The effects of different doses of IGF-1 on cartilage and subchondral bone during the repair of full-thickness articular cartilage defects in rabbits

Reduced Cell Migration in Human Chondrocyte Sheets Increases Tissue Stiffness and Cartilage Protein Production

BACKGROUND

Chondrogenic differentiation medium (CDM) is usually used to maintain chondrogenic activity during chondrocyte sheet production. However, tissue qualities remain to be determined as to what factors improve cell functions. Moreover, the relationship between CDM and cell migration proteins has not been reported.

METHOD

In this study, the effect of CDM on the behavior of chondrocyte sheets was investigated. Structural analysis, mechanical testing and proteomics were performed to observe tissue qualities. The relationship between CDM and cell migration proteins were investigated using time-lapse observations and bioinformatic analysis.

RESULTS

During 48 h, CDM affected the chondrocyte behaviors by reducing cell migration. Compared to the basal medium, CDM impacted the contraction of monolayered chondrocyte sheets. At day 7, the contracted sheets increased tissue thickness and improved tissue stiffness. Cartilage specific proteins were also upregulated. Remarkedly, the chondrocyte sheets in CDM displayed downregulated proteins related to cell migration. Bioinformatic analysis revealed that TGFβ1 was shown to be associated with cartilage functions and cell migration. Pathway analysis of chondrocyte sheets in CDM also revealed the presence of a TGFβ pathway without activating actin production, which might be involved in synthesizing cartilage-specific proteins. Cell migration pathway showed MAPK signaling in both cultures of the chondrocyte sheets.

CONCLUSION

Reduced cell migration in the chondrocyte sheet affected the tissue quality. Using CDM, TGFβ1 might trigger cartilage protein production through the TGFβ pathway and be involved in cell migration via the MAPK signaling pathway. Understanding cell behaviors and their protein expression would be beneficial for developing high-quality tissue-engineered cartilage.

Profound Properties of Protein-Rich, Platelet-Rich Plasma Matrices as Novel, Multi-Purpose Biological Platforms in Tissue Repair, Regeneration, and Wound Healing

Autologous platelet-rich plasma (PRP) preparations are prepared at the point of care. Centrifugation cellular density separation sequesters a fresh unit of blood into three main fractions: a platelet-poor plasma (PPP) fraction, a stratum rich in platelets (platelet concentrate), and variable leukocyte bioformulation and erythrocyte fractions. The employment of autologous platelet concentrates facilitates the biological potential to accelerate and support numerous cellular activities that can lead to tissue repair, tissue regeneration, wound healing, and, ultimately, functional and structural repair. Normally, after PRP preparation, the PPP fraction is discarded. One of the less well-known but equally important features of PPP is that particular growth factors (GFs) are not abundantly present in PRP, as they reside outside of the platelet alpha granules. Precisely, insulin-like growth factor-1 (IGF-1) and hepatocyte growth factor (HGF) are mainly present in the PPP fraction. In addition to their roles as angiogenesis activators, these plasma-based GFs are also known to inhibit inflammation and fibrosis, and they promote keratinocyte migration and support tissue repair and wound healing. Additionally, PPP is known for the presence of exosomes and other macrovesicles, exerting cell-cell communication and cell signaling. Newly developed ultrafiltration technologies incorporate PPP processing methods by eliminating, in a fast and efficient manner, plasma water, cytokines, molecules, and plasma proteins with a molecular mass (weight) less than the pore size of the fibers. Consequently, a viable and viscous protein concentrate of functional total proteins, like fibrinogen, albumin, and alpha-2-macroglobulin is created. Consolidating a small volume of high platelet concentrate with a small volume of highly concentrated protein-rich PPP creates a protein-rich, platelet-rich plasma (PR-PRP) biological preparation. After the activation of proteins, mainly fibrinogen, the PR-PRP matrix retains and facilitates interactions between invading resident cells, like macrophages, fibroblast, and mesenchymal stem cells (MSCs), as well as the embedded concentrated PRP cells and molecules. The administered PR-PRP biologic will ultimately undergo fibrinolysis, leading to a sustained release of concentrated cells and molecules that have been retained in the PR-PRP matrix until the matrix is dissolved. We will discuss the unique biological and tissue reparative and regenerative properties of the PR-PRP matrix.

Intra-articular injection of modified citrus pectin and hyaluronate gel induces synergistic effects in treating osteoarthritis

We previously found that modified citrus pectin (MCP), an inhibitor of pro-inflammatory factor Galectin-3 (Gal-3), has significant anti-inflammatory and chondroprotective effects. In this study, a hyaluronate (HA) gel-based sustained release system of MCP (MCP-HA) was developed as an anti-inflammatory agent for chronic inflammation for osteoarthritis (OA) treatment. The MCP-HA gel was injected into the knee joint cavities of OA rabbit models induced by anterior cruciate ligament transection (ACLT) or modified Hulth method once a week for five weeks. We found that MCP-HA could improve the symptoms and signs of OA, protect articular cartilage from degeneration, suppress synovial inflammation, and therefore alleviate OA progression. Proteomic analysis of the synovial fluid obtained from the knee joints of OA rabbits revealed that MCP-HA synergistically regulated the levels of multiple inflammatory mediators and proteins involved in metabolic pathways. Taken together, our results demonstrate that the MCP-HA shows a synergistic effect of HA and MCP by modulating both inflammation and metabolic processes, thereby alleviating OA progression. The MCP-HA sustained release system has promising potential for long-term use in OA treatment.

On-demand release of a selective MMP-13 blocker from an enzyme-responsive injectable hydrogel protects cartilage from degenerative progression in osteoarthritis

In osteoarthritis (OA), the degradation of cartilage is primarily driven by matrix metalloprotease-13 (MMP-13). Hence, the inhibition of MMP-13 has emerged as an attractive target for OA treatment. Among the various approaches that are being explored for MMP-13 regulation, blocking of the enzyme with specific binding molecules appears to be a more promising strategy for preventing cartilage degeneration. To enhance effectiveness and ensure patient compliance, it is preferable for the binding molecule to exhibit sustained activity when administered directly into the joint. Herein, we present an enzyme-responsive hydrogel that was designed to exhibit on-demand, the sustained release of BI-4394, a potent and highly selective MMP-13 blocker. The stable and compatible hydrogel was prepared using triglycerol monostearate. The efficacy of the hydrogel to prevent cartilage damage was assessed in a rat model of OA induced by anterior cruciate ligament transection (ACLT). The results revealed that in comparison to the rats administrated weekly with intra-articular BI-4394, the hydrogel implanted rats had reduced levels of inflammation and bone erosion. In comparison to untreated control, the cartilage in animals administered with BI-4394/hydrogel exhibited significant levels of collagen-2 and aggrecan along with reduced MMP-13. Overall, this study confirmed the potential of BI-4394 delivery using an enzyme-responsive hydrogel as a promising treatment option to treat the early stages of OA by preventing further cartilage degradation.

Evaluating the potential of Vitamin D and curcumin to alleviate inflammation and mitigate the progression of osteoarthritis through their effects on human chondrocytes: A proof-of-concept investigation

Osteoarthritis (OA) is a chronic degenerative joint disorder primarily affecting the elderly, characterized by a prominent inflammatory component. The long-term side effects associated with current therapeutic approaches necessitate the development of safer and more efficacious alternatives. Nutraceuticals, such as Vitamin D and curcumin, present promising therapeutic potentials due to their safety, efficacy, and cost-effectiveness. In this study, we utilized a proinflammatory human chondrocyte model of OA to assess the anti-inflammatory properties of Vitamin D and curcumin, with a particular focus on the Protease-Activated Receptor-2 (PAR-2) mediated inflammatory pathway. Employing a robust siRNA approach, we effectively modulated the expression of PAR-2 to understand its role in the inflammatory process. Our results reveal that both Vitamin D and curcumin attenuate the expression of PAR-2, leading to a reduction in the downstream proinflammatory cytokines, such as Tumor Necrosis Factor-alpha (TNF-α), Interleukin 6 (IL-6), and Interleukin 8 (IL-8), implicated in the OA pathogenesis. Concurrently, these compounds suppressed the expression of Receptor Activator of Nuclear Factor kappa-Β Ligand (RANKL) and its receptor RANK, which are associated with PAR-2 mediated TNF-α stimulation. Additionally, Vitamin D and curcumin downregulated the expression of Interferon gamma (IFN-γ), known to elevate RANKL levels, underscoring their potential therapeutic implications in OA. This study, for the first time, provides evidence of the mitigating effect of Vitamin D and curcumin on PAR-2 mediated inflammation, employing an siRNA approach in OA. Thus, our findings pave the way for future research and the development of novel, safer, and more effective therapeutic strategies for managing OA.

