Shape or size matters? Towards standard reporting of tensile testing parameters for human soft tissues: systematic review and finite element analysis.

Material properties of soft-tissue samples are often derived through uniaxial tensile testing. For engineering materials, testing parameters (e.g., sample geometries and clamping conditions) are described by international standards; for biological tissues, such standards do not exist. To investigate what testing parameters have been reported for tensile testing of human soft-tissue samples, a systematic review of the literature was performed using PRISMA guidelines. Soft tissues are described as anisotropic and/or hyperelastic. Thus, we explored how the retrieved parameters compared against standards for engineering materials of similar characteristics. All research articles published in English, with an Abstract, and before 1 January 2023 were retrieved from databases of PubMed, Web of Science, and BASE. After screening of articles based on search terms and exclusion criteria, a total 1,096 articles were assessed for eligibility, from which 361 studies were retrieved and included in this review. We found that a non-tapered shape is most common (209 of 361), followed by a tapered sample shape (92 of 361). However, clamping conditions varied and were underreported (156 of 361). As a preliminary attempt to explore how the retrieved parameters might influence the stress distribution under tensile loading, a pilot study was performed using finite element analysis (FEA) and constitutive modeling for a clamped sample of little or no fiber dispersion. The preliminary FE simulation results might suggest the hypothesis that different sample geometries could have a profound influence on the stress-distribution under tensile loading. However, no conclusions can be drawn from these simulations, and future studies should involve exploring different sample geometries under different computational models and sample parameters (such as fiber dispersion and clamping effects). Taken together, reporting and choice of testing parameters remain as challenges, and as such, recommendations towards standard reporting of uniaxial tensile testing parameters for human soft tissues are proposed.

Physical Activity on Telomere Length as a Biomarker for Aging: A Systematic Review.

BACKGROUND: Overall life expectancy continues to rise, approaching 80 years of age in several developed countries. However, healthy life expectancy lags far behind, which has, in turn, contributed to increasing costs in healthcare. One way to improve health and attenuate the socio-economic impact of an aging population is to increase overall fitness through physical activity. Telomere attrition or shortening is a well-known molecular marker in aging. As such, several studies have focused on whether exercise influences health and aging through telomere biology. This systematic review examines the recent literature on the effect of physical activity on telomere length (TL) and/or telomerase activity as molecular markers of aging. METHODS: A focused search was performed in the databases PubMed and Web of Science for retrieving relevant articles over the past ten years. The search contained the following keywords: exercise, sport, physical activity, fitness, sedentary, physical inactivity, telomere, telomere length, t/s ratio, and telomerase. PRISMA guidelines for systematic reviews were observed. RESULTS: A total of 43 articles were identified and categorized into randomized controlled trials (RCT), observational or interventional studies. RCTs (n = 8) showed inconsistent findings of increased TL length with physical activity in, e.g. obese, post-menopausal women. In comparison with a predominantly sedentary lifestyle, observational studies (n = 27) showed significantly longer TL with exercise of moderate to vigorous intensity; however, there was no consensus on the duration and type of physical activity and training modality. Interventional studies (n = 8) also showed similar findings of significantly longer TL prior to exercise intervention; however, these studies had smaller numbers of enrolled participants (mostly of high-performance athletes), and the physical activities covered a range of exercise intensities and duration. Amongst the selected studies, aerobic training of moderate to vigorous intensity is most prevalent. For telomere biology analysis, TL was determined mainly from leukocytes using qPCR. In some cases, especially in RCT and interventional studies, different sample types such as saliva, sperm, and muscle biopsies were analyzed; different leukocyte cell types and potential genetic markers in regulating telomere biology were also investigated. CONCLUSIONS: Taken together, physical activity with regular aerobic training of moderate to vigorous intensity appears to help preserve TL. However, the optimal intensity, duration of physical activity, as well as type of exercise still need to be further elucidated. Along with TL or telomerase activity, participants' fitness level, the type of physical activity, and training modality should be assessed at different time points in future studies, with the plan for long-term follow-up. Reducing the amount of sedentary behavior may have a positive effect of preserving and increasing TL. Further molecular characterization of telomere biology in different cell types and tissues is required in order to draw definitive causal conclusions on how physical activity affects TL and aging.

Reply to "On Clinical Utility and Systematic Reporting in Case Studies of Healthcare Process Mining. Comment on: 10.3390/ijerph17041348 'Towards the Use of Standardised Terms in Clinical Case Studies for Process Mining in Healthcare' ".

