Practical Relevance of Institutional Guidelines in Translational Large Animal Studies of Cartilage Repair-A Multidisciplinary Survey

Background and Objective: Translational large animal models are inevitable to transfer cartilage repair methods into clinical practice. Guidelines for these trials have been published by guiding agencies (FDA, ASTM, EMEA) including recommendations for study descriptors and study outcomes. However, practical adherence to these recommendations is not achieved in all aspects. This study includes an assessment of the recommended aspects regarding practical relevance in large animal models for cartilage repair by professionals in the field. Materials and Methods: In an online based survey, 11 aspects regarding study design and 13 aspects regarding study outcome from previously published guidelines were evaluated (0-10 points, with 10 being most important) by study participants. Additionally, the survey contained questions related to professional experience (years), professional focus (preclinical, clinical, veterinarian, industry) and the preferred translational large animal model for cartilage repair. Results: The total number of survey participants was 37. Rated as most important for study design parameters was lesion size (9.54 pts., SD 0.80) followed by study duration (9.43 pts., SD 1.21); and method of scaffold fixation (9.08 pts., SD 1.30) as well as depth of the lesion (9.03 pts., SD 1.77). The most important aspects of study outcome were considered histology (9.41 pts., SD 0.86) and defect filling (8.97 pts., SD 1.21), while gene expression was judged as the least important (6.11 pts., SD 2.46) outcome. A total of 62.2% of all participants were researchers, 18.9% clinicians, 13.5% veterinarians and 5.4% industry employees. Conclusions: In translational research, recommendations published by guiding agencies receive broad theoretical consensus within the community, including both clinically and preclinically orientated scientists. However, implementation into practical research lacks in major aspects. Ongoing re-evaluation of the guidelines under involvement of all stakeholders and approaches to overcome financial and infrastructural limitations could support the acceptance of the guidance documents and contribute to standardization in the field.

Tenomodulin knockout mice exhibit worse late healing outcomes with augmented trauma-induced heterotopic ossification of Achilles tendon

Heterotopic ossification (HO) represents a common problem after tendon injury with no effective treatment yet being developed. Tenomodulin (Tnmd), the best-known mature marker for tendon lineage cells, has important effects in tendon tissue aging and function. We have reported that loss of Tnmd leads to inferior early tendon repair characterized by fibrovascular scaring and therefore hypothesized that its lack will persistently cause deficient repair during later stages. Tnmd knockout (Tnmd-/-) and wild-type (WT) animals were subjected to complete Achilles tendon surgical transection followed by end-to-end suture. Lineage tracing revealed a reduction in tendon-lineage cells marked by ScleraxisGFP, but an increase in alpha smooth muscle actin myofibroblasts in Tnmd-/- tendon scars. At the proliferative stage, more pro-inflammatory M1 macrophages and larger collagen II cartilaginous template were detected in this group. At the remodeling stage, histological scoring revealed lower repair quality in the injured Tnmd-/- tendons, which was coupled with higher HO quantified by micro-CT. Tendon biomechanical properties were compromised in both groups upon injury, however we identified an abnormal stiffening of non-injured Tnmd-/- tendons, which possessed higher static and dynamic E-moduli. Pathologically thicker and abnormally shaped collagen fibrils were observed by TEM in Tnmd-/- tendons and this, together with augmented HO, resulted in diminished running capacity of Tnmd-/- mice. These novel findings demonstrate that Tnmd plays a protecting role against trauma-induced endochondral HO and can inspire the generation of novel therapeutics to accelerate repair.

Dental follicle cell differentiation towards periodontal ligament-like tissue in a self-assembly three-dimensional organoid model

Periodontitis remains an unsolved oral disease, prevalent worldwide and resulting in tooth loss due to dysfunction of the periodontal ligament (PDL), a tissue connecting the tooth root with the alveolar bone. A scaffold-free three-dimensional (3D) organoid model for in vitro tenogenesis/ligamentogeneis has already been described. As PDL tissue naturally arises from the dental follicle, the aim of this study was to investigate the ligamentogenic differentiation potential of dental follicle cells (DFCs) in vitro by employing this 3D model. Human primary DFCs were compared, in both two- and three-dimensions, to a previously published PDL- hTERT cell line. The 3D organoids were evaluated by haematoxylin and eosin, 4',6-diamidino-2-phenylindole and F-actin staining combined with detailed histomorphometric analyses of cell-row structure, angular deviation and cell density. Furthermore, the expression of 48 tendon/ligament- and multilineage-related genes was evaluated using quantitative polymerase chain reaction, followed by immunofluorescent analyses of collagen 1 and 3. The results showed that both cell types were successful in the formation of scaffold-free 3D organoids. DFC organoids were comparable to PDL-hTERT in terms of cell density; however, DFCs exhibited superior organoid morphology, cell-row organisation (p < 0.0001) and angular deviation (p < 0.0001). Interestingly, in 2 dimensions as well as in 3D, DFCs showed significantly higher levels of several ligament- related genes compared to the PDL-hTERT cell line. In conclusion, DFCs exhibited great potential to form PDL-like 3D organoids in vitro suggesting that this strategy can be further developed for functional PDL engineering.

Reversed shoulder arthroplasty leads to significant histological changes of the deltoid muscle: a prospective intervention trial

INTRODUCTION

Reverse shoulder arthroplasty (RSA) shows promising short- and mid-term results in cuff tear arthropathy. However, functional impairments are described in long-term findings. Micromorphological changes in the periarticular musculature could be in part responsible for this, but have not yet been analysed. Thus, histological changes of the deltoid muscle and their association to the functional outcome were evaluated in this study.