Engineered biochemical cues of regenerative biomaterials to enhance endogenous stem/progenitor cells (ESPCs)-mediated articular cartilage repair

As a highly specialized shock-absorbing connective tissue, articular cartilage (AC) has very limited self-repair capacity after traumatic injuries, posing a heavy socioeconomic burden. Common clinical therapies for small- to medium-size focal AC defects are well-developed endogenous repair and cell-based strategies, including microfracture, mosaicplasty, autologous chondrocyte implantation (ACI), and matrix-induced ACI (MACI). However, these treatments frequently result in mechanically inferior fibrocartilage, low cost-effectiveness, donor site morbidity, and short-term durability. It prompts an urgent need for innovative approaches to pattern a pro-regenerative microenvironment and yield hyaline-like cartilage with similar biomechanical and biochemical properties as healthy native AC. Acellular regenerative biomaterials can create a favorable local environment for AC repair without causing relevant regulatory and scientific concerns from cell-based treatments. A deeper understanding of the mechanism of endogenous cartilage healing is furthering the (bio)design and application of these scaffolds. Currently, the utilization of regenerative biomaterials to magnify the repairing effect of joint-resident endogenous stem/progenitor cells (ESPCs) presents an evolving improvement for cartilage repair. This review starts by briefly summarizing the current understanding of endogenous AC repair and the vital roles of ESPCs and chemoattractants for cartilage regeneration. Then several intrinsic hurdles for regenerative biomaterials-based AC repair are discussed. The recent advances in novel (bio)design and application regarding regenerative biomaterials with favorable biochemical cues to provide an instructive extracellular microenvironment and to guide the ESPCs (e.g. adhesion, migration, proliferation, differentiation, matrix production, and remodeling) for cartilage repair are summarized. Finally, this review outlines the future directions of engineering the next-generation regenerative biomaterials toward ultimate clinical translation.

The Dual-Responsive Interaction of Particulated Hyaline Cartilage and Plasma Rich in Growth Factors (PRGF) in the Repair of Cartilage Defects: An In Vitro Study

The treatment of chondral and osteochondral defects is challenging. These types of lesions are painful and progress to osteoarthritis over time. Tissue engineering offers tools to address this unmet medical need. The use of an autologous cartilage construct consisting of hyaline cartilage chips embedded in plasma rich in growth factors (PRGF) has been proposed as a therapeutic alternative. The purpose of this study was to dig into the potential mechanisms behind the in vitro remodelling process that might explain the clinical success of this technique and facilitate its optimisation. Chondrocyte viability and cellular behaviour over eight weeks of in vitro culture, type II collagen synthesis, the dual delivery of growth factors by hyaline cartilage and PRGF matrix, and the ultrastructure of the construct and its remodelling were characterised. The main finding of this research is that the cartilage fragments embedded in the three-dimensional PRGF scaffold contain viable chondrocytes that are able to migrate into the fibrin network, proliferate and synthesise extracellular matrix after the second week of in vitro culture. The characterization of this three-dimensional matrix is key to unravelling the molecular kinetics responsible for its efficacy.

Transcriptomic changes in porcine articular cartilage one year following disruption of the anterior cruciate ligament

To determine the transcriptomic changes seen in early- to mid-stage posttraumatic osteoarthritis (PTOA) development, 72 Yucatan minipigs underwent transection of the anterior cruciate ligament. Subjects were randomized to no further intervention, ligament reconstruction, or ligament repair, followed by articular cartilage harvesting and RNA-sequencing at three different postoperative timepoints (1, 4, and 52 weeks). Six additional subjects received no ligament transection and provided cartilage tissue to serve as controls. Differential gene expression analysis between post-transection cartilage and healthy cartilage revealed an initial increase in transcriptomic differences at 1 and 4 weeks followed by a stark reduction in transcriptomic differences at 52 weeks. This analysis also showed how different treatments genetically modulate the course of PTOA following ligament disruption. Specific genes (e.g., MMP1, POSTN, IGF1, PTGFR, HK1) were identified as being upregulated in the cartilage of injured subjects across all timepoints regardless of treatment. At the 52-week timepoint, 4 genes (e.g., A4GALT, EFS, NPTXR, ABCA3) that-as far as we know-have yet to be associated with PTOA were identified as being concordantly differentially expressed across all treatment groups when compared to controls. Functional pathway analysis of injured subject cartilage compared to control cartilage revealed overarching patterns of cellular proliferation at 1 week, angiogenesis, ECM interaction, focal adhesion, and cellular migration at 4 weeks, and calcium signaling, immune system activation, GABA signaling, and HIF-1 signaling at 52 weeks.

Subchondral Bone Cyst Development in Osteoarthritis: From Pathophysiology to Bone Microarchitecture Changes and Clinical Implementations

Osteoarthritis is a degenerative joint disease affecting middle-aged and elderly patients. It mainly involves weight-bearing joints such as the hip, knee and spine as well as the basilar joint of the thumb, causing dysfunction and painful symptoms. Often, joint arthritis is accompanied by cartilage defects, joint space narrowing, osteophytes, bone sclerosis and subchondral bone cysts (SBC). The aim of the present study was to explore the pathophysiology responsible for the development of SBCs as well as the association between SBCs and disease progress, the level of clinical symptoms and their impact on postoperative outcomes and risk of possible complications following joint replacements if left untreated. A literature review on PubMed articles was conducted to retrieve and evaluate all available evidence related to the main objective mentioned above. A few theories have been put forth to explain the formation process of SBCs. These involve MMPs secretion, angiogenesis, and enhanced bone turnover as a biological response to abnormal mechanical loads causing repeated injuries on cartilage and subchondral tissue during the development of arthritis. However, the application of novel therapeutics, celecoxib-coated microspheres, local administration of IGF-1 and activated chondrocytes following surgical debridement of SBCs hinders the expansion of SBCs and prevents the progression of osteoarthritis.

Seamless and early gap healing of osteochondral defects by autologous mosaicplasty combined with bioactive supramolecular nanofiber-enabled gelatin methacryloyl (BSN-GelMA) hydrogel

Autologous mosaicplasty is a common approach used to treat osteochondral defects in clinical practice. Gap integration between host and transplanted plugs requires bone tissue reservation and hyaline cartilage regeneration without uneven surface, graft necrosis and sclerosis. However, poor gap integration is a serious concern, which eventually leads to deterioration of joint function. To deal with such complications, this study has developed a strategy to effectively enhance integration of the gap region following mosaicplasty by applying injectable bioactive supramolecular nanofiber-enabled gelatin methacryloyl (GelMA) hydrogel (BSN-GelMA). A rabbit osteochondral defect model demonstrated that BSN-GelMA achieved seamless osteochondral healing in the gap region between plugs of osteochondral defects following mosaicplasty, as early as six weeks. Moreover, the International Cartilage Repair Society score, histology score, glycosaminoglycan content, subchondral bone volume, and collagen II expression were observed to be the highest in the gap region of BSN-GelMA treated group. This improved outcome was due to bio-interactive materials, which acted as tissue fillers to bridge the gap, prevent cartilage degeneration, and promote graft survival and migration of bone marrow mesenchymal stem cells by releasing bioactive supramolecular nanofibers from the GelMA hydrogel. This study provides a powerful and applicable approach to improve gap integration after autologous mosaicplasty. It is also a promising off-the-shelf bioactive material for cell-free in situ tissue regeneration.

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A novel strategy that can effectively enhance post-mosaicplasty interstitial integration was developed.

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The bioactive supramolecular nanofibers (BSN) exhibited comparable bioactivity to insulin-like growth factor-1 (IGF-1).

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The BSN-GelMA hydrogel is a promising off-the-shelf bioactive material for cell-free in situ tissue regeneration.

Relationship between osteoporosis and Cushing syndrome based on bioinformatics

BACKGROUND

Many clinical studies have reported a relatively high incidence of osteoporosis and fragility fractures in patients with Cushing syndrome (CS). However, few papers have investigated osteoporosis and CS in terms of pathogenesis, so this study explores the association between the 2 and predicts upstream micro-ribonucleic acids (miRNAs) through bioinformatics, which provides potential targets for simultaneous pharmacological interventions in both diseases and also provides a basis for pathological screening.

METHODS

We used Genecards, Online Mendelian Inheritance in Man and Therapeutic Target Database databases to screen the targets of osteoporosis and Cushing syndrome; import target genes to Database for Annotation, Visualization and Integrated Discovery for Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis; the intersecting genes were uploaded to Search Tool for the Retrieval of Genes and Genomes database to construct protein-protein interaction network; Cytoscape software was used to screen core genes, and Molecular Complex Detection module was used to analyze cluster modules; finally, the NetworkAnalyst data platform was used to predict the miRNAs that interact with core genes.