Many thanks to Dr. Mordaunt for his thoughtful Comment, which we were delighted to read with great interest[...].

Towards the Use of Standardized Terms in Clinical Case Studies for Process Mining in Healthcare.

Process mining can provide greater insight into medical treatment processes and organizational processes in healthcare. To enhance comparability between processes, the quality of the labelled-data is essential. A literature review of the clinical case studies by Rojas et al. in 2016 identified several common aspects for comparison, which include methodologies, algorithms or techniques, medical fields, and healthcare specialty. However, clinical aspects are not reported in a uniform way and do not follow a standard clinical coding scheme. Further, technical aspects such as details of the event log data are not always described. In this paper, we identified 38 clinically-relevant case studies of process mining in healthcare published from 2016 to 2018 that described the tools, algorithms and techniques utilized, and details on the event log data. We then correlated the clinical aspects of patient encounter environment, clinical specialty and medical diagnoses using the standard clinical coding schemes SNOMED CT and ICD-10. The potential outcomes of adopting a standard approach for describing event log data and classifying medical terminology using standard clinical coding schemes are further discussed. A checklist template for the reporting of case studies is provided in the Appendix A to the article.

Beta-catenin signaling plays a disparate role in different phases of fracture repair: implications for therapy to improve bone healing.

BACKGROUND: Delayed fracture healing causes substantial disability and usually requires additional surgical treatments. Pharmacologic management to improve fracture repair would substantially improve patient outcome. The signaling pathways regulating bone healing are beginning to be unraveled, and they provide clues into pharmacologic management. The beta-catenin signaling pathway, which activates T cell factor (TCF)-dependent transcription, has emerged as a key regulator in embryonic skeletogenesis, positively regulating osteoblasts. However, its role in bone repair is unknown. The goal of this study was to explore the role of beta-catenin signaling in bone repair. METHODS AND FINDINGS: Western blot analysis showed significant up-regulation of beta-catenin during the bone healing process. Using a beta-Gal activity assay to observe activation during healing of tibia fractures in a transgenic mouse model expressing a TCF reporter, we found that beta-catenin-mediated, TCF-dependent transcription was activated in both bone and cartilage formation during fracture repair. Using reverse transcription-PCR, we observed that several WNT ligands were expressed during fracture repair. Treatment with DKK1 (an antagonist of WNT/beta-catenin pathway) inhibited beta-catenin signaling and the healing process, suggesting that WNT ligands regulate beta-catenin. Healing was significantly repressed in mice conditionally expressing either null or stabilized beta-catenin alleles induced by an adenovirus expressing Cre recombinase. Fracture repair was also inhibited in mice expressing osteoblast-specific beta-catenin null alleles. In stark contrast, there was dramatically enhanced bone healing in mice expressing an activated form of beta-catenin, whose expression was restricted to osteoblasts. Treating mice with lithium activated beta-catenin in the healing fracture, but healing was enhanced only when treatment was started subsequent to the fracture. CONCLUSIONS: These results demonstrate that beta-catenin functions differently at different stages of fracture repair. In early stages, precise regulation of beta-catenin is required for pluripotent mesenchymal cells to differentiate to either osteoblasts or chondrocytes. Once these undifferentiated cells have become committed to the osteoblast lineage, beta-catenin positively regulates osteoblasts. This is a different function for beta-catenin than has previously been reported during development. Activation of beta-catenin by lithium treatment has potential to improve fracture healing, but only when utilized in later phases of repair, after mesenchymal cells have become committed to the osteoblast lineage.

Investigating the ultrastructure of fibrous long spacing collagen by parallel atomic force and transmission electron microscopy.

The ultrastructure of fibrous long spacing (FLS) collagen fibrils has been investigated by performing both atomic force microscopy (AFM) and transmission electron microscopy (TEM) on exactly the same area of FLS collagen fibril samples. These FLS collagen fibrils were formed in vitro from type I collagen and alpha1-acid glycoprotein (AAG) solutions. On the basis of the correlated AFM and TEM images obtained before and after negative staining, the periodic dark bands observed in TEM images along the longitudinal axis of the FLS collagen fibril correspond directly to periodic protrusions seen by AFM. This observation is in agreement with the original surmise made by Gross, Highberger, and Schmitt (Gross J, Highberger JH, Schmitt FO, Proc Natl Acad Sci USA 1954;40:679-688) that the major repeating dark bands of FLS collagen fibrils observed under TEM are thick relative to the interband region. Although these results do not refute the idea of negative stain penetration into gap regions proposed by Hodge and Petruska (Petruska JA, Hodge AJ. Aspects of protein structure. Ramachandran GN, editor. New York: Academic Press; 1963. p. 289-300), there is no need to invoke the presence of gap regions to explain the periodic dark bands observed in TEM images of FLS collagen fibrils.