MATERIAL AND METHODS

A total of 15 patients treated with RSA were included in this prospective study. Functional outcome was assessed using the Constant Score (CS) and the DASH (disabilities of the arm, shoulder and hand) Score before RSA and after a mean follow-up of 12 months. Deltoid muscle biopsies were harvested intraoperatively and 12 months postoperatively. Mean deltoid muscle fibre area (MMFA) was calculated histologically after haematoxylin-eosin staining.

RESULTS

Postoperative shoulder function significantly improved within 12 months (CS: Δ 37.4 ± 22.6, p = 0.001; DASH: Δ 27.1 ± 29.1, p = 0.006). The MMFA significantly decreased (p = 0.02), comparing the results from the intraoperative biopsy (MMFA: 8435.8 µm², SD ± 5995.9 µm²) to the 12 months biopsy (MMFA: 5792. µm², SD ± 3223.6 µm²). No correlation could be found between the functional score results and MMFA.

CONCLUSION

Signs of deltoid muscle changes in terms of a reduced MMFA can be detected 1 year after RSA and thus already a long time before long-term functional impairments become apparent. Further studies with larger patient series and longer follow-up periods as well as extended histological assessments and simultaneous radiological examinations are required.

Post-operative septic arthritis after arthroscopy: modern diagnostic and therapeutic concepts

PURPOSE

Septic arthritis is a significant complication following arthroscopic surgery, with an estimated overall incidence of less than 1%. Despite the low incidence, an appropriate diagnostic and therapeutic pathway is required to avoid serious long-term consequences, eradicate the infection, and ensure good treatment outcomes. The aim of this current review article is to summarize evidence-based literature regarding diagnostic and therapeutic options of post-operative septic arthritis after arthroscopy.

METHODS

Through a literature review, up-to-date treatment algorithms and therapies have been identified. Additionally, a supportive new algorithm is proposed for diagnosis and treatment of suspected septic arthritis following arthroscopic intervention.

RESULTS

A major challenge in diagnostics is the differentiation of the post-operative status between a non-infected hyperinflammatory joint versus septic arthritis, due to clinical symptoms, (e.g., rubor, calor, or tumor) can appear identical. Therefore, joint puncture for microbiological evaluation, especially for fast leukocyte cell-count diagnostics, is advocated. A cell count of more than 20.000 leukocyte/µl with more than 70% of polymorphonuclear cells is the generally accepted threshold for septic arthritis.

CONCLUSION

The therapy is based on arthroscopic or open surgical debridement for synovectomy and irrigation of the joint, in combination with an adequate antibiotic therapy for 6-12 weeks. Removal of indwelling hardware, such as interference screws for ACL repair or anchors for rotator cuff repair, is recommended in chronic cases.

LEVEL OF EVIDENCE

IV.

Rebuilding Tendons: A Concise Review on the Potential of Dermal Fibroblasts

Tendons are vital to joint movement by connecting muscles to bones. Along with an increasing incidence of tendon injuries, tendon disorders can burden the quality of life of patients or the career of athletes. Current treatments involve surgical reconstruction and conservative therapy. Especially in the elderly population, tendon recovery requires lengthy periods and it may result in unsatisfactory outcome. Cell-mediated tendon engineering is a rapidly progressing experimental and pre-clinical field, which holds great potential for an alternative approach to established medical treatments. The selection of an appropriate cell source is critical and remains under investigation. Dermal fibroblasts exhibit multiple similarities to tendon cells, suggesting they may be a promising cell source for tendon engineering. Hence, the purpose of this review article was in brief, to compare tendon to dermis tissues, and summarize in vitro studies on tenogenic differentiation of dermal fibroblasts. Furthermore, analysis of an open source Gene Expression Omnibus (GEO) data repository was carried out, revealing great overlap in the molecular profiles of both cell types. Lastly, a summary of in vivo studies employing dermal fibroblasts in tendon repair as well as pilot clinical studies in this area is included. Altogether, dermal fibroblasts hold therapeutic potential and are attractive cells for rebuilding injured tendons.

Aged Tendon Stem/Progenitor Cells Are Less Competent to Form 3D Tendon Organoids Due to Cell Autonomous and Matrix Production Deficits

Tendons are dense connective tissues, which are critical for the integrity and function of our musculoskeletal system. During tendon aging and degeneration, tendon stem/progenitor cells (TSPCs) experience profound phenotypic changes with declined cellular functions that can be linked to the known increase in complications during tendon healing process in elderly patients. Tissue engineering is a promising approach for achieving a complete recovery of injured tendons. However, use of autologous cells from aged individuals would require restoring the cellular fitness prior to implantation. In this study, we applied an established cell sheet model for in vitro tenogenesis and compared the sheet formation of TSPC derived from young/healthy (Y-TSPCs) versus aged/degenerative (A-TSPCs) human Achilles tendon biopsies with the purpose to unravel differences in their potential to form self-assembled three-dimensional (3D) tendon organoids. Using our three-step protocol, 4 donors of Y-TSPCs and 9 donors of A-TSPCs were subjected to cell sheet formation and maturation in a period of 5 weeks. The sheets were then cross evaluated by weight and diameter measurements; quantification of cell density, proliferation, senescence and apoptosis; histomorphometry; gene expression of 48 target genes; and collagen type I protein production. The results revealed very obvious and significant phenotype in A-TSPC sheets characterized by being fragile and thin with poor tissue morphology, and significantly lower cell density and proliferation, but significantly higher levels of the senescence-related gene markers and apoptotic cells. Quantitative gene expression analyses at the mRNA and protein levels, also demonstrated abnormal molecular circuits in the A-TSPC sheets. Taken together, we report for the first time that A-TSPCs exhibit profound deficits in forming 3D tendon tissue organoids, thus making the cell sheet model suitable to investigate the molecular mechanisms involved in tendon aging and degeneration, as well as examining novel pharmacologic strategies for rejuvenation of aged cells.

Spectrum of Tendon Pathologies: Triggers, Trails and End-State

The biggest compartment of the musculoskeletal system is the tendons and ligaments. In particular, tendons are dense tissues connecting muscle to bone that are critical for the integrity, function and locomotion of this system. Due to the increasing age of our society and the overall rise in engagement in extreme and overuse sports, there is a growing prevalence of tendinopathies. Despite the recent advances in tendon research and due to difficult early diagnosis, a multitude of risk factors and vague understanding of the underlying biological mechanisms involved in the progression of tendon injuries, the toolbox of treatment strategies remains limited and non-satisfactory. This review is designed to summarize the current knowledge of triggers, trails and end state of tendinopathies.

TGF-β Signalling is Suppressed under Pro-Hypertrophic Conditions in MSC Chondrogenesis Due to TGF-β Receptor Downregulation

Background and Objectives

Mesenchymal stem cells (MSCs) become hypertrophic in long term despite chondrogenic differentiation following the pathway of growth plate chondrocytes. This terminal differentiation leads to phenotypically unstable cartilage and was mirrored in vitro by addition of hypertrophy inducing medium. We investigated how intrinsic TGF-β signaling is altered in pro-hypertrophic conditions.

Methods and Results

Human bone marrow derived MSC were chondrogenically differentiated in 3D culture. At day 14 medium conditions were changed to 1. pro-hypertrophic by addition of T3 and withdrawal of TGF-β and dexamethasone 2. pro-hypertrophic by addition of BMP 4 and withdrawal of TGF-β and dexamethasone and 3. kept in prochondrogenic medium conditions. All groups were treated with and without TGFβ-type-1-receptor inhibitor SB431542 from day 14 on. Aggregates were harvested for histo- and immunohistological analysis at d14 and d28, for gene expression analysis (rt-PCR) on d1, d3, d7, d14, d17, d21 and d28 and for Western blot analysis on d21 and d28. Induction of hypertrophy was achieved in the pro-hypertrophic groups while expression of TGFβ-type-1- and 2-receptor and Sox 9 were significantly downregulated compared to pro-chondrogenic conditions. Western blotting showed reduced phosphorylation of Smad 2 and 3 in hypertrophic samples, reduced TGF-β-1 receptor proteins and reduced SOX 9. Addition of SB431542 did not initiate hypertrophy under pro-chondrogenic conditions, but was capable of enhancing hypertrophy when applied simultaneously with BMP-4.

Conclusions

Our results suggest that the enhancement of hypertrophy in this model is a result of both activation of pro-hypertrophic BMP signaling and reduction of anti-hypertrophic TGFβ signaling.

Bone Marrow Aspirate Concentrate for the Treatment of Avascular Meniscus Tears in a One-Step Procedure-Evaluation of an In Vivo Model

Avascular meniscus tears show poor intrinsic regenerative potential. Thus, lesions within this area predispose the patient to developing knee osteoarthritis. Current research focuses on regenerative approaches using growth factors or mesenchymal stem cells (MSCs) to enhance healing capacity within the avascular meniscus zone. The use of MSCs especially as progenitor cells and a source of growth factors has shown promising results. However, present studies use bone-marrow-derived BMSCs in a two-step procedure, which is limiting the transfer in clinical praxis. So, the aim of this study was to evaluate a one-step procedure using bone marrow aspirate concentrate (BMAC), containing BMSCs, for inducing the regeneration of avascular meniscus lesions. Longitudinal meniscus tears of 4 mm in size of the lateral New Zealand White rabbit meniscus were treated with clotted autologous PRP (platelet-rich plasma) or BMAC and a meniscus suture or a meniscus suture alone. Menisci were harvested at 6 and 12 weeks after initial surgery. Macroscopical and histological evaluation was performed according to an established Meniscus Scoring System. BMAC significantly enhanced regeneration of the meniscus lesions in a time-dependent manner and in comparison to the PRP and control groups, where no healing could be observed. Treatment of avascular meniscus lesions with BMAC and meniscus suturing seems to be a promising approach to promote meniscus regeneration in the avascular zone using a one-step procedure.

Understanding Tendons: Lessons from Transgenic Mouse Models

Tendons and ligaments are connective tissues that have been comparatively less studied than muscle and cartilage/bone, even though they are crucial for proper function of the musculoskeletal system. In tendon biology, considerable progress has been made in identifying tendon-specific genes (Scleraxis, Mohawk, and Tenomodulin) in the past decade. However, besides tendon function and the knowledge of a small number of important players in tendon biology, neither the ontogeny of the tenogenic lineage nor signaling cascades have been fully understood. This results in major drawbacks in treatment and repair options following tendon degeneration. In this review, we have systematically evaluated publications describing tendon-related genes, which were studied in depth and characterized by using knockout technologies and the subsequently generated transgenic mouse models (Tg) (knockout mice, KO). We report in a tabular manner, that from a total of 24 tendon-related genes, in 22 of the respective knockout mouse models, phenotypic changes were detected. Additionally, in some of the models it was described at which developmental stages these changes appeared and progressed. To summarize, only loss of Scleraxis and TGFβ signaling led to severe tendon developmental phenotypes, while mice deficient for various proteoglycans, Mohawk, EGR1 and 2, and Tenomodulin presented mild phenotypes. These data suggest that the tendon developmental system is well organized, orchestrated, and backed up; this is even more evident among the members of the proteoglycan family, where the compensatory effects are much clearer. In future, it will be of great importance to discover additional master tendon transcription factors and the genes that play crucial roles in tendon development. This would improve our understanding of the genetic makeup of tendons, and will increase the chances of generating tendon-specific drugs to advance overall treatment strategies.

