3, mean age ± SD 33.1 ± 10.7 years) treated for OCL (size 1.0-3.5 cm²) were clinically and radiologically evaluated at 1 year postoperatively. The data were prospectively collected including SPECT/CT, Tegner and Lysholm scores. BTU was anatomically localised and volumetrically quantified in SPECT/CT. Defect filling was analysed in CT. Spearman's rho and Wilcoxon test were used for correlation of BTU in SPECT/CT and clinical scores (p < 0.05).

RESULTS

A significant improvement in Lysholm knee score (p < 0.001) and slight deterioration in Tegner score were found (p < 0.01). A complete filling of the defect was shown in 14%, a partial filling in 14% and only minor filling was seen in 72%. A significant correlation (p < 0.001) was found between location of osteochondral lesions and increased BTU. At the lesion sites pre- and postoperative BTU was markedly increased and did not show any decrease at 12-month follow-up. Median Tegner and mean Lysholm scores did not correlate with BTU at any time.

CONCLUSIONS

Treatment of OCL in the knee joint with a nano-composite multi-layered three-dimensional biomaterial scaffold resulted in a significant clinical improvement at 1-year follow-up. However, osseointegration was still ongoing at 12-month follow-up.

LEVEL OF EVIDENCE

Case series, Level IV.

Hybrid fixation in adult osteochondritis dissecans of the knee

Osteochondritis dissecans progresses to osteoarthritis if integration of the fragment is not obtained. The prognosis of osteochondritis dissecans is more severe in adults, as spontaneous integration due to physeal closure does not occur. Hybrid fixation consists in combining screw fixation of the fragment with mosaicplasty through the fragment to promote integration into the native condyle. We describe this technique with reference to 17 patients.

Emerging Concepts in Treating Cartilage, Osteochondral Defects, and Osteoarthritis of the Knee and Ankle

The management and treatment of cartilage lesions, osteochondral defects, and osteoarthritis remain a challenge in orthopedics. Moreover, these entities have different behaviors in different joints, such as the knee and the ankle, which have inherent differences in function, biology, and biomechanics. There has been a huge development on the conservative treatment (new technologies including orthobiologics) as well as on the surgical approach. Some surgical development upraises from technical improvements including advanced arthroscopic techniques but also from increased knowledge arriving from basic science research and tissue engineering and regenerative medicine approaches. This work addresses the state of the art concerning basic science comparing the knee and ankle as well as current options for treatment. Furthermore, the most promising research developments promising new options for the future are discussed.

Beneficial clinical effects but limited tissue quality following osteochondral repair with a cell-free multilayered nano-composite scaffold in the talus

BACKGROUND

The treatment of larger osteochondral lesions of the talus remains an operative challenge. In addition to micro fracturing and osteochondral transplantation one promising strategy could be the operative repair with a cell-free multilayered nano-composite scaffold with the potential to regenerate bone and cartilage in one treatment.

METHODS

In this prospective case series four consecutive patients who suffered from a single osteochondral lesion (≥1.5cm²) on the medial talus were enrolled. The repair potential of the implant was assessed using MRI based biochemical, compositional MR sequences (T2 mapping) as well as semi-quantitative morphological analyses (MOCART score) at 18 months follow-up after the surgery. The clinical outcome was determined at 6-, 12-, 18-, and 24 months follow-up by using the Ankle Disability Index and the AOFAS score.

RESULTS

At 18 months after the surgery, the clinical outcome was significantly improved compared to the preoperative baseline. Global T2 relaxation times of the repair tissue were significantly increased compared to the healthy control cartilage.

CONCLUSIONS

Osteochondral repair with a cell-free, biomimetic scaffold provides good clinical, short-term results. However, biochemical MR imaging provides strong evidence for limited repair tissue quality at 18 months after the implantation.

LEVEL OF EVIDENCE

IV.

Evaluation of reproducibility of the MOCART score in patients with osteochondral lesions of the talus repaired using the autologous matrix-induced chondrogenesis technique

PURPOSE

To evaluate the applicability and reproducibility of magnetic resonance observation of cartilage repair tissue (MOCART) score for morphological evaluation of osteochondral lesions of the talus (OLT) repaired using autologous matrix-induced chondrogenesis (AMIC) technique.

