Housekeeping Gene Stability in Human Mesenchymal Stem and Tendon Cells Exposed to Tenogenic Factors

Evaluation of suitable reference genes for qPCR normalisation of gene expression in a Achilles tendon injury model

Tendons are one of the major load-bearing tissues in the body; subjected to enormous peak stresses, and thus vulnerable to injury. Cellular responses to tendon injury are complex, involving inflammatory and repair components, with the latter employing both resident and recruited exogenous cell populations. Gene expression analyses are valuable tools for investigating tendon injury, allowing assessment of repair processes and pathological responses such as fibrosis, and permitting evaluation of therapeutic pharmacological interventions. Quantitative polymerase chain reaction (qPCR) is a commonly used approach for such studies, but data obtained by this method must be normalised to reference genes: genes known to be stably expressed between the experimental conditions investigated. Establishing suitable tendon injury reference genes is thus essential. Accordingly we investigated mRNA expression stability in a rat model of tendon injury, comparing both injured and uninjured tendons, and the effects of rapamycin treatment, at 1 and 3 weeks post injury. We used 11 candidate genes (18S, ACTB, AP3D1, B2M, CSNK2A2, GAPDH, HPRT1, PAK1IP1, RPL13a, SDHA, UBC) and assessed stability via four complementary algorithms (Bestkeeper, deltaCt, geNorm, Normfinder). Our results suggests that ACTB, CSNK2A2, HPRT1 and PAK1IP1 are all stably expressed in tendon, regardless of injury or drug treatment: any three of these would serve as universally suitable reference gene panel for normalizing qPCR expression data in the rat tendon injury model. We also reveal 18S, UBC, GAPDH, and SDHA as consistently poor scoring candidates (with the latter two exhibiting rapamycin- and injury-associated changes, respectively): these genes should be avoided.

Stable Housekeeping Genes in Bone Marrow, Adipose Tissue, and Amniotic Membrane-Derived Mesenchymal Stromal Cells for Orthopedic Regenerative Medicine Approaches

The therapeutic effect of mesenchymal stromal cells (MSCs) has been described for a variety of disorders, including those affecting musculoskeletal tissues. In this context, the literature reports several data about the regenerative effectiveness of MSCs derived from bone marrow, adipose tissue, and an amniotic membrane (BMSCs, ASCs, and hAMSCs, respectively), either when expanded or when acting as clinical-grade biologic pillars of products used at the point of care. To date, there is no evidence about the superiority of one source over the others from a clinical perspective. Therefore, a reliable characterization of the tissue-specific MSC types is mandatory to identify the most effective treatment, especially when tailored to the target disease. Because molecular characterization is a crucial parameter for cell definition, the need for reliable normalizers as housekeeping genes (HKGs) is essential. In this report, the stability levels of five commonly used HKGs (ACTB, EF1A, GAPDH, RPLP0, and TBP) were sifted into BMSCs, ASCs, and hAMSCs. Adult and fetal/neonatal MSCs showed opposite HKG stability rankings. Moreover, by analyzing MSC types side-by-side, comparison-specific HKGs emerged. The effect of less performant HKG normalization was also demonstrated in genes coding for factors potentially involved in and predicting MSC therapeutic activity for osteoarthritis as a model musculoskeletal disorder, where the choice of the most appropriate normalizer had a higher impact on the donors rather than cell populations when compared side-by-side. In conclusion, this work confirms HKG source-specificity for MSCs and suggests the need for cell-type specific normalizers for cell source or condition-tailored gene expression studies.

Housekeeping Gene Stability in Adipose Mesenchymal Stromal Cells Cultivated in Serum/Xeno-Free Media for Osteoarthritis