RESULTS

The core genes of osteoporosis and Cushing syndrome were insulin, tumor necrosis factor, signal transducer and activator of transcription 3 (STAT3), interleukin-6, insulin-like growth factor 1, etc. A total of 340 upstream miRNAs including hsa-let-7a-5p, hsa-mir-30a-5p and hsa-mir-125b-5p were predicted. The biological processes involved include regulating the transcription of ribonucleic acid polymerase II promoter and participating in the transduction of cytokine signaling pathways, which focus on the binding of nerve system ligand, JAK-STAT signaling pathway, Rap1 signaling pathway, PI3K-Akt signaling pathway, etc.

CONCLUSION

Osteoporosis and Cushing syndrome are closely related in terms of targets and molecular mechanisms. In this study, bioinformatics methods were used to identify their targets and mechanisms, providing potential targets for drug simultaneous regulation of the 2 diseases, and providing a new direction for exploring the relationship between diseases.

Advanced injectable hydrogels for cartilage tissue engineering

The rapid development of tissue engineering makes it an effective strategy for repairing cartilage defects. The significant advantages of injectable hydrogels for cartilage injury include the properties of natural extracellular matrix (ECM), good biocompatibility, and strong plasticity to adapt to irregular cartilage defect surfaces. These inherent properties make injectable hydrogels a promising tool for cartilage tissue engineering. This paper reviews the research progress on advanced injectable hydrogels. The cross-linking method and structure of injectable hydrogels are thoroughly discussed. Furthermore, polymers, cells, and stimulators commonly used in the preparation of injectable hydrogels are thoroughly reviewed. Finally, we summarize the research progress of the latest advanced hydrogels for cartilage repair and the future challenges for injectable hydrogels.

Single-cell RNA-Seq reveals changes in immune landscape in post-traumatic osteoarthritis

Osteoarthritis (OA) is the most common joint disease, affecting over 300 million people world-wide. Accumulating evidence attests to the important roles of the immune system in OA pathogenesis. Understanding the role of various immune cells in joint degeneration or joint repair after injury is vital for improving therapeutic strategies for treating OA. Post-traumatic osteoarthritis (PTOA) develops in ~50% of individuals who have experienced an articular trauma like an anterior cruciate ligament (ACL) rupture. Here, using the high resolution of single-cell RNA sequencing, we delineated the temporal dynamics of immune cell accumulation in the mouse knee joint after ACL rupture. Our study identified multiple immune cell types in the joint including neutrophils, monocytes, macrophages, B cells, T cells, NK cells and dendritic cells. Monocytes and macrophage populations showed the most dramatic changes after injury. Further characterization of monocytes and macrophages reveled 9 major subtypes with unique transcriptomics signatures, including a tissue resident Lyve1hiFolr2hi macrophage population and Trem2hiFcrls+ recruited macrophages, both showing enrichment for phagocytic genes and growth factors such as Igf1, Pdgfa and Pdgfc. We also identified several genes induced or repressed after ACL injury in a cell type-specific manner. This study provides new insight into PTOA-associated changes in the immune microenvironment and highlights macrophage subtypes that may play a role in joint repair after injury.

In vitro production of mouse morphological sperm in artificial testis bioengineered by 3D printing of extracellular matrix

Since autologous stem cell transplantation is prone to cancer recurrence, in vitro sperm production is regarded a safer approach to fertility preservation. In this study, the spermatogenesis process on testicular tissue extracellular matrix (T-ECM)-derived printing structure was evaluated. Ram testicular tissue was decellularized using a hypertonic solution containing triton and the extracted ECM was used as a bio-ink to print an artificial testis. Following cell adhesion and viability examination, pre-meiotic and post-meiotic cells in the study groups (as testicular suspension and co-culture with Sertoli cells) were confirmed by real-time PCR, flow-cytometry and immunocytochemistry methods. Morphology of differentiated cells was evaluated using transmission electron microscopy (TEM), toluidine blue, Giemsa, and hematoxylin and eosin (H&E) staining. The functionality of Leydig and Sertoli cells was determined by their ability for hormone secretion. The decellularization of testicular tissue fragments was successful and had efficiently removed the cellular debris and preserved the ECM compounds. High cell viability, colonization, and increased expression of pre-meiotic markers in cultured testicular cells on T-ECM-enriched scaffolds confirmed their proliferation. Furthermore, the inoculation of neonatal mouse testicular cells onto T-ECM-enriched scaffolds resulted in the generation of sperm. Morphology evaluation showed that the structure of these cells was quite similar to mature sperm with a specialized tail structure. The hormonal analysis also confirmed production and secretion of testosterone and inhibin B by Leydig and Sertoli cells. T-ECM printed artificial testis is a future milestone that promises for enhancing germ cell maintenance and differentiation, toxicology studies, and fertility restoration to pave the way for new human infertility treatments in the future.

Exploring the relationship between osteoporosis and polycystic ovary syndrome based on bioinformatics

BACKGROUND

In recent years, clinical studies have found that there is a close relationship between osteoporosis and polycystic ovary syndrome. However, there are few literature on the pathogenesis of osteoporosis and polycystic ovary syndrome. In order to clarify their common pathogenic mechanism and provide potential targets for drugs to regulate them at the same time, bioinformatics methods are used to explore, so as to provide a new direction for the study of the relationship between diseases in the future.

METHODS

To screen the targets of osteoporosis and polycystic ovary syndrome by Genecards, Online Mendelian Inheritance in Man databases and Therapeutic Target Database to take the intersection of the two mappings and upload the intersection targets to the STRING database to construct protein-protein interaction network; to screen the core targets by degree value and import them to Metascape database for Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis; and finally, to construct the visualization network of core targets and pathways by Cytoscape software. Ethical approval and informed consent of patients are not required because the data used in this study is publicly available and does not involve individual patient data or privacy.

RESULTS

The core targets of polycystic ovary syndrome and osteoporosis were insulin gene, insulin-like growth factor 1, CTNNB1, serine/threonine kinase 1, signal transducer and activator of transcription 3, LEP, etc. The biological processes involved include the regulation of protein phosphorylation, cell proliferation and differentiation, hormone endocrine, reproductive system and skeletal system. The related pathways were concentrated in Foxo signaling pathway, HTLV-I infection, PI3K-AKT signaling pathway, MAPK signaling pathway and AGE-RAGE signaling pathway in diabetic complications.

CONCLUSIONS

There is a close relationship between osteoporosis and polycystic ovary syndrome in terms of target and molecular mechanism. This study used bioinformatics to clarify their targets and mechanisms, providing potential targets for drugs to regulate both diseases simultaneously and providing new directions to explore the relationship between the diseases.

The synthetic artificial stem cell (SASC): Shifting the paradigm of cell therapy in regenerative engineering

This paper presents the synthetic artificial stem cell (SASC) system: a versatile therapy which provides the ability to tailor paracrine responses of different cells and provide a more potent regenerative effect for targeted tissues. Upon challenging the SASC system against an osteoarthritis model, we demonstrate that the factors combined tailored for chondrogenesis have a potent antiinflammatory and chondroprotective effect. This paper also demonstrates the in vivo capacity of SASC to attenuate proteoglycan depletion in the cartilage extracellular matrix while also improving biomechanical properties of the resulting cartilage. We report the first of many applications of the SASC system, which provides a promising step toward clinical translation of a minimally immunogenic stem cell with many commercial advantages over its biological counterpart.

Stem cells are of great interest in tissue regeneration due to their ability to modulate the local microenvironment by secreting bioactive factors (collectively, secretome). However, secretome delivery through conditioned media still requires time-consuming cell isolation and maintenance and also may contain factors antagonistic to targeted tissue regeneration. We have therefore engineered a synthetic artificial stem cell (SASC) system which mimics the paracrine effect of the stem cell secretome and provides tailorability of the composition for targeted tissue regeneration. We report the first of many applications of the SASC system we have formulated to treat osteoarthritis (OA). Choosing growth factors important to chondrogenesis and encapsulating respective recombinant proteins in poly (lactic-coglycolic acid) 85:15 (PLGA) we fabricated the SASC system. We compared the antiinflammatory and chondroprotective effects of SASC to that of adipose-derived stem cells (ADSCs) using in vitro interleukin 1B-induced and in vivo collagenase-induced osteoarthritis rodent models. We have designed SASC as an injectable therapy with controlled release of the formulated secretome. In vitro, SASC showed significant antiinflammatory and chondroprotective effects as seen by the up-regulation of SOX9 and reduction of nitric oxide, ADAMTS5, and PRG4 genes compared to ADSCs. In vivo, treatment with SASC and ADSCs significantly attenuated cartilage degeneration and improved the biomechanical properties of the articular cartilage in comparison to OA control. This SASC system demonstrates the feasibility of developing a completely synthetic, tailorable stem cell secretome which reinforces the possibility of developing a new therapeutic strategy that provides better control over targeted tissue engineering applications.

