Increasing Collagen to Bioink Drives Mesenchymal Stromal Cells-Chondrogenesis from Hyaline to Calcified Layers

The bioextrusion of mesenchymal stromal cells (MSCs) directly seeded in a bioink enables the production of three-dimensional (3D) constructs, promoting their chondrogenic differentiation. Our study aimed to evaluate the effect of different type I collagen concentrations in the bioink on MSCs' chondrogenic differentiation. We printed 3D constructs using an alginate, gelatin, and fibrinogen-based bioink cellularized with MSCs, with four different quantities of type I collagen addition (0.0, 0.5, 1.0, and 5.0 mg per bioink syringe). We assessed the influence of the bioprinting process, the bioink composition, and the growth factor (TGF-ꞵ1) on the MSCs' survival rate. We confirmed the biocompatibility of the process and the bioinks' cytocompatibility. We evaluated the chondrogenic effects of TGF-ꞵ1 and collagen addition on the MSCs' chondrogenic properties through macroscopic observation, shrinking ratio, reverse transcription polymerase chain reaction, glycosaminoglycan synthesis, histology, and type II collagen immunohistochemistry. The bioink containing 0.5 mg of collagen produces the richest hyaline-like extracellular matrix, presenting itself as a promising tool to recreate the superficial layer of hyaline cartilage. The bioink containing 5.0 mg of collagen enhances the synthesis of a calcified matrix, making it a good candidate for mimicking the calcified cartilaginous layer. Type I collagen thus allows the dose-dependent design of specific hyaline cartilage layers.

Rat synovial tissue and blood rapamycin pharmacokinetics after intra-articular injection of free solution or nanoparticles vs free rapamycin intravenous shot

Intra-articular (IA) injection of a chondroprotective candidate may delay the osteoarthritis (OA) course, but its rapid absorption into systemic circulation may limit efficacy and produce untoward effects. We compared the pharmacokinetics (PK) of IA rapamycin injected as sustained release in nanoparticles (NPs) versus a free rapamycin suspension in the rat knee compared to an intravenous (IV) free rapamycin shot taken as a reference. Rats received either a single IV injection of free rapamycin (10 µM) or an IA of free or NPs-loaded rapamycin. After sequential exsanguination (15, 30, 60, 180, 360 min, D1, and D7), knee synovial tissue (ST) and cartilage histology were performed. Blood and ST concentrations (LC-MS/MS), PK parameters (area under the curve: AUC; mean residence time: MRT; elimination half-life: T_1/2), and IA biocompatibility were assessed. AUC_IV was significantly higher for IV than for both IA injections (AUC_{IA free} and AUC_{IA NPs}), with 4248 vs 28 and 74 µg.min.L^-1. For ST parameters, we observed a significant difference between AUC_{IA free} and AUC_{IA NPs} with 3735 and 10513 µg.min.L^-1 correspondingly. Articular T_1/2 and MRT were higher after NPs than after free rapamycin injection: 57.8 and 5.0 h for T_1/2 and 80.6 and 5.5 h for MRT, respectively. Histological analysis revealed no chondral injuries and slight transient synovitis only 3 h after the administration of NPs. In the rat knee, rapamycin-loaded NPs delivery via a single IA injection is biocompatible and prolongs synovium joint residency, diminishes blood levels, and reduces detrimental systemic exposure.

Study of the influence of autoclave sterilization on the properties of citrate functionalized iron oxide nanoparticles

Superparamagnetic Iron Oxide Nanoparticles (SPIONs) are widely used in various areas of the biomedical field: for diagnosis (Magnetic Resonance Imaging), for therapeutic applications (hyperthermia, nanovectorization). These applications require a good stability in water and no aggregation of SPIONs, with well-controlled physicochemical and magnetic properties. In this work, SPIONs functionalized by citrate ligands are synthesized in a one-step process with the aim of producing stable water-dispersible nanoparticles with a well-crystallized spinel structure. Microwave technology is implemented to achieve this objective given the ease, speed and reproducibility of the method. For their future use in biomedical applications, the sterilization of these SPIONs are essential by an autoclave treatment. The influence of this treatment on the physicochemical and magnetic properties of the SPIONs is determined by a systematic characterization before and after sterilization by Transmission Electronic Microscopy, Dynamic Light Scattering, X-ray Diffraction, Fourier Transformed Infra-Red, ThermoGravimetric Analysis and magnetic measurements.