Among the available therapeutics for the conservative treatment of osteoarthritis (OA), mesenchymal stromal cells (MSCs)-based products appear to be the most promising. Alongside minimally manipulated cell-based orthobiologics, where MSCs are the engine of the bioactive properties, cell expansion under good manufacturing practice (GMP) settings is actively studied to obtain clinical-grade pure populations able to concentrate the biological activity. One of the main characteristics of GMP protocols is the use of clinical-grade reagents, including the recently released serum-free/xeno-free (SFM/XFM) synthetic media, which differ significantly from the traditional reagents like those based on fetal bovine serum (FBS). As SFM/XFM are still poorly characterized, a main lack is the notion of reliable housekeeping genes (HKGs) for molecular studies, either standalone or in combination with standard conditions. Indeed, the aim of this work was to test the stability of five commonly used HKGs (ACTB, EF1A, GAPDH, RPLP0, and TBP) in adipose-derived MSCs (ASCs) cultivated in two commercially available SFM/XFM and to compare outcomes with those obtained in FBS. Four different applets widely recognized by the scientific community (NormFinder, geNorm, comparative ΔCt method, and BestKeeper) were used and data were merged to obtain a final stability order. The analysis showed that cells cultured in both synthetic media had a similar ranking for HKGs stability (GAPDH being best), albeit divergent from FBS expanded products (EF1A at top). Moreover, it was possible to identify specific HKGs for side by side studies, with EF1A/TBP being the most reliable normalizers for single SFM/XFM vs. FBS cultured cells and TBP the best one for a comprehensive analysis of all samples. In addition, stability of HKGs was donor-dependent. The normalization effect on selected genes coding for factors known to be involved in OA pathology, and whose amount should be carefully considered for the selection of the most appropriate MSC-based treatment, showed how HKGs choice might affect the perceived amount for the different media or donor. Overall, this work confirms the impact of SFM/XFM conditions on HKGs stability performance, which resulted similarly for both synthetic media analyzed in the study.

YWHAZ and TBP are potential reference gene candidates for qPCR analysis of response to radiation therapy in colorectal cancer

The expression profiles of conventional reference genes (RGs), including ACTB and GAPDH, used in quantitative real-time PCR (qPCR), vary depending on tissue types and environmental conditions. We searched for suitable RGs for qPCR to determine the response to radiotherapy in colorectal cancer (CRC) cell lines, organoids, and patient-derived tissues. Ten CRC cell lines (Caco-2, COLO 205, DLD-1, HCT116, HCT-15, HT-29, RKO, SW1116, SW480, and SW620) and organoids were selected and irradiated with 2, 10 or 21 grays (Gy) based on the previous related studies conducted over the last decade. The expression stability of 14 housekeeping genes (HKGs; ACTB, B2M, G6PD, GAPDH, GUSB, HMBS, HPRT1, IPO8, PGK1, PPIA, TBP, TFRC, UBC, and YWHAZ) after irradiation was evaluated using RefFinder using raw quantification cycle (Cq) values obtained from samples before and after irradiation. The expression stability of HKGs were also evaluated for paired fresh frozen tissues or formalin-fixed, paraffin-embedded samples obtained from CRC patients before and after chemoradiotherapy. The expression of YWHAZ and TBP encoding 14-3-3-zeta protein and TATA-binding protein were more stable than the other 12 HKGs in CRC cell lines, organoids, and patient-derived tissues after irradiation. The findings suggest that YWHAZ and TBP are potential RG candidates for normalizing qPCR results in CRC radiotherapy experiments.

Nicotine and Cotinine Induce Neutrophil Extracellular Trap Formation-Potential Risk for Impaired Wound Healing in Smokers

Smoking undoubtedly affects human health. Investigating 2318 representative patients at a level 1 trauma center identified delayed wound healing, tissue infections, and/or sepsis as main complications in smokers following trauma and orthopedic surgery. Therefore, smoking cessation is strongly advised to improve the clinical outcome in these patients, although smoking cessation often fails despite nicotine replacement therapy raising the need for specific interventions that may reduce the complication rate. However, the underlying mechanisms are still unknown. In diabetics, delayed wound healing and infections/sepsis are associated with increased neutrophilic PADI4 expression and formation of neutrophil extracellular traps (NETs). The aim was to investigate if similar mechanisms hold for smokers. Indeed, our results show higher PADI4 expression in active and heavy smokers than non-smokers, which is associated with an increased complication rate. However, in vitro stimulation of neutrophils with cigarette smoke extract (CSE) only moderately induced NET formation despite accumulation of reactive oxygen species (ROS). Physiological levels of nicotine and its main metabolite cotinine more effectively induced NET formation, although they did not actively induce the formation of ROS, but interfered with the activity of enzymes involved in anti-oxidative defense and NET formation. In summary, we propose increased formation of NETs as possible triggers for delayed wound healing, tissue infections, and/or sepsis in smokers after a major trauma and orthopedic surgery. Smoking cessation might reduce this effect. However, our data show that smoking cessation supported by nicotine replacement therapy should be carefully considered as nicotine and its metabolite cotinine effectively induced NET formation in vitro, even without active formation of ROS.