Sprifermin: Effects on Cartilage Homeostasis and Therapeutic Prospects in Cartilage-Related Diseases

When suffering from osteoarthritis (OA), articular cartilage homeostasis is out of balance and the living quality declines. The treatment of knee OA has always been an unsolved problem in the world. At present, symptomatic treatment is mainly adopted for OA. Drug therapy is mainly used to relieve pain symptoms, but often accompanied with adverse reactions; surgical treatment involves the problem of poor integration between the repaired or transplanted tissues and the natural cartilage, leading to the failure of repair. Biotherapy which aims to promote cartilage in situ regeneration and to restore endochondral homeostasis is expected to be an effective method for the prevention and treatment of OA. Disease-modifying osteoarthritis drugs (DMOADs) are intended for targeted treatment of OA. The DMOADs prevent excessive destruction of articular cartilage through anti-catabolism and stimulate tissue regeneration via excitoanabolic effects. Sprifermin (recombinant human FGF18, rhFGF18) is an effective DMOAD, which can not only promote the proliferation of articular chondrocyte and the synthesis of extracellular matrix, increase the thickness of cartilage in a dose-dependent manner, but also inhibit the activity of proteolytic enzymes and remarkedly slow down the degeneration of cartilage. This paper reviews the unique advantages of Sprifermin in repairing cartilage injury and improving cartilage homeostasis, aiming to provide an important strategy for the effective prevention and treatment of cartilage injury-related diseases.

Using Platelet-Rich Plasma Hydrogel to Deliver Mesenchymal Stem Cells into Three-Dimensional PLGA Scaffold for Cartilage Tissue Engineering

The synthetic biodegradable polyester-based rigid porous scaffolds and cell-laden hydrogels have been separately employed as therapeutic modality for cartilage repair. However, the synthetic rigid scaffolds alone may be limited due to the inherent lack of bioactivity for cartilage regeneration, while the hydrogels have insufficient mechanical properties that are not ideal for load-bearing cartilage applications. In the present study, a hybrid construct was designed to merge the advantage of 3D-printed rigid poly(lactic-co-glycolic acid) (PLGA) scaffolds with cell-laden platelet-rich plasma (PRP) hydrogels that can release growth factors to regulate the tissue healing process. PRP hydrogels potentially achieved the effective delivery of mesenchymal stem cells (MSCs) into PLGA scaffolds. This hybrid construct could obtain adequate mechanical properties and independently provide MSCs with appropriate clues for proliferation and differentiation. Real-time gene expression analysis showed that PRP stimulated both chondrogenic and osteogenic differentiation of MSC seeding into PLGA scaffolds. Finally, the hybrid constructs were implanted into rabbits to simultaneously regenerate both articular cartilage and subchondral bone within osteochondral defects. Our findings suggest that this unique hybrid system could be practically applied for osteochondral regeneration due to its capacity for cell transportation, growth factors release, and excellent mechanical strength, which would greatly contribute to the progress of cartilage tissue engineering.

Mechanical Stress-Induced IGF-1 Facilitates col-I and col-III Synthesis via the IGF-1R/AKT/mTORC1 Signaling Pathway

Mechanical stress promotes human ligamentum flavum cells (LFCs) to synthesize multitype collagens, leading to ligamentum flavum hypertrophy (LFH). However, the mechanism of mechanical stress in the formation of collagen remains unclear. Therefore, we investigated the relationship between mechanical stress and collagen synthesis in the present study. First, LFCs were isolated from 9 patients and cultured with or without mechanical stress exposure for different times. IGF-1, collagen I (col-I), and collagen III (col-III) protein and mRNA levels were then detected via ELISA and qPCR, respectively. Moreover, the activation of pIGF-1R, pAKT, and pS6 was examined by Western blot analysis. To further explore the underlying mechanism, an IGF-1 neutralizing antibody, NVP-AEW541, and rapamycin were used. IGF-1, col-I, and col-III were significantly increased in stressed LFCs compared to nonstressed LFCs. In addition, the activation of pIGF-1R, pAKT, and pS6 was obviously enhanced in stressed LFCs. Interestingly, col-I protein, col-I mRNA, col-III protein, col-III mRNA, and IGF-1 protein, but not IGF-1 mRNA, were inhibited by IGF-1 neutralizing antibody. In addition, col-I and col-III protein and mRNA, but not IGF-1, were inhibited by both NVP-AEW541 and rapamycin. Moreover, the activation of pIGF-1R, pAKT, and pS6 was reduced by the IGF-1 neutralizing antibody and NVP-AEW541, and the activation of pS6 was reduced by rapamycin. In summary, these results suggested that mechanical stress promotes LFCs to produce IGF-1, which facilitates col-I and col-III synthesis via the IGF-1R/AKT/mTORC1 signaling pathway.

Smoking Is Associated with Anterior Ankle Impingement After Isolated Autologous Matrix-Induced Chondrogenesis for Osteochondral Lesions of the Talus

OBJECTIVE

To determine potential predictive associations between patient-/lesion-specific factors, clinical outcome and anterior ankle impingement in patients that underwent isolated autologous matrix-induced chondrogenesis (AMIC) for an osteochondral lesion of the talus (OLT).

DESIGN

Thirty-five patients with a mean age of 34.7 ± 15 years who underwent isolated cartilage repair with AMIC for OLTs were evaluated at a mean follow-up of 4.5 ± 1.9 years. Patients completed AOFAS (American Orthopaedic Foot and Ankle Society) scores at final follow-up, as well as Tegner scores at final follow-up and retrospectively for preinjury and presurgery time points. Pearson correlation and multivariate regression models were used to distinguish associations between patient-/lesion-specific factors, the need for subsequent surgery due to anterior ankle impingement and patient-reported outcomes.

RESULTS

At final follow-up, AOFAS and Tegner scores averaged 92.6 ± 8.3 and 5.1 ± 1.8, respectively. Both body mass index (BMI) and duration of symptoms were independent predictors for postoperative AOFAS and Δ preinjury to postsurgery Tegner with positive smoking status showing a trend toward worse AOFAS scores, but this did not reach statistical significance (P = 0.054). Nine patients (25.7%) required subsequent surgery due to anterior ankle impingement. Smoking was the only factor that showed significant correlation with postoperative anterior ankle impingement with an odds ratio of 10.61 when adjusted for BMI and duration of symptoms (95% CI, 1.04-108.57; P = 0.047).

CONCLUSION

In particular, patients with normal BMI and chronic symptoms benefit from AMIC for the treatment of OLTs. Conversely, smoking cessation should be considered before AMIC due to the increased risk of subsequent surgery and possibly worse clinical outcome seen in active smokers.

Methods of Modification of Mesenchymal Stem Cells and Conditions of Their Culturing for Hyaline Cartilage Tissue Engineering

The use of mesenchymal stromal cells (MSCs) for tissue engineering of hyaline cartilage is a topical area of regenerative medicine that has already entered clinical practice. The key stage of this procedure is to create conditions for chondrogenic differentiation of MSCs, increase the synthesis of hyaline cartilage extracellular matrix proteins by these cells and activate their proliferation. The first such works consisted in the indirect modification of cells, namely, in changing the conditions in which they are located, including microfracturing of the subchondral bone and the use of 3D biodegradable scaffolds. The most effective methods for modifying the cell culture of MSCs are protein and physical, which have already been partially introduced into clinical practice. Genetic methods for modifying MSCs, despite their effectiveness, have significant limitations. Techniques have not yet been developed that allow studying the effectiveness of their application even in limited groups of patients. The use of MSC modification methods allows precise regulation of cell culture proliferation, and in combination with the use of a 3D biodegradable scaffold, it allows obtaining a hyaline-like regenerate in the damaged area. This review is devoted to the consideration and comparison of various methods used to modify the cell culture of MSCs for their use in regenerative medicine of cartilage tissue.

Insulin-like growth factor-1 in articular cartilage repair for osteoarthritis treatment

Articular cartilage repair is a critical issue in osteoarthritis (OA) treatment. The insulin-like growth factor (IGF) signaling pathway has been implicated in articular cartilage repair. IGF-1 is a member of a family of growth factors that are structurally closely related to pro-insulin and can promote chondrocyte proliferation, enhance matrix production, and inhibit chondrocyte apoptosis. Here, we reviewed the role of IGF-1 in cartilage anabolism and catabolism. Moreover, we discussed the potential role of IGF-1 in OA treatment. Of note, we summarized the recent progress on IGF delivery systems. Optimization of IGF delivery systems will facilitate treatment application in cartilage repair and improve OA treatment efficacy.

Chondrogenic Potential of Dental-Derived Mesenchymal Stromal Cells

The field of tissue engineering has revolutionized the world in organ and tissue regeneration. With the robust research among regenerative medicine experts and researchers, the plausibility of regenerating cartilage has come into the limelight. For cartilage tissue engineering, orthopedic surgeons and orthobiologists use the mesenchymal stromal cells (MSCs) of various origins along with the cytokines, growth factors, and scaffolds. The least utilized MSCs are of dental origin, which are the richest sources of stromal and progenitor cells. There is a paradigm shift towards the utilization of dental source MSCs in chondrogenesis and cartilage regeneration. Dental-derived MSCs possess similar phenotypes and genotypes like other sources of MSCs along with specific markers such as dentin matrix acidic phosphoprotein (DMP) -1, dentin sialophosphoprotein (DSPP), alkaline phosphatase (ALP), osteopontin (OPN), bone sialoprotein (BSP), and STRO-1. Concerning chondrogenicity, there is literature with marginal use of dental-derived MSCs. Various studies provide evidence for in-vitro and in-vivo chondrogenesis by dental-derived MSCs. With such evidence, clinical trials must be taken up to support or refute the evidence for regenerating cartilage tissues by dental-derived MSCs. This article highlights the significance of dental-derived MSCs for cartilage tissue regeneration.

An Insulin-like Growth Factor-1 Conjugated Bombyx mori Silk Fibroin Film for Diabetic Wound Healing: Fabrication, Physicochemical Property Characterization, and Dosage Optimization In Vitro and In Vivo

This study aimed to develop a silk fibroin (SF)-film for the treatment of chronic diabetic wounds. Silk fibroin was purified through a newly developed heating degumming (HD) process and casted on a hydrophobic surface to form SF-films. The process allowed the fabricated film to achieve a 42% increase in transparency and a 32% higher proliferation rate for BALB/3T3 fibroblasts compared to that obtained by conventional alkaline degumming treatment. Fourier transform infrared analysis demonstrated that secondary structure was retained in both HD- and alkaline degumming-derived SF preparations, although the crystallinity of beta-sheet in SF-film after the HD processing was slightly increased. This study also investigated whether conjugating insulin-like growth factor-1 (IGF-1) would promote diabetic wound healing and what the optimal dosage is. Using BALB/3T3 cells grown in hyperglycemic medium as a model, it was demonstrated that the optimal IGF-1 dosage to promote the cell growth was approximately 0.65 pmol. Further analysis of wound healing in a diabetic mouse model indicated that SF-film loaded with 3.25 pmol of IGF-1 showed significantly superior wound closure, a 13% increase at the 13th day after treatment relative to treatment with 65 pmol of free IGF-1. Improvement in diabetic wound healing was exerted synergistically by SF-film and IGF-1, as reflected by parameters including levels of re-epithelialization, epithelial tissue area, and angiogenesis. Finally, IGF-1 increased the epithelial tissue area and micro-vessel formation in a dose-dependent manner in a low dosage range (3.25 pmol) when loaded to SF-films. Together, these results strongly suggest that SF-film produced using HD and loaded with a low dosage of IGF-1 is a promising dressing for diabetic wound therapy.

Microfracture Augmentation With Trypsin Pretreatment and Growth Factor-Functionalized Self-assembling Peptide Hydrogel Scaffold in an Equine Model

BACKGROUND

Microfracture augmentation can be a cost-effective single-step alternative to current cartilage repair techniques. Trypsin pretreatment combined with a growth factor-functionalized self-assembling KLD hydrogel ("functionalized hydrogel") has been shown to improve overall cartilage repair and integration to surrounding tissue in small animal models of osteochondral defects.

HYPOTHESIS

Microfracture combined with trypsin treatment and a functionalized hydrogel will improve reparative tissue quality and integration as compared with microfracture alone in an equine model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Bilateral cartilage defects (15-mm diameter) were created on the medial trochlear ridge of the femoropatellar joints in 8 adult horses (16 defects total). One defect was randomly selected to receive the treatment, and the contralateral defect served as the control (microfracture only). Treatment consisted of 2-minute trypsin pretreatment of the surrounding cartilage, subchondral bone microfracture, and functionalized hydrogel premixed with growth factors (platelet-derived growth factor and heparin-binding insulin-like growth factor 1). After surgery, all horses were subjected to standardized controlled exercise on a high-speed treadmill. Clinical evaluation was conducted monthly, and radiographic examinations were performed at 2, 16, 24, 32, 40, and 52 weeks after defect creation. After 12 months, all animals were euthanized. Magnetic resonance imaging, arthroscopy, gross pathologic evaluation of the joint, histology, immunohistochemistry, and biomechanical analyses were performed. Generalized linear mixed models (with horse as random effect) were utilized to assess outcome parameters. When P values were <.05, pairwise comparisons were made using least squares means.

RESULTS

Improved functional outcome parameters were observed for the treatment group, even though mildly increased joint effusion and subchondral bone sclerosis were noted on imaging. Microscopically, treatment resulted in improvement of several histologic parameters and overall quality of repaired tissue. Proteoglycan content based on safranin O-fast green staining was also significantly higher in the treated defects.

CONCLUSION

Trypsin treatment combined with functionalized hydrogel resulted in improved microfracture augmentation.

CLINICAL RELEVANCE

Therapeutic strategies for microfracture augmentation, such as those presented in this study, can be cost-effective ways to improve cartilage healing outcomes, especially in more active patients.

Autologous conditioned serum for degenerative diseases and prospects

Autologous conditioned serum (ACS) is a blood-derived product that is prepared by the incubation of whole blood with medical-grade glass beads, resulting in serum enrichment in interleukin-1 receptor antagonist (IL-1Ra), anti-inflammatory cytokines (IL-4, IL-10, and IL-13), and high concentrations of growth factors. ACS has shown qualitatively and quantitatively better therapeutic effects than most established pharmacological treatments and surgery for joint diseases given its ability to both target the inflammatory cascade to decrease cartilage destruction as well as improve endogenous repair mechanisms. ACS application is simple and safe with limited adverse effects. This article reviews the role of ACS in degenerative joint disease, in addition to other inflammatory and autoimmune diseases, given its regenerative and immune-modulating properties.

A roadmap to target interleukin-6 in osteoarthritis

Joint inflammation is present in the majority of OA patients and pro-inflammatory mediators, such as IL-6, are actively involved in disease progression. Increased levels of IL-6 in serum or synovial fluid from OA patients correlate with disease incidence and severity, with IL-6 playing a pivotal role in the development of cartilage pathology, e.g. via induction of matrix-degrading enzymes. However, IL-6 also increases expression of anti-catabolic factors, suggesting a protective role. Until now, this dual role of IL-6 is incompletely understood and may be caused by differential effects of IL-6 classic vs trans-signalling. Here, we review current evidence regarding the role of IL-6 classic- and trans-signalling in local joint pathology of cartilage, synovium and bone. Furthermore, we discuss targeting of IL-6 in experimental OA models and provide future perspective for OA treatment by evaluating currently available IL-6 targeting strategies.

Mesenchymal stem cells genetically engineered to express platelet-derived growth factor and heme oxygenase-1 ameliorate osteoarthritis in a canine model

BACKGROUND

Mesenchymal stem cells (MSCs) are used for the treatment of osteoarthritis (OA), and MSC genetic engineering is expected to enhance cartilage repair. Here, we aimed to investigate the effect of MSCs overexpressing platelet-derived growth factor (PDGF) or heme oxygenase-1 (HO-1) in chondrocytes and synovial cells with an OA phenotype and assess the in vivo efficacy of intra-articular injections of these MSCs in canine OA models.

METHODS

Canine adipose-derived MSCs were transfected with canine PDGF (PDGF-MSCs) or HO-1 (HO-1-MSCs) using lentiviral vectors. Canine chondrocytes or synovial cells were stimulated with lipopolysaccharide (LPS) to mimic the inflammatory OA model and then co-cultured with MSCs, PDGF-MSCs, or HO-1-MSCs for 24 h and 72 h. The mRNA levels of pro-inflammatory, extracellular matrix-degradative/synthetic, or pain-related factors were measured after co-culture by real-time PCR. Furthermore, a surgery-induced canine OA model was established and the dogs were randomized into four groups: normal saline (n = 4), MSCs (n = 4), PDGF-MSCs (n = 4), and HO-1-MSCs (n = 4). The OA symptoms, radiographic OA severity, and serum matrix metallopeptidase (MMP)-13 levels were assessed before and 10 weeks after treatment, to evaluate the safety and efficacy of the modified MSCs.

RESULTS

PDGF or HO-1 overexpression significantly reduced the expression of pro-inflammatory factors, MMP-13, and nerve growth factor elicited by LPS and increased that of aggrecan and collagen type 2 in chondrocytes (P < 0.05). In addition, the expression of aggrecanases was significantly downregulated in synovial cells, whereas that of tissue inhibitor of metalloproteinases was upregulated (P < 0.05). Furthermore, the co-cultured MSCs highly expressed genes that contributed to the maintenance of joint homeostasis (P < 0.05). In vivo studies showed that OA symptoms improved after administration of all MSCs. Also, PDGF-MSCs significantly improved limb function and reduced pain (P < 0.05). The results of the radiographic assessment and serum MMP-13 levels did not vary significantly compared to those of the control.

CONCLUSIONS

Genetically modifying PDGF and HO-1 in MSCs is an effective strategy for treating OA, suggesting that PDGF-MSCs can be novel therapeutic agents for improving OA symptoms.

Advanced protein adsorption properties of a novel silicate-based bioceramic: A proteomic analysis

Silicate bioceramics have been shown to possess excellent cytocompatibility and osteogenic activity, but the exact mechanism is still unclear. Protein adsorption is the first event taking place at the biomaterial-tissue interface, which is vital to the subsequent cellular behavior and further influence the biomaterial-tissue interaction. In this work, the protein adsorption behavior of a novel CPS bioceramic was evaluated using the proteomics technology. The results showed that CPS adsorbed more amount and types of serum proteins than HA. FN1 and IGF1 proteins selected from proteomics results were validated by Western-blot experiment. Pathway analysis also revealed mechanistic insights how these absorbed proteins by CPS help mediate cell adhesion and promotes osteogenic activity. Firstly, the dramatically enhanced adsorption of FN1 could greatly promote cell adhesion and growth. Secondly, IGF1 was uniquely adsorbed on CPS bioceramic and IGF1 could activate Rap1 signaling pathway to promote cell adhesion. Thirdly, the increased adsorption of FN1, IGF1 and COL1A2 proteins on CPS explains its better ability on bone regeneration than HA. Fourthly, the increased adsorption of IGF1, CHAD, COL2A1 and THBS4 proteins on CPS explains its ability on cartilage formation. Lastly, the increased adsorption of immunological related proteins on CPS may also play a positive role in bone regeneration. In addition, CPS had a much better cell adhesion ability than HA, proving that more adsorbed proteins really had a positive effect on cell behavior. The more adsorbed proteins on CPS than HA might indicated a better bone regeneration rate at early stage of implantation.

HA-g-CS Implant and Moderate-intensity Exercise Stimulate Subchondral Bone Remodeling and Promote Repair of Osteochondral Defects in Mice

Background: Substantial evidence shows that crosstalk between cartilage and subchondral bone may play an important role in cartilage repair. Animal models have shown that hydroxyapatite-grafted-chitosan implant (HA-g-CS) and moderate-intensity exercise promote regeneration of osteochondral defects. However, no in vivo studies have demonstrated that these two factors may have a synergistic activity to facilitate subchondral bone remodeling in mice, thus supporting bone-cartilage repair. Questions: This study was to clarify whether HA-g-CS and moderate-intensity exercise might have a synergistic effect on facilitating (1) regeneration of osteochondral defects and (2) subchondral bone remodeling in a mouse model of osteochondral defects. Methods: Mouse models of osteochondral defects were created and divided into four groups. BC Group was subjected to no treatment, HC Group to HA-g-CS implantation into osteochondral defects, ME group to moderate-intensity treadmill running exercise, and HC+ME group to both HA-g-CS implantation and moderate-intensity exercise until sacrifice. Extent of subchondral bone remodeling at the injury site and subsequent cartilage repair were assessed at 4 weeks after surgery. Results: Compared with BC group, HC, ME and HC+ME groups showed more cartilage repair and thicker articular cartilage layers and HC+ME group acquired the best results. The extent of cartilage repair was correlated positively to bone formation activity at the injured site as verified by microCT and correlation analysis. Histology and immunofluorescence staining confirmed that bone remodeling activity was increased in HC and ME groups, and especially in HC+ME group. This bone formation process was accompanied by an increase in osteogenesis and chondrogenesis factors at the injury site which promoted cartilage repair. Conclusions: In a mouse model of osteochondral repair, HA-g-CS implant and moderate-intensity exercise may have a synergistic effect on improving osteochondral repair potentially through promotion of subchondral bone remodeling and generation of osteogenesis and chondrogenesis factors. Clinical Relevance: Combination of HA-g-CS implantation and moderate-intensity exercise may be considered potentially in clinic to promote osteochondral defect repair. Also, cartilage and subchondral bone forms a functional unit in an articular joint and subchondral bone may regulate cartilage repair by secreting growth factors in its remodeling process. However, a deeper insight into the exact role of HA-g-CS implantation and moderate-intensity exercise in promoting osteochondral repair in other animal models should be explored before they can be applied in clinic in the future.

Hyaluronic acid-binding insulin-like growth factor-1: Creation of a gene encoding a bifunctional fusion protein

Chondrogenic growth factors are promising therapeutic agents for articular cartilage repair. A persistent impediment to fulfilling this promise is a limited ability to apply and retain the growth factors within the region of cartilage damage that is in need of repair. Current therapies successfully deliver cells and/or matrices, but growth factors are subject to diffusion into the joint space and then loss from the joint. To address this problem, we created a novel gene that encodes a bifunctional fusion protein comprised by a matrix binding domain and a growth factor. The gene encodes the hyaluronic acid binding region of the cartilage matrix molecule, versican, and the chondrogenic growth factor, insulin-like growth factor-1 (IGF-1). We delivered the gene in an adeno-associated virus-based plasmid vector to articular chondrocytes. The cells synthesized and secreted the fusion protein gene product. The fusion protein bound to hyaluronic acid and retained the anabolic and mitogenic actions of IGF-1 on the chondrocytes. This proof-of-concept study suggests that the bifunctional fusion protein, in concert with chondrocytes and a hyaluronic acid-based delivery vehicle, may serve as an intra-articular therapy to help achieve articular cartilage repair.

Potential of Soluble Decellularized Extracellular Matrix for Musculoskeletal Tissue Engineering - Comparison of Various Mesenchymal Tissues

Background

It is well studied that preparations of decellularized extracellular matrix (ECM) obtained from mesenchymal tissues can function as biological scaffolds to regenerate injured musculoskeletal tissues. Previously, we reported that soluble decellularized ECMs derived from meniscal tissue demonstrated excellent biocompatibility and produced meniscal regenerate with native meniscal anatomy and biochemical characteristics. We therefore hypothesized that decellularized mesenchymal tissue ECMs from various mesenchymal tissues should exhibit tissue-specific bioactivity. The purpose of this study was to test this hypothesis using porcine tissues, for potential applications in musculoskeletal tissue engineering.

Methods

Nine types of porcine tissue, including cartilage, meniscus, ligament, tendon, muscle, synovium, fat pad, fat, and bone, were decellularized using established methods and solubilized. Although the current trend is to develop tissue specific decellularization protocols, we selected a simple standard protocol across all tissues using Triton X-100 and DNase/RNase after mincing to compare the outcome. The content of sulfated glycosaminoglycan (sGAG) and hydroxyproline were quantified to determine the biochemical composition of each tissue. Along with the concentration of several growth factors, known to be involved in tissue repair and/or maturation, including bFGF, IGF-1, VEGF, and TGF-β1. The effect of soluble ECMs on cell differentiation was explored by combining them with 3D collagen scaffold culturing human synovium derived mesenchymal stem cells (hSMSCs).

Results

The decellularization of each tissue was performed and confirmed both histologically [hematoxylin and eosin (H&E) and 4’,6-diamidino-2-phenylindole (DAPI) staining] and on the basis of dsDNA quantification. The content of hydroxyproline of each tissue was relatively unchanged during the decellularization process when comparing the native and decellularized tissue. Cartilage and meniscus exhibited a significant decrease in sGAG content. The content of hydroxyproline in meniscus-derived ECM was the highest when compared with other tissues, while sGAG content in cartilage was the highest. Interestingly, a tissue-specific composition of most of the growth factors was measured in each soluble decellularized ECM and specific differentiation potential was particularly evident in cartilage, ligament and bone derived ECMs.

Conclusion

In this study, soluble decellularized ECMs exhibited differences based on their tissue of origin and the present results are important going forward in the field of musculoskeletal regeneration therapy.

Influence of Conditioned Media on the Re-Differentiation Capacity of Human Chondrocytes in 3D Spheroid Cultures

A major challenge of cell-based therapy for cartilage lesions is the preservation of the chondrogenic phenotype during ex vivo cell cultivation. In this in vitro study, the chondro-inductive capacity of two different hyaline cartilage-conditioned cell culture media on human chondrocytes in 3D spheroids was determined. Media were conditioned by incubation of 200 mg/mL vital or devitalized cartilage matrix in growth media over 35 days. The media were analyzed for the content of soluble procollagen type (Col) II and glycosaminoglycans (GAGs) as well as released TGF-β1, IGF-1 and IGFBP3. Unconditioned medium served as a negative control while the positive medium control was supplemented with TGF-β1 and IGF-1. Spheroid cultures prepared from human chondrocytes were cultivated at 37 °C, 5% CO₂ and 21% O₂ in the respective media and controls. After 14 and 35 days, the deposition of ECM components was evaluated by histological analysis. Vital cartilage-conditioned medium contained significantly higher levels of Col II and active TGF-β1 compared to medium conditioned with the devitalized cartilage matrix. Despite these differences, the incubation with vital as well as devitalized cartilage conditioned medium led to similar results in terms of deposition of proteoglycans and collagen type II, which was used as an indicator of re-differentiation of human chondrocytes in spheroid cultures. However, high density 3D cell cultivation showed a positive influence on re-differentiation.