Boosting tendon repair: interplay of cells, growth factors and scaffold-free and gel-based carriers

Background

Tendons are dense connective tissues and critical components for the integrity and function of the musculoskeletal system. Tendons connect bone to muscle and transmit forces on which locomotion entirely depends. Due to trauma, overuse and age-related degeneration, many people suffer from acute or chronic tendon injuries. Owing to their hypovascularity and hypocellularity, tendinopathies remain a substantial challenge for both clinicians and researchers. Surgical treatment includes suture or transplantation of autograft, allograft or xenograft, and these serve as the most common technique for rescuing tendon injuries. However, the therapeutic efficacies are limited by drawbacks including inevitable donor site morbidity, poor graft integration, adhesion formations and high rates of recurrent tearing. This review summarizes the literature of the past 10 y concerning scaffold-free and gel-based approaches for treating tendon injuries, with emphasis on specific advantages of such modes of application, as well as the obtained results regarding in vitro and in vivo tenogenesis.

Results

The search was focused on publications released after 2006 and 83 articles have been analysed. The main results are summarizing and discussing the clear advantages of scaffold-free and hydrogels carriers that can be functionalized with cells alone or in combination with growth factors.

Conclusion

The improved understanding of tissue resident adult stem cells has made a significant progress in recent years as well as strategies to steer their fate toward tendon lineage, with the help of growth factors, have been identified. The field of tendon tissue engineering is exploring diverse models spanning from hard scaffolds to gel-based and scaffold-free approaches seeking easier cell delivery and integration in the site of injury. Still, the field needs to consider a multifactorial approach that is based on the combination and fine-tuning of chemical and biomechanical stimuli. Taken together, tendon tissue engineering has now excellent foundations and enters the period of precision and translation to models with clinical relevance on which better treatment options of tendon injuries can be shaped up.

Clinical and Radiological Regeneration of Large and Deep Osteochondral Defects of the Knee by Bone Augmentation Combined With Matrix-Guided Autologous Chondrocyte Transplantation

BACKGROUND

Large osteochondral defects of the knee are a challenge for regenerative treatment. While matrix-guided autologous chondrocyte transplantation (MACT) represents a successful treatment for chondral defects, the treatment potential in combination with bone grafting by cancellous bone or bone block augmentation for large and deep osteochondral defects has not been evaluated.

PURPOSE

To evaluate 1- to 3-year clinical outcomes and radiological results on magnetic resonance imaging (MRI) after the treatment of large osteochondral defects of the knee with bone augmentation and MACT. Special emphasis is placed on different methods of bone grafting (cancellous bone grafting or bone block augmentation).

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Fifty-one patients were included. Five patients were lost to follow-up. This left 46 patients (mean age, 28.2 years) with a median follow-up time of 2 years. The 46 patients had 47 deep, large osteochondral defects of the knee joint (1 patient with bilateral defects; mean defect size, 6.7 cm²). The origin of the osteochondral defects was osteochondritis dissecans (n = 34), osteonecrosis (n = 8), or subchondral cysts (n = 5). Depending on the depth, all defects were treated by cancellous bone grafting (defect depth ≤10 mm; n = 16) or bone block augmentation (defect depth >10 mm; n = 31) combined with MACT. Clinical outcomes were followed at 3 months, 6 months, 1 year, 2 years, and 3 years and evaluated using the International Knee Documentation Committee (IKDC) score and Cincinnati score. A magnetic resonance imaging (MRI) evaluation was performed at 1 and 2 years, and the magnetic resonance observation of cartilage repair tissue (MOCART) score with additional specific subchondral bone parameters (bone regeneration, bone signal quality, osteophytes, sclerotic areas, and edema) was analyzed.

RESULTS

The clinical outcome scores revealed a significant increase at follow-up (6 months to 3 years) compared with the preclinical results. The median IKDC score increased from 42.6 preoperatively to 75.3 at 1 year, 79.7 at 2 years, and 84.3 at 3 years. The median Cincinnati score significantly increased from 39.8 preoperatively to 72.0 at 1 year, 78.0 at 2 years, and 80.3 at 3 years. The MRI evaluation revealed a MOCART score of 82.6 at 1 year without a deterioration at the later follow-up time point. Especially, the subchondral bone analysis showed successful regeneration. All bone blocks and cancellous bone grafts were integrated in the bony defects, and no chondrocyte transplant failure could be detected throughout the follow-up.

CONCLUSION

Large and deep osteochondral defects of the knee joint can be treated successfully with bone augmentation and MACT. The treatment of shallow bony defects with cancellous bone grafting and deep bony defects with bone block augmentation shows promising results.

Anatomical and radiological evaluation of less invasive stabilisation system (LISS) in correlation with knee lateral collateral ligament insertion

INTRODUCTION

The Less Invasive Stabilisation System (LISS) is an angle-stable plate that enables treatment of distal femoral comminuted and periprosthetic fracture. As it is placed through a minimally-invasive lateral approach, lateral knee pain is a commonly described symptom after its application. This study investigates knee lateral collateral ligament (LCL) iatrogenic injury during LISS plate fixation. A cadaver study was performed and a retrospective radiological investigation with the analysis of its clinical application was conducted to evaluate possible knee LCL damage.

