Human osteoarthritic chondrons outnumber patient- and joint-matched chondrocytes in hydrogel culture-Future application in autologous cell-based OA cartilage repair?

Single-Stage Arthroscopic Minced Cartilage Implantation for Focal Cartilage Defects of the Glenoid Including Glenolabral Articular Disruption Lesions: A Technical Note

Anterior shoulder dislocations often are associated with cartilage defects of the anterior glenoid (glenolabral articular disruption, or GLAD lesions). However, the importance of GLAD lesions for shoulder stability is usually greatly underestimated. Moreover, glenoid cartilage defects may have a high clinical relevance as the result of persistent pain and possible progression to osteoarthritis. Therefore, surgical treatment appears to be necessary. Although in older patients prosthetic arthroplasty is a useful treatment option for progressive symptomatic cartilage defects, there is still disagreement about the ideal joint-preserving method for the treatment of isolated glenoid cartilage defects, especially in younger and more active patients. In recent years, autologous chondrocyte implantation has been established as a promising treatment option for focal cartilage defects. However, most autologous chondrocyte implantation techniques have the disadvantage of requiring 2 surgical procedures and the availability of specialized laboratories, making the techniques complex and expensive. In contrast, the AutoCart procedure (Arthrex, Munich, Germany) is a cost-effective one-step procedure in which the cartilage defect is filled with a mixture of minced autologous cartilage and autologous conditioned plasma and has already shown good clinical results in the knee joint. We present an arthroscopic technique for use in glenoid cartilage defects.

Articular Cartilage-From Basic Science Structural Imaging to Non-Invasive Clinical Quantitative Molecular Functional Information for AI Classification and Prediction

This review presents the changes that the imaging of articular cartilage has undergone throughout the last decades. It highlights that the expectation is no longer to image the structure and associated functions of articular cartilage but, instead, to devise methods for generating non-invasive, function-depicting images with quantitative information that is useful for detecting the early, pre-clinical stage of diseases such as primary or post-traumatic osteoarthritis (OA/PTOA). In this context, this review summarizes (a) the structure and function of articular cartilage as a molecular imaging target, (b) quantitative MRI for non-invasive assessment of articular cartilage composition, microstructure, and function with the current state of medical diagnostic imaging, (c), non-destructive imaging methods, (c) non-destructive quantitative articular cartilage live-imaging methods, (d) artificial intelligence (AI) classification of degeneration and prediction of OA progression, and (e) our contribution to this field, which is an AI-supported, non-destructive quantitative optical biopsy for early disease detection that operates on a digital tissue architectural fingerprint. Collectively, this review shows that articular cartilage imaging has undergone profound changes in the purpose and expectations for which cartilage imaging is used; the image is becoming an AI-usable biomarker with non-invasive quantitative functional information. This may aid in the development of translational diagnostic applications and preventive or early therapeutic interventions that are yet beyond our reach.

Cell morphology as a biological fingerprint of chondrocyte phenotype in control and inflammatory conditions

Introduction

Little is known how inflammatory processes quantitatively affect chondrocyte morphology and how single cell morphometric data could be used as a biological fingerprint of phenotype.

Methods

We investigated whether trainable high-throughput quantitative single cell morphology profiling combined with population-based gene expression analysis can be used to identify biological fingerprints that are discriminatory of control vs. inflammatory phenotypes. The shape of a large number of chondrocytes isolated from bovine healthy and human osteoarthritic (OA) cartilages was quantified under control and inflammatory (IL-1β) conditions using a trainable image analysis technique measuring a panel of cell shape descriptors (area, length, width, circularity, aspect ratio, roundness, solidity). The expression profiles of phenotypically relevant markers were quantified by ddPCR. Statistical analysis, multivariate data exploration, and projection-based modelling were used for identifying specific morphological fingerprints indicative of phenotype.