Tendon Cells Derived From The Long Head Of The Biceps And The Supraspinatus Tendons Of Patients Affected By Rotator Cuff Tears Show Different Expression Of Inflammatory Markers

AIM OF THE STUDY

Tendons are exposed to mechanical stress constantly during movements and thus they are frequently subjected to injuries. Rotator cuff tears are common musculoskeletal disorders, mainly involving the supraspinatus tendon. The characterization of the tenocytes derived from this tendon and the comparison to cells isolated from the long head of the biceps tendon obtained from donors affected by rotator cuff disease may improve the knowledge of the cellular mechanisms involved in the initiation and progression of the pathology. Thus, the aim of the present study was to characterize and compare donor-matched human tendon cells (TCs) isolated from the long head of the biceps (LHB-TCs) and the supraspinatus tendons (SSP-TCs) of patients affected by rotator cuff tears.

METHODS

donor-matched LHB-TCs and SSP-TCs were isolated and cultured up to passage 3. Phenotypic appearance, metabolic activity, DNA content, production of soluble mediators (IL-1Ra, IL-1β, IL-6, and VEGF) and gene expression of tendon markers (SCX, COL1A1, COL3A1), inflammatory (PTGS2), and catabolic enzymes (MMP-1, MMP-3) were evaluated.

RESULTS

LHB-TCs showed an elongated fibroblast-like shape, while SSP-TCs appeared irregular with jagged membrane. SSP-TCs gene expression revealed an augmented production of PTGS2, a marker of inflammation, whereas they produced a reduced amount of IL-6, in respect to LHB-TCs.

CONCLUSION

SSP-TCs showed higher cellular stress and expression of inflammatory markers with respect to donor-matched LHB-TCs, suggesting that addressing the physio-pathological state of supraspinatus tendon cells during treatment of rotator cuff tears could favor tissue healing and possibly prevent relapses.

The Effect of L-Ascorbic Acid and Serum Reduction on Tenogenic Differentiation of Human Mesenchymal Stromal Cells

Background and Objectives

Despite significant improvement in the treatment of tendon injuries, the full tissue recovery is often not possible because of its limited ability to auto-repair. The transplantation of mesenchymal stromal cells (MSCs) is considered as a novel approach in the treatment of tendinopathies. The question about the optimal culture conditions remains open. In this study we aimed to investigate if serum reduction, L-ascorbic acid supplementation or a combination of both factors can induce tenogenic differentiation of human adipose-derived MSCs (ASCs).

Methods and Results

Human ASCs from 3 healthy donors were used in the study. The tested conditions were: 0.5 mM of ascorbic acid 2-phosphate (AA-2P), reduced serum content (2% FBS) or combination of these two factors. The combination of AA-2P and 2% FBS was the only experimental condition that caused a significant increase of the expression of all analyzed genes related to tenogenesis (SCLERAXIS, MOHAWK, COLLAGEN_1, COLLAGEN_3, DECORIN) in comparison to the untreated control (evaluated by RT-PCR, 5^th day of experiment). Moreover, this treatment significantly increased the synthesis of SCLERAXIS, MOHAWK, COLLAGEN_1, COLLAGEN_3 proteins at the same time point (evaluated by Western blot method). Double immunocytochemical staining revealed that AA-2P significantly increased the extracellular deposition of both types of collagens. Semi-quantitative Electron Spin Resonance analysis of ascorbyl free radical revealed that AA-2P do not induce harmful transition metals-driven redox reactions in cell culture media.

Conclusions

Obtained results justify the use of reduced content of serum with the addition of 0.5 mM of AA-2P in tenogenic inducing media.