METHODS

The cadaver study included 13 human lower extremities, treated with LISS. After application, lateral knee side was dissected, implants were removed and distances between the drill holes and LCL origin were measured. In the retrospective radiological evaluation, postoperative X-rays for patients treated with distal femoral LISS plate in the University Hospital Regensburg, Germany from January 2010 to December 2015 were examined. Following a protocol described by Pietrini et al., the LCL origin on postoperative X-rays was calculated, both in lateral and anterior-posterior (AP) view, and distances between the plate and its closest locking screw to the LCL origin were measured.

RESULTS

In the cadaver study, the mean distance between the closest drilling hole and the ligament origin was 14.0mm (range 9-21mm; SD 3.8mm). Twenty-two patients matched the inclusion criteria for the retrospective radiological study. In lateral view, the mean distance between the origin and the closest locking screw was 6.3mm (range 0-16.4mm; SD 4.7mm); the mean distance between the origin and the plate was 3.1mm (range 0-13.9mm; SD 4.1mm). In AP view, the mean distance between LCL origin and the nearest screw was 2.4mm (range 0-7.6mm; SD 2.4mm). The mean distance between the origin and the most distal locking screw was 9.2mm (range 0-17.5mm; SD 4.0mm).

DISCUSSION

The LISS is a safe option to treat distal femoral fractures in respect to the LCL. Due to close proximity, the LCL might be harmed; therefore, lateral knee pain or lateral instability after implantation should be assessed in further treatment.

Age-Dependent Subchondral Bone Remodeling and Cartilage Repair in a Minipig Defect Model

After cartilage injury and repair, the subchondral bone plate remodels. Skeletal maturity likely impacts both bone remodeling and inherent cartilage repair capacity. The objective of this study was to evaluate subchondral bone remodeling as a function of injury type, repair scenario, and skeletal maturity in a Yucatan minipig model. Cartilage defects (4 mm) were created bilaterally in the trochlear groove. Treatment conditions included a full thickness chondral defect (full chondral defect, n = 3 adult/3 juvenile), a partial thickness (∼50%) chondral defect (PCD, n = 3/3), and FCD treated with microfracture (MFX, n = 3/3). At 6 weeks postoperatively, osteochondral samples containing the lesion site were imaged by micro-computed tomography (CT) and analyzed by histology and immunohistochemistry. Via micro-CT, FCD and MFX groups showed increased bone loss in juveniles compared with adults. Quantification of histology using the ICRS II scoring system showed equal overall assessment for the FCD groups and better overall assessment in juvenile animals treated with MFX compared with adults. All FCD and MFX groups were inferior to control samples. For the PCD injury, both age groups had values close to the control values. For the FCD groups, there were greater alterations in the subchondral bone in juveniles compared with adults. Staining for collagen II showed more intense signals in juvenile FCD and MFX groups compared with adults. This large animal study of cartilage repair shows the significant impact of skeletal maturity on the propensity of subchondral bone to remodel as a result of chondral injury. This will improve selection criteria for animal models for studying cartilage injury, repair, and treatment.

Autologous mesenchymal stem cells or meniscal cells: what is the best cell source for regenerative meniscus treatment in an early osteoarthritis situation?

Background

Treatment of meniscus tears within the avascular region represents a significant challenge, particularly in a situation of early osteoarthritis. Cell-based tissue engineering approaches have shown promising results. However, studies have not found a consensus on the appropriate autologous cell source in a clinical situation, specifically in a challenging degenerative environment. The present study sought to evaluate the appropriate cell source for autologous meniscal repair in a demanding setting of early osteoarthritis.

Methods

A rabbit model was used to test autologous meniscal repair. Bone marrow and medial menisci were harvested 4 weeks prior to surgery. Bone marrow-derived mesenchymal stem cells (MSCs) and meniscal cells were isolated, expanded, and seeded onto collagen-hyaluronan scaffolds before implantation. A punch defect model was performed on the lateral meniscus and then a cell-seeded scaffold was press-fit into the defect. Following 6 or 12 weeks, gross joint morphology and OARSI grade were assessed, and menisci were harvested for macroscopic, histological, and immunohistochemical evaluation using a validated meniscus scoring system. In conjunction, human meniscal cells isolated from non-repairable bucket handle tears and human MSCs were expanded and, using the pellet culture model, assessed for their meniscus-like potential in a translational setting through collagen type I and II immunostaining, collagen type II enzyme-linked immunosorbent assay (ELISA), and gene expression analysis.

Results

After resections of the medial menisci, all knees showed early osteoarthritic changes (average OARSI grade 3.1). However, successful repair of meniscus punch defects was performed using either meniscal cells or MSCs. Gross joint assessment demonstrated donor site morbidity for meniscal cell treatment. Furthermore, human MSCs had significantly increased collagen type II gene expression and production compared to meniscal cells (p < 0.05).

Conclusions

The regenerative potential of the meniscus by an autologous cell-based tissue engineering approach was shown even in a challenging setting of early osteoarthritis. Autologous MSCs and meniscal cells were found to have improved meniscal healing in an animal model, thus demonstrating their feasibility in a clinical setting. However, donor site morbidity, reduced availability, and reduced chondrogenic differentiation of human meniscal cells from debris of meniscal tears favors autologous MSCs for clinical use for cell-based meniscus regeneration.

