Quantitative histological grading methods to assess subchondral bone and synovium changes subsequent to medial meniscus transection in the rat

Preclinical Studies and Clinical Trials on Cell-Based Treatments for Meniscus Regeneration

This study aims at performing a thorough review of cell-based treatment strategies for meniscus regeneration in preclinical and clinical studies. The PubMed, Embase, and Web of Science databases were searched for relevant studies (both preclinical and clinical) published from the time of database construction to December 2022. Data related to cell-based therapies for in situ regeneration of the meniscus were extracted independently by two researchers. Assessment of risk of bias was performed according to the Cochrane Handbook for Systematic Reviews of Interventions. Statistical analyses based on the classification of different treatment strategies were performed. A total of 5730 articles were retrieved, of which 72 preclinical studies and 6 clinical studies were included in this review. Mesenchymal stem cells (MSCs), especially bone marrow MSCs (BMSCs), were the most commonly used cell type. Among preclinical studies, rabbit was the most commonly used animal species, partial meniscectomy was the most commonly adopted injury pattern, and 12 weeks was the most frequently chosen final time point for assessing repair outcomes. A range of natural and synthetic materials were used to aid cell delivery as scaffolds, hydrogels, or other morphologies. In clinical trials, there was large variation in the dose of cells, ranging from 16 × 106 to 150 × 106 cells with an average of 41.52 × 106 cells. The selection of treatment strategy for meniscus repair should be based on the nature of the injury. Cell-based therapies incorporating various "combination" strategies such as co-culture, composite materials, and extra stimulation may offer greater promise than single strategies for effective meniscal tissue regeneration, restoring natural meniscal anisotropy, and eventually achieving clinical translation. Impact Statement This review provides an up-to-date and comprehensive overview of preclinical and clinical studies that tested cell-based treatments for meniscus regeneration. It presents novel perspectives on studies published in the past 30 years, giving consideration to the cell sources and dose selection, delivery methods, extra stimulation, animal models and injury patterns, timing of outcome assessment, and histological and biomechanical outcomes, as well as a summary of findings for individual studies. These unique insights will help to shape future research on the repair of meniscus lesions and inform the clinical translation of new cell-based tissue engineering strategies.

Intra-articular delivery of an indoleamine 2,3-dioxygenase galectin-3 fusion protein for osteoarthritis treatment in male Lewis rats

OBJECTIVE

Osteoarthritis (OA) is driven by low-grade inflammation, and controlling local inflammation may offer symptomatic relief. Here, we developed an indoleamine 2,3-dioxygenase and galectin-3 fusion protein (IDO-Gal3), where IDO increases the production of local anti-inflammatory metabolites and Gal3 binds carbohydrates to extend IDO's joint residence time. In this study, we evaluated IDO-Gal3's ability to alter OA-associated inflammation and pain-related behaviors in a rat model of established knee OA.

METHODS

Joint residence was first evaluated with an analog Gal3 fusion protein (NanoLuc™ and Gal3, NL-Gal3) that produces luminescence from furimazine. OA was induced in male Lewis rats via a medial collateral ligament and medial meniscus transection (MCLT + MMT). At 8 weeks, NL or NL-Gal3 were injected intra-articularly (n = 8 per group), and bioluminescence was tracked for 4 weeks. Next, IDO-Gal3s's ability to modulate OA pain and inflammation was assessed. Again, OA was induced via MCLT + MMT in male Lewis rats, with IDO-Gal3 or saline injected into OA-affected knees at 8 weeks post-surgery (n = 7 per group). Gait and tactile sensitivity were then assessed weekly. At 12 weeks, intra-articular levels of IL6, CCL2, and CTXII were assessed.

RESULTS

The Gal3 fusion increased joint residence in OA and contralateral knees (p < 0.0001). In OA-affected animals, both saline and IDO-Gal3 improved tactile sensitivity (p = 0.008), but IDO-Gal3 also increased walking velocities (p ≤ 0.033) and improved vertical ground reaction forces (p ≤ 0.04). Finally, IDO-Gal3 decreased intra-articular IL6 levels within the OA-affected joint (p = 0.0025).