Autologous microfragmented adipose tissue reduces inflammatory and catabolic markers in supraspinatus tendon cells derived from patients affected by rotator cuff tears

PURPOSE

Rotator cuff tears are common musculoskeletal disorders, and surgical repair is characterized by a high rate of re-tear. Regenerative medicine strategies, in particular mesenchymal stem cell-based therapies, have been proposed to enhance tendon healing and reduce the re-tear rate. Autologous microfragmented adipose tissue (μFAT) allows for the clinical application of cell therapies and showed the ability to improve tenocyte proliferation and viability in previous in vitro assessments. The hypothesis of this study is that μFAT paracrine action would reduce the catabolic and inflammatory marker expression in tendon cells (TCs) derived from injured supraspinatus tendon (SST).

METHODS

TCs derived from injured SST were co-cultured with autologous μFAT in transwell for 48 h. Metabolic activity, DNA content, the content of soluble mediators in the media, and the gene expression of tendon-specific, inflammatory, and catabolic markers were analyzed.

RESULTS

μFAT-treated TCs showed a reduced expression of PTGS2 and MMP-3 with respect to untreated controls. Increased IL-1Ra, VEGF, and IL-6 content were observed in the media of μFAT-treated samples, in comparison with untreated TCs.

CONCLUSION

μFAT exerted an anti-inflammatory action on supraspinatus tendon cells in vitro through paracrine action, resulting in the reduction of catabolic and inflammatory marker expression. These observations potentially support the use of μFAT as adjuvant therapy in the treatment of rotator cuff disease.

Autologous Microfragmented Adipose Tissue Reduces the Catabolic and Fibrosis Response in an In Vitro Model of Tendon Cell Inflammation

Background

Mesenchymal stem cells (MSCs) emerged as a promising therapy for tendon pathologies. Microfragmented adipose tissue (μFAT) represents a convenient autologous product for the application of MSC-based therapies in the clinical setting. In the present study, the ability of μFAT to counteract inflammatory processes induced by IL-1β on human tendon cells (TCs) was evaluated.

Methods

Cell viability and proliferation were evaluated after 48 hours of transwell coculture of TCs and autologous μFAT in the presence or absence of IL-1β. Gene expression of scleraxis, collagen type I and type III, metalloproteinases-1 and -3, and cyclooxygenase-2 was evaluated by real-time RT-PCR. The content of VEGF, IL-1Ra, TNFα, and IL-6 was evaluated by ELISA.

Results

IL-1β-treated TCs showed augmented collagen type III, metalloproteases, and cyclooxygenase-2 expression. μFAT was able to reduce the expression of collagen type III and metalloproteases-1 in a significant manner, and at the same time, it enhanced the production of VEGF, IL-1Ra, and IL-6.

Conclusions

In this in vitro model of tendon cell inflammation, the paracrine action of μFAT, exerted by anti-inflammatory molecules and growth factors, was able to inhibit the expression of fibrosis and catabolic markers. Then, these results suggest that the application of μFAT may represent an effective conservative or adjuvant therapy for the treatment of tendon disorders.

Reliable Reference Genes for Gene Expression Assessment in Tendon-Derived Cells under Inflammatory and Pro-Fibrotic/Healing Stimuli

Tendon cells (TCs) are important for homeostatic maintenance in the healthy tendon and to promote tissue healing after injury. Further, resident and rare populations of tendon stem/progenitor cells, located at various sites within the tendon, contribute to tendon recovery by differentiating into repairing TCs. Gene expression analysis, through quantitative reverse-transcription polymerase chain reaction (qRT-PCR), constitutes a useful tool to study cellular responses, including the transition from initial inflammation to healing processes. A critical step required for data normalization is the choice of reliable reference genes (RGs), a process highly underestimated in tendon biology. In this study, the suitability of five commonly used RGs (ACTB, B2M, GAPDH, HPRT1, and RPLP0) was evaluated using TCs samples cultured in both standard and progenitor-enriching conditions, as well as under either inflammatory (IFNγ + TNFα) or pro-fibrotic/healing (CTGF) stimulation. The stability of the candidate RGs was computationally determined using NormFinder, geNorm, BestKeeper, and DeltaCt applets. Overall, ACTB resulted as the most stable RG on the basis of the integration of each gene weight, whereas B2M and RPLP0 performed poorly. To further validate ACTB’s optimal performance, we evaluated the expression of ICAM1, coding for an immune-related cell surface glycoprotein, and COL1A1, encoding collagen type I that is the main component of the tendon extracellular matrix (ECM), both known to be modulated by inflammation. The expression of both genes was heavily affected by the RGs used. Consequently, when analyzing gene expression in tendon-derived cells subjected to various stimulatory protocols, the use of a suitable RG should be considered carefully. On the basis of our results, ACTB can be reliably used when analyzing different TC types exposed to pathological conditions.