In vivo performance of an acellular disc-like angle ply structure (DAPS) for total disc replacement in a small animal model

Total intervertebral disc replacement with a biologic engineered disc may be an alternative to spinal fusion for treating end-stage disc disease. In previous work, we developed disc-like angle ply structures (DAPS) that replicate the structure and function of the native disc and a rat tail model to evaluate DAPS in vivo. Here, we evaluated a strategy in which, after in vivo implantation, endogenous cells could colonize the acellular DAPS and form an extracellular matrix organized by the DAPS topographical template. To do so, acellular DAPS were implanted into the caudal spines of rats and evaluated over 12 weeks by mechanical testing, histology, and microcomputed tomography. An external fixation device was used to stabilize the implant site and various control groups were included to evaluate the effect of immobilization. There was robust tissue formation within the DAPS after implantation and compressive mechanical properties of the implant matched that of the native motion segment. Immobilization provided a stable site for fibrous tissue formation after either a discectomy or a DAPS implantation, but bony fusion eventually resulted, with segments showing intervertebral bridging after long-term implantation, a process that was accelerated by the implanted DAPS. Thus, while compressive mechanical properties were replicated after DAPS implantation, methods to actively prevent fusion must be developed. Future work will focus on limiting fusion by remobilizing the motion segment after a period of integration, delivering pro-chondrogenic factors, and pre-seeding DAPS with cells prior to implantation. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:23-31, 2017.

Impact of guidance documents on translational large animal studies of cartilage repair

Promising therapies for cartilage repair are translated through large animal models toward human application. To guide this work, regulatory agencies publish recommendations ("guidance documents") to direct pivotal large animal studies. These are meant to aid in study design, outline metrics for judging efficacy, and facilitate comparisons between studies. To determine the penetrance of these documents in the field, we synthesized the recommendations of the American Society for Testing and Materials, U.S. Food and Drug Administration, and European Medicines Agency into a scoring system and performed a systematic review of the past 20 years of preclinical cartilage repair studies. Our hypothesis was that the guidance documents would have a significant impact on how large animal cartilage repair studies were performed. A total of 114 publications meeting our inclusion criteria were reviewed for adherence to 24 categories extracted from the guidance documents, including 11 related to study design and description and 13 related to study outcomes. Overall, a weak positive trend was observed over time (P = 0.004, R(2) = 0.07, slope = 0.63%/year), with overall adherence (the sum of study descriptors and outcomes) ranging from 32 ± 16% to 58 ± 14% in any individual year. There was no impact of the publication of the guidance documents on adherence (P = 0.264 to 0.50). Given that improved adherence would expedite translation, we discuss the reasons for poor adherence and outline approaches to increase and promote their more widespread adoption.

Higher Ratios of Hyaluronic Acid Enhance Chondrogenic Differentiation of Human MSCs in a Hyaluronic Acid-Gelatin Composite Scaffold

Mesenchymal stem cells (MSCs) seeded on specific carrier materials are a promising source for the repair of traumatic cartilage injuries. The best supportive carrier material has not yet been determined. As natural components of cartilage’s extracellular matrix, hyaluronic acid and collagen are the focus of biomaterial research. In order to optimize chondrogenic support, we investigated three different scaffold compositions of a hyaluronic acid (HA)-gelatin based biomaterial. Methods: Human MSCs (hMSCs) were seeded under vacuum on composite scaffolds of three different HA-gelatin ratios and cultured in chondrogenic medium for 21 days. Cell-scaffold constructs were assessed at different time points for cell viability, gene expression patterns, production of cartilage-specific extracellular matrix (ECM) and for (immuno-)histological appearance. The intrinsic transforming growth factor beta (TGF-beta) uptake of empty scaffolds was evaluated by determination of the TGF-beta concentrations in the medium over time. Results: No significant differences were found for cell seeding densities and cell viability. hMSCs seeded on scaffolds with higher ratios of HA showed better cartilage-like differentiation in all evaluated parameters. TGF-beta uptake did not differ between empty scaffolds. Conclusion: Higher ratios of HA support the chondrogenic differentiation of hMSCs seeded on a HA-gelatin composite scaffold.

Analysis of 213 currently used rehabilitation protocols in foot and ankle fractures

INTRODUCTION

Fractures of the ankle, hind- and midfoot are amongst the five most common fractures. Besides initial operative or non-operative treatment, rehabilitation of the patients plays a crucial role for fracture union and long term functional outcome. Limited evidence is available with regard to what a rehabilitation regimen should include and what guidelines should be in place for the initial clinical course of these patients. This study therefore investigated the current rehabilitation concepts after fractures of the ankle, hind- and midfoot.

METHODS

Written rehabilitation protocols provided by orthopedic and trauma surgery institutions in terms of recommendations for weight bearing, range of motion (ROM), physiotherapy and choice of orthosis were screened and analysed. All protocols for lateral ankle fractures type AO 44A1, AO 44B1 and AO 44C1, for calcaneal fractures and fractures of the metatarsal as well as other not specific were included. Descriptive analysis was carried out and statistical analysis applied where appropriate.

RESULTS

209 rehabilitation protocols for ankle fractures type AO 44B1 and AO 44C1, 98 for AO 44A1, 193 for metatarsal fractures, 142 for calcaneal fractures, 107 for 5(th) metatarsal base fractures and 70 for 5(th) metatarsal Jones fractures were evaluated. The mean time recommended for orthosis treatment was 6.04 (SD 0.04) weeks. While the majority of protocols showed a trend towards increased weight bearing and increased ROM over time, the best consensus was noted for weight bearing recommendations.

CONCLUSION

Our study shows that there exists a huge variability in rehabilitation of fractures of the ankle-, hind- and midfoot. This may be contributed to a lack of consensus (e.g. missing publication of guidelines), individualized patient care (e.g. in fragility fractures) or lack of specialization. This study might serve as basis for prospective randomized controlled trials in order to optimize rehabilitation for these common fractures.