CONCLUSION

Intra-articular IDO-Gal3 delivery provided long-term modulation of joint inflammation and pain-related behaviors in rats with established OA.

Intra-Articular Delivery of an Indoleamine 2,3-Dioxygenase Galectin-3 Fusion Protein for Osteoarthritis Treatment in Male Lewis Rats

Objective : Controlling joint inflammation can improve osteoarthritis (OA) symptoms; however, current treatments often fail to provide long-term effects. We have developed an indoleamine 2,3-dioxygenase and galectin-3 fusion protein (IDO-Gal3). IDO converts tryptophan to kynurenines, directing the local environment toward an anti-inflammatory state; Gal3 binds carbohydrates and extends IDO's joint residence time. In this study, we evaluated IDO-Gal3's ability to alter OA-associated inflammation and pain-related behaviors in a rat model of established knee OA. Methods : Joint residence was first evaluated with an analog Gal3 fusion protein (NanoLuc™ and Gal3, NL-Gal3) that produces luminescence from furimazine. OA was induced in male Lewis rats via a medial collateral ligament and medial meniscus transection (MCLT+MMT). At 8 weeks, NL or NL-Gal3 were injected intra-articularly (n=8 per group), and bioluminescence was tracked for 4 weeks. Next, IDO-Gal3's ability to modulate OA pain and inflammation was assessed. Again, OA was induced via MCLT+MMT in male Lewis rats, with IDO-Gal3 or saline injected into OA-affected knees at 8 weeks post-surgery (n=7 per group). Gait and tactile sensitivity were then assessed weekly. At 12 weeks, intra-articular levels of IL6, CCL2, and CTXII were assessed. Results : The Gal3 fusion increased joint residence in OA and contralateral knees (p<0.0001). In OA-affected animals, IDO-Gal3 improved tactile sensitivity (p=0.002), increased walking velocities (p≤0.033), and improved vertical ground reaction forces (p≤0.04). Finally, IDO-Gal3 decreased intra-articular IL6 levels within the OA-affected joint (p=0.0025). Conclusion : Intra-articular IDO-Gal3 delivery provided long-term modulation of joint inflammation and pain-related behaviors in rats with established OA.

Transcriptomic analyses of joint tissues during osteoarthritis development in a rat model reveal dysregulated mechanotransduction and extracellular matrix pathways

OBJECTIVE

Transcriptomic changes in joint tissues during the development of osteoarthritis (OA) are of interest for the discovery of biomarkers and mechanisms of disease. The objective of this study was to use the rat medial meniscus transection (MMT) model to discover stage and tissue-specific transcriptomic changes.

DESIGN

Sham or MMT surgeries were performed in mature rats. Cartilage, menisci and synovium were scored for histopathological changes at 2, 4 and 6 weeks post-surgery and processed for RNA-sequencing. Differentially expressed genes (DEG) were used to identify pathways and mechanisms. Published transcriptomic datasets from animal models and human OA were used to confirm and extend present findings.

RESULTS

The total number of DEGs was already high at 2 weeks (723 in meniscus), followed by cartilage (259) and synovium (42) and declined to varying degrees in meniscus and synovium but increased in cartilage at 6 weeks. The most upregulated genes included tenascins. The 'response to mechanical stimulus' and extracellular matrix-related pathways were enriched in both cartilage and meniscus. Pathways that were enriched in synovium at 4 weeks indicate processes related to synovial hyperplasia and fibrosis. Synovium also showed upregulation of IL-11 and several MMPs. The mechanical stimulus pathway included upregulation of the mechanoreceptors PIEZO1, PIEZO2 and TRPV4 and nerve growth factor. Analysis of data from prior RNA-sequencing studies of animal models and human OA support these findings.

CONCLUSION

These results indicate several shared pathways that are affected during OA in cartilage and meniscus and support the role of mechanotransduction and other pathways in OA pathogenesis.