Results

Cell morphology was sensitive to both cell density and IL-1β. In both cell types, all shape descriptors correlated with expression of extracellular matrix (ECM)- and inflammatory-regulating genes. A hierarchical clustered image map revealed that individual samples sometimes responded differently in control or IL-1β conditions than the overall population. Despite these variances, discriminative projection-based modeling revealed distinct morphological fingerprints that discriminated between control and inflammatory chondrocyte phenotypes: the most essential morphological characteristics attributable to non-treated control cells was a higher cell aspect ratio in healthy bovine chondrocytes and roundness in OA human chondrocytes. In contrast, a higher circularity and width in healthy bovine chondrocytes and length and area in OA human chondrocytes indicated an inflammatory (IL-1β) phenotype. When comparing the two species/health conditions, bovine healthy and human OA chondrocytes exhibited comparable IL-1β-induced morphologies in roundness, a widely recognized marker of chondrocyte phenotype, and aspect ratio.

Discussion

Overall, cell morphology can be used as a biological fingerprint for describing chondrocyte phenotype. Quantitative single cell morphometry in conjunction with advanced methods for multivariate data analysis allows identifying morphological fingerprints that can discriminate between control and inflammatory chondrocyte phenotypes. This approach could be used to assess how culture conditions, inflammatory mediators, and therapeutic modulators regulate cell phenotype and function.

Enzymatic Isolation of Articular Chondrons: Is It Much Different Than That of Chondrocytes?

In native articular cartilage, chondrocytes (Chy) are completely capsulated by a pericellular matrix (PCM), together called the chondron (Chn). Due to its unique properties (w.r.t. territorial matrix) and importance in mechanotransduction, the PCM and Chn may be important in regenerative strategies. The current gold standard for the isolation of Chns from cartilage dates from 1997. Although previous research already showed the low cell yield and the heterogeneity of the isolated populations, their compositions and properties have never been thoroughly characterized. This study aimed to compare enzymatic isolation methods for Chy and Chns and characterizes the isolation efficiency and quality of the PCM. Bovine articular cartilage was digested according to the 5-h (5H) gold standard Chn isolation method (0.3% dispase +0.2% collagenase II), an overnight (ON) Chn isolation (0.15% dispase +0.1% collagenase II), and an ON Chy isolation (0.15% collagenase II +0.01% hyaluronidase). Type VI collagen staining, fluorescence-activated cell sorting (FACS) analysis, specific cell sorting, and immunohistochemistry were performed using a type VI collagen staining, to study their isolation efficiency and quality of the PCM. These analyses showed a heterogeneous mixture of Chy and Chns for all three methods. Although the 5H Chn isolation resulted in the highest percentage of Chns, the cell yield was significantly lower compared to the other isolation methods. FACS, based on the type VI collagen staining, successfully sorted the three identified cell populations. To maximize Chn yield and homogeneity, the ON Chn enzymatic digestion method should be combined with type VI collagen staining and specific cell sorting. Impact statement Since chondrocytes are highly dependent on their microenvironment for maintaining phenotypic stability, it is hypothesized that using chondrons results in superior outcomes in cartilage tissue engineering. This study reveals the constitution of cell populations obtained after enzymatic digestion of articular cartilage tissue and presents an alternative method to obtain a homogeneous population of chondrons. These data can improve the impact of studies investigating the effect of the pericellular matrix on neocartilage formation.

Characterization and In Vitro Cytotoxicity Safety Screening of Fractionated Organosolv Lignin on Diverse Primary Human Cell Types Commonly Used in Tissue Engineering

Simple Summary

As global efforts to use eco-friendly and reusable materials increase, the use of lignin from waste biomass will continue to intensify. Lignin is an underutilized biowaste macromolecule that is gaining considerable interest in biomedical research. However, the source of lignin and the extraction process heavily influence its chemistry, which can influence a cell’s reaction to lignin. Organosolv lignin is extracted via an eco-friendly process from leftover waste material. Few studies have tested the biocompatibility of organosolv lignins with human cells. We extensively characterized fractionated organosolv lignin and performed in vitro cytotoxicity safety screening on diverse primary human cell types commonly used in tissue engineering. This is the first study to show that, at a balanced concentration, fractionated low MW beechwood-derived organosolv lignin is non-cytotoxic to highly relevant human cell types used in tissue engineering including human bone marrow-derived mesenchymal stromal cells (MSCs), chondrocytes, osteoblasts, periodontal ligament fibroblasts, gingival fibroblasts and keratinocytes. Additionally, we show that organosolv lignin can be used to fabricate cell scaffolds and that addition of lignin increased the stiffness and viscosity of the scaffolds as well as cell attachment. This suggests that organosolv lignin may be used in the generation of tissue-like biomaterial-based constructs for tissue repair.

