Serum-free cultures of C2C12 cells show different muscle phenotypes which can be estimated by metabolic profiling

In vitro skeletal muscle cell production is emerging in the field of artificial lab-grown meat as alternative future food. Currently, there is an urgent paradigm shift towards a serum replacement culture system. Surprisingly, little is known about the impact of serum-free culture on skeletal muscle cells to date. Therefore, we performed metabolic profiling of the C2C12 myoblasts and myotubes in serum-free mediums (B27, AIM-V) and compared it with conventional serum supplementation culture. Furthermore, cell morphology, viability, and myogenic differentiation were observed for 7 days of cultivation. Intriguingly, the metabolic difference is more dominant between the cell status than medium effects. In addition, proliferative myoblast showed more distinct metabolic differences than differentiated myotubes in different culture conditions. The intracellular levels of GL3P and UDP-GlcNAc were significantly increased in myotubes versus myoblast. Non-essential amino acids and pyruvate reduction and transamination showed significant differences among serum, B27, and AIM-V cultures. Intracellular metabolite profiles indicated that C2C12 myotubes cultured in serum and B27 had predominant glycolytic and oxidative metabolism, respectively, indicating fast and slow types of muscle confirmed by MHC immunostaining. This work might be helpful to understand the altered metabolism of skeletal muscle cells in serum-free culture and contribute to future artificial meat research work.

AB0144 STRATIFICATION OF PATIENTS WITH PRIMARY SJÖGREN’S SYNDROME BY MEASURING B-CELL HEALTH

Background:

Primary Sjögren’s syndrome (pSS) is a heterogeneous immune disorder with broad clinical phenotypes that can arise from a large number of genetic, hormonal, and environmental causes. B-cell hyperactivity is considered to be a pathogenic hallmark of pSS. However, whether B-cell hyperactivity in pSS patients is a result of polygenic, B cell-intrinsic factors, extrinsic factors, or both, is unclear. Despite controversies about the efficacy of rituximab, new B-cell targeting therapies are under investigation with promising early results. However, for such therapies to be successful, the etiology of B-cell hyperactivity in pSS needs to be clarified at the individual patient level.

Objectives:

To measure naïve B-cell function in pSS patients and healthy donors using quantitative immunology.

Methods:

We have developed standardised, quantitative functional assays of B-cell responses that measure division, death, differentiation and isotype switching, to reveal the innate programming of B cells in response to T-independent and dependent stimuli. This novel pipeline to measure B-cell health was developed to reveal the sum total of polygenic defects and underlying B-cell dysfunction at an individual level. For the current study, 25 pSS patients, fulfilling 2016 ACR-EULAR criteria, and 15 age-and gender-matched healthy donors were recruited. Standardized quantitative assays were used to directly measure B cell division, death and differentiation in response to T cell-independent (anti-Ig + CpG) and T-cell dependent (CD40L + IL-21) stimuli. Naïve B cells (IgD+CD27-) were sorted from peripheral blood mononuclear cells and were labeled with Cell Trace Violet at day 0 to track cell division until day 6. B cell differentiation was measured at day 5.

Results:

Application of our standardized assays, and accompanying parametric models, allowed us to study B cell-intrinsic defects in pSS patients to a range of stimuli. Strikingly, we demonstrated a hyperresponse of naïve B cells to combined B cell receptor (BCR) and Toll-like receptor (TLR)-9 stimulation in pSS patients. This hyperresponse was revealed by an increased mean division number (MDN) at day 5 in pSS patients compared with healthy donors (p=0.021). A higher MDN in pSS patients was observed at the cohort level and was likely attributed to an increased division burst (division destiny) time. The MDN upon BCR/TLR-9 stimulation correlated with serum IgG levels (rs=0.52; p=0.011). No difference in MDN of naïve B cells after T cell-dependent stimulation was observed between pSS patients and healthy donors. B cell differentiation capacity (e.g., plasmablast formation and isotype switching) after T cell-dependent stimulation was also assessed. At the cohort level, no difference in differentiation capacity between groups was observed, although some pSS patients showed higher plasmablast frequencies than healthy donors.