Measures of cardiovascular function suggest autonomic nervous system dysregulation after surgical induction of joint injury in the male Lewis rat

OBJECTIVES

Functional changes in the autonomic nervous system may help explain variability in the progression of knee osteoarthritis (OA). Thus, the objective of this study was to evaluate autonomic nervous system shifts, measured via heart rate response variables, in rat knee joint injury and OA models.

METHODS

Cardiovascular characteristics were measured at baseline and bi-weekly for 8 weeks after skin incision, medial collateral ligament transection (MCLT), or MCLT+medial meniscus transection (MCLT+MMT). Heart rate was also assessed during a mild stressor (elevated maze). At endpoint, cardiovascular responses to mechanical knee stimuli were evaluated, as well as responses to 1-phenylbiguanide, a 5HT_3A receptor agonist with reported ability to stimulate vagal responses.

RESULTS

During low activity, a slower heart rate occurred in MCLT (299 ± 10 bpm) and MCLT+MMT (310 ± 10 bpm) animals compared to controls (325 ± 10 bpm). Furthermore, patellar ligament mechanical stimuli produced an immediate decrease in heart rate and blood pressure in all groups. Finally, a larger drop in heart rate was observed in MCLT (252 ± 40 bpm) and MCLT+MMT (263 ± 49 bpm) following administration of 1-phenylbiguanide compared to skin incision (168 ± 45 bpm).

CONCLUSIONS

Acute mechanical stimulation of the patellar ligament produced drops in heart rate, suggesting a possible joint-brain connection that modulates autonomic responses. With both joint injury, cardiac vagal activation was altered in response to pharmacological stimulation, with chronic longitudinal heart rate reduction. These data provide some preliminary evidence of potential functional shifts in autonomic nervous system function in models of joint injury and OA.

Sodium alginate microencapsulation of human mesenchymal stromal cells modulates paracrine signaling response and enhances efficacy for treatment of established osteoarthritis

Mesenchymal stromal cells (MSCs) have shown promise as osteoarthritis (OA) treatments; however, effective translation has been limited by high variability and heterogeneity of MSCs, suboptimal delivery strategies, and poor understanding of critical quality and potency attributes. Furthermore, most pre-clinical studies of MSC therapeutics for OA have focused on delaying OA development and not on treating established OA, which brings added clinical relevance. Thus, the objective of the current study was to assess the effects of sodium alginate microencapsulation on human MSC (hMSC) secretion of immunomodulatory cytokines in an OA microenvironment and therapeutic efficacy in treating established OA. A Medial Meniscal Transection (MMT) pre-clinical model of OA was implemented. Three weeks post-surgery, after OA was established, intra-articular injections of encapsulated hMSCs or nonencapsulated hMSCs were administered. Six weeks post-surgery, microstructural changes in the knee joint were quantified using microCT. Encapsulated hMSCs reduced articular cartilage degeneration and subchondral bone remodeling. A multiplexed immunoassay panel was used to profile the in vitro secretome of hMSCs in response to IL-1β. Nonencapsulated hMSCs showed an indiscriminate increase in all cytokines in response to IL-1β while encapsulated hMSCs showed a targeted secretory response with increased expression of pro-inflammatory (IL-1β, IL-6, IL-7, IL-8), anti-inflammatory (IL-1RA), and chemotactic (G-CSF, MDC, IP10) cytokines. These data show that sodium alginate microencapsulation can modulate hMSC paracrine signaling and enhance the therapeutic efficacy of the hMSCs in treating established OA. This cytokine profile provides a foundation for the identification of key factors affecting the overall potency of hMSC therapeutics for OA. STATEMENT OF SIGNIFICANCE: While there has been considerable interest in material based MSC encapsulation for treatment of OA, there are critical gaps in our translational understanding of these biomaterial-based technologies for OA. More specifically, previous studies have several important limitations: (1) they have been largely focused on preventing OA development, which limits their translational utility and (2) little prior work has been done to delineate potential routes/mechanisms by which material encapsulation alters MSC therapeutic action. In our manuscript, we aimed to fill these gaps in knowledge by testing the hypotheses that: (1) hMSC encapsulation can attenuate established disease progression, which is a more clinically relevant scenario and (2) hMSC encapsulation significantly changes the secreted paracrine factors from hMSCs.