Abstract

There is limited data assessing the cytotoxic effects of organosolv lignin with cells commonly used in tissue engineering. Structural and physico-chemical characterization of fractionated organosolv lignin showed that a decrease of the molecular weight (MW) is accompanied by a less branched conformation of the phenolic biopolymer (higher S/G ratio) and an increased number of aliphatic hydroxyl functionalities. Enabling stronger polymer−solvent interactions, as proven by the Hansen solubility parameter analysis, low MW organosolv lignin (2543 g/mol) is considered to be compatible with common biomaterials. Using low MW lignin, high cell viability (70–100%) was achieved after 2 h, 24 h and 7 days using the following lignin concentrations: MSCs and osteoblasts (0.02 mg/mL), gingival fibroblasts and keratinocytes (0.02 to 0.04 mg/mL), periodontal ligament fibroblasts and chondrocytes (0.02 to 0.08 mg/mL). Cell viability was reduced at higher concentrations, indicating that high concentrations are cytotoxic. Higher cell viability was attained using 30/70 (w/v) NaOH vs. 40/60 (w/v) EtOH as the initial lignin solvent. Hydrogels containing low MW lignin (0.02 to 0.3 mg/mL) in agarose dose-dependently increased chondrocyte attachment (cell viability 84–100%) and hydrogel viscosity and stiffness to 3–11 kPa, similar to the pericellular matrix of chondrocytes. This suggests that low MW organosolv lignin may be used in many tissue engineering fields.

Autologous Minced Cartilage Implantation for Treatment of Chondral and Osteochondral Lesions in the Knee Joint: An Overview

Cartilage defects in the knee are being diagnosed with increased frequency and are treated with a variety of techniques. The aim of any cartilage repair procedure is to generate the highest tissue quality, which might correlate with improved clinical outcomes, return-to-sport, and long-term durability. Minced cartilage implantation (MCI) is a relatively simple and cost-effective technique to transplant autologous cartilage fragments in a single-step procedure. Minced cartilage has a strong biologic potential since autologous, activated non-dedifferentiated chondrocytes are utilized. It can be used both for small and large cartilage lesions, as well as for osteochondral lesions. As it is purely an autologous and homologous approach, it lacks a significant regulatory oversight process and can be clinically adopted without such limitations. The aim of this narrative review is to provide an overview of the current evidence supporting autologous minced cartilage implantation.

Minced Cartilage Procedure for One-Stage Arthroscopic Repair of Chondral Defects at the Glenohumeral Joint

Chondral defects of the glenohumeral joint are common but still remain a diagnostic and management challenge. Whereas arthroplasty is a reasonable treatment option in the elderly and low-demand population, joint preservation should be aimed for the remaining patients. For larger defects the current gold standard of treatment is autologous chondrocyte implantation. However, disadvantages such as high cost, the restriction in availability of specialized laboratories, and the 2-stage surgical design need to be accounted for if choosing this option. Showing first good clinical results for the knee joint, minced cartilage implantation is moreover a cost-effective procedure bringing autologous cartilage chips harvested from the defect walls and bringing them into the area of damage in a single-step open or arthroscopic approach. We describe an arthroscopic strategy of this technique to treat chondral defects at the glenohumeral joint.