Rapamycin-loaded Poly(lactic-co-glycolic) acid nanoparticles: Preparation, characterization, and in vitro toxicity study for potential intra-articular injection

Osteoarthritis (OA) is the most common degenerative joint disease. Rapamycin is a potential candidate for OA treatment by increasing the autophagy process implicated in its physiopathology. To optimize Rapamycin profit and avoid systemic side effects, intra-articular (i.a.) administration appeared helpful. However, Rapamycin's highly hydrophobic nature and low bioavailability made it challenging to develop purpose-made drug delivery systems to overcome these limitations. We developed Rapamycin-loaded nanoparticles (NPs) using poly (lactic-co-glycolic acid) by emulsion/evaporation method. We evaluated these NPs' cytocompatibility towards cartilage (chondrocytes) and synovial membrane cells (synoviocytes) for a potential i.a. administration. The in vitro characterization of Rapamycin-loaded NPs had shown a suitable profile for an i.a. administration. In vitro biocompatibility of NPs was highlighted to 10 µM of Rapamycin for both synoviocytes and chondrocytes, but significant toxicity was observed with higher concentrations. Besides, synoviocytes are more sensitive to Rapamycin-loaded NPs than chondrocytes. Finally, we observed in vitro that an adapted formulated Rapamycin-loaded NPs could be safe at suitable i.a. injection concentrations. The toxic effect of Rapamycin encapsulated in these NPs on both articular cells was dose-dependent. After Rapamycin-loaded NPs i.a. administration, local retention, in situ safety, and systemic release should be evaluated with experimental in vivo models.

Stem Cells and Extrusion 3D Printing for Hyaline Cartilage Engineering

Hyaline cartilage is deficient in self-healing properties. The early treatment of focal cartilage lesions is a public health challenge to prevent long-term degradation and the occurrence of osteoarthritis. Cartilage tissue engineering represents a promising alternative to the current insufficient surgical solutions. 3D printing is a thriving technology and offers new possibilities for personalized regenerative medicine. Extrusion-based processes permit the deposition of cell-seeded bioinks, in a layer-by-layer manner, allowing mimicry of the native zonal organization of hyaline cartilage. Mesenchymal stem cells (MSCs) are a promising cell source for cartilage tissue engineering. Originally isolated from bone marrow, they can now be derived from many different cell sources (e.g., synovium, dental pulp, Wharton’s jelly). Their proliferation and differentiation potential are well characterized, and they possess good chondrogenic potential, making them appropriate candidates for cartilage reconstruction. This review summarizes the different sources, origins, and densities of MSCs used in extrusion-based bioprinting (EBB) processes, as alternatives to chondrocytes. The different bioink constituents and their advantages for producing substitutes mimicking healthy hyaline cartilage is also discussed.

Respective stemness and chondrogenic potential of mesenchymal stem cells isolated from human bone marrow, synovial membrane, and synovial fluid

BACKGROUND

MSCs isolated from bone marrow (BM-MSCs) have well-established chondrogenic potential, but MSCs derived from the synovial membrane (SM-MSCs) and synovial fluid (SF-MSCs) are thought to possess superior chondrogenicity. This study aimed to compare the in vitro immunophenotype and trilineage and chondrogenic potential of BM-MSCs to SM-MSCs and SF-MSCs.

METHODS

MSCs were isolated from bone marrow (BM-MSCs), synovial membrane (SM-MSCs), and synovial fluid (SF-MSCs) extracted from the hips (BM) and knees (SM and SF) of advanced OA patients undergoing arthroplasty. Flow cytometric analysis was used at P2 to evaluate cell stemness. The trilinear differentiation test was performed at P2. At P3, MSC-seeded collagen sponges were cultured in chondrogenic medium for 28 days. Chondrogenic gene expression was quantified by qRT-PCR. Finally, the implants were stained to assess the deposition of proteoglycans and type II collagen.

