Rest reduces venous lactate levels significantly in patients in outpatient clinic

Lactate is produced in the human body during physical activity and elimination takes time with a half-life of approximately 18 min. We, therefore, investigated the potential impact of resting time (RT) duration on lactate concentration in our outpatient venipuncture clinic for all lactate requests during a 4½-year period. All samples drawn for venous lactate analysis during a 4½-year period in our hospital outpatient venipuncture clinics were included in this study. RT was reported electronically at each visit. Results from a total of 831 samples were obtained for further analysis. We found varying lactate concentrations across resting time <15min (median 1.6 mmol/L, IQR[1.2-2.1] mmol/L), between <15 min and >30 min (median 1.4 mmol/L, IQR[1.0-1.9] mmol/L) and for >30 min (median 1.3 mmol/L, IQR[1.0-1.7] mmol/L). There was a significant difference between <15 min versus 15-30 min (p = 0.015), which gives a 17.7% higher lactate from 15-30 min to <15 min. There was a significant 28.3% increase in mean lactate concentration from >30min to <15min (p < 0.0001) when corrected for age. We found that lactate concentration was dependent on RT in the outpatient clinic. The difference was clinically significant. Based on the results of this study, we, therefore, conclude that a 15 min waiting time before venipuncture for lactate sampling in an outpatient clinic is of clinical importance.

Intermittent Hypoxic Therapy Inhibits Allogenic Bone-Graft Resorption by Inhibition of Osteoclastogenesis in a Mouse Model

Systemic Intermittent Hypoxic Therapy (IHT) relies on the adaptive response to hypoxic stress. We investigated allogenic bone-graft resorption in the lumbar spine in 48 mice. The mice were exposed to IHT for 1 week before surgery or 1 week after surgery and compared with controls after 1 and 4 weeks. Complete graft resorption was observed in 33-36% of the animals in the control group, but none in the preoperative IHT group. Increased bone-graft volume was demonstrated by micro-computed tomography in the preoperative IHT group after 1 week (p = 0.03) while a non-significant difference was observed after 4 weeks (p = 0.12). There were no significant differences in the postoperative IHT group. Increased concentration of immune cells was localized in the graft area, and more positive tartrate-resistant acid phosphatase (TRAP) staining was found in controls compared with IHT allogenic bone grafts. Systemic IHT resulted in a significant increase of the major osteoclast inhibitor osteoprotegerin as well as osteogenic and angiogenic regulators Tgfbr3, Fst3l, Wisp1, and Vegfd. Inflammatory cytokines and receptor activator of nuclear factor kappa-B ligand (RANKL) stimulators IL-6, IL-17a, IL-17f, and IL-23r increased after 1 and 4 weeks, and serum RANKL expression remained constant while Ccl3 and Ccl5 decreased. We conclude that the adaptive response to IHT activates numerous pathways leading to inhibition of osteoclastic activity and inhibition of allogenic bone-graft resorption.

Particulated Cartilage for Chondral and Osteochondral Repair: A Review

INTRODUCTION

Injuries to articular cartilage have a poor spontaneous repair potential and no gold standard treatment exist. Particulated cartilage, both auto- and allograft, is a promising new treatment method that circumvents the high cost of scaffold- and cell-based treatments.

MATERIALS AND METHODS

A comprehensive database search on particulated cartilage was performed.

RESULTS

Fourteen animal studies have found particulated cartilage to be an effective treatment for cartilage injuries. Many studies suggest that juvenile cartilage has increased regenerative potential compared to adult cartilage. Sixteen clinical studies on 4 different treatment methods have been published. (1) CAIS, particulated autologous cartilage in a scaffold, (2) Denovo NT, juvenile human allograft cartilage embedded in fibrin glue, (3) autologous cartilage chips-with and without concomitant bone grafting, and (4) augmented autologous cartilage chips.

CONCLUSION

Implantation of allogeneic and autologous particulated cartilage provides a low cost and effective treatment alternative to microfracture and autologous chondrocyte implantation. The methods are promising, but large randomized controlled studies are needed.

Inflammatory proteins in infected bone tissue - An explorative porcine study

Objective

To explore the in situ inflammatory proteins in the local extracellular fluid of infected bone tissue.

Material and methods

Seven pigs went through a two-step surgery performing a traumatically implant-associated Staphylococcus aureus osteomyelitis in the proximal tibia. Five days later, microdialysis catheters (membrane cut off: 20 kDa) were placed in the implant cavity, infected and healthy cancellous bone, and infected and healthy subcutaneous tissue. Plasma samples were collected simultaneously. We employed an antibody-based proximity extension assay (Olink Inflammatory panel) for the measurement of inflammatory molecules within plasma and extracellular fluid of the investigated tissue compartments.

Results

A higher normalized protein expression in the infected bone tissue in comparison to healthy bone tissue was identified for proteins associated with angiogenesis and bone remodeling: OPG, TGFα, MCP-1, VEGFA, and uPA. Moreover, a parallel detectability of the systemic range of cytokines and chemokines as from the investigated local tissue compartments was demonstrated, indicating the same occurrence of proteins in the local environment as within plasma.