Dual delivery of stem cells and insulin-like growth factor-1 in coacervate-embedded composite hydrogels for enhanced cartilage regeneration in osteochondral defects

Exogenous dual delivery of progenitor cell population and therapeutic growth factors (GFs) is one of alternative tissue engineering strategies for osteochondral tissue regeneration. In the present study, an implantable dual delivery platform was developed using coacervates (Coa) (i.e., a tertiary complex of poly(ethylene argininylaspartate diglyceride) (PEAD) polycation, heparin, and cargo insulin-like growth factor-1 (IGF-1), in thiolated gelatin (gelatin-SH)/ poly(ethylene glycol) diacrylate (PEGDA) interpenetrating network (IPN) hydrogels. Since Coa is able to protect cargo GF and maintain its long-term bioactivity, it is speculated that Coa-mediated delivery of chondrogenic factor IGF-1 with the aid of adipose-derived stem cells (ADSCs) would synergistically facilitate osteochondral tissue repair during physiological regeneration process. Our results indicate that gelatin-SH/PEGDA IPN hydrogels demonstrated biocompatibility and mechanical properties for a possible long-term transplantation, and PEAD-base Coa exhibited a sustained release of bioactive IGF-1 over 3 weeks. Subsequently, released IGF-1 from Coa could effectively induce chondrogenic differentiation of embedded ADSCs in the hydrogel, by showing enhanced glycosaminoglycan deposition and expression of chondrogenesis-associated genes. More importantly, at 12 weeks post-implantation in a rabbit full thickness osteochondral defect model, the quality of regenerative tissues in both chondral and subchondral layers was significantly improved in dual delivery of ADSC and IGF-1 in Coa encapsulated in gelatin-SH/PEGDA IPN hydrogels, as compared with a single delivery of ADSC only and a dual delivery without Coa. Therefore, we conclude that our Coa-embedded composite hydrogel platform could effectively augment osteochondral tissue regeneration holds promise for a feasible osteoarthritis therapeutic application.

Stimulating Factors and Origins of Precursor Cells in Traumatic Heterotopic Ossification Around the Temporomandibular Joint in Mice

The contributing factors and the origins of precursor cells in traumatic heterotopic ossification around the temporomandibular joint (THO-TMJ), which causes obvious restriction of mouth opening and maxillofacial malformation, remain unclear. In this study, our findings demonstrated that injured chondrocytes in the condylar cartilage, but not osteoblasts in the injured subchondral bone, played definite roles in the development of THO-TMJ in mice. Injured condylar chondrocytes without articular disc reserves might secrete growth factors, such as IGF1 and TGFβ2, that stimulate precursor cells, such as endothelial cells and muscle-derived cells, to differentiate into chondrocytes or osteoblasts and induce THO-TMJ. Preserved articular discs can alleviate the pressure on the injured cartilage and inhibit the development of THO-TMJ by inhibiting the secretion of these growth factors from injured chondrocytes. However, the exact molecular relationships among trauma, the injured condylar cartilage, growth factors such as TGFβ2, and pressure need to be explored in detail in the future.

Is clinical effect of autologous conditioned serum in spontaneously occurring equine articular lameness related to ACS cytokine profile?

Background

Biologic’ therapies, such as autologous conditioned serum (ACS), are gaining popularity in treating orthopaedic conditions in equine veterinary medicine. Evidence is scarce regarding ACS constituents, and large inter-individual differences in cytokine and growth factor content have been demonstrated. The objective of the current study was to investigate the potential association between cytokine and growth factor content of ACS and clinical effect in harness racehorses with spontaneously occurring low-grade articular lameness. Horses received 3 intra-articular injections of ACS administered at approximately 2-week intervals. Lameness evaluation consisting of a trot-up with subsequent flexions tests was performed at inclusion and approximately 2 weeks after the last treatment (re-evaluation); horses were classified as responders when there was no detectable lameness on trot-up and a minimum of 50% reduction in flexion test scores at re-evaluation. Association between clinical outcome (responders vs. non-responders) and age, lameness grades at inclusion (both initial trot-up and after flexion tests), treatment interval, follow-up time and the ACS content of IL-1Ra, IGF-1 and TGF-β was determined by regression modelling.

Results

Outcome analysis was available for 19 of 20 included horses; 11 responded to treatment whereas 8 did not. There was considerable inter-individual variability in cytokine/growth factor content of ACS, and in the majority of the horses, the level of IL-10, IL-1β and TNF-α was below the detection limit. In the final multivariate logistic regression model, ACS content of IGF-1 and IL-1Ra was significantly associated with clinical response (P = 0.01 and P = 0.03, respectively). No association with clinical response was found for the other tested variables.

Conclusions

The therapeutic benefit of ACS may be related to higher levels of IL-1Ra and IGF-1. Our study corroborates previous findings of considerable inter-individual variability of cytokine- and growth factor content in ACS.

Tissue-Adhesive Paint of Silk Microparticles for Articular Surface Cartilage Regeneration

Current biomaterials and tissue engineering techniques have shown a promising efficacy on full-thickness articular cartilage defect repair in clinical practice. However, due to the difficulty of implanting biomaterials or tissue engineering constructs into a partial-thickness cartilage defect, it remains a challenge to provide a satisfactory cure in joint surface regeneration in the early and middle stages of osteoarthritis. In this study, we focused on a ready-to-use tissue-adhesive joint surface paint (JS-Paint) capable of promoting and enhancing articular surface cartilage regeneration. The JS-Paint is mainly composed of N-(2-aminoethyl)-4-(4-(hydroxymethyl)-2-methoxy-5-nitrosophenoxy) butanamide (NB)-coated silk fibroin microparticles and possess optimal cell adhesion, migration, and proliferation properties. NB-modified silk fibroin microparticles can directly adhere to the cartilage and form a smooth layer on the surface via the photogenerated aldehyde group of NB reacting with the -NH₂ groups of the cartilage tissue. JS-Paint treatment showed a significant promotion of cartilage regeneration and restored the smooth joint surface at 6 weeks postsurgery in a rabbit model of a partial-thickness cartilage defect. These findings revealed that silk fibroin can be utilized to bring about a tissue-adhesive paint. Thus, the JS-Paint strategy has some great potential to enhance joint surface regeneration and revolutionize future therapeutics of early and middle stages of osteoarthritis joint ailments.

Carbonic Anhydrase 12 Protects Endplate Cartilage From Degeneration Regulated by IGF-1/PI3K/CREB Signaling Pathway

Lumbar intervertebral disc degeneration (IVDD) is the most common cause of low back pain (LBP). Among all the factors leading to IVDD, lumbar cartilage endplate (LCE) degeneration is considered a key factor. In the present study, we investigate the effect and regulation of carbonic anhydrase 12 (CA12) in LCE, which catalyzes hydration of CO₂ and participates in a variety of biological processes, including acid-base balance and calcification. Our results show that CA12, downregulated in degenerated LCE, could maintain anabolism and prevent calcification in the endplate. Furthermore, CA12 is regulated by the IGF-1/IGF-1R/PI3K/CREB signaling pathway. When we overexpressed CA12 in LCE, the decreased anabolism induced by inflammatory cytokine could be rescued. In contrast, reducing CA12 expression, either with siRNA, PI3Kinhibitor, or CREB inhibitor, could downregulate anabolism and cause apoptosis and then calcification in LCE. The protective effects of IGF-1 are even diminished with low-expressed CA12. Similar results are also obtained in an ex vivo model. Consequently, our results reveal a novel pathway, IGF-1/IGF-1R/PI3K/CREB/CA12, that takes a protective role in LCE degeneration by maintaining anabolism and preventing calcification and apoptosis. This study proposes a novel molecular target, CA12, to delay LCE degeneration.