RESULTS

Despite variability, the immunophenotyping of BM-MSCs, SM-MSCs, and SF-MSCs was quite similar. All cell types were positive for the expression of stem cell markers and negative for exclusion markers. Additionally, chondrogenic differentiation and hypertrophy were more pronounced in BM-MSCs (ACAN, SOX9, COL2B, and COL10A) than in SF-MSCs, with SM-MSCs having intermediate characteristics. Concerning matrix synthesis, the three cell types were equipotent in terms of GAG content, while BM-MSC ECM synthesis of type II collagen was superior.

CONCLUSIONS

Chondrogenic MSCs are easily collected from SM and SF in advanced human OA, but in vitro chondrogenesis that is superior to age-matched BM-MSCs should not be expected. However, due to intra-articular priming, SF-MSCs did not overexpress hypertrophic gene.

In vitro and in vivo potentialities for cartilage repair from human advanced knee osteoarthritis synovial fluid-derived mesenchymal stem cells

Background

Mesenchymal stem cells (MSCs) are found in synovial fluid (SF) and can easily be harvested during arthrocentesis or arthroscopy. However, SF-MSC characterization and chondrogenicity in collagen sponges have been poorly documented as well as their hypothetical in vivo chondroprotective properties with intra-articular injections during experimental osteoarthritis (OA).

Methods

SF-MSCs were isolated from human SF aspirates in patients suffering from advanced OA undergoing total knee joint replacements. SF-MSCs at passage 2 (P2) were characterized by flow cytometry for epitope profiling. SF-MSCs at P2 were subsequently cultured in vitro to assess their multilineage potentials. To assess their chondrogenicity, SF-MSCs at P4 were seeded in collagen sponges for 4 weeks under various oxygen tensions and growth factors combinations to estimate their gene profile and matrix production. Also, SF-MSCs were injected into the joints in a nude rat anterior cruciate ligament transection (ACLT) to macroscopically and histologically assess their possible chondroprotective properties,.

Results

We characterized the stemness (CD73+, CD90+, CD105+, CD34−, CD45−) and demonstrated the multilineage potency of SF-MSCs in vitro. Furthermore, the chondrogenic induction (TGF-ß1 ± BMP-2) of these SF-MSCs in collagen sponges demonstrated a good capacity of chondrogenic gene induction and extracellular matrix synthesis. Surprisingly, hypoxia did not enhance matrix synthesis, although it boosted chondrogenic gene expression (ACAN, SOX9, COL2A1). Besides, intra-articular injections of xenogenic SF-MSCs did exert neither chondroprotection nor inflammation in ACLT-induced OA in the rat knee.

Conclusions

Advanced OA SF-MSCs seem better candidates for cell-based constructs conceived for cartilage defects rather than intra-articular injections for diffuse OA.

Label-free relative quantification of secreted proteins as a non-invasive method for the quality control of chondrogenesis in bioengineered substitutes for cartilage repair

Cartilage tissue engineering is making progress, but the competing available strategies still leave room for improvement and consensual overviews regarding the best combinations of scaffolds and cell sources are limited by the capacity to compare them directly. In addition, because most strategies involve autologous cell transfer, once these are optimized, the resulting implants require individual quality control prior to grafting in order to emphasize patient-to-patient differential responsiveness to engineering processes. Here, cartilage substitutes prepared from human mesenchymal stem cells undergoing chondrogenic differentiation within distinct scaffolds were used as pilot samples to investigate the pertinence of a novel method with the aim of characterizing the implants. The limits and advantages of analysing, by label-free liquid chromatography-coupled matrix-assisted laser desorption and ionization (LC-MALDI) mass spectrometry, the secreted proteome released into culture medium by engineered cartilage tissues were investigated and compared with more classically used methods for biomaterial characterization. This method did not require sacrificing the biomaterials and robustly evidenced their chondrogenic statuses. In more detail, the method highlighted differences between batches prepared from distinct donors. It was adapted to distinct scaffolds and allowed a comparison of the influence of individual engineering steps, such as growth factor combinations and oxygen tension. Finally, it evidenced subtle changes between replicate substitutes within a series, thereby distinguishing the least and most accomplished ones. We conclude that relative quantification of secreted proteins through label-free LC-MALDI will be useful, not only to orientate engineering methodologies, but also to ultimately provide non-invasive quality control of engineered tissue substitutes for the repair of cartilage and possibly other connective tissues.