METHODS

Two radiologists (R1-R2) and two orthopaedists (O1-O2) independently reviewed 26 ankle MRIs performed on 13 patients (6 females; age: 38.9 ± 15.9, 14-63) with OLT repaired using AMIC. The MRIs were performed at 6 and 12 months from surgery. For inter/intra-observer agreement evaluation for each variable of the MOCART, we used Cohen's kappa coefficient. Progression of MOCART between 6- and 12-month evaluation was assessed using the Wilcoxon test. The Spearman's correlation coefficient was used to evaluate the correlation between baseline lesion size and MOCART.

RESULTS

The inter-observer agreement between R1 and R2 ranged from poor (adhesions, k = 0.124) to almost perfect (subchondral bone, k = 0.866), between O1 and O2 from absent (effusion, k = -0.190) to poor (surface, k = 0.172), and between R1 and O1 from absent (cartilage interface, k = -0.324) to fair (signal intensity, k = 0.372). The intra-observer agreement of R1 ranged from poor (signal intensity, k = 0.031) to substantial (subchondral lamina, k = 0.677), while that of O1 from absent (subchondral bone, k = -0.061) to substantial (surface, k = 0.663). There was a significant increase of MOCART between 6- and 12-month evaluation of R1 (Z = -2.672; P = 0.008), R2 (Z = -2.721; P = 0.007) and O1 (Z = -3.034; P = 0.002). Conversely, the increase of MOCART of O2 was not significant (Z = -1.665; P = 0.096). Inverse correlation between lesion size at baseline and MOCART was significant at 12-month evaluation (-0.726; P = 0.005).

CONCLUSION

MRI has an important role in the follow-up of surgical repaired OLT, but MOCART score does not seem to be sufficiently reproducible to be applied for this purpose.

Human adipose-derived mesenchymal stem cells seeded into a collagen-hydroxyapatite scaffold promote bone augmentation after implantation in the mouse

Traumatic injury or surgical excision of diseased bone tissue usually require the reconstruction of large bone defects unable to heal spontaneously, especially in older individuals. This is a big challenge requiring the development of biomaterials mimicking the bone structure and capable of inducing the right commitment of cells seeded within the scaffold. In particular, given their properties and large availability, the human adipose-derived stem cells are considered as the better candidate for autologous cell transplantation. In order to evaluate the regenerative potential of these cells along with an osteoinductive biomaterial, we have used collagen/hydroxyapatite scaffolds to test ectopic bone formation after subcutaneous implantation in mice. The process was analysed both in vivo, by Fluorescent Molecular Tomography (FMT), and ex vivo, to evaluate the formation of bone and vascular structures. The results have shown that the biomaterial could itself be able of promoting differentiation of host cells and bone formation, probably by means of its intrinsic chemical and structural properties, namely the microenvironment. However, when charged with human mesenchymal stem cells, the ectopic bone formation within the scaffold was increased. We believe that these results represent an important advancement in the field of bone physiology, as well as in regenerative medicine.

Clinical and imaging outcome of osteochondral lesions of the talus treated using autologous matrix-induced chondrogenesis technique with a biomimetic scaffold

BACKGROUND

The purpose of our study was to assess the clinical and imaging outcome of autologous matrix-induced chondrogenesis (AMIC) technique consisting of microfractures followed by the filling of osteochondral lesions of the talus (OLTs) with a cell-free biphasic collagen-hydroxyapatite osteochondral scaffold (MaioRegen).

METHODS

Sixteen patients (eight males, age: 42.6 ± 18.4, range 14-74) with OLT repaired using AMIC technique, with implantation of MaioRegen, were clinically evaluated through the American Orthopedic Foot and Ankle Society Score (AOFAS) and a 10-point Visual Analogue Scale (VAS) pain score after a mean follow-up of 30 ± 16.9 months. The MRI examinations were performed 12 and 24 months after surgery. A paired t-test was applied to compare pre- and post-operative clinical findings (VAS and AOFAS) and Magnetic resonance observation of cartilage repair tissue (MOCART) score changes in the follow-up. To assess the correlation between variation of AOFAS and MOCART scores, the Pearson's correlation coefficient was calculated.