Fibrous Scaffolds with Varied Fiber Chemistry and Growth Factor Delivery Promote Repair in a Porcine Cartilage Defect Model

Current clinically approved methods for cartilage repair are generally based on either endogenous cell recruitment (e.g., microfracture) or chondrocyte delivery (e.g., autologous chondrocyte implantation). However, both methods culminate in repair tissue with inferior mechanical properties and the addition of biomaterials to these clinical interventions may improve their efficacy. To this end, the objective of this study was to investigate the ability of multipolymer acellular fibrous scaffolds to improve cartilage repair when combined with microfracture in a large animal (i.e., minipig) model. Composite scaffolds were formulated from a combination of hyaluronic acid (HA) fibers and poly(ɛ-caprolactone) (PCL) fibers, either with or without transforming growth factor-β3 (TGFβ3). After 12 weeks in vivo, material choice and TGFβ3 delivery had a significant impact on outcomes; specifically, PCL scaffolds without TGFβ3 had inferior gross appearance and reduced mechanical properties, whereas HA scaffolds that released TGFβ3 resulted in improved histological scores and increased type 2 collagen content. Importantly, analysis of the overall dataset revealed that histology, but not gross appearance, was a better predictor of mechanical properties. This study highlights the importance of scaffold properties on in vivo cartilage repair as well as the need for numerous quantitative outcome measures to fully evaluate treatment methods.

Development of a Large Animal Model of Osteochondritis Dissecans of the Knee: A Pilot Study

Background:

Treatment of osteochondritis dissecans (OCD) of the knee is challenging, and evidence for stage-dependent treatment options is lacking. Basic science approaches utilizing animal models have provided insight into the etiology of OCD but have yet to produce a reliable and reproducible large animal model of the disease on which to test new surgical strategies.

Purpose/Hypotheses:

The purpose of this study was to develop an animal model featuring an OCD-like lesion in terms of size, location, and International Cartilage Repair Society (ICRS) grading. The hypothesis was that surgical creation of an osteochondral defect followed by placement of a barrier between parent bone and progeny fragment would generate a reproducible OCD-like lesion.

Study Design:

Controlled laboratory study.

Methods:

Bilateral osteochondral lesions were created in the medial femoral condyles of 9 Yucatan minipigs. After lesion creation, a biodegradable membrane was interposed between the progeny and parent bone. Five different treatment groups were evaluated at 2 weeks: a control with no membrane (ctrl group; n = 4), a slowly degrading nanofibrous poly(∊-caprolactone) membrane (PCL group; n = 4), a fenestrated PCL membrane with 1.5-mm holes covering 25% of surface area (fenPCL group; n = 4), a collagen membrane (Bio-Gide) (CM group; n = 3), and a fenestrated CM (fenCM group; n = 3). Five unperturbed lateral condyles (1 from each treatment group) served as sham controls. After euthanasia on day 14, the lesion was evaluated by gross inspection, fluoroscopy, micro–computed tomography (micro-CT), and histology. To quantify changes between groups, a scoring system based on gross appearance (0-2), fluoroscopy (0-2), and micro-CT (0-6) was established. Micro-CT was used to quantify bone volume per total volume (BV/TV) in a defined region surrounding and inclusive of the defect.

Results:

The no scaffold group showed healing of the subchondral bone at 2 weeks, with continuity of subchondral bone elements. Conversely, condyles treated with PCL or CM showed substantial remodeling, with loss of bone in both the progeny fragment and surrounding parent bone. When these membranes were fenestrated (fenPCL and fenCM groups), bone loss was less severe. Histological analysis showed no integration in the cartilage layer in any treatment group, while fibrous tissue formed between the parent and progeny fragments. Micro-CT showed significant differences in mean BV/TV between the PCL (27.4% ± 2.3%) and the sham (47.7% ± 1.4%) or no scaffold (54.9% ± 15.1%) groups (P < .01 and P < .05, respectively). In addition, a significant difference in bone loss was evident between the PCL and fenPCL groups (mean BV/TV, 46.6% ± 15.2%; P < .05), as well as between the PCL and fenCM (mean BV/TV, 50.9% ± 3.5%) and fenPCL groups (P < .01). Grading by 6 blinded reviewers using an OCD scoring system with 3 subcategories showed a significant difference between control and PCL groups.

Conclusion:

This study successfully developed a large animal model of OCD-like lesions in the knee joint of Yucatan minipigs. The lesions generated matched characteristics of an ICRS grade 3 OCD lesion in humans. These findings set the stage for ongoing model refinement as well as exploration of novel interventional therapies to restore function and bone and cartilage patency in individuals affected by this rare but significant disease.

Clinical Relevance:

This developed model will serve as a platform on which to further investigate the natural course as well as emerging treatment options for OCD.

Activation of Akt/protein kinase B in epithelial cells by the Salmonella typhimurium effector sigD

The serine-threonine kinase Akt is a protooncogene involved in the regulation of cell proliferation and survival. Activation of Akt is initiated by binding to the phospholipid products of phosphoinositide 3-kinase at the inner leaflet of the plasma membranes followed by phosphorylation at Ser(473) and Thr(308). We have found that Akt is activated by Salmonella enterica serovar Typhimurium in epithelial cells. A bacterial effector protein, SigD, which is translocated into host cells via the specialized type III secretion system, is essential for Akt activation. In HeLa cells, wild type S. typhimurium induced translocation of Akt to membrane ruffles and phosphorylation at residues Thr(308) and Ser(473) and increased kinase activity. In contrast, infection with a SigD deletion mutant did not induce phosphorylation or activity although Akt was translocated to membrane ruffles. Complementation of the SigD deletion strain with a mutant containing a single Cys to Ser mutation (C462S), did not restore the Akt activation phenotype. This residue has previously been shown to be essential for inositol phosphatase activity of the SigD homologue, SopB. Our data indicate a novel mechanism of Akt activation in which the endogenous cellular pathway does not convert membrane-associated Akt into its active form. SigD is also the first bacterial effector to be identified as an activator of Akt.

Salmonella pathogenicity islands: big virulence in small packages

Reflecting a complex set of interactions with its host, Salmonella spp. require multiple genes for full virulence. Many of these genes are found in 'pathogenicity islands' in the chromosome. Salmonella typhimurium possesses at least five such pathogenicity islands (SPI), which confer specific virulence traits and may have been acquired by horizontal transfer from other organisms. We highlight recent progress in characterizing these SPIs and the function of some of their genes. The role of virulence genes found on a highly conserved plasmid is also discussed. Collectively, these packages of virulence cassettes are essential for Salmonella pathogenesis.

Salmonella typhimurium virulence genes are induced upon bacterial invasion into phagocytic and nonphagocytic cells

Survival and growth of salmonellae within host cells are important aspects of bacterial virulence. We have developed an assay to identify Salmonella typhimurium genes that are induced inside Salmonella-containing vacuoles within macrophage and epithelial cells. A promoterless luciferase gene cassette was inserted randomly into the Salmonella chromosome, and the resulting mutants were screened for genes upregulated in intracellular bacteria compared to extracellular bacteria. We identified four genes in S. typhimurium that were upregulated upon bacterial invasion of both phagocytic and nonphagocytic cells. Expression of these genes was not induced by factors secreted by host cells or media alone. All four genes were induced at early time points (2 to 4 h) postinvasion and continued to be upregulated within host cells at later times (5 to 7 h). One mutant contained an insertion in the ssaR gene, within Salmonella pathogenicity island 2 (SPI-2), which abolished bacterial virulence in a murine typhoid model. Two other mutants contained insertions within SPI-5, one in the sopB/sigD gene and the other in a downstream gene, pipB. The insertions within SPI-5 resulted in the attenuation of S. typhimurium in the mouse model. The fourth mutant contained an insertion within a previously undescribed region of the S. typhimurium chromosome, iicA (induced intracellularly A). We detected no effect on virulence as a result of this insertion. In conclusion, all but one of the genes identified in this study were virulence factors within pathogenicity islands, illustrating the requirement for specific gene expression inside mammalian cells and indicating the key role that virulence factor regulation plays in Salmonella pathogenesis.

Functional expression of Nramp1 in vitro in the murine macrophage line RAW264.7

Mutations at the Nramp1 locus in vivo cause susceptibility to infection by unrelated intracellular microbes. Nramp1 encodes an integral membrane protein abundantly expressed in the endosomal-lysosomal compartment of macrophages and is recruited to the phagosomal membrane following phagocytosis. The mechanism by which Nramp1 affects the biochemical properties of the phagosome to control microbial replication is unknown. To devise an in vitro assay for Nramp1 function, we introduced a wild-type Nramp1(G169) cDNA into RAW 264.7 macrophages (which bear a homozygous mutant Nramp1(D169) allele and thus are permissive to replication of specific intracellular parasites). Recombinant Nramp1 was expressed in a membranous compartment in RAW264.7 cells and was recruited to the membrane of Salmonella typhimurium and Yersinia enterocolitica containing phagosomes. Evaluation of the antibacterial activity of RAW264.7 transfectants showed that expression of the recombinant Nramp1 protein abrogated intracellular replication of S. typhimurium. Studies with a replication-defective S. typhimurium mutant suggest that this occurs through an enhanced bacteriostatic activity. The effect of Nramp1 expression was specific, since (i) it was not seen in RAW264.7 transfectants overexpressing the closely related Nramp2 protein, and (ii) control RAW264.7 cells, Nramp1, and Nramp2 transfectants could all efficiently kill a temperature-sensitive, replication-defective mutant of S. typhimurium. Finally, increased antibacterial activity of the Nramp1 RAW264.7 transfectants was linked to increased phagosomal acidification, a distinguishing feature of primary macrophages expressing a wild-type Nramp1 allele. Together, these results indicate that transfection of Nramp1 cDNAs in the RAW264.7 macrophage cell line can be used as a direct assay to study both Nramp1 function and mechanism of action as well as to identify structure-function relationships in this protein.

Effect of Haemophilus somnus on phagocytosis and hydrogen peroxide production by bovine polymorphonuclear leukocytes

The interactions between bovine polymorphonuclear leukocytes (PMNs) and the bacterium Haemophilus somnus are known to be complex. In this paper, we evaluated the effect of H. somnus on PMN function using a flow cytometric (FC) technique that simultaneously determined the extent of phagocytosis and hydrogen peroxide production by PMNs, as well as using conventional techniques, such as the nitroblue tetrazolium (NBT) and chemiluminescence assays, to analyse the PMN respiratory burst. Results from the FC and chemiluminescence assays demonstrated that in vitro exposure of PMNs to logarithmically growing H. somnus reduced the respiratory burst of PMNs obtained from healthy calves. However, this reduction was not detected by the NBT assay. A decrease in phagocytosis by PMNs could also be shown using the FC assay. In addition, PMNs from calves with acute Hemophilosis (i.e. exposed to H. somnus in vivo) showed reduced activity when compared to PMNs from healthy calves. These in vitro and in vivo observations indicate that the modulation of bovine PMN function by H. somnus may contribute significantly towards the pathogenesis of the disease.

An investigation of somatic pairing in the muntjak (Muntiacus muntjak)

The Asiatic deer possesses the lowest diploid chromosome number known in mammals: 2N = 6 ♀; 2N = 7 ♂. Since all chromosomes of the idiogram are individually identifiable, pairs of homologs are seasily discernible. Distances between centromeres of all possible pairs of chromosomes were measured in a total of 169 cells (88 male and 81 female). Statistical analysis revealed no statistically significant somatic association between homologs.