In vitro collagen biomarkers in mechanically stimulated human tendon cells: a systematic review

OBJECTIVE

The aim of this study was to comprehensively examine and summarize the available in vitro evidence regarding the relationship between mechanical stimulation and biomarkers of collagen synthesis in human-derived tendon cells.

METHODS

Systematic review with narrative analyses and risk of bias assessment guided by the Health Assessment and Translation tool. The electronic databases MEDLINE (Ovid), EMBASE (Ovid), CENTRAL (Ovid) and COMPENDEX (Engineering Village) were systematically searched from inception to 3 August 2023. Inclusion criteria encompassed English language, original experimental, or quasi-experimental in vitro publications that subjected human tendon cells to mechanical stimulation, with collagen synthesis (total collagen, type I, III, V, XI, XII, and XIV) and related biomarkers (matrix metalloproteinases, transforming growth factor β, scleraxis, basic fibroblast growth factor) as outcomes.

RESULTS

Twenty-one publications were included. A pervasive definite high risk of bias was evident in all included studies. Owing to incomplete outcome reporting and heterogeneity in mechanical stimulation protocols, planned meta-analyses were unfeasible. Reviewed data suggested that human tendon cells respond to mechanical stimulation with increased synthesis of collagen (e.g., COL1A1, procollagen, total soluble collagen, etc.), scleraxis and several matrix metalloproteinases. Results also indicate that mechanical stimulation dose magnitude may influence synthesis in several biomarkers.

CONCLUSIONS

A limited number of studies, unfortunately characterized by a definite high risk of bias, suggest that in vitro mechanical stimulation primarily increases type I collagen synthesis by human tendon cells. Findings from this systematic review provide researchers and clinicians with biological evidence concerning the possible beneficial influence of exercise and loading on cellular-level tendon adaptation.

The Distal Free Achilles Tendon Is Longer in People with Tendinopathy than in Controls: A Retrospective Case-Control Study

Objectives

The free Achilles tendon is defined as the region of tendon distal to the soleus which is "unbuttressed," i.e., unsupported by muscular tissue. We reasoned that a relative lack of distal buttressing could place the tendon at a greater risk for developing Achilles tendinopathy. Therefore, our primary goal was to compare the free Achilles tendon length between those with midportion or insertional Achilles tendinopathy and healthy controls.

Design

This is a retrospective case-control study. Setting. Hospital in Vancouver, Canada. Participants. 66 cases with Achilles tendinopathy (25 insertional, 41 midportion) consecutively drawn from a hospital database within a 5-year period and matched to 66 controls (without tendinopathy) based on sex, age, and weight. Main outcome measures. Odds ratio of the risk of developing Achilles tendinopathy given the length of free tendon, defined anatomically on MRI, after adjustment for confounders.

Results

MRI-defined free Achilles tendon length is a statistically significant predictor of having midportion Achilles tendinopathy (odds ratio = 0.53, 95% confidence interval 1.13 to 2.07). Midportion Achilles tendinopathy cases had significantly longer free tendons (Mdn = 51.2 mm, IQR = 26.9 mm) compared to controls (Mdn = 40.8 mm, IQR = 20.0 mm), p = 0.007. However, there was no significant difference between the free Achilles tendon lengths in insertional AT cases (Mdn = 47.9 mm, IQR = 15.1 mm) and controls (Mdn = 39.2 mm, IQR = 17.9 mm), p = 0.158. Free Achilles tendon length was also correlated with the tendon thickness among those with Achilles tendinopathy, rτ = 0.25, and p = 0.003.

Conclusions

The MRI-defined length of the free Achilles tendon is positively associated with the risk of midportion Achilles tendinopathy. A relative lack of distal muscular buttressing of the Achilles tendon may therefore influence the development of tendinopathy.

Using the VERT wearable device to monitor jumping loads in elite volleyball athletes

Sport is becoming increasingly competitive and athletes are being exposed to greater physical demands, leaving them prone to injuries. Monitoring athletes with the use of wearable technology could provide a way to potentially manage training and competition loads and reduce injuries. One such technology is the VERT inertial measurement unit, a commercially available discrete wearable device containing a 3-axis accelerometer, 3-axis gyroscope and 3-axis magnetometer. Some of the main measurement outputs include jump count, jump height and landing impacts. While several studies have examined the accuracy of the VERT's measures of jump height and jump count, landing impact force has not yet been investigated. The objective of this research study was to explore the validity of the VERT landing impact values. We hypothesized that the absolute peak VERT acceleration values during a jump-land cycle would fall within 10% of the peak acceleration values derived simultaneously from a research-grade accelerometer (Shimmer). Fourteen elite university-level volleyball players each performed 10 jumps while wearing both devices simultaneously. The results showed that VERT peak accelerations were variable (limits of agreement of -84.13% and 52.37%) and had a propensity to be lower (mean bias of -15.88%) when compared to the Shimmer. In conclusion, the validity of the VERT device's landing impact values are generally poor, when compared to the Shimmer.

What have we learned about exfoliation syndrome since its discovery by John Lindberg 100 years ago?

Exfoliation syndrome (XFS) is a systemic disease with significant ocular manifestations, including glaucoma and cataract. The disease impacts close to 70 million people globally and is now recognised as the most common identifiable cause of open-angle glaucoma. Since the discovery of XFS 100 years ago by Dr John G. Lindberg, there has been considerable advancement in understanding its pathogenesis and resulting clinical implications. The purpose of this paper is to summarise information regarding the epidemiology, pathophysiology, ocular manifestations and systemic associations of XFS with the objective of sharing clinical pearls to assist in early detection and enhanced management of patients.

The bldD gene of Streptomyces coelicolor A3(2): a regulatory gene involved in morphogenesis and antibiotic production

The bld mutants of Streptomyces coelicolor A3(2) are blocked at the earliest stage of sporulation, the formation of aerial hyphae, and are pleiotropically defective in antibiotic production. Using a phage library of wild-type S. coelicolor DNA, we isolated a recombinant phage which restored both sporulation and antibiotic production to strains carrying the single known bldD mutation. Nucleotide sequence analysis of a 1.3-kb complementing subclone identified an open reading frame, designated bldD, encoding a translation product of 167 amino acid residues. Nucleotide sequence analysis of the bldD-containing fragment amplified from the chromosome of a bldD mutant strain revealed a point mutation changing a tyrosine residue at amino acid position 62 to a cysteine. Although a comparison of the BldD sequence to known proteins in the databases failed to show any strong similarities, analysis of the BldD sequence for secondary structural elements did reveal a putative helix-turn-helix, DNA recognition element near the C terminus of the protein. A comparison of bldD transcript levels in the bldD+ and bldD mutant strains using both Northern blot analysis and S1 nuclease protection studies showed vast overexpression of bldD transcripts in the mutant, suggesting that BldD negatively regulates its own synthesis. High-resolution S1 nuclease mapping identified the transcription start point as a G residue 63 nucleotides upstream from the bldD start codon and 7 nucleotides downstream from -10 and -35 sequences resembling E. coli-like streptomycete promoters.