Jagdeep Nanchahal

Role of interleukin-1beta in postoperative cognitive dysfunction.

Although postoperative cognitive dysfunction (POCD) often complicates recovery from major surgery, the pathogenic mechanisms remain unknown. We explored whether systemic inflammation, in response to surgical trauma, triggers hippocampal inflammation and subsequent memory impairment, in a mouse model of orthopedic surgery.

Alarmins: awaiting a clinical response.

Alarmins are endogenous molecules that are constitutively available and released upon tissue damage and activate the immune system. Current evidence indicates that uncontrolled and excessive release of alarmins contributes to the dysregulated processes seen in many inflammatory and autoimmune conditions, as well as tumorigenesis and cancer spread. Conversely, alarmins have also been found to play a major role in the orchestration of tissue homeostasis, including repair and remodeling in the heart, skin, and nervous system. Here, we provide an update and overview on alarmins, highlighting the areas that may benefit from this clinical translation.

TNF-alpha promotes fracture repair by augmenting the recruitment and differentiation of muscle-derived stromal cells.

With an aging population, skeletal fractures are increasing in incidence, including the typical closed and the less common open fractures in normal bone, as well as fragility fractures in patients with osteoporosis. For the older age group, there is an urgent unmet need to induce predictable bone formation as well as improve implant fixation in situations such as hip joint replacement. Using a murine model of slow-healing fractures, we have previously shown that coverage of the fracture with muscle accelerated fracture healing and increased union strength. Here, we show that cells from muscle harvested after 3 d of exposure to an adjacent fracture differentiate into osteoblasts and form bone nodules in vitro. The osteogenic potential of these cells exceeds that of adipose and skin-derived stromal cells and is equivalent to bone marrow stromal cells. Supernatants from human fractured tibial bone fragments promote osteogenesis and migration of muscle-derived stromal cells (MDSC) in vitro. The main factor responsible for this is TNF-α, which promotes first MDSC migration, then osteogenic differentiation at low concentrations. However, TNF-α is inhibitory at high concentrations. In our murine model, addition of TNF-α at 1 ng/mL at the fracture site accelerated healing. These data indicate that manipulating the local inflammatory environment to recruit, then differentiate adjacent MDSC, may be a simple yet effective way to enhance bone formation and accelerate fracture repair. Our findings are based on a combination of human specimens and an in vivo murine model and may, therefore, translate to clinical care.

Management of severe open tibial fractures: THE NEED FOR COMBINED ORTHOPAEDIC AND PLASTIC SURGICAL TREATMENT IN SPECIALIST CENTRES

Although it is widely accepted that grade IIIB open tibial fractures require combined specialised orthopaedic and plastic surgery, the majority of patients in the UK initially present to local hospitals without access to specialised trauma facilities. The aim of this study was to compare the outcome of patients presenting directly to a specialist centre (primary group) with that of patients initially managed at local centres (tertiary group). We reviewed 73 consecutive grade IIIB open tibial shaft fractures with a mean follow-up of 14 months (8 to 48). There were 26 fractures in the primary and 47 in the tertiary group. The initial skeletal fixation required revision in 22 (47%) of the tertiary patients. Although there was no statistically-significant relationship between flap timing and flap failure, all the failures (6 of 63; 9.5%) occurred in the tertiary group. The overall mean time to union of 28 weeks was not influenced by the type of skeletal fixation. Deep infection occurred in 8.5% of patients, but there were no persistently infected fractures. The infection rate was not increased in those patients debrided more than six hours after injury. The limb salvage rate was 93%. The mean limb functional score was 74% of that of the normal limb. At review, 67% of patients had returned to employment, with a further 10% considering a return after rehabilitation. The times to union, infection rates and Enneking limb reconstruction scores were not statistically different between the primary and tertiary groups. The increased complications and revision surgery encountered in the tertiary group suggest that severe open tibial fractures should be referred directly to specialist centres for simultaneous combined management by orthopaedic and plastic surgeons.