Dual growth factor delivery using PLGA nanoparticles in silk fibroin/PEGDMA hydrogels for articular cartilage tissue engineering

Degeneration of articular cartilage due to damages, diseases, or age-related factors can significantly decrease the mobility of the patients. Various tissue engineering approaches which take advantage of stem cells and growth factors in a three-dimensional constructs have been used for reconstructing articular tissue. Proliferative impact of basic fibroblast growth factor (bFGF) and chondrogenic differentiation effect of transforming growth factor-beta 1 (TGF-β1) over mesenchymal stem cells have previously been verified. In this study, silk fibroin (SF) and of poly(ethylene glycol) dimethacrylate (PEGDMA) were used to provide a versatile platform for preparing hydrogels with tunable mechanical, swelling and degradation properties through physical and chemical crosslinking as a microenvironment for chondrogenic differentiation in the presence of bFGF and TGF-β1 releasing nanoparticles (NPs) for the first time. Scaffolds with compressive moduli ranging from 95.70 ± 17.82 to 338.05 ± 38.24 kPa were obtained by changing both concentration PEGDMA and volume ratio of PEGDMA with 8% SF. Highest cell viability was observed in PEGDMA 10%-SF 8% (1:1) [PEG10-SF8(1:1)] hydrogel group. Release of bFGF and TGF-β1 within PEG10-SF8(1:1) hydrogels resulted in higher DNA and glycosaminoglycans amounts indicating synergistic effect of dual release over proliferation and chondrogenic differentiation of dental pulp stem cells in hydrogels, respectively. Our results suggested that simultaneous delivery of bFGF and TGF-β1 through utilization of PLGA NPs within PEG10-SF8(1:1) hydrogel provided a novel and versatile means for articular cartilage regeneration as they allow for dosage- and site-specific multiple growth factor delivery.

Trypsin Pre-Treatment Combined With Growth Factor Functionalized Self-Assembling Peptide Hydrogel Improves Cartilage Repair in Rabbit Model

The objective of this study was to improve cartilage repair and integration using self-assembling KLD hydrogel functionalized with platelet-derived growth factor-BB and heparin-binding insulin-like growth factor-1 with associated enzymatic trypsin pre-treatment of the native cartilage. Bilateral osteochondral defects were created at the central portion of the femoral trochlear groove of 48 skeletally mature, white New Zealand rabbits. One limb received a randomly assigned treatment and the contralateral limb served as the control. Treated defects were exposed to trypsin for 2 min and filled with self-assembling KLD hydrogel only, or associated to growth factors. All control limbs received KLD hydrogel alone or received only trypsin but not hydrogel. Ninety days post-defect creation, the rabbits were euthanized and magnetic resonance imaging, radiography, macroscopic evaluation, histology, and immunohistochemistry of the joint and repaired tissue were performed. Mixed model analyses of variance were utilized to assess the outcome parameters and individual comparisons were performed using Least Square Means procedure and differences with p-value < 0.05 were considered significant. Trypsin enzymatic pre-treatment improved cellular morphology, cluster formation and subchondral bone reconstitution. Platelet-derived growth factor-BB improved subchondral bone healing and basal integration. Heparin-binding insulin-like growth factor-1 associated with platelet-derived growth factor improved tissue and cell morphology. The authors conclude that self-assembling KLD hydrogel functionalized with platelet-derived growth factor and heparin-binding insulin-like growth factor-1 with associated enzymatic pre-treatment of the native cartilage with trypsin resulted in an improvement on the cartilage repair process. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2307-2315, 2019.

Cartilage-penetrating nanocarriers improve delivery and efficacy of growth factor treatment of osteoarthritis

Osteoarthritis is a debilitating joint disease affecting nearly 30 million people for which there are no disease-modifying therapies. Several drugs that have failed clinical trials have shown inefficient and inadequate delivery to target cells. Anabolic growth factors are one class of such drugs that could be disease-modifying if delivered directly to chondrocytes, which reside deep within dense, anionic cartilage tissue. To overcome this biological barrier, we conjugated a growth factor to a cationic nanocarrier for targeted delivery to chondrocytes and retention within joint cartilage after direct intra-articular injection. The nanocarrier uses reversible electrostatic interactions with anionic cartilage tissue to improve tissue binding, penetration, and residence time. Amine terminal polyamidoamine (PAMAM) dendrimers were end functionalized with variable molar ratios of poly(ethylene glycol) (PEG) to control surface charge. From this small family of variably PEGylated dendrimers, an optimal formulation showing 70% uptake into cartilage tissue and 100% cell viability was selected. When conjugated to insulin-like growth factor 1 (IGF-1), the dendrimer penetrated bovine cartilage of human thickness within 2 days and enhanced therapeutic IGF-1 joint residence time in rat knees by 10-fold for up to 30 days. In a surgical model of rat osteoarthritis, a single injection of dendrimer-IGF-1 rescued cartilage and bone more effectively than free IGF-1. Dendrimer-IGF-1 reduced width of cartilage degeneration by 60% and volumetric osteophyte burden by 80% relative to untreated rats at 4 weeks after surgery. These results suggest that PEGylated PAMAM dendrimer nanocarriers could improve pharmacokinetics and efficacy of disease-modifying osteoarthritis drugs in the clinic.

The Concentration of Plasma Provides Additional Bioactive Proteins in Platelet and Autologous Protein Solutions

BACKGROUND

Currently, platelet-poor plasma (PPP) is a discarded waste product of platelet-rich plasma (PRP) and may contain valuable proteins.

PURPOSE/HYPOTHESIS

The study's goal was to evaluate the concentration of plasma as a potential additive biotherapy for the treatment of osteoarthritis. We hypothesized that a novel polyacrylamide concentration device would efficiently concentrate insulin-like growth factor-1 (IGF-1) from PPP and be additive to PRP or autologous protein solution (APS).

STUDY DESIGN

Descriptive laboratory study.

METHODS

A laboratory study was conducted with human and equine whole blood from healthy volunteers/donors. Fresh samples of blood and plasma were processed and characterized for platelet, white blood cell, and growth factor/cytokine content and then quantified by enzyme-linked immunosorbent assays specific for IGF-1, transforming growth factor-β, interleukin-1β, and interleukin-1 receptor antagonist as representatives of cartilage anabolic and inflammatory mediators.

RESULTS

A potent cartilage anabolic protein, IGF-1, was significantly concentrated by the polyacrylamide concentration device in both human and equine PPP. The polyacrylamide device also substantially increased plasma proteins over whole blood, most dramatically key proteins relevant to the treatment of osteoarthritis, including transforming growth factor-β (29-fold over blood) and interleukin-1 receptor antagonist (70-fold over plasma).

CONCLUSION

Concentrated PPP is a unique source for biologically relevant concentrations of IGF-1. PRP and APS can produce greater concentrations of other anabolic and anti-inflammatory proteins not found in plasma.

CLINICAL RELEVANCE

The polyacrylamide device efficiently concentrated PPP to create a unique source of IGF-1 that may supplement orthopaedic biologic therapies.

Secreted α-Klotho maintains cartilage tissue homeostasis by repressing NOS2 and ZIP8-MMP13 catabolic axis

Progressive loss of tissue homeostasis is a hallmark of numerous age-related pathologies, including osteoarthritis (OA). Accumulation of senescent chondrocytes in joints contributes to the age-dependent cartilage loss of functions through the production of hypertrophy-associated catabolic matrix-remodeling enzymes and pro-inflammatory cytokines. Here, we evaluated the effects of the secreted variant of the anti-aging hormone α-Klotho on cartilage homeostasis during both cartilage formation and OA development. First, we found that α-Klotho expression was detected during mouse limb development, and transiently expressed during in vitro chondrogenic differentiation of bone marrow-derived mesenchymal stem cells. Genome-wide gene array analysis of chondrocytes from OA patients revealed that incubation with recombinant secreted α-Klotho repressed expression of the NOS2 and ZIP8/MMP13 catabolic remodeling axis. Accordingly, α-Klotho expression was reduced in chronically IL1β-treated chondrocytes and in cartilage of an OA mouse model. Finally, in vivo intra-articular secreted α-Kotho gene transfer delays cartilage degradation in the OA mouse model. Altogether, our results reveal a new tissue homeostatic function for this anti-aging hormone in protecting against OA onset and progression.

Estrogen Promotes Mandibular Condylar Fibrocartilage Chondrogenesis and Inhibits Degeneration via Estrogen Receptor Alpha in Female Mice

Temporomandibular joint degenerative disease (TMJ-DD) is a chronic form of TMJ disorder that specifically afflicts people over the age of 40 and targets women at a higher rate than men. Prevalence of TMJ-DD in this population suggests that estrogen loss plays a role in the disease pathogenesis. Thus, the goal of the present study was to determine the role of estrogen on chondrogenesis and homeostasis via estrogen receptor alpha (ERα) during growth and maturity of the joint. Young and mature WT and ERαKO female mice were subjected to ovariectomy procedures and then given placebo or estradiol treatment. The effect of estrogen via ERα on fibrocartilage morphology, matrix production, and protease activity was assessed. In the young mice, estrogen via ERα promoted mandibular condylar fibrocartilage chondrogenesis partly by inhibiting the canonical Wnt signaling pathway through upregulation of sclerostin (Sost). In the mature mice, protease activity was partly inhibited with estrogen treatment via the upregulation and activity of protease inhibitor 15 (Pi15) and alpha-2-macroglobulin (A2m). The results from this work provide a mechanistic understanding of estradiol on TMJ growth and homeostasis and can be utilized for development of therapeutic targets to promote regeneration and inhibit degeneration of the mandibular condylar fibrocartilage.