Refining surgical models of osteoarthritis in mice and rats alters pain phenotype but not joint pathology

The relationship between osteoarthritis (OA) structural change and pain is complex. Surgical models of OA in rodents are often rapid in onset, limiting mechanistic utility and translational validity. We aimed to investigate the effect of refining surgical small rodent models of OA on both joint pathology and pain behaviour. Adult male C57BL/6 mice (n = 76, 10-11 weeks of age at time of surgery) underwent either traditional (transection of the medial meniscotibial ligament [MMTL]) or modified (MMTL left intact, transection of the coronary ligaments) DMM surgery, or sham surgery. Adult male Sprague Dawley rats (n = 76, weight 175-199g) underwent either modified meniscal transection (MMNX) surgery (transection of the medial meniscus whilst the medial collateral ligament is left intact) or sham surgery. Pain behaviours (weight bearing asymmetry [in mice and rats] and paw withdrawal thresholds [in rats]) were measured pre-surgery and weekly up to 16 weeks post-surgery. Post-mortem knee joints were scored for cartilage damage, synovitis, and osteophyte size. There was a significant increase in weight bearing asymmetry from 13 weeks following traditional, but not modified, DMM surgery when compared to sham operated mice. Both traditional and modified DMM surgery led to similar joint pathology. There was significant pain behaviour from 6 weeks following MMNX model compared to sham operated control rats. Synovitis was significant 4 weeks after MMNX surgery, whereas significant chondropathy was first evident 8 weeks post-surgery, compared to sham controls. Pain behaviour is not always present despite significant changes in medial tibial plateau cartilage damage and synovitis, reflecting the heterogeneity seen in human OA. The development of a slowly progressing surgical model of OA pain in the rat suggests that synovitis precedes pain behaviour and that chondropathy is evident later, providing the foundations for future mechanistic studies into the disease.

Use of magnetic capture to identify elevated levels of CCL2 following intra-articular injection of monoiodoacetate in rats

PURPOSE

Synovial fluid biomarkers help evaluate osteoarthritis (OA) development. Magnetic capture, our new magnetic nanoparticle-based technology, has proven to be effective for determining extracellular matrix fragment levels in two rat OA models. Here, the feasibility of magnetic capture for detecting monocyte chemoattractant protein-1 (MCP-1 or CCL2) is demonstrated after intra-articular injection of monoiodoacetate (MIA) in the rat knee.

METHODS

Forty-eight male Lewis rats received a right hind limb, intra-articular injection of MIA (1 mg in 25 µl of saline) or 25 µl of saline. Magnetic capture and lavage were performed at 7 days after injection (n = 6 per treatment per procedure), with magnetic capture additionally performed at 14 and 28 days post-injection (n = 6 per treatment per time point). CCL2 was also assessed in serum.

RESULTS

Serum CCL2 levels revealed no difference between MIA and saline animals (p = 0.0851). In contrast, magnetic capture and lavage detected a significant increase of CCL2 in the MIA-injected knee, with the MIA-injected knee having elevated CCL2 compared to contralateral and saline-injected knees (p = 0.00016 (contralateral) and p = 0.00016 (saline) for magnetic capture; p = 0.00023 (contralateral) and p = 0.00049 (saline) for lavage).

CONCLUSIONS

Magnetic capture of CCL2 was successfully developed and applied to determine levels of CCL2 in a rat knee. Magnetic capture detected a statistically significant increase of CCL2 in MIA-injected knees compared to controls, and CCL2 levels stayed relatively stable from week 1 through week 4 post-MIA injection.