Modulating hedgehog signaling can attenuate the severity of osteoarthritis.

Osteoarthritis is associated with the irreversible degeneration of articular cartilage. Notably, in this condition, articular cartilage chondrocytes undergo phenotypic and gene expression changes that are reminiscent of their end-stage differentiation in the growth plate during skeletal development. Hedgehog (Hh) signaling regulates normal chondrocyte growth and differentiation; however, the role of Hh signaling in chondrocytes in osteoarthritis is unknown. Here we examine human osteoarthritic samples and mice in which osteoarthritis was surgically induced and find that Hh signaling is activated in osteoarthritis. Using several genetically modified mice, we found that higher levels of Hh signaling in chondrocytes cause a more severe osteoarthritic phenotype. Furthermore, we show in mice and in human cartilage explants that pharmacological or genetic inhibition of Hh signaling reduces the severity of osteoarthritis and that runt-related transcription factor-2 (RUNX2) potentially mediates this process by regulating a disintegrin and metalloproteinase with thrombospondin type 1 motif-5 (ADAMTS5) expression. Together, these findings raise the possibility that Hh blockade can be used as a therapeutic approach to inhibit articular cartilage degeneration.

Beta-catenin signaling pathway is crucial for bone morphogenetic protein 2 to induce new bone formation.

Endochondral ossification is recapitulated during bone morphogenetic protein (BMP)-induced ectopic bone formation. Although BMP and beta-catenin have been investigated in bone development and in mesenchymal cells, how they interact in this process is not clear. We implanted recombinant BMP-2 into the muscle of mice to investigate the effect of beta-catenin signaling on BMP-induced in vivo endochondral bone formation. BMP-2 induced expression of several Wnt ligands and their receptors and also activated beta-catenin-mediated T cell factor-dependent transcriptional activity. An adenovirus expressing Dickkopf-1 (Dkk-1, an inhibitor of canonical Wnt pathway) inhibited beta-catenin signaling and endochondral bone formation. Interestingly, Dkk-1 inhibited both chondrogenesis and osteogenesis. Likewise, mice expressing conditional beta-catenin null alleles also displayed an inhibition of BMP-induced chondrogenesis and osteogenesis. This is in contrast to studies of embryonic skeletogenesis, which demonstrate that beta-catenin is required for osteogenesis but is dispensable for chondrogenesis. These findings suggest that embryonic development pathways are not always recapitulated during post-natal regenerative processes, and the biochemical pathways utilized to regulate cell differentiation may be different. During in vivo ectopic bone formation, BMP-2 induces beta-catenin-mediated signaling through Wnt ligands, and beta-catenin is required for both chondrogenesis and osteogenesis.

Constitutive hedgehog signaling in chondrosarcoma up-regulates tumor cell proliferation.

Chondrosarcoma is a malignant cartilage tumor that may arise from benign precursor lesions, such as enchondromas. Some cases of multiple enchondromas are caused by a mutation that results in constitutive activation of Hedgehog-mediated signaling. We found that chondrosarcomas expressed high levels of the Hedgehog target genes PTCH1 and GLI1. Treatment with parathyroid hormone-related protein down-regulated Indian Hedgehog (IHH) expression in normal growth plates but not in chondrosarcoma or enchondroma organ cultures. Treatment of the chondrosarcoma organ cultures with Hedgehog protein increased cell proliferation rate, whereas addition of chemical inhibitors of Hedgehog signaling decreased the proliferation rate. Chondrosarcoma xenografts from 12 different human tumors were established in NOD-SCID mice. Treatment with triparanol, an inhibitor of Hedgehog signaling, resulted in a 60% decrease in tumor volume, a 30% decrease in cellularity, and a 20% reduction in proliferation rate. These results show that Hedgehog signaling is active in chondrosarcoma and benign cartilage tumors and regulates tumor cell proliferation. Our data raise the intriguing possibility that Hedgehog blockade could serve as an effective treatment for chondrosarcoma, a tumor for which there are currently no universally effective nonsurgical management options.