Architecture-Promoted Biomechanical Performance-Tuning of Tissue-Engineered Constructs for Biological Intervertebral Disc Replacement

Background: Biological approaches to intervertebral disc (IVD) restoration and/or regeneration have become of increasing interest. However, the IVD comprises a viscoelastic system whose biological replacement remains challenging. The present study sought to design load-sharing two-component model systems of circular, nested, concentric elements reflecting the nucleus pulposus and annulus fibrosus. Specifically, we wanted to investigate the effect of architectural design variations on (1) model system failure loads when testing the individual materials either separately or homogeneously mixed, and (2) also evaluate the potential of modulating other mechanical properties of the model systems. Methods: Two sets of softer and harder biomaterials, 0.5% and 5% agarose vs. 0.5% agarose and gelatin, were used for fabrication. Architectural design variations were realized by varying ring geometries and amounts while keeping the material composition across designs comparable. Results: Variations in the architectural design, such as lamellar width, number, and order, combined with choosing specific biomaterial properties, strongly influenced the biomechanical performance of IVD constructs. Biomechanical characterization revealed that the single most important parameter, in which the model systems vastly exceeded those of the individual materials, was failure load. The model system failure loads were 32.21- and 84.11-fold higher than those of the agarose materials and 55.03- and 2.14-fold higher than those of the agarose and gelatin materials used for system fabrication. The compressive strength, dynamic stiffness, and viscoelasticity of the model systems were always in the range of the individual materials. Conclusions: Relevant architecture-promoted biomechanical performance-tuning of tissue-engineered constructs for biological IVD replacement can be realized by slight modifications in the design of constructs while preserving the materials’ compositions. Minimal variations in the architectural design can be used to precisely control structure–function relations for IVD constructs rather than choosing different materials. These fundamental findings have important implications for efficient tissue-engineering of IVDs and other load-bearing tissues, as potential implants need to withstand high in situ loads.

Combination of chondrocytes and chondrons improves extracellular matrix production to promote the repairs of defective knee cartilage in rabbits

Background

Chondrons are composed of chondrocytes and the surrounding pericellular matrix (PCM) and function to enhance chondrocyte-mediated cartilage tissue engineering. This study aimed at investigating the potential effect of combined chondrocytes with chondrons on the production of proteoglycan and collagen-II (Col-2) and the repair of defective knee cartilage in rabbits.

Methods

Chondrocytes and chondrons were isolated from the knee cartilage of rabbits, and cultured alone or co-cultured for varying periods in vitro. Their morphology was characterized by histology. The levels of aggrecan (AGG), Col-2 and glycosaminoglycan (GAG) expression were quantified by qRT-PCR, Alcian blue-based precipitation and ELISA. The effect of combined chondrocytes with chondrons in alginate spheres on the repair of defective knee cartilage was examined in rabbits.

Results

The isolated chondrocytes and chondrons displayed unique morphology and began to proliferate on day 3 and 6 post culture, respectively, accompanied by completely degenerated PCM on day 6 post culture. Evidently, chondrocytes had stronger proliferation capacity than chondrons. Longitudinal analyses indicated that culture of chondrons, but not chondrocytes, increased AGG mRNA transcripts and GAG levels with time and Col-2 mRNA transcripts only on day 3 post culture. Compared with chondrocytes or chondrons alone, co-culture of chondrocytes and chondrons significantly up-regulated AGG and Col-2 expression and GAG production, particularly at a ratio of 1:1. Implantation with chondrocytes and chondrons at 1:1 significantly promoted the repair of defective knee cartilage in rabbits, accompanied by reduced the Wakiteni scores with time.

Conclusion

Combined chondrons with chondrocytes promoted the production of extracellular matrix and the repair of defective knee cartilage in rabbits.

The translational potential of this article

This study explores that the combination of chondrons and chondrocytes may be new therapeutic strategy for cartilage tissue engineering and repair of defective cartilage.