Interaction with hyaluronan matrix and miRNA cargo as contributors for in vitro potential of mesenchymal stem cell-derived extracellular vesicles in a model of human osteoarthritic synoviocytes

BACKGROUND

Osteoarthritis (OA) is the most prevalent joint disease, and to date, no options for effective tissue repair and restoration are available. With the aim of developing new therapies, the impact of mesenchymal stem cells (MSCs) has been explored, and the efficacy of MSCs started to be deciphered. A strong paracrine capacity relying on both secreted and vesicle-embedded (EVs) protein or nucleic acid-based factors has been proposed as the principal mechanism that contributes to tissue repair. This work investigated the mechanism of internalization of extracellular vesicles (EVs) released by adipose-derived MSCs (ASCs) and the role of shuttled miRNAs in the restoration of homeostasis in an in vitro model of human fibroblast-like synoviocytes (FLSs) from OA patients.

METHODS

ASC-EVs were isolated by differential centrifugation and validated by flow cytometry and nanoparticle tracking analysis. ASC-EVs with increased hyaluronan (HA) receptor CD44 levels were obtained culturing ASCs on HA-coated plastic surfaces. OA FLSs with intact or digested HA matrix were co-cultured with fluorescent ASC-EVs, and incorporation scored by flow cytometry and ELISA. ASC-EV complete miRNome was deciphered by high-throughput screening. In inflamed OA FLSs, genes and pathways potentially regulated by ASC-EV miRNA were predicted by bioinformatics. OA FLSs stimulated with IL-1β at physiological levels (25 pg/mL) were treated with ASC-EVs, and expression of inflammation and OA-related genes was measured by qRT-PCR over a 10-day time frame with modulated candidates verified by ELISA.

RESULTS

The data showed that HA is involved in ASC-EV internalization in FLSs. Indeed, both removal of HA matrix presence on FLSs and modulation of CD44 levels on EVs affected their recruitment. Bioinformatics analysis of EV-embedded miRNAs showed their ability to potentially regulate the main pathways strictly associated with synovial inflammation in OA. In this frame, ASC-EVs reduced the expression of pro-inflammatory cytokines and chemokines in a chronic model of FLS inflammation.

CONCLUSIONS

Given their ability to affect FLS behavior in a model of chronic inflammation through direct interaction with HA matrix and miRNA release, ASC-EVs confirm their role as a novel therapeutic option for osteoarthritic joints.

Identification of miRNA Reference Genes in Extracellular Vesicles from Adipose Derived Mesenchymal Stem Cells for Studying Osteoarthritis