RESULTS

No complications after surgery were encountered. From pre-operative to post-operative values, there was a significant (P < 0.001) reduction of mean VAS pain score (6.3 ± 0.9,range: 4-8 and 2.9 ± 1.8,range: 0-6, respectively) and increase of AOFAS score (60.2 ± 7.8,range: 50-74 and 77.4 ± 16.2,range: 50-100, respectively). Among 16 patients, six (37%) were not satisfied at the end of follow-up, six (37%) were moderately satisfied and four (25%) were highly satisfied. The treatment was considered failed in five out of 16 patients (31%). Among them, four (25%) required re-interventions with implantation of ankle prostheses, whereas one patient was treated with a further AMIC technique combined with autologous bone graft and platelet-rich plasma. The mean MOCART score was 41.9 ± 14.6 (25-70) 12 months after surgery and 51.9 ± 11.6 (30-70) after 24 months, with a statistically significant increase (P = 0.012). However, no correlation was seen between AOFAS and MOCART changes (r = 0.215, p = 0.609).

CONCLUSION

The high rates of treatment failure encountered in our study using MaioRegen need to be confirmed by larger studies and should induce the scientific community questioning the reliability of this biomimetic scaffold for the treatment of OLTs.

Nanotechnology in orthopedics

Nanotechnology has revolutionized science and consumer products for several decades. Most recently, its applications to the fields of medicine and biology have improved drug delivery, medical diagnostics, and manufacturing. Recent research of this modern technology has demonstrated its potential with novel forms of disease detection and intervention, particularly within orthopedics. Nanomedicine has transformed orthopedics through recent advances in bone tissue engineering, implantable materials, diagnosis and therapeutics, and surface adhesives. The potential for nanotechnology within the field of orthopedics is vast and much of it appears to be untapped, though not without accompanying obstacles.

Injectable and 3D Bioprinted Polysaccharide Hydrogels: From Cartilage to Osteochondral Tissue Engineering

Biomechanical performance of functional cartilage is executed by the exclusive anisotropic composition and spatially varying intricate architecture in articulating ends of diarthrodial joint. Osteochondral tissue constituting the articulating ends comprise superfical soft cartilage over hard subchondral bone sandwiching interfacial soft-hard tissue. The shock-absorbent, lubricating property of cartilage and mechanical stability of subchondral bone regions are rendered by extended chemical structure of glycosaminoglycans and mineral deposition, respectively. Extracellular matrix glycosaminoglycans analogous polysaccharides are major class of hydrogels investigated for restoration of functional cartilage. Recently, injectable hydrogels have gained momentum as it offers patient compliance, tunable mechanical properties, cell deliverability, and facile administration at physiological condition with long-term functionality and hyaline cartilage construction. Interestingly, facile modifiable functional groups in carbohydrate polymers impart tailorability of desired physicochemical properties and versatile injectable chemistry for the development of highly potent biomimetic in situ forming scaffold. The scaffold design strategies have also evolved from single component to bi- or multilayered and graded constructs with osteogenic properties for deep subchondral regeneration. This review highlights the significance of polysaccharide structure-based functions in engineering cartilage tissue, injectable chemistries, strategies for combining analogous matrices with cells/stem cells and biomolecules and multicomponent approaches for osteochondral mimetic constructs. Further, the rheology and precise spatiotemporal positioning of cells in hydrogel bioink for rapid prototyping of complex three-dimensional anisotropic cartilage have also been discussed.

Can a biomimetic osteochondral scaffold be a reliable alternative to prosthetic surgery in treating late-stage SPONK?

BACKGROUND

This study aimed to assess the reliability of the Maioregen® biomimetic osteochondral scaffold (Finceramica Faenza SpA, Faenza, Italy) as a salvage and joint-preserving procedure in the treatment of late-stage osteonecrosis of the knee.

METHODS

Eleven active patients aged under 65years and presenting with clinical and radiological signs of SPONK were treated with Maioregen®. All were clinically evaluated pre-operatively and yearly thereafter for a minimum of two years. Subjective IKDC and Lysholm Knee Scale scores were used to assess clinical outcome. A VAS scale served to quantify pre-operative pain and post-operative pain. Activity levels were evaluated pre-operatively and at follow-up using the Tegner Activity Scale.

RESULTS

Subjective IKDC (40±15.0 to 65.7±14.8 (mean±SD)) and Lysholm Knee Scale (49.7±17.9 to 86.6±12.7 (mean±SD)) scores improved significantly from pre-operative evaluation (p<.01). VAS scores decreased from a pre-operative mean (±SD) of 6.3±2.5 to 1.6±2.7 at two years. The Tegner Activity Scale showed no significant differences between pre-injury and two-year follow-up. Two out of the 11 patients were symptomatic at 18months post implant and progressed to condylar collapse. These patients required total knee arthroplasty.

