Gene expression markers in horse articular chondrocytes: Chondrogenic differentiaton IN VITRO depends on the proliferative potential and ageing. Implication for tissue engineering of cartilage

Promotion of diced cartilage survival and regeneration with grafting of small intestinal submucosa loaded with urine-derived stem cells

Cartilage absorption and calcification are prone to occur after the implantation of diced cartilage wrapped with autologous materials, as well as prolong the operation time, aggravate surgical trauma and postoperative pain during the acquisition process. Small intestinal submucosa (SIS) has suitable toughness and excellent degradability, which has been widely used in the clinic. Urine-derived stem cells (USCs), as a new type of stem cells, have multi-directional differentiation potential. In this study, we attempt to create the tissue engineering membrane material, termed USCs-SIS (U-SIS), and wrap the diced cartilage with it, assuming that they can promote the survival and regeneration of cartilage. In this study, after co-culture with the SIS and U-SIS, the proliferation, migration and chondrogenesis ability of the auricular-derived chondrocyte cells (ACs) were significantly improved. Further, the expression levels of chondrocyte phenotype-related genes were up-regulated, whilst that of dedifferentiated genes was down-regulated. The signal pathway proteins (Wnt3a and Wnt5a) were also participated in regulation of chondrogenesis. In vivo, compared with perichondrium, the diced cartilage wrapped with the SIS and U-SIS attained higher survival rate, less calcification and absorption in both short and long terms. Particularly, USCs promoted chondrogenesis and modulated local immune responses via paracrine pathways. In conclusion, SIS have the potential to be a new choice of membrane material for diced cartilage graft. U-SIS can enhance survival and regeneration of diced cartilage as a bioactive membrane material.

Osmolarity modulates the de-differentiation of horse articular chondrocytes during cell expansion in vitro: implications for tissue engineering in cartilage repair

Due to the importance of joint disease and ostearthritis (OA) in equine athletes, new regenerative treatments to improve articular cartilage repair after damage are gaining relevance. Chondrocyte de-differentiation, an important pathogenetic mechanism in OA, is a limiting factor when differentiated articular chondrocytes are used for cell-based therapies. Current research focuses on the prevention of this de-differentiation and/or on the re-differentiation of chondrocytes by employing different strategies in vitro and in vivo. Articular chondrocytes normally live in a condition of higher osmolarity (350-450 mOsm/L) compared to normal physiological fluids (~ 300 mOsm/L) and some studies have demonstrated that osmolarity has a chondroprotective effect in vitro and in vivo. Therefore, the response of horse articular chondrocytes to osmolarity changes (280, 380, and 480 mOsm/L) was studied both in proliferating, de-differentiated chondrocytes grown in adhesion, and in differentiated chondrocytes grown in a 3D culture system. To this aim, cell proliferation (cell counting), morphology (optical microscopy), and differentiation (gene expression of specific markers) were monitored along with the expression of osmolyte transporters involved in volume regulation [betaine-GABA transporter (BGT-1), taurine transporter (SLC6A6), and neutral amino acid transporter (SNAT)] real-time qPCR. Proliferating chondrocytes cultured under hyperosmolar conditions showed low proliferation, spheroidal morphology, a significant reduction of de-differentiation markers [collagen type I (Col1) and RUNX2] and an increase of differentiation markers [collagen type II (Col2) and aggrecan]. Notably, a persistently high level of BGT-1 gene expression was maintained in chondrocyte cultures at 380 mOsm/L, and particularly at 480 mOsm/L both in proliferating and differentiated chondrocytes. These preliminary data encourage the study of osmolarity as a microenvironmental co-factor to promote/maintain chondrocyte differentiation in both 2D and 3D in vitro culture systems.

Biomimetic approach for an articular cartilage patch: Combination of decellularized cartilage matrix and silk-elastin-like-protein (SELP) hydrogel