Conclusion

An angiogenic and osteogenic inflammatory protein composition within the extracellular fluid of infected bone tissue was described. The findings support the current histopathological knowledge and, therefore, microdialysis may represent a valid method for sampling of material for protein investigation of the in vivo inflammatory composition within the extracellular environment in infected bone tissue.

Age-Dependent Systemic Effects of a Systemic Intermittent Hypoxic Therapy In Vivo

Introduction: The adaptive response to systemic intermittent hypoxic therapy (SIHT) may be used for therapeutic advances due to the activation of multiple pathways involved in angiogenesis, immunomodulation, and tissue homeostasis. The aim of this study was to investigate the early age-dependent systemic response of different exposures of SIHT in mice. Materials and Methods: Sixty-four C57BL/6NRj female mice in three different age groups, young (4-5 weeks), adolescent (8-10 weeks), and adults (23-32 weeks), were exposed to SIHT. Different algorithms for equal hypoxic challenges (oxygen-decrease*time) were investigated to allow examination of the role of absolute hypoxia (oxygen-decrease) compared with relative hypoxia (total oxygen depletion over time). The systemic effects of angiogenetic regulation were investigated using blood samples analyzed by ELISA, proteome profiles, and proximity extension immunoassay. One-way analysis of variance with post hoc Bonferroni analyses was performed. Results: The early systemic response to SIHT was dependent on the absolute hypoxia rather than relative hypoxia over time. Serum erythropoietin (EPO) levels were increased significantly in young mice receiving low-oxygen SIHT treatments (10% and 15% oxygen). The expression of angiogenic proteins differed between the different age groups indicating an age-dependent response to SIHT. Focusing on hypoxia-inducible factor-1 (HIF-1) signaling, there was a trend toward upregulated angiogenetic response with younger age. Furthermore, clustering of protein expression in low-oxygen SIHT algorithms were found between young and adolescent mice. In adult mice, the majority of the proteins were downregulated as a response to SIHT. The systemic response of metabolites expressions was most pronounced in young mice. Systemic levels of cardiac troponin I (Tnni3) was unaffected by SIHT independent of age groups. Conclusions: The systemic response to SIHT is dependent on the absolute hypoxic exposure rather than the relative hypoxic depletion over time. Age-dependent effects of a short-term SIHT were associated with an increase in EPO, upregulation of angiogenetic pathways, and select metabolic and cell-surface proteins.

A Standardized Method of Applying Toluidine Blue Metachromatic Staining for Assessment of Chondrogenesis

OBJECTIVES

Staining with toluidine blue is a well-established procedure for the histological assessment of cartilaginous- and chondrogenic-differentiated tissues. Being a cationic dye, toluidine blue staining visualizes proteoglycans in a tissue because of its high affinity for the sulfate groups in proteoglycans. It is generally accepted that metachromatic staining with toluidine blue represents cartilaginous matrix and that the degree of positive staining corresponds with the amount of proteoglycans.

DESIGN

Articular cartilage and pellets of chondrocytes or bone marrow stromal cells were analyzed with a standardized staining procedure for toluidine blue.

RESULTS

In the present study, we illustrate why such an assumption is invalid unless a detailed description of the procedure and/or reference to a detailed published method are provided. This is because the staining specificity and intensity depend, as we have shown, on the pH of the staining solution, the use of dehydration, and on staining time.

CONCLUSIONS

We can, therefore, suggest a well-controlled standardized protocol for toluidine blue staining, which provides an easy and simple selective staining technique for the assessment of cartilage tissue and proteoglycan development in chondrogenic differentiation. If this procedure is not used, then investigators must provide sufficient technical information concerning the staining protocol to allow an assessment of the validity of the staining results.

Surface chemistry, substrate, and topography guide the behavior of human articular chondrocytes cultured in vitro

Understanding the behavior of chondrocytes in contact with artificial culture surfaces is becoming increasingly important in attaining appropriate ex vivo culture conditions of chondrocytes in cartilage regeneration. Chondrocyte transplantation-based cartilage repair requires efficiently expanded chondrocytes, and the culture surface plays an important role in guiding the behavior of the cell. Micro- and nano-engineered surfaces make it possible to modulate cell behavior. We hypothesized that the combined influence of topography, substrate, and surface chemistry may affect the chondrocyte culturing in terms of proliferation and phenotypic means. Human chondrocytes were cultured on polystyrene fabricated microstructures, flat polydimethylsiloxane (PDMS), or polystyrene treated with fibronectin or oxygen plasma and cultured for 1, 4, 7, and 10 days. The behavior of chondrocytes was evaluated by proliferation, viability, chondrogenic gene expression, and cell morphology. Contrary to our hypothesis, microstructures in polystyrene did not significantly influence the behavior of chondrocytes neither under normoxic- nor hypoxic conditions. However, changes in the substrate stiffness and surface chemistry were found to influence cell viability, gene expression, and morphology of human chondrocytes. Oxygen plasma treatment was the most important parameter followed by the softer substrate type PDMS. The findings indicate the culture of human chondrocytes on softer substratum and surface activation by oxygen plasma may prevent dedifferentiation and may improve chondrocyte transplantation-based cartilage repair. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2805-2816, 2018.