* Hypoxia for Mesenchymal Stem Cell Expansion and Differentiation: The Best Way for Enhancing TGFß-Induced Chondrogenesis and Preventing Calcifications in Alginate Beads

We examined the respective influence of a sequential or a continuous hypoxia during expansion and transforming growth factor beta 1-driven chondrogenic differentiation of human bone marrow mesenchymal stem cells (MSCs). The differentiation was performed within alginate beads, a classical tool for the implantation of MSCs within the joint. The standard normoxic 2D (expansion) and 3D (differentiation) MSCs cultures served as reference. To determine the quality of chondrogenesis, we analyzed typical markers such as type II and X collagens, SOX9, COMP, versican, and aggrecan mRNAs using polymerase chain reaction and we assessed the production of type II collagen and hypoxia-inducible factor (HIF)-1α by histological stainings. We simultaneously assessed the expression of osteogenic mRNAs (Alkaline Phosphatase, RUNX2, and Osteocalcin) and the presence of micro-calcifications by Alizarin red and Raman spectroscopy. Chondrogenic differentiation is clearly improved by hypoxia in 3D. Best results were obtained when the entire process, that is, 2D expansion and 3D differentiation, was performed under continuous 5% hypoxic condition. In addition, no calcification (hydroxyapatite, proved by RAMAN) was observed after 2D hypoxic expansion even in the case of a normoxic differentiation, in contrast with controls. Finally, a better chondrogenic differentiation of human MSCs is achieved when a reduced oxygen tension is applied during both expansion and differentiation times, avoiding in vitro osteogenic commitment of cells and subsequently the calcification deposition.

New tools for non-invasive exploration of collagen network in cartilaginous tissue-engineered substitute

In tissue engineering approaches, the quality of substitutes is a key element to determine its ability to treat cartilage defects. However, in clinical practice, the evaluation of tissue-engineered cartilage substitute quality is not possible due to the invasiveness of the standard procedure, which is to date histology. The aim of this work was to validate a new innovative system performed from two-photon excitation laser adapted to an optical macroscope to evaluate at macroscopic scale the collagen network in cartilage tissue-engineered substitutes in confrontation with gold standard histologic techniques or immunohistochemistry to visualize type II collagen. This system permitted to differentiate the quality of collagen network between ITS and TGF-β1 treatments. Multiscale large field imaging combined to multimodality approaches (SHG-TCSPC) at macroscopical scale represent an innovative and non-invasive technique to monitor the quality of collagen network in cartilage tissue-engineered substitutes before in vivo implantation.

Chondrogenic induction of mesenchymal stromal/stem cells from Wharton's jelly embedded in alginate hydrogel and without added growth factor: an alternative stem cell source for cartilage tissue engineering

Background

Due to their intrinsic properties, stem cells are promising tools for new developments in tissue engineering and particularly for cartilage tissue regeneration. Although mesenchymal stromal/stem cells from bone marrow (BM-MSC) have long been the most used stem cell source in cartilage tissue engineering, they have certain limits. Thanks to their properties such as low immunogenicity and particularly chondrogenic differentiation potential, mesenchymal stromal/stem cells from Wharton’s jelly (WJ-MSC) promise to be an interesting source of MSC for cartilage tissue engineering.

Methods

In this study, we propose to evaluate chondrogenic potential of WJ-MSC embedded in alginate/hyaluronic acid hydrogel over 28 days. Hydrogels were constructed by the original spraying method. Our main objective was to evaluate chondrogenic differentiation of WJ-MSC on three-dimensional scaffolds, without adding growth factors, at transcript and protein levels. We compared the results to those obtained from standard BM-MSC.

Results

After 3 days of culture, WJ-MSC seemed to be adapted to their new three-dimensional environment without any detectable damage. From day 14 and up to 28 days, the proportion of WJ-MSC CD73⁺, CD90⁺, CD105⁺ and CD166⁺ decreased significantly compared to monolayer marker expression. Moreover, WJ-MSC and BM-MSC showed different phenotype profiles. After 28 days of scaffold culture, our results showed strong upregulation of cartilage-specific transcript expression. WJ-MSC exhibited greater type II collagen synthesis than BM-MSC at both transcript and protein levels. Furthermore, our work highlighted a relevant result showing that WJ-MSC expressed Runx2 and type X collagen at lower levels than BM-MSC.