CONCLUSIONS

Use of a biomimetic scaffold can be a valid option in the surgical treatment of SPONK in relatively young active patients. Indeed, this surgical technique, originally developed for osteochondritis dissecans, has been found to give good clinical results at medium-term follow-up of late-stage osteonecrosis treatment and could postpone or even avoid the need for joint replacement procedures.

Biological Treatment Approaches for Degenerative Disc Disease: A Review of Clinical Trials and Future Directions

Biologic-based treatment strategies for musculoskeletal diseases have gained traction over the past 20 years as alternatives to invasive, costly, and complicated surgical interventions. Spinal degenerative disc disease (DDD) is among the anatomic areas being investigated among this group, notably due to its high incidence and functional debilitation. In this review, we report the literature encompassing the use of biologic-based therapies for DDD. Articles published between January 1995 and November 2015 were reviewed, with a subset meeting the primary and secondary inclusion criteria of clinical trial results that could be sub-classified into bimolecular, cell-based, or gene therapies, as well as studies investigating the utility of allogeneic and tissue-engineered intervertebral discs. Ongoing clinical trials that have not yet published results are also mentioned to present the current state of the field. This exciting area has demonstrated positive and encouraging results across multiple strategies; thus, future bimolecular and regenerative techniques and understanding will likely lead to an increase in the number of human clinical trials assessing these therapies.

Bone augmentation after ectopic implantation of a cell-free collagen-hydroxyapatite scaffold in the mouse

The bone grafting is the classical way to treat large bone defects. Among the available techniques, autologous bone grafting is still the most used but, however, it can cause complications such as infection and donor site morbidity. Alternative and innovative methods rely on the development of biomaterials mimicking the structure and properties of natural bone. In this study, we characterized a cell-free scaffold, which was subcutaneously implanted in mice and then analyzed both in vivo and ex vivo after 1, 2, 4, 8 and 16 weeks, respectively. Two types of biomaterials, made of either collagen alone or collagen plus magnesium-enriched hydroxyapatite have been used. The results indicate that bone augmentation and angiogenesis could spontaneously occur into the biomaterial, probably by the recruitment of host cells, and that the composition of the scaffolds is crucial. In particular, the biomaterial more closely mimicking the native bone drives the process of bone augmentation more efficiently. Gene expression analysis and immunohistochemistry demonstrate the expression of typical markers of osteogenesis by the host cells populating the scaffold. Our data suggest that this biomaterial could represent a promising tool for the reconstruction of large bone defects, without using exogenous living cells or growth factors.

Poor osteochondral repair by a biomimetic collagen scaffold: 1- to 3-year clinical and radiological follow-up

INTRODUCTION

Treatment of osteochondral injuries is challenging, and no gold standard has been established. Layered cell-free scaffolds are a new treatment option for these defects. The aim of this study was to evaluate the osteochondral repair in patients treated with the MaioRegen(®) scaffold, a cell-free biomimetic scaffold consisting of type I collagen and hydroxyapatite. Treatment using this scaffold has previously shown promising clinical results.

METHODS

Ten patients with osteochondral lesions in the knee (n = 6) or in the talus (n = 4) were enrolled. The patients underwent pre-operative MRI and CT scans and were assessed at 1- and 2.5-year timescales post-operatively. The cartilage and bone formations were evaluated semi-quantitatively using the MOCART score. Knee patients were clinically evaluated using KOOS, subjective IKDC and Tegner scores, whereas ankle patients were evaluated using AOFAS Hindfoot and Tegner scores.

RESULTS

Two patients were re-operated and excluded from further follow-up due to treatment failure. None of the patients had complete regeneration of the subchondral bone evaluated using CT. At 2.5 years, 6/8 patients had no or very limited (<10 %) bone formation in the defects and 2/8 had 50-75 % bone formation in the treated defect. MRI showed no improvement in the MOCART score at any time point. The IKDC score improved from 41.3 to 80.7, and the KOOS pain subscale improved from 63.8 to 90.8 at 2.5-year follow-up. No improvement was found with the remaining KOOS subscales, the Tegner or AOFAS Ankle-Hindfoot score.

CONCLUSION

Treatment of osteochondral defects in the ankle and knee joint with a biomimetic scaffold resulted in incomplete cartilage repair and poor subchondral bone repair at 1- and 2.5-year follow-up. Clinical significant improvements were observed. These results raise serious concerns about the biological repair potential of the MaioRegen(®) scaffold, and we advise to use the MaioRegen(®) scaffold with caution.