Histological scoring system for subchondral bone changes in murine models of joint aging and osteoarthritis

To establish a histopathological scoring system for changes in subchondral bone in murine models of knee osteoarthritis (OA), three key parameters, subchondral bone plate (Subcho.BP) consisting of the combination of Subcho.BP.thickness (Subcho.BP.Th) and angiogenesis, bone volume (BV/TV) and osteophytes, were selected. The new grading system was tested in two mouse OA models, (1) senescence accelerated mouse (SAM)-prone 8 (SAMP8) as spontaneous OA model with SAM-resistant 1 (SAMR1) as control; (2) destabilization of the medial meniscus in C57BL/6 mice as surgical OA model. Results of the spontaneous OA model showed that Subcho.BP.Th was significantly wider, angiogenesis was greater, and BV/TV was higher in SAMP8 than SAMR1. Notably, subchondral bone score was dramatically higher in SAMP8 at 6 weeks than SAMR1, while OARSI cartilage scores became higher only at 14 weeks. In the surgical OA model, the results were similar to the spontaneous OA model, but osteophytes appeared earlier. There were strong correlations both in Subcho.BP.Th and BV/TV between this scoring system and µCT (r = 0.89, 0.84, respectively). Inter-rater reliabilities for each parameter using this system were more than 0.943. We conclude that this new histopathological scoring system is readily applicable for evaluating the early changes in aging and OA-affected murine subchondral bone.

The effects of age on the severity of joint damage and intra-articular inflammation following a simulated medial meniscus injury in 3, 6, and 9 month old male rats

Purpose: Aging is a known risk factor for osteoarthritis (OA). Several transgenic rodent models have been used to investigate the effects of accelerated or delayed aging in articular joints. However, age-effects on the progression of post-traumatic OA are less frequently evaluated. The objective of this study is to evaluate how animal age affects the severity of intra-articular inflammation and joint damage in the rat medial collateral ligament plus medial meniscus transection (MCLT+MMT) model of knee OA.Methods: Forty-eight, male Lewis rats were aged to 3, 6, or 9 months old. At each age, eight rats received either an MCLT+MMT surgery or a skin-incision. At 2 months post-surgery, intra-articular evidence of CTXII, IL1β, IL6, TNFα, and IFNγ was evaluated using a multiplex magnetic capture technique, and histological evidence of OA was assessed via a quantitative histological scoring technique.Results: Elevated levels of CTXII and IL6 were found in MCLT+MMT knees relative to skin-incision and contralateral controls; however, animal age did not affect the severity of joint inflammation. Conversely, histological investigation of cartilage damage showed larger cartilage lesion areas, greater width of affected cartilage, and more evidence of hypertrophic cartilage damage in MCLT+MMT knees with age.Conclusions: These data indicate the severity of cartilage damage subsequent to MCLT+MMT surgery is related to the rat's age at the time of injury. However, despite greater levels of cartilage damage, the level of intra-articular inflammation was not necessarily affected in 3, 6, and 9 month old male rats.

Erxian Decoction Attenuates TNF-α Induced Osteoblast Apoptosis by Modulating the Akt/Nrf2/HO-1 Signaling Pathway

Erxian decoction (EXD), a traditional Chinese medicine formula, has been used for treatment of osteoporosis for many years. The purpose of this study was to investigate the pharmacological effect of EXD in preventing osteoblast apoptosis and the underlying mechanism of prevention. Putative targets of EXD were predicted by network pharmacology, and functional and pathway enrichment analyses were also performed. Evaluations of bone mineral density, serum estradiol level, trabecular area fraction, serum calcium levels, and tumor necrosis factor (TNF)-α levels in ovariectomized rats, as well as cell proliferation assays, apoptosis assays, and western blotting in MC3T3-E1 osteoblasts were performed for further experimental validation. Ninety-three active ingredients in the EXD formula and 259 potential targets were identified. Functional and pathway enrichment analyses indicated that EXD significantly influenced the PI3K-Akt signaling pathway. In vivo experiments indicated that EXD treatment attenuated bone loss and decreased TNF-α levels in rats with osteoporosis. In vitro experiments showed that EXD treatment increased cell viability markedly and decreased levels of caspase-3 and the rate of apoptosis. It also promoted phosphorylation of Akt, nuclear translocation of transcription factor NF-erythroid 2-related factor (Nrf2), and hemeoxygenase-1 (HO-1) expression in TNF-α-induced MC3T3-E1 cells. Our results suggest that EXD exerted profound anti-osteoporosis effects, at least partially by reducing production of TNF-α and attenuating osteoblast apoptosis via Akt/Nrf2/HO-1 signaling pathway.