Conclusions

Once seeded in the hydrogel scaffold, WJ-MSC and BM-MSC have different profiles of chondrogenic differentiation at both the phenotypic level and matrix synthesis. After 4 weeks, WJ-MSC, embedded in a three-dimensional environment, were able to adapt to their environment and express specific cartilage-related genes and matrix proteins. Today, WJ-MSC represent a real alternative source of stem cells for cartilage tissue engineering.

New trends in articular cartilage repair

Damage to the articular cartilage is an important, prevalent, and unsolved clinical issue for the orthopaedic surgeon. This review summarizes innovative basic research approaches that may improve the current understanding of cartilage repair processes and lead to novel therapeutic options. In this regard, new aspects of cartilage tissue engineering with a focus on the choice of the best-suited cell source are presented. The importance of non-destructive cartilage imaging is highlighted with the recent availability of adapted experimental tools such as Second Harmonic Generation (SHG) imaging. Novel insights into cartilage pathophysiology based on the involvement of the infrapatellar fat pad in osteoarthritis are also described. Also, recombinant adeno-associated viral vectors are discussed as clinically adapted, efficient tools for potential gene-based medicines in a variety of articular cartilage disorders. Taken as a whole, such advances in basic research in diverse fields of articular cartilage repair may lead to the development of improved therapies in the clinics for an improved, effective treatment of cartilage lesions in a close future.

Dose-response of superparamagnetic iron oxide labeling on mesenchymal stem cells chondrogenic differentiation: a multi-scale in vitro study

Aim

The aim of this work was the development of successful cell therapy techniques for cartilage engineering. This will depend on the ability to monitor non-invasively transplanted cells, especially mesenchymal stem cells (MSCs) that are promising candidates to regenerate damaged tissues.

Methods

MSCs were labeled with superparamagnetic iron oxide particles (SPIO). We examined the effects of long-term labeling, possible toxicological consequences and the possible influence of progressive concentrations of SPIO on chondrogenic differentiation capacity.

Results

No influence of various SPIO concentrations was noted on human bone marow MSC viability or proliferation. We demonstrated long-term (4 weeks) in vitro retention of SPIO by human bone marrow MSCs seeded in collagenic sponges under TGF-β1 chondrogenic conditions, detectable by Magnetic Resonance Imaging (MRI) and histology. Chondrogenic differentiation was demonstrated by molecular and histological analysis of labeled and unlabeled cells. Chondrogenic gene expression (COL2A2, ACAN, SOX9, COL10, COMP) was significantly altered in a dose-dependent manner in labeled cells, as were GAG and type II collagen staining. As expected, SPIO induced a dramatic decrease of MRI T2 values of sponges at 7T and 3T, even at low concentrations.

Conclusions

This study clearly demonstrates (1) long-term in vitro MSC traceability using SPIO and MRI and (2) a deleterious dose-dependence of SPIO on TGF-β1 driven chondrogenesis in collagen sponges. Low concentrations (12.5–25 µg Fe/mL) seem the best compromise to optimize both chondrogenesis and MRI labeling.

Effect of dynamic loading on MSCs chondrogenic differentiation in 3-D alginate culture

Mesenchymal stem cells (MSCs) are regarded as a potential autologous source for cartilage repair, because they can differentiate into chondrocytes by transforming growth factor-beta (TGF-β) treatment under the 3-dimensional (3-D) culture condition. In addition to these molecular and biochemical methods, the mechanical regulation of differentiation and matrix formation by MSCs is only starting to be considered. Recently, mechanical loading has been shown to induce chondrogenesis of MSCs in vitro. In this study, we investigated the effects of a calibrated agitation on the chondrogenesis of human bone MSCs (MSCs) in a 3-D alginate culture (day 28) and on the maintenance of chondrogenic phenotypes. Biomechanical stimulation of MSCs increased: (i) types 1 and 2 collagen formation; (ii) the expression of chondrogenic markers such as COMP and SOX9; and (iii) the capacity to maintain the chondrogenic phenotypes. Notably, these effects were shown without TGF-β treatment. These results suggest that a mechanical stimulation could be an efficient method to induce chondrogenic differentiation of MSCs in vitro for cartilage tissue engineering in a 3-D environment. Additionally, it appears that MSCs and chondrocyte responses to mechanical stimulation are not identical.

