Differential protein expression between chondrogenic differentiated MSCs, undifferentiated MSCs and adult chondrocytes derived from Oryctolagus cuniculus in vitro

Phosphoproteomics reveals the BRAF-ERK1/2 axis as an important pathogenic signaling node in cartilage degeneration

OBJECTIVE

Osteoarthritis (OA) causes gradual cellular alterations, structural anomalies and joint dysfunction. Progressive decline of chondrocyte function plays a vital role on OA pathogenesis. Although protein phosphorylation controls cartilage metabolism, its regulation mechanism in OA remains unclear. Thus, proteomic methods were used to investigate phosphorylation changes in preserved and OA articular cartilage samples, and to explore the intervention targets of phosphorylated kinase.

METHODS

Preserved (control) and lesioned (OA) cartilage samples from OA cases were assessed by phosphoproteomics. Immobilized metal affinity chromatography was performed for phosphopeptide enrichment. Quantitated phosphosites were comparatively assessed in the cartilage sample pair. Kinase-substrate enrichment analyses were carried out for identifying OA-related kinases. BRAF expression in cartilage tissues was assessed by immunohistochemical staining. The effects of BRAF inhibitor on cartilage degeneration were examined in mouse chondrocytes and OA mouse model.

RESULTS

High-sensitivity mass spectrometry-based proteomics revealed 7,471 peptides and 4,375 phosphorylated peptides differing between preserved and lesioned cartilage samples, which represented the significant alteration of kinase hubs and transduction pathways. Phosphoproteomics identified BRAF may be involved in developing OA. BRAF regulated the downstream ERK signaling pathway. In addition, BRAF was upregulated in human OA cartilage as shown by immunohistochemistry. Remarkably, BRAF inhibition alleviated cartilage degradation in a mouse model of OA through its downstream of ERK pathway activation.

CONCLUSIONS

Jointly, these findings provide an overview of phosphoproteomic alterations occurring during cartilage degeneration, identifying the BRAF-ERK1/2 Axis signaling as a potential signaling pathway involved in OA.

In vitro preconditioning of equine adipose mesenchymal stem cells with prostaglandin E2, substance P and their combination changes the cellular protein secretomics and improves their immunomodulatory competence without compromising stemness

Mesenchymal stem cells (MSC) are modern tools in regenerative therapies of humans and animals owed to their immunomodulatory properties, which are activated in a pro-inflammatory environment. Different preconditioning strategies had been devised to enhance the immunomodulatory properties of MSC. In this research, we evaluated the immunological attributes of equine adipose MSC (eAMSC) before and after preconditioning in vitro with prostaglandin E₂ (PGE₂), substance P (SP), their combination and IFNγ. PGE₂/SP was the best combination to keep or enhance the mesodermal lineage differentiation of eAMSC. Alongside with this, preconditioning of eMSC with PGE₂ and SP did not affect expression of stemness MSC surface phenotype: CD90⁺, CD44⁺, MHC class I⁺, MHC class II^- and CD45^-, assessed by cytometry. Both naïve and preconditioned eAMSC expressed genes related with immune properties, such as MHC-I, PTGES, IL6, IL1A, TNFα and IL8 assessed by qPCR. Only TNFα was under expressed in treated cells, while the other markers were either overexpressed or not changed. In no cases MHC-II expression was detected. The antiproliferative effect of preconditioned eAMSC exposed to activated peripheral blood mononuclear cells (PBMC) showed that SP treatment significantly inhibited proliferation of LPS stimulated PBMC. When eAMSC were stimulated with Poly I:C, all the treatments significantly inhibited proliferation of stimulated PBMC (p < 0.05). Direct contact (coculture) between the preconditioned eAMSC and PBMC, induced a shift of significantly more (CD4/CD25/FOXP3)⁺ T-regulatory PBMC than naïve eAMSC. In the experiments of this research, we investigated the secreted proteomic profile of naïve and preconditioned eAMSC, 42 up-regulated and 40 down-regulated proteins were found in the proteomic assay. Our proteomic data revealed profound changes in the secretory pattern of MSC exposed to different treatments, compared to naïve eAMSC as well as among treatments. In overall, compared to naïve cells, the protein profile of preconditioned cells resembled the mesenchymal-epithelial transition (MET). Here we showed that the combined use of PGE₂ and SP provoked in overall the highest expression of anti-inflammatory markers as well as lead to an increased acquisition of a T-regulatory phenotype in preconditioned eAMSC without affecting their "stemness".

Chondrogenic differentiation of human bone marrow-derived mesenchymal stromal cells in a three-dimensional environment

Cell therapy combined with biomaterial scaffolds is used to treat cartilage defects. We hypothesized that chondrogenic differentiation bone marrow-derived mesenchymal stem cells (BM-MSCs) in three-dimensional biomaterial scaffolds would initiate cartilaginous matrix deposition and prepare the construct for cartilage regeneration in situ. The chondrogenic capability of human BM-MSCs was first verified in a pellet culture. The BM-MSCs were then either seeded onto a composite scaffold rhCo-PLA combining polylactide and collagen type II (C2) or type III (C3), or commercial collagen type I/III membrane (CG). The BM-MSCs were either cultured in a proliferation medium or chondrogenic culture medium. Adult human chondrocytes (ACs) served as controls. After 3, 14, and 28 days, the constructs were analyzed with quantitative polymerase chain reaction and confocal microscopy and sulfated glycosaminoglycans (GAGs) were measured. The differentiated BM-MSCs entered a hypertrophic state by Day 14 of culture. The ACs showed dedifferentiation with no expression of chondrogenic genes and low amount of GAG. The CG membrane induced the highest expression levels of hypertrophic genes. The two different collagen types in composite scaffolds yielded similar results. Regardless of the biomaterial scaffold, culturing BM-MSCs in chondrogenic differentiation medium resulted in chondrocyte hypertrophy. Thus, caution for cell fate is required when designing cell-biomaterial constructs for cartilage regeneration.