Comparison of the Healing of Open Tibial Fractures Covered with Either Muscle or Fasciocutaneous Tissue in a Murine Model

The objective of this study was to compare the effects of soft tissue coverage by either muscle or fasciocutaneous tissue on the healing of open tibial fractures in a murine model. An open tibial fracture, stripped of periosteum with intramedullary fixation, was created in mice. Experimental groups were devised to allow exclusive comparison of either muscle alone or skin plus fascia in direct contact with healing bone. To exclusively assess the relative efficacy of muscle and fasciocutaneous tissue to promote healing of a fracture stripped of periosteum, a piece of sterile inert material (polytetrafluoroethylene) was positioned anteriorly, excluding skin and fascia (muscle group) or posteriorly, excluding muscle (fasciocutaneous group). Skeletal repair was assessed histologically and quantified by histomorphometry; quantitative peripheral computed tomography (pQCT) and mechanical testing using a four‐point bending technique. This standardized, reproducible model allowed characterization of the morphology of open fracture healing. At 28 days postfracture, there was faster healing in the experimental muscle coverage group compared to skin and fascia alone. Furthermore, there was almost 50% more cortical bone content and a threefold stronger union beneath muscle compared to fasciocutaneous tissue (p < 0.05 by one‐way ANOVA). Exclusive comparison of muscle and fasciocutaneous tissue in our novel murine model demonstrates that muscle is superior for the coverage of open tibial fractures for both the rate and quality of fracture healing.

Production of cytokines, vascular endothelial growth factor, matrix metalloproteinases, and tissue inhibitor of metalloproteinases 1 by tenosynovium demonstrates its potential for tendon destruction in rheumatoid arthritis.

OBJECTIVE To investigate the role of proinflammatory cytokines, vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMPs), and tissue inhibitor of metalloproteinases 1 (TIMP-1) in the destruction of tendons by tenosynovium in rheumatoid arthritis (RA). METHODS Synovial specimens were obtained from encapsulating tenosynovium (n = 17), invasive tenosynovium (n = 13), and wrist joints (n = 17) in 18 RA patients undergoing wrist extensor tenosynovectomy. Synovial membrane cells were dissociated from connective tissue by enzyme digestion and cultured in vitro for 48 hours, and harvested supernatants were assayed for the cytokines tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6), VEGF, MMPs 1, 2, 3, and 13, and TIMP-1 by enzyme-linked immunosorbent assay. Gelatin zymography was performed to demonstrate enzyme activity. Statistical analysis was performed using Students paired 2-tailed t-tests for parametric data and the Wilcoxon signed rank test for nonparametric data. RESULTS MMP-1 and MMP-13 levels were approximately 2.5-fold higher in invasive tenosynovium compared with encapsulating tenosynovium. Levels of MMP-2 were approximately 1.5-fold higher in invasive tenosynovium compared with both encapsulating tenosynovium and wrist joint synovium. MMP-13 (P = 0.009) and IL-6 (P = 0.03) levels were significantly lower in encapsulating tenosynovium compared with wrist joint synovium. Levels of VEGF, TIMP-1, TNFalpha, and MMP-3 were similar in all synovial sample groups. Zymography demonstrated enzyme activity in all synovium samples from all 9 patients assessed. CONCLUSION Tenosynovium produces proinflammatory cytokines and proteolytic enzymes that are important in the tissue degradation seen in RA. Increased production of the enzymes MMP-1, MMP-2, and MMP-13 by invasive tenosynovium suggests a possible explanation for the worse prognosis and increased rupture rate associated with invasive tenosynovitis in RA. Production of VEGF by tenosynovium suggests that angiogenesis may have a role in tenosynovial proliferation and invasion of tendons.

Membrane type 1 matrix metalloproteinase is a crucial promoter of synovial invasion in human rheumatoid arthritis

OBJECTIVE A hallmark of rheumatoid arthritis (RA) is invasion of the synovial pannus into cartilage, and this process requires degradation of the collagen matrix. The aim of this study was to explore the role of one of the collagen-degrading matrix metalloproteinases (MMPs), membrane type 1 MMP (MT1-MMP), in synovial pannus invasiveness. METHODS The expression and localization of MT1-MMP in human RA pannus were investigated by Western blot analysis of primary synovial cells and immunohistochemical analysis of RA joint specimens. The functional role of MT1-MMP was analyzed by 3-dimensional (3-D) collagen invasion assays and a cartilage invasion assay in the presence or absence of tissue inhibitor of metalloproteinases 1 (TIMP-1), TIMP-2, or GM6001. The effect of adenoviral expression of a dominant-negative MT1-MMP construct lacking a catalytic domain was also examined. RESULTS MT1-MMP was highly expressed at the pannus-cartilage junction in RA joints. Freshly isolated rheumatoid synovial tissue and isolated RA synovial fibroblasts invaded into a 3-D collagen matrix in an MT1-MMP-dependent manner. Invasion was blocked by TIMP-2 and GM6001 but not by TIMP-1. Invasion was also inhibited by the overexpression of a dominant-negative MT1-MMP, which inhibits collagenolytic activity and proMMP-2 activation by MT1-MMP on the cell surface. Synovial fibroblasts also invaded into cartilage in an MT1-MMP-dependent manner. This process was further enhanced by removing aggrecan from the cartilage matrix. CONCLUSION MT1-MMP serves as an essential collagen-degrading proteinase during pannus invasion in human RA. Specific inhibition of MT1-MMP-dependent invasion may represent a novel therapeutic strategy for RA.