Ambivalent properties of hyaluronate and hylan during post-traumatic OA in the rat knee

AIM

To determine whether viscosupplementation with intra-articular (i.a.) low- or high-molecular-weight hyaluronate (HA) injections influenced both chondral and synovial lesions in rats with surgically-induced OA knee.

METHODS

On D0, rats underwent anterior cruciate ligament transection (ACLX) and were divided in 4 groups: sham group, ACLX-saline control group, ACLX-hyaluronate group, ACLX-hylan group. IA injections were performed on D7, D14 and D21. Histological grading of chondral and synovial lesions were performed on D28. Concomitant immunostainings of Caspase3a and Hsp70 were also performed.

RESULTS

Articular damages were significantly reduced in both HAs-treated knee joints. In contrast, a significant increase of histological score of synovial inflammation was noted in both ACLX + HAs groups. Apoptotic events significantly decreased as anti-apoptotic Hsp70 expression increased significantly in both HAs groups.

CONCLUSION

HAs may exert, independently of its molecular weight, ambivalent properties on articular structures, simultaneously exerting chondroprotective properties and promoting long-term subacute synovitis.

Original approach for cartilage tissue engineering with mesenchymal stem cells

Cartilage tissue engineering gives the ability to product adaptable neocartilage to lesion with autologous cells. Our work aimed to develop a stratified scaffold with a simple and progressive spraying build-up to mimic articular cartilage environment. An Alginate/Hyaluronic Acid (Alg/HA) hydrogel seeded with human Mesenchymal Stem Cells (hMSC) was construct by spray. First, cells repartition and actin organization were study with confocal microscopy. Then, we analyzed cells viability and finally, metabolic activity. Our results indicated a homogenous cells repartition in the hydrogel and a pericellular actin repartition. After 3 days of culture, we observed about 52% of viable cells in the scaffold. Then, from day 7 until the end of culture (D28), the proportion of living cells and their metabolic activity increased, what indicates that culture conditions are not harmful for the cells. We report here that sprayed method allowed to product a scaffold with hMSCs that confer a favorable environment for neocartilage construction: 3D conformation and ability of cells to increase their metabolic activity, therefore with few impact on hMSCs.

Evaluation of intra-articular delivery of hyaluronic acid functionalized biopolymeric nanoparticles in healthy rat knees

The aim of this study is to evaluate the toxicity of nanoparticles of poly(D,L-lactic acid) (PLA) or poly(D,L-lactic-co-glycolic acid) (PLGA) covered by chemically esterified amphiphilic hyaluronate (HA) which will be used for intra-articular injection as a drug carrier for the treatment of arthritis (RA) and/or osteoarthritis (OA). PLA and PLGA are FDA approved polymers that are already used for the preparation of nano or microparticles. HA is a natural polysaccharide already present in the articulations known to interact with the CD44 receptors of the cells (especially chondrocytes). Therefore, we can envisage that the HA covering can improve the interactions between the cells and the nanoparticles, leading to better targeting or biodistribution. The knee of healthy male rats was injected one to two times weekly, with various concentrations of nanoparticles encapsulating Dextran-FITC. The synovial membranes and the patellae were collected aseptically and histologically analyzed to assess the effects and localization of the nanocapsules in the knee joint. We did not observe significant modifications in the synovial membranes (weak hyperplasia) or patellae integrity after local administration of nanodevices into the rats. While we found some nanoparticles in the synovial membrane, none were detected in the patellae. Moreover, the histological observations for patellae were confirmed by radiosulfate intake, which depicted no decrease in proteoglycans biosynthesis in nanoparticles treated animals. Concerning the safety towards synovial membranes, we also had a look at the inflammatory response after injections of nanoparticles covered by amphiphilic HA or polyvinyl alcohol (PVA) by monitoring the mRNA expression levels of some specific early cytokines (IL-1β and TNF-α). Once again, no differences were observed between the control rats and the rats treated with nanoparticles. Considering these preliminary results obtained in healthy rats, we can establish that neither the amphiphilic HA-covered PLGA nanoparticles nor their degradation products induce major modifications of articular tissues functions, while injected into the knee of healthy rats. These results should be confirmed in OA or RA rat models, in order to confirm that nanoparticles do not worsen already altered (degenerative or inflamed) articular tissues. Once confirmed, such tuneable nanoparticles could be proposed as a safe drug delivery system for the treatment of articular disease, allowing a wide range of encapsulating molecules.