Osteoarthritis (OA) leads to chronic pain and disability, and traditional conservative treatments are not effective in the long term. The intra-articular injection of mesenchymal stem cells (MSCs) is considered a novel therapy for OA whose efficacy mainly relies on the adaptive release of paracrine molecules which are either soluble or extracellular vesicles (EVs) embedded. The correct quantification of EV-miRNAs using reliable reference genes (RGs) is a crucial step in optimizing this future therapeutic cell-free approach. The purpose of this study is to rate the stabilities of literature-selected proposed RGs for EV-miRNAs in adipose derived-MSCs (ASCs). EVs were isolated by ultracentrifugation from ASCs cultured with or without inflammatory priming mimicking OA synovial fluid condition. Expression of putative RGs (let-7a-5p, miR-16-5p, miR-23a-3p, miR-26a-5p, miR-101-3p, miR-103a-3p, miR-221-3p, miR-423-5p, miR-425-5p, U6 snRNA) was scored by using the algorithms geNorm, NormFinder, BestKeeper and ΔCt method. miR-16a-5p/miR-23a-3p yielded the most stable RGs, whereas let-7a-5p/miR-425-5p performed poorly. Outcomes were validated by qRT-PCR on miR-146a-5p, reported to be ASC-EVs enriched and involved in OA. Incorrect RG selection affected the evaluation of miR-146a-5p abundance and modulation by inflammation, with both values resulting strongly donor-dependent. Our findings demonstrated that an integrated approach of multiple algorithms is necessary to identify reliable, stable RGs for ASC-EVs miRNAs evaluation. A correct approach would increase the accuracy of embedded molecule assessments aimed to develop therapeutic strategies for the treatment of OA based on EVs.

In Vitro Induction of Tendon-Specific Markers in Tendon Cells, Adipose- and Bone Marrow-Derived Stem Cells is Dependent on TGFβ3, BMP-12 and Ascorbic Acid Stimulation

Mesenchymal Stem Cells (MSCs) and tissue-specific progenitors have been proposed as useful tools for regenerative medicine approaches in bone, cartilage and tendon-related pathologies. The differentiation of cells towards the desired, target tissue-specific lineage has demonstrated advantages in the application of cell therapies and tissue engineering. Unlike osteogenic and chondrogenic differentiation, there is no consensus on the best tenogenic induction protocol. Many growth factors have been proposed for this purpose, including BMP-12, b-FGF, TGF-β3, CTGF, IGF-1 and ascorbic acid (AA). In this study, different combinations of these growth factors have been tested in the context of a two-step differentiation protocol, in order to define their contribution to the induction and maintenance of tendon marker expression in adipose tissue and bone marrow derived MSCs and tendon cells (TCs), respectively. Our results demonstrate that TGF-β3 is the main inducer of scleraxis, an early expressed tendon marker, while at the same time inhibiting tendon markers normally expressed later, such as decorin. In contrast, we find that decorin is induced by BMP-12, b-FGF and AA. Our results provide new insights into the effect of different factors on the tenogenic induction of MSCs and TCs, highlighting the importance of differential timing in TGF-β3 stimulation.

Effect of a Collagen-Based Compound on Morpho-Functional Properties of Cultured Human Tenocytes

Background: Greater Trochanter Pain Syndrome (GTPS) is the main reason for recalcitrant lateral hip pain. Gluteus medius and minimus tendinopathy plays a key role in this setting. An injectable medical compound containing collagen type I (MD-Tissue, Guna) has been produced with the aim to counteract the physiological and pathological degeneration of tendons. In this study we aimed at characterizing the effect of this medical compound on cultured human gluteal tenocytes, focusing on the collagen turnover pathways, in order to understand how this medical compound could influence tendon biology and healing. Methods: Tenocytes were obtained from gluteal tendon fragments collected in eight patients without any gluteal tendon pathology undergoing total hip replacement through an anterior approach. Cell proliferation and migration were investigated by growth curves and wound healing assay, respectively. The expression of genes and proteins involved in collagen turnover were analysed by real-time PCR, Slot blot and SDS-zymography. Results: Our data show that tenocytes cultured on MD-Tissue, compared to controls, have increased proliferation rate and migration potential. MD-Tissue induced collagen type I (COL-I) secretion and mRNA levels of tissue inhibitor of matrix metalloproteinases (MMP)-1 (TIMP-1). Meanwhile, lysyl hydroxylase 2b and matrix metalloproteinases (MMP)-1 and -2, involved, respectively, in collagen maturation and degradation, were not affected. Conclusions: Considered as a whole, our results suggest that MD-Tissue could induce in tenocytes an anabolic phenotype by stimulating tenocyte proliferation and migration and COL-I synthesis, maturation, and secretion, thus favouring tendon repair. In particular, based on its effect on gluteal tenocytes, MD-Tissue could be effective in the discouraging treatment of GTPS. From now a rigorous clinical investigation is desirable to understand the real clinical potentials of this compound.