LEVEL OF EVIDENCE

Prospective therapeutic study, Level IV.

Novel Vanadium-Loaded Ordered Collagen Scaffold Promotes Osteochondral Differentiation of Bone Marrow Progenitor Cells

Bone and cartilage regeneration can be improved by designing a functionalized biomaterial that includes bioactive drugs in a biocompatible and biodegradable scaffold. Based on our previous studies, we designed a vanadium-loaded collagen scaffold for osteochondral tissue engineering. Collagen-vanadium loaded scaffolds were characterized by SEM, FTIR, and permeability studies. Rat bone marrow progenitor cells were plated on collagen or vanadium-loaded membranes to evaluate differences in cell attachment, growth and osteogenic or chondrocytic differentiation. The potential cytotoxicity of the scaffolds was assessed by the MTT assay and by evaluation of morphological changes in cultured RAW 264.7 macrophages. Our results show that loading of VOAsc did not alter the grooved ordered structure of the collagen membrane although it increased membrane permeability, suggesting a more open structure. The VOAsc was released to the media, suggesting diffusion-controlled drug release. Vanadium-loaded membranes proved to be a better substratum than C0 for all evaluated aspects of BMPC biocompatibility (adhesion, growth, and osteoblastic and chondrocytic differentiation). In addition, there was no detectable effect of collagen or vanadium-loaded scaffolds on macrophage viability or cytotoxicity. Based on these findings, we have developed a new ordered collagen scaffold loaded with VOAsc that shows potential for osteochondral tissue engineering.

Autologous chondrocyte implantation: Is it likely to become a saviour of large-sized and full-thickness cartilage defect in young adult knee?

PURPOSE

A literature review of the first-, second- and third-generation autologous chondrocyte implantation (ACI) technique for the treatment of large-sized (>4 cm(2)) and full-thickness knee cartilage defects in young adults was conducted, examining the current literature on features, clinical scores, complications, magnetic resonance image (MRI) and histological outcomes, rehabilitation and cost-effectiveness.

METHODS

A literature review was carried out in the main medical databases to evaluate the several studies concerning ACI treatment of large-sized and full-thickness knee cartilage defects in young adults.

RESULTS

ACI technique has been shown to relieve symptoms and improve functional assessment in large-sized (>4 cm(2)) and full-thickness knee articular cartilage defect of young adults in short- and medium-term follow-up. Besides, low level of evidence demonstrated its efficiency and durability at long-term follow-up after implantation. Furthermore, MRI and histological evaluations provided the evidence that graft can return back to the previous nearly normal cartilage via ACI techniques. Clinical outcomes tend to be similar in different ACI techniques, but with simplified procedure, low complication rate and better graft quality in the third-generation ACI technique.

CONCLUSION

ACI based on the experience of cell-based therapy, with the high potential to regenerate hyaline-like tissue, represents clinical development in treatment of large-sized and full-thickness knee cartilage defects.

LEVEL OF EVIDENCE

IV.

Regeneration of hyaline-like cartilage and subchondral bone simultaneously by poly(l-glutamic acid) based osteochondral scaffolds with induced autologous adipose derived stem cells

Osteochondral tissue engineering is challenged by the difficulty in the regeneration of hyaline cartilage and the simultaneous regeneration of subchondral bone. In the present study, nhydroxyapatite-graft-poly(l-glutamic acid) (nHA-g-PLGA) was prepared by surface-initiated ring-opening polymerization, which was then used to fabricate an osteogenic scaffold (scaffold O) instead of nHA to achieve better mechanical performance. Then, a single osteochondral scaffold was fabricated by combining the poly(l-glutamic acid) (PLGA)/chitosan (CS) amide bonded hydrogel and the PLGA/CS/nHA-g-PLGA polyelectrolyte complex (PEC), possessing two different regions to support both hyaline cartilage and underlying bone regeneration, respectively. Autologous adipose derived stem cells (ASCs) were seeded into the osteochondral scaffold. The chondrogenesis of ASCs in the scaffold was triggered in vitro by TGF-β1 and IGF-1 for 7 days. In vitro, a chondrogenic scaffold (scaffold C) exhibited the ability to drive adipose derived stem cell (ASC) aggregates to form multicellular spheroids with a diameter of 80-110 μm in situ, thus promoting the chondrogenesis while limiting COL I deposition when compared to ASCs adhered in scaffold O. Scaffold O showed the ability to bind abundant BMP-2. Osteochondral scaffolds with induced ASC spheroids in scaffold C and bonded BMP-2 in scaffold O were transplanted into rabbit osteochondral defects as group I for in vivo regeneration. At the same time, osteochondral scaffolds with only bonded BMP-2 in scaffold O and bare osteochondral scaffolds were filled into rabbit osteochondral defects to serve as group II and group III, respectively. After 12 weeks post-implantation, cartilage and subchondral bone tissues were both regenerated with the support of induced ASC spheroids and bonded BMP-2 in group I. However, in group II, cartilage was not repaired while subchondral bone was regenerated. In group III, the regeneration of both cartilage and subchondral bone was limited.