The Flavonoid Glabridin Induces OCT4 to Enhance Osteogenetic Potential in Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are a promising tool for studying intractable diseases. Unfortunately, MSCs can easily undergo cellular senescence during in vitro expansion by losing stemness. The aim of this study was to improve the stemness and differentiation of MSCs by using glabridin, a natural flavonoid. Assessments of cell viability, cell proliferation, β-galactosidase activity, differentiation, and gene expression by reverse transcription PCR were subsequently performed in the absence or presence of glabridin. Glabridin enhanced the self-renewal capacity of MSCs, as indicated by the upregulation of the OCT4 gene. In addition, it resulted in an increase in the osteogenic differentiation potential by inducing the expression of osteogenesis-related genes such as DLX5 and RUNX2. We confirmed that glabridin improved the osteogenesis of MSCs with a significant elevation in the expression of OSTEOCALCIN and OSTEOPONTIN genes. Taken together, these results suggest that glabridin enhances osteogenic differentiation of MSCs with induction of the OCT4 gene; thus, glabridin could be useful for stem cell-based therapies.

Rho-kinase inhibitor Y-27632 and hypoxia synergistically enhance chondrocytic phenotype and modify S100 protein profiles in human chondrosarcoma cells

Articular chondrocytes are slowly dividing cells that tend to lose their cell type-specific phenotype and ability to produce structurally and functionally correct cartilage tissue when cultured. Thus, culture conditions, which enhance the maintenance of chondrocyte phenotype would be very useful for cartilage research. Here we show that Rho-kinase inhibition by Y-27632 under hypoxic conditions efficiently maintains and even enhances chondrocyte-specific extracellular matrix production by chondrocytic cells. The effects of long-term Y-27632 exposure to human chondrosarcoma 2/8 cell phenotype maintenance and extracellular matrix production were studied at normoxia and at a 5% low oxygen atmosphere. Y-27632 treatment at normoxia induced ACAN and COL2A1 gene up-regulation and a minor increase of sulfated glycosaminoglycans (sGAGs), while type II collagen expression was not significantly up-regulated. A further increase in expression of ACAN and COL2A1 was achieved with Y-27632 treatment and hypoxia. The production of sGAGs increased by 65.8%, and ELISA analysis revealed a 6-fold up-regulation of type II collagen. Y-27632 also induced the up-regulation of S100-A1 and S100-B proteins and modified the expression of several other S100 protein family members, such as S100-A4, S100-A6, S100-A13 and S100-A16. The up-regulation of S100-A1 and S100-B proteins is suggested to enhance the chondrocytic phenotype of these cells.

Poly-L-lysine Prevents Senescence and Augments Growth in Culturing Mesenchymal Stem Cells Ex Vivo

Mesenchymal stem cells (MSCs) possess great therapeutic potential. Efficient in vitro expansion of MSCs is however necessary for their clinical application. The extracellular matrix (ECM) provides structural and biochemical support to the surrounding cells, and it has been used as a coating substrate for cell culture. In this study, we have aimed to improve the functionality and stemness of MSCs during culture using poly-L-lysine (PLL). Functionality of MSCs was analysed by cell cycle analysis, differentiation assay, β-galactosidase staining, and RT-PCR. Furthermore, we assessed the global gene expression profile of MSCs on uncoated and PLL-coated plates. MSCs on PLL-coated plates exhibited a faster growth rate with increased S-phase and upregulated expression of the stemness markers. In addition, their osteogenic differentiation potential was increased, and genes involved in cell adhesion, FGF-2 signalling, cell cycle, stemness, cell differentiation, and cell proliferation were upregulated, compared to that of the MSCs cultured on uncoated plates. We also confirmed that MSCs on uncoated plates expressed higher β-galactosidase than the MSCs on PLL-coated plates. We demonstrate that PLL provides favourable microenvironment for MSC culture by reversing the replicative senescence. This method will significantly contribute to effective preparation of MSCs for cellular therapy.

Cells and secretome--towards endogenous cell re-activation for cartilage repair

Regenerative medicine approaches to cartilage tissue repair have mainly been concerned with the implantation of a scaffold material containing monolayer expanded cells into the defect, with the aim to differentiate the cells into chondrocytes. While this may be a valid approach, the secretome of the implanted cells and its effects on the endogenous resident cells, is gaining in interest. This review aims to summarize the knowledge on the secretome of mesenchymal stem cells, including knowledge from other tissues, in order to indicate how these mechanisms may be of value in repairing articular cartilage defects. Potential therapies and their effects on the repair of articular cartilage defects will be discussed, with a focus on the transition from classical cell therapy to the implantation of cell free matrices releasing specific cytokines.