An Evidence-Based Systematic Review of Human Knee Post-Traumatic Osteoarthritis (PTOA): Timeline of Clinical Presentation and Disease Markers, Comparison of Knee Joint PTOA Models and Early Disease Implications

Understanding the causality of the post-traumatic osteoarthritis (PTOA) disease process of the knee joint is important for diagnosing early disease and developing new and effective preventions or treatments. The aim of this review was to provide detailed clinical data on inflammatory and other biomarkers obtained from patients after acute knee trauma in order to (i) present a timeline of events that occur in the acute, subacute, and chronic post-traumatic phases and in PTOA, and (ii) to identify key factors present in the synovial fluid, serum/plasma and urine, leading to PTOA of the knee in 23-50% of individuals who had acute knee trauma. In this context, we additionally discuss methods of simulating knee trauma and inflammation in in vivo, ex vivo articular cartilage explant and in vitro chondrocyte models, and answer whether these models are representative of the clinical inflammatory stages following knee trauma. Moreover, we compare the pro-inflammatory cytokine concentrations used in such models and demonstrate that, compared to concentrations in the synovial fluid after knee trauma, they are exceedingly high. We then used the Bradford Hill Framework to present evidence that TNF-α and IL-6 cytokines are causal factors, while IL-1β and IL-17 are credible factors in inducing knee PTOA disease progresssion. Lastly, we discuss beneficial infrastructure for future studies to dissect the role of local vs. systemic inflammation in PTOA progression with an emphasis on early disease.

Intermittent pressure imitating rolling manipulation ameliorates injury in skeletal muscle cells through oxidative stress and lipid metabolism signalling pathways

BACKGROUND

Traditional Chinese medicine manipulation (TCMM) is often used to treat human skeletal muscle injury, but its mechanism remains unclear due to difficulty standardizing and quantifying manipulation parameters.

METHODS

Here, dexamethasone sodium phosphate (DSP) was utilized to induce human skeletal muscle cell (HSkMC) impairments. Cells in a three-dimensional environment were divided into the control normal group (CNG), control injured group (CIG) and rolling manipulation group (RMG). The RMG was exposed to intermittent pressure imitating rolling manipulation (IPIRM) of TCMM via the FX‑5000™ compression system. Skeletal muscle damage was assessed via the cell proliferation rate, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content and creatine kinase (CK) activity. Isobaric tagging for relative and absolute protein quantification (iTRAQ) and bioinformatic analysis were used to evaluate differentially expressed proteins (DEPs).

RESULTS

Higher-pressure IPIRM ameliorated the skeletal muscle cell injury induced by 1.2 mM DSP. Thirteen common DEPs after IPIRM were selected. Key biological processes, molecular functions, cellular components, and pathways were identified as mechanisms underlying the protective effect of TCMM against skeletal muscle damage. Some processes (response to oxidative stress, response to wounding, response to stress and lipid metabolism signalling pathways) were related to skeletal muscle cell injury. Western blotting for 4 DEPs confirmed the reliability of iTRAQ.

CONCLUSIONS

Higher-pressure IPIRM downregulated the CD36, Hsp27 and FABP4 proteins in oxidative stress and lipid metabolism pathways, alleviating excessive oxidative stress and lipid metabolism disorder in injured HSkMCs. The techniques used in this study might provide novel insights into the mechanism of TCMM.

Mechanotransduction and Stiffness-Sensing: Mechanisms and Opportunities to Control Multiple Molecular Aspects of Cell Phenotype as a Design Cornerstone of Cell-Instructive Biomaterials for Articular Cartilage Repair

Since material stiffness controls many cell functions, we reviewed the currently available knowledge on stiffness sensing and elucidated what is known in the context of clinical and experimental articular cartilage (AC) repair. Remarkably, no stiffness information on the various biomaterials for clinical AC repair was accessible. Using mRNA expression profiles and morphology as surrogate markers of stiffness-related effects, we deduced that the various clinically available biomaterials control chondrocyte (CH) phenotype well, but not to equal extents, and only in non-degenerative settings. Ample evidence demonstrates that multiple molecular aspects of CH and mesenchymal stromal cell (MSC) phenotype are susceptible to material stiffness, because proliferation, migration, lineage determination, shape, cytoskeletal properties, expression profiles, cell surface receptor composition, integrin subunit expression, and nuclear shape and composition of CHs and/or MSCs are stiffness-regulated. Moreover, material stiffness modulates MSC immuno-modulatory and angiogenic properties, transforming growth factor beta 1 (TGF-β1)-induced lineage determination, and CH re-differentiation/de-differentiation, collagen type II fragment production, and TGF-β1- and interleukin 1 beta (IL-1β)-induced changes in cell stiffness and traction force. We then integrated the available molecular signaling data into a stiffness-regulated CH phenotype model. Overall, we recommend using material stiffness for controlling cell phenotype, as this would be a promising design cornerstone for novel future-oriented, cell-instructive biomaterials for clinical high-quality AC repair tissue.