Articular cartilage degradation due to injury, disease and aging is a common clinical issue as current regenerative therapies are unable to fully replicate the complex microenvironment of the native tissue which, being avascular, is featured by very low ability to self-regenerate. The extracellular matrix (ECM), constituting almost 90% of the entire tissue, plays a critical role in its function and resistance to compressive forces. In this context, the current tissue engineering strategies are only partially effective in restoring the biology and function of the native tissue. A main issue in tissue regeneration is treatment failure due to scarce integration of the engineered construct, often following a gradual detachment of the graft. In this scenario, we aimed to create an adhesive patch able to adequately support cartilage regeneration as a promising tool for the treatment of cartilage injuries and diseases. For this, we produced an engineered construct composed of decellularized ECM (dECM) obtained from horse joint cartilage, to support tissue regeneration, coupled with a Silk-Elastin-Like Proteins (SELP) hydrogel, which acts as a biological glue, to guarantee an adequate adherence to the host tissue. Following the production of the two biomaterials we characterized them by assessing: 1) dECM morphological, chemical, and ultrastructural features along with its capability to support chondrocyte proliferation, specific marker expression and ECM synthesis; 2) SELP microarchitecture, cytocompatibility and mechanical properties. Our results demonstrated that both materials hold unique properties suitable to be exploited to produce a tailored microenvironment to support cell growth and differentiation providing a proof of concept concerning the in vitro biological and mechanical efficacy of the construct. The SELP hydrogel displayed a very interesting physical behavior due to its high degree of resistance to mechanical stress, which is generally associated with physiological mechanical load during locomotion. Intriguingly, the shear-thinning behavior of the hydrogel may also make it suitable to be applied and spread over non-homogeneous surfaces, therefore, we hypothesize that the hybrid biomaterial proposed may be a real asset in the treatment of cartilage defects and injuries.

Pro-Inflammatory Cytokine Priming and Purification Method Modulate the Impact of Exosomes Derived from Equine Bone Marrow Mesenchymal Stromal Cells on Equine Articular Chondrocytes

Osteoarthritis (OA) is a widespread osteoarticular pathology characterized by progressive hyaline cartilage degradation, exposing horses to impaired well-being, premature career termination, alongside substantial financial losses for horse owners. Among the new therapeutic strategies for OA, using mesenchymal stromal cell (MSC)-derived exosomes (MSC-exos) appears to be a promising option for conveying MSC therapeutic potential, yet avoiding the limitations inherent to cell therapy. Here, we first purified and characterized exosomes from MSCs by membrane affinity capture (MAC) and size-exclusion chromatography (SEC). We showed that intact MSC-exos are indeed internalized by equine articular chondrocytes (eACs), and then evaluated their functionality on cartilaginous organoids. Compared to SEC, mRNA and protein expression profiles revealed that MAC-exos induced a greater improvement of eAC-neosynthesized hyaline-like matrix by modulating collagen levels, increasing PCNA, and decreasing Htra1 synthesis. However, because the MAC elution buffer induced unexpected effects on eACs, an ultrafiltration step was included to the isolation protocol. Finally, exosomes from MSCs primed with equine pro-inflammatory cytokines (IL-1β, TNF-α, or IFN-γ) further improved the eAC hyaline-like phenotype, particularly IL-1β and TNF-α. Altogether, these findings indicate the importance of the exosome purification method and further demonstrate the potential of pro-inflammatory priming in the enhancement of the therapeutic value of MSC-exos for equine OA treatment.

Investigation of MicroRNA Biomarkers in Equine Distal Interphalangeal Joint Osteoarthritis

Osteoarthritis of the equine distal interphalangeal joint is a common cause of lameness. MicroRNAs from biofluids are promising biomarkers and therapeutic candidates. Synovial fluid samples from horses with mild and severe equine distal interphalangeal joint osteoarthritis were submitted for small RNA sequencing. The results demonstrated that miR-92a was downregulated in equine synovial fluid from horses with severe osteoarthritis and there was a significant increase in COMP, COL1A2, RUNX2 and SOX9 following miR-92a mimic treatment of equine chondrocytes in monolayer culture. This is the first equine study to evaluate the role of miR-92a in osteoarthritic chondrocytes in vitro.

The potential utility of hybrid photo-crosslinked hydrogels with non-immunogenic component for cartilage repair

Finding a suitable biomaterial for scaffolding in cartilage tissue engineering has proved to be far from trivial. Nonetheless, it is clear that biomimetic approaches based on gelatin (Gel) and hyaluronic acid (HA) have particular promise. Herein, a set of formulations consisting of photo-polymerizable Gel; photo-polymerizable HA, and allogenic decellularized cartilage matrix (DCM), is synthesized and characterized. The novelty of this study lies particularly in the choice of DCM, which was harvested from an abnormal porcine with α-1,3-galactose gene knockout. The hybrid hydrogels were prepared and studied extensively, by spectroscopic methods, for their capacity to imbibe water, for their behavior under compression, and to characterize microstructure. Subsequently, the effects of the hydrogels on contacting cells (in vitro) were studied, i.e., cytotoxicity, morphology, and differentiation through monitoring the specific markers ACAN, Sox9, Coll2, and Col2α1, hypertrophy through monitoring the specific markers alkaline phosphatase (ALP) and Col 10A1. In vivo performance of the hydrogels was assessed in a rat knee cartilage defect model. The new data expand our understanding of hydrogels built of Gel and HA, since they reveal that a significant augmenting role can be played by DCM. The data strongly suggest that further experimentation in larger cartilage-defect animal models is worthwhile and has potential utility for tissue engineering and regenerative medicine.