New trends in MRI of cartilage: Advances and limitations in small animal studies

Due to the actual interest for bioengineering in the osteoarthritis (OA) healing context, researchers need accurate qualitative and quantitative methodologies to evaluate in vivo the integration and functionality of their cartilage-like biomaterials. As in clinical diagnostic strategies, advances in Magnetic Resonance Imaging (MRI) seem promising for non-vulnerant assessments of articular cartilage bio-architecture and morphology in small animal models. These experimental models are commonly used to monitor the physiopathology of OA and to evaluate therapeutic responses mediated by chondroprotective drugs or tissue engineering. Nowadays, the application of MR protocols to in vivo small animal cartilage imaging is achievable with the development of high magnetic fields and the adaptation of methodologies to reach the required spatial resolution and contrast. The purpose of this article is to summarize these current MRI strategies used for in vivo small animal articular cartilage assessments.

Expression of chondrogenic genes by undifferentiated vs. differentiated human mesenchymal stem cells using array technology

This study investigated the gene expression profile of human mesenchymal stem cells seeded in collagen sponge for 28 days in three different mediums: (1) basal medium as control containing ITS alone, (2) ITS+TGF-β1 alone or (3) ITS 1% supplemented sequentially by TGF-β1 (D3-D14) followed by BMP-2 (D15-D28). Differential expression of 84 genes implicated in chondrogenic and osteogenic differentiation of MSCs was analyzed at D28 by real-time RT-PCR array technology. TGF-β1 alone down-regulated two genes, CD36 and cathepsin K. Sixteen genes were significantly up-regulated, notably type 2 and type 10 collagens, COMP and Sox9. The sequential combination of TGF-β1 and BMP-2 produced a similar profile with prominent expression of type 2 collagen and the alkaline phosphatase gene. Interestingly, in this in vitro condition, RUNX2 was not up-regulated, suggesting that the sequential combination of TGF-β1/BMP2 enhances the hypertrophic chondrogenic profile without turning towards the osteoblastic pathway.

Local induction of heat shock protein 70 (Hsp70) by proteasome inhibition confers chondroprotection during surgically induced osteoarthritis in the rat knee

AIM

to determine if chondrocytic Hsp70 induction, via intra-articular injections of a reversible proteasome inhibitor (MG132), can protect articular chondrocytes from cellular death in experimental rat OA knee induced surgically by anterior cruciate ligament transection (ACLT).

MATERIALS AND METHODS

ACLT was performed on D0. Histological lesions in naive (sham) controls (ACLT+saline) and treated (ACLT+MG132) rats were assessed according to Mankin's score. Repeated intra-articular injections (1.5 muM MG132 or saline were performed on D1, D7, D14 and D21. Rats were sacrificed sequentially on D7, D14 and D28. Detection of active caspase-3 and protein expression of Hsp70 was also determined on D7, D14 and D28 by immunostaining methods.

RESULTS

MG132 significantly reduced OA lesions on D28 in the MG132 treated group. The expression of Hsp70 increased 11-fold in the MG132-treated group versus 2-3-fold in ACLT-control rats on D28. Concomitantly, cells expressing caspase-3 increased 4-fold in ACLT model and decreased 2-fold with MG132 treatment.

CONCLUSIONS

Intra-articular induction of Hsp70 by MG132 could be a safe and interesting tool in chondrocytes protection from cellular injuries and thus might be a novel chondroprotective modality in rat OA.