Collagen-Hydroxyapatite Scaffolds Induce Human Adipose Derived Stem Cells Osteogenic Differentiation In Vitro

Mesenchymal stem cells (MSCs) play a crucial role in regulating normal skeletal homeostasis and, in case of injury, in bone healing and reestablishment of skeletal integrity. Recent scientific literature is focused on the development of bone regeneration models where MSCs are combined with biomimetic three-dimensional scaffolds able to direct MSC osteogenesis. In this work the osteogenic potential of human MSCs isolated from adipose tissue (hADSCs) has been evaluated in vitro in combination with collagen/Mg doped hydroxyapatite scaffolds. Results demonstrate the high osteogenic potential of hADSCs when cultured in specific differentiation induction medium, as revealed by the Alizarin Red S staining and gene expression profile analysis. In combination with collagen/hydroxyapatite scaffold, hADSCs differentiate into mature osteoblasts even in the absence of specific inducing factors; nevertheless, the supplement of the factors markedly accelerates the osteogenic process, as confirmed by the expression of specific markers of pre-osteoblast and mature osteoblast stages, such as osterix, osteopontin (also known as bone sialoprotein I), osteocalcin and specific markers of extracellular matrix maturation and mineralization stages, such as ALPL and osteonectin. Hence, the present work demonstrates that the scaffold per se is able to induce hADSCs differentiation, while the addition of osteo-inductive factors produces a significant acceleration of the osteogenic process. This observation makes the use of our model potentially interesting in the field of regenerative medicine for the treatment of bone defects.

Electrical stimulation of adipose-derived mesenchymal stem cells in conductive scaffolds and the roles of voltage-gated ion channels

Since electrical stimulation (ES) can significantly accelerate bone healing, a conductive scaffold that can deliver ES locally at the defect site is desirable for bone defect therapy. Herein, an electrically conductive scaffold was prepared via incorporation of polypyrrole (PPY) in a polycaprolactone (PCL) template scaffold. In vitro tests with mouse osteoblasts indicate that the PPY/PCL scaffold has good biocompatibility, and is suitable for use as an ES substrate. When human adipose-derived mesenchymal stem cells (AD-MSCs) were cultured in the PPY/PCL scaffold and subjected to 200 μA of direct current for 4h per day for 21 days, the amount of calcium deposited was 100% higher than that without ES. When these cells were subjected to ES together with blockers of voltage-gated calcium (Ca(2+)v), sodium (Na(+)v), potassium (K(+)v), or chloride (Cl(-)v) channels, the ES-induced enhancement of AD-MSCs' functions was reduced with Na(+)v, K(+)v, or Cl(-)v blockers and completely nullified with Ca(2+)v blocker. These results indicate that ion fluxes through these channels activated by ES induce different cascades of reactions in the cells, which subsequently regulate AD-MSCs' functions, and Ca(2+)v plays a more critical role than the other three channels. Our results further the current understanding of the mechanisms by which ES regulates stem cells' behavior, and also showed that the conductive PPY/PCL scaffold with application of ES has good potential in bone defect therapy.

STATEMENT OF SIGNIFICANCE

In this work, an electrically conductive and biocompatible scaffold was prepared by incorporating polypyrrole in a polycaprolactone template scaffold. Application of 200 μA direct current for 4h per day to human adipose derived-mesenchymal stem cells cultured on this scaffold promoted migration of these cells into the inner region of the scaffold and enhanced their osteogenic differentiation. The roles of voltage-gated ion channels (Ca(2+)v, Na(+)v, K(+)v and Cl(-)v) in osteogenic differentiation stimulated by the electric current were investigated. The results from these experiments further the current understanding of the mechanisms by which electrical stimulation regulates stem cells' behavior, and also show that the polypyrrole-polycaprolactone scaffold with application of electrical stimulation has good potential in bone defect therapy.