Cultured Horse Articular Chondrocytes in 3D-Printed Chitosan Scaffold With Hyaluronic Acid and Platelet Lysate

Three-dimensional (3D) printing has gained popularity in tissue engineering and in the field of cartilage regeneration. This is due to its potential to generate scaffolds with spatial variation of cell distribution or mechanical properties, built with a variety of materials that can mimic complex tissue architecture. In the present study, horse articular chondrocytes were cultured for 2 and 4 weeks in 3D-printed chitosan (CH)-based scaffolds prepared with or without hyaluronic acid and in the presence of fetal bovine serum (FBS) or platelet lysate (PL). These 3D culture systems were analyzed in terms of their capability to maintain chondrocyte differentiation in vitro. This was achieved by evaluating cell morphology, immunohistochemistry (IHC), gene expression of relevant cartilage markers (collagen type II, aggrecan, and Sox9), and specific markers of dedifferentiated phenotype (collagen type I, Runx2). The morphological, histochemical, immunohistochemical, and molecular results demonstrated that the 3D CH scaffold is sufficiently porous to be colonized by primary chondrocytes. Thereby, it provides an optimal environment for the colonization and synthetic activity of chondrocytes during a long culture period where a higher rate of dedifferentiation can be generally observed. Enrichment with hyaluronic acid provides an optimal microenvironment for a more stable maintenance of the chondrocyte phenotype. The use of 3D CH scaffolds causes a further increase in the gene expression of most relevant ECM components when PL is added as a substitute for FBS in the medium. This indicates that the latter system enables a better maintenance of the chondrocyte phenotype, thereby highlighting a fair balance between proliferation and differentiation.

Safety and efficacy of engineered tissue composed of silk fibroin/collagen and autologous chondrocytes in two patients with cartilage defects: A pilot clinical trial study

BACKGROUND

The objective of this pilot clinical trial study was to evaluate safety and effectiveness of the newly engineered tissue composed of autologous chondrocytes and collagen/fibroin scaffold in repair of osteochondral defects.

METHODS

We implemented a pilot clinical study in two patients with knee osteochondral lesions using engineered tissue composed of scaffold and autologous chondrocytes. Patients were clinically evaluated using the International Repair Cartilage Society score and magnetic resonance imaging (MRI) for one year.

RESULTS

Improved clinical outcomes and objective scores indicated a normal or nearly normal knee in both patients. International Knee Documentation Committee score was upgraded from 34.5 at baseline to 72.4 in the first patient, and 28.7 to 81.6 in the second patient. Visual analogue scale, showing the suffering pain score, was lowered from 8 to 0 in both patients, Western Ontario and McMaster Universities Osteoarthritis Index score representing the physical ability of the patients was changed from 68.1 to 87.1 in Patient 1 and 58.3 to 87.1 in Patient 2, the knee function score, related to the functional ability of the knee, was improved from 70 to 100 in the first patient and from 45 to 91 in the second patient. MRI showed great coverage and integration of the graft in patients, with no effusion, decreased edema and cartilage formation signals.

CONCLUSIONS

The functional and clinical outcomes alongside MRI data showed promising results for regenerating osteochondral defects. A randomized clinical trial study is required to confirm feasibility of this novel engineered tissue in repair of osteochondral defects.

Platelet lysate reduces the chondrocyte dedifferentiation during in vitro expansion: Implications for cartilage tissue engineering

In vitro studies have demonstrated that platelet lysate (PL) can serve as an alternative to platelet-rich plasma (PRP) to sustain chondrocyte proliferation and production of extracellular matrix components in chondrocytes. The present study aimed to evaluate the direct effects of PL on equine articular chondrocytes in vitro in order to provide a rationale for in vivo use of PL. An in vitro cell proliferation and de-differentiation model was used: primary articular chondrocytes isolated from horse articular cartilage were cultured at low density under adherent conditions to promote cell proliferation. Chondrocytes were cultured in serum-free medium, 10% foetal bovine serum (FBS) supplemented medium, or in the presence of alginate beads containing 5%, 10% and 20% PL. Cell proliferation and gene expression of relevant chondrocyte differentiation markers were investigated. The proliferative capacity of cultured chondrocytes, was sustained more effectively at certain concentrations of PL as compared to that with FBS. In addition, as opposed to FBS, PL, particularly at percentages of 5% and 10%, could maintain the gene expression pattern of relevant chondrocyte differentiation markers. In particular, 5% PL supplementation showed the best compromise between chondrocyte proliferation capacity and maintenance of differentiation. The results of the present study provide a rationale for using PL as an alternative to FBS for in vitro expansion of chondrocytes for matrix-assisted chondrocyte implantation, construction of 3D scaffolds for tissue engineering, and treatment of damaged articular cartilage.