Regenerative Medicine: A Review of the Evolution of Autologous Chondrocyte Implantation (ACI) Therapy

Articular cartilage is composed of chondrons within a territorial matrix surrounded by a highly organized extracellular matrix comprising collagen II fibrils, proteoglycans, glycosaminoglycans, and non-collagenous proteins. Damaged articular cartilage has a limited potential for healing and untreated defects often progress to osteoarthritis. High hopes have been pinned on regenerative medicine strategies to meet the challenge of preventing progress to late osteoarthritis. One such strategy, autologous chondrocyte implantation (ACI), was first reported in 1994 as a treatment for deep focal articular cartilage defects. ACI has since evolved to become a worldwide well-established surgical technique. For ACI, chondrocytes are harvested from the lesser weight bearing edge of the joint by arthroscopy, their numbers expanded in monolayer culture for at least four weeks, and then re-implanted in the damaged region under a natural or synthetic membrane via an open joint procedure. We consider the evolution of ACI to become an established cell therapy, its current limitations, and on-going strategies to improve its efficacy. The most promising developments involving cells and natural or synthetic biomaterials will be highlighted.

A New Bone Substitute Developed from 3D-Prints of Polylactide (PLA) Loaded with Collagen I: An In Vitro Study

Although a lot of research has been performed, large segmental bone defects caused by trauma, infection, bone tumors or revision surgeries still represent big challenges for trauma surgeons. New and innovative bone substitutes are needed. Three-dimensional (3D) printing is a novel procedure to create 3D porous scaffolds that can be used for bone tissue engineering. In the present study, solid discs as well as porous cage-like 3D prints made of polylactide (PLA) are coated or filled with collagen, respectively, and tested for biocompatibility and endotoxin contamination. Microscopic analyses as well as proliferation assays were performed using various cell types on PLA discs. Stromal-derived factor (SDF-1) release from cages filled with collagen was analyzed and the effect on endothelial cells tested. This study confirms the biocompatibility of PLA and demonstrates an endotoxin contamination clearly below the FDA (Food and Drug Administration) limit. Cells of various cell types (osteoblasts, osteoblast-like cells, fibroblasts and endothelial cells) grow, spread and proliferate on PLA-printed discs. PLA cages loaded with SDF-1 collagen display a steady SDF-1 release, support cell growth of endothelial cells and induce neo-vessel formation. These results demonstrate the potential for PLA scaffolds printed with an inexpensive desktop printer in medical applications, for example, in bone tissue engineering.

Engineering the geometrical shape of mesenchymal stromal cells through defined cyclic stretch regimens

Stem cells have been predicted to improve disease outcomes and patient lives. Steering stem cell fate - through controlling cell shape - may substantially accelerate progress towards this goal. As mesenchymal stromal cells (MSCs) are continuously exposed in vivo to a dynamically changing biomechanical environment, we hypothesized that exogenous forces can be applied for engineering a variety of significantly different MSC shapes. We applied specific cyclic stretch regimens to human MSCs and quantitatively measured the resulting cell shape, alignment, and expression of smooth muscle (SMC) differentiation markers, as those have been associated with elongated morphology. As proof of principle, a range of different shapes, alignments, and correlating SMC marker levels were generated by varying strain, length, and repetition of stretch. However, the major determinant of biomechanically engineering cellular shape was the repetition of a chosen stretch regimen, indicating that the engineered shape and associated differentiation were complex non-linear processes relying on sustained biomechanical stimulation. Thus, forces are key regulators of stem cell shape and the targeted engineering of specific MSC shapes through biomechanical forces represents a novel mechanobiology concept that could exploit naturally occurring in vivo forces for improving stem cell fate in clinical regenerative therapies.