TREM-1 expression is increased in the synovium of rheumatoid arthritis patients and induces the expression of pro-inflammatory cytokines.

OBJECTIVES To investigate the expression and function of triggering receptor expressed on myeloid cells-1 (TREM-1) in the synovium of human RA patients as well as the level of soluble TREM-1 in the plasma of RA patients. METHODS Twenty-four RA synovial samples were analysed by gene expression oligonucleotide microarrays. Expression levels of TREM-1 mRNA in murine CIA paws were determined by quantitative PCR (qPCR). TREM-1 protein expression was detected by immunohistochemistry in five RA synovial samples and two OA synovial samples. TREM-1-positive cells from five RA synovial tissues were analysed by FACS staining to determine the cell type. Activation of TREM-1 was tested in five RA synovial samples. Soluble TREM-1 was measured in serum from 32 RA patients. RESULTS The expression of TREM-1 mRNA was found to increase 6.5-fold in RA synovial samples, whereas it was increased 132-fold in CIA paws. Increased numbers of TREM-1-positive cells were seen in RA synovium sections and these cells co-expressed CD14. Using a TREM-1-activating cross-linking antibody in RA synovial cultures, multiple pro-inflammatory cytokines were induced. The average amount of soluble TREM-1 in plasma from RA patients was found to be higher than that in plasma from healthy volunteers. CONCLUSIONS These findings suggest that the presence of high levels of functionally active TREM-1 in RA synovium may contribute to the development or maintenance of RA, or both. Inhibiting TREM-1 activity may, therefore, have a therapeutic effect on RA. High levels of soluble TREM-1 in the plasma of RA patients compared with healthy volunteers may indicate disease activity.

Unraveling the signaling pathways promoting fibrosis in Dupuytren's disease reveals TNF as a therapeutic target

Significance Fibrosis, a hallmark of many clinical disorders, occurs because of uncontrolled myofibroblast activity. We studied Dupuytrens disease, a common hereditable fibrotic condition that causes the fingers to irreversibly curl toward the palm. We found that freshly isolated tissue from Dupuytrens patients contained macrophages and released proinflammatory protein mediators (cytokines). Of the cytokines, only TNF selectively converted normal fibroblasts from the palm of patients with Dupuytrens disease into myofibroblasts via activation of the Wnt signaling pathway. Conversely, blockade of TNF resulted in reversal of the myofibroblast phenotype. Therefore, TNF inhibition may prevent progression or recurrence of Dupuytrens disease. Dupuytrens disease is a very common progressive fibrosis of the palm leading to flexion deformities of the digits that impair hand function. The cell responsible for development of the disease is the myofibroblast. There is currently no treatment for early disease or for preventing recurrence following surgical excision of affected tissue in advanced disease. Therefore, we sought to unravel the signaling pathways leading to the development of myofibroblasts in Dupuytrens disease. We characterized the cells present in Dupuytrens tissue and found significant numbers of immune cells, including classically activated macrophages. High levels of proinflammatory cytokines were also detected in tissue from Dupuytrens patients. We compared the effects of these cytokines on contraction and profibrotic signaling pathways in fibroblasts from the palmar and nonpalmar dermis of Dupuytrens patients and palmar fibroblasts from non-Dupuytrens patients. Exogenous addition of TNF, but not other cytokines, including IL-6 and IL-1β, promoted differentiation into specifically of palmar dermal fibroblasts from Dupuytrens patients in to myofibroblasts. We also demonstrated that TNF acts via the Wnt signaling pathway to drive contraction and profibrotic signaling in these cells. Finally, we examined the effects of targeted cytokine inhibition. Neutralizing antibodies to TNF inhibited the contractile activity of myofibroblasts derived from Dupuytrens patients, reduced their expression of α-smooth muscle actin, and mediated disassembly of the contractile apparatus. Therefore, we showed that localized inflammation in Dupuytrens disease contributes to the development and progression of this fibroproliferative disorder and identified TNF as a therapeutic target to down-regulate myofibroblast differentiation and activity.

Systematic review of molecular mechanism of action of negative-pressure wound therapy.

Negative‐pressure wound therapy (NPWT) promotes angiogenesis and granulation, in part by strain‐induced production of growth factors and cytokines. As their expression profiles are being unravelled, it is pertinent to consider the mode of action of NPWT at the molecular level.