Therapeutic efficacy of intra-articular delivery of encapsulated human mesenchymal stem cells on early stage osteoarthritis

Mesenchymal stem cells (MSCs) represent a great therapeutic promise in pre-clinical models of osteoarthritis (OA), but many questions remain as to their therapeutic mechanism of action: engraftment versus paracrine action. Encapsulation of human MSCs (hMSCs) in sodium alginate microspheres allowed for the paracrine signaling properties of these cells to be isolated and studied independently of direct cellular engraftment. The objective of the present study was to quantitatively assess the efficacy of encapsulated hMSCs as a disease-modifying therapeutic for OA, using a medial meniscal tear (MMT) rat model. It was hypothesized that encapsulated hMSCs would have a therapeutic effect, through paracrine-mediated action, on early OA development. Lewis rats underwent MMT surgery to induce OA. 1 d post-surgery, rats received intra-articular injections of encapsulated hMSCs or controls (i.e., saline, empty capsules, non-encapsulated hMSCs). Microstructural changes in the knee joint were quantified using equilibrium partitioning of a ionic contrast agent based micro-computed tomography (EPIC-μCT) at 3 weeks post-surgery, an established time point for early OA. Encapsulated hMSCs significantly attenuated MMT-induced increases in articular cartilage swelling and surface roughness and augmented cartilaginous and mineralized osteophyte volumes. Cellular encapsulation allowed to isolate the hMSC paracrine signaling effects and demonstrated that hMSCs could exert a chondroprotective therapeutic role on early stage OA through paracrine signaling alone. In addition to this chondroprotective role, encapsulated hMSCs augmented the compensatory increases in osteophyte formation. The latter should be taken into strong consideration as many clinical trials using MSCs for OA are currently ongoing.

A graphic user interface for the evaluation of knee osteoarthritis (GEKO): an open-source tool for histological grading

OBJECTIVE

In osteoarthritis (OA) models, histology is commonly used to evaluate the severity of joint damage. Unfortunately, semi-quantitative histological grading systems include some level of subjectivity, and quantitative grading systems can be tedious to implement. The objective of this work is to introduce an open source, graphic user interface (GUI) for quantitative grading of knee OA.

METHODS

Inspired by the 2010 OARSI histopathology recommendations for the rat, our laboratory has developed a GUI for the evaluation of knee OA, nicknamed GEKO. In this work, descriptions of the quantitative measures acquired by GEKO are presented and measured in 42 histological images from a rat knee OA model. Using these images, across-session and within-session reproducibility for individual graders is evaluated, and inter-grader reliability across different levels of OA severity is also assessed.

RESULTS

GEKO allowed histological images to be quantitatively scored in less than 1 min per image. In addition, intra-class coefficients (ICCs) were largely above 0.8 for across-session reproducibility, within-session reproducibility, and inter-grader reliability. These data indicate GEKO aided in the reproducibility and repeatability of quantitative OA grading across graders and grading sessions.

CONCLUSIONS

Our data demonstrate GEKO is a reliable and efficient method to calculate quantitative histological measures of knee OA in a rat model. GEKO reduced quantitative grading times relative to manual grading systems and allowed grader reproducibility and repeatability to be easily assessed within a grading session and across time. Moreover, GEKO is being provided as a free, open-source tool for the OA research community.