Conclusion:

Here, we demonstrate defects in B-cell responses both at the cohort level, as well as individual signatures of defective responses. Personalized profiles of B cell health in pSS patients reveal a group of hyperresponsive patients, specifically to combined BCR/TLR stimulation. These patients may benefit most from B-cell targeted therapies. Future studies will address whether profiles of B cell health might serve additional roles, such as prediction of disease trajectories, and thus accelerate early intervention and access to precision therapies.

Disclosure of Interests:

Gwenny M. Verstappen: None declared, Jessica Catherine Tempany: None declared, HoChan Cheon: None declared, Anthony Farchione: None declared, Sarah Downie-Doyle: None declared, Maureen Rischmueller Consultant of: Abbvie, Bristol-Meyer-Squibb, Celgene, Glaxo Smith Kline, Hospira, Janssen Cilag, MSD, Novartis, Pfizer, Roche, Sanofi, UCB, Ken R. Duffy: None declared, Frans G.M. Kroese Grant/research support from: Unrestricted grant from Bristol-Myers Squibb, Consultant of: Consultant for Bristol-Myers Squibb, Speakers bureau: Speaker for Bristol-Myers Squibb, Roche and Janssen-Cilag, Hendrika Bootsma Grant/research support from: Unrestricted grants from Bristol-Myers Squibb and Roche, Consultant of: Consultant for Bristol-Myers Squibb, Roche, Novartis, Medimmune, Union Chimique Belge, Speakers bureau: Speaker for Bristol-Myers Squibb and Novartis., Philip D. Hodgkin Grant/research support from: Medimmune, Vanessa L. Bryant Grant/research support from: CSL

Platelet-derived growth factor-AA increases IL-1beta and IL-8 expression and activates NF-kappaB in rheumatoid fibroblast-like synoviocytes

The effect of platelet-derived growth factor (PDGF)-AA on the inflammation in rheumatoid arthritis (RA) and osteoarthritis (OA) was investigated using cultured fibroblast-like synoviocytes (FLS) obtained from RA and OA patients as well as control nonarthritic (NA) individuals. PDGF-AA increased the mRNA and protein expressions of proinflammatory cytokines, interleukin (IL)-1beta and IL-8 in RA FLS. Biological activity of IL-1 in the culture supernatant of RA FLS was also increased by PDGF-AA stimulation. Interestingly, PDGF-AA synergized with tumour necrosis factor (TNF)-alpha to upregulate the protein expressions of IL-1beta and IL-8. PDGF-induced enhancement of the IL-1beta and IL-8 mRNA expressions was also observed in OA FLS. However, the expression of these proinflammatory cytokines in NA FLS did not change by PDGF treatment, suggesting that the inflammatory condition might have modified the biological effects of PDGF. In accordance with the enhanced expression of inflammatory cytokines, the activity of nuclear factor kappaB was also induced in response to PDGF-AA in RA FLS. These results suggest that PDGF-AA plays an important role in the progression of RA inflammation, and inhibiting PDGF activity may be useful for the effective RA treatment.

Increased expression of pro-inflammatory cytokines and metalloproteinase-1 by TGF-beta1 in synovial fibroblasts from rheumatoid arthritis and normal individuals

Transforming growth factor (TGF)-beta1 is expressed abundantly in the rheumatoid synovium. In this study, the inflammatory effect of TGF-beta1 in rheumatoid arthritis (RA) was investigated using cultured fibroblast-like synoviocytes (FLS) from RA and osteoarthritis (OA) patients, as well as non-arthritic individuals. mRNA expressions of IL-1beta, tumour necrosis factor (TNF)-alpha, IL-8, macrophage inflammatory protein (MIP)-1alpha and metalloproteinase (MMP)-1 were increased in RA and OA FLS by TGF-beta1 treatment, but not in non-arthritic FLS. Enhanced protein expression of IL-1beta, IL-8 and MMP-1 was also observed in RA FLS. Moreover, TGF-beta1 showed a synergistic effect in increasing protein expression of IL-1beta and matrix metalloproteinase (MMP)-1 with TNFalpha and IL-1beta, respectively. Biological activity of IL-1 determined by mouse thymocyte proliferation assay was also enhanced by 50% in response to TGF-beta1 in the culture supernatant of RA FLS. DNA binding activities of nuclear factor (NF)-kappaB and activator protein (AP)-1 were shown to increase by TGF-beta1 as well. These results suggest that TGF-beta1 contributes for the progression of inflammation and joint destruction in RA, and this effect is specific for the arthritic synovial fibroblasts.

Effects of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) on the expression of inflammatory cytokines and apoptosis induction in rheumatoid synovial fibroblasts and monocytes

This study was performed to investigate whether peroxisome proliterator-activated receptor-gamma (PPAR-gamma) exerted an anti-inflammatory effect on rheumatoid synovial cells and inhibited dysregulated proliferation. The expression of PPAR-gamma mRNA in cultured human synoviocytes and THP-1 cells was analysed by RT-PCR. PPAR-gamma was expressed in normal, osteoarthritis (OA), rheumatoid arthritis (RA) synovial cells as well as a human monocytic cell line, THP-1. In RA and OA synoviocytes, the induction of inflammatory cytokine mRNA expression such as TNF-alpha and IL-1beta was significantly inhibited by the natural PPAR-gamma agonist, 15 deoxy-Delta(12,14)prostaglandin J(2)(15d-PGJ(2)). The effect of PPAR-gamma on the nuclear factor (NF)-kappaB activity was tested by electrophoretic mobility shift assay (EMSA). Both troglitazone and 15d-PGJ(2)markedly inhibited TNF-alpha-induced NF-kappaB activation at 30 microM. However, PPAR-gamma agonist neither reduced proliferation nor induced apoptosis in RA synoviocytes when measured by XTT assay and fluorescence activated cell sorter (FACS) analysis. In contrast, it induced apoptosis in a dose-dependent manner in THP-1 cells and augmented TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis as well. In conclusion, these data demonstrate that PPAR-gamma is expressed in human synoviocytes and THP-1 cells, and the PPAR-gamma activation inhibits expression of inflammatory cytokines in RA synoviocytes. Furthermore, PPAR-gamma activation induces apoptosis by itself and augments TRAIL/Apo2L-induced apoptosis in THP-1 cells. These results suggest that PPAR-gamma agonists may provide a new therapeutic approach for RA.

Indomethacin treatment decreases renal blood flow velocity in human neonates

This study was designed to evaluate the effect of indomethacin (ID) on renal perfusion in 13 neonates with symptomatic patent ductus arteriosus (PDA). Serial blood flow velocity in the left renal artery was measured just before and at 10, 30, 45, 60, 75 and 90 min after ID administration. Serum creatinine (Cr), sodium (Na), and osmolarity were measured just before, at 12 and 24 h, and at 3 days after ID administration. Timed urine also was collected for measurement of amount, fractional excretion of Na (FE(Na)), and creatinine clearance (C(Cr)). ID decreased end-diastolic flow velocity of renal artery and increased Pourcelot's index, starting at 10 min and lasting for 75 min (p < 0.05). Serum Cr significantly increased at 12 h, and hourly urine output and C(Cr) decreased for 24 h. Serum Na and osmolarity decreased for a period of at least 3 days (p < 0.05). FE(Na) decreased at 12-24 h (p < 0.05). We conclude that ID treatment can induce significant renal dysfunction due to diminution of renal perfusion in human neonates.