Exposure to Varying Strain Magnitudes Influences the Conversion of Normal Skin Fibroblasts Into Hypertrophic Scar Cells

Effect of wound drainage on the wound infection and healing in patients undergoing spinal surgery: A meta-analysis

A meta-analysis was conducted to comprehensively evaluate the impact of wound drainage on postoperative wound infection and healing in patients undergoing spinal surgery. Computer searches were performed, from database inception to October 2023, in EMBASE, Google Scholar, Cochrane Library, PubMed, Wanfang and China National Knowledge Infrastructure databases for studies related to the application of wound drainage in spinal surgery. Two researchers independently screened the literature, extracted data and conducted quality assessments. Stata 17.0 software was employed for data analysis. Overall, 11 articles involving 2102 spinal surgery patients were included. The analysis showed that, compared to other treatment methods, the use of wound drainage in spinal surgery patients significantly shortened the wound healing time (standardized mean difference [SMD]: -1.35, 95% confidence intervals [CI]: -1.91 to -0.79, p < 0.001). However, there was no statistical difference in the incidence of wound infection (odds ratio: 1.35, 95% CI: 0.83-2.19, p = 0.226). This study indicates that wound drainage in patients undergoing spinal surgery is effective, can accelerate wound healing and is worth promoting in clinical practice.

Cyclic Stretch Promotes Cellular Reprogramming Process through Cytoskeletal-Nuclear Mechano-Coupling and Epigenetic Modification

Advancing the technologies for cellular reprogramming with high efficiency has significant impact on regenerative therapy, disease modeling, and drug discovery. Biophysical cues can tune the cell fate, yet the precise role of external physical forces during reprogramming remains elusive. Here the authors show that temporal cyclic-stretching of fibroblasts significantly enhances the efficiency of induced pluripotent stem cell (iPSC) production. Generated iPSCs are proven to express pluripotency markers and exhibit in vivo functionality. Bulk RNA-sequencing reveales that cyclic-stretching enhances biological characteristics required for pluripotency acquisition, including increased cell division and mesenchymal-epithelial transition. Of note, cyclic-stretching activates key mechanosensitive molecules (integrins, perinuclear actins, nesprin-2, and YAP), across the cytoskeletal-to-nuclear space. Furthermore, stretch-mediated cytoskeletal-nuclear mechano-coupling leads to altered epigenetic modifications, mainly downregulation in H3K9 methylation, and its global gene occupancy change, as revealed by genome-wide ChIP-sequencing and pharmacological inhibition tests. Single cell RNA-sequencing further identifies subcluster of mechano-responsive iPSCs and key epigenetic modifier in stretched cells. Collectively, cyclic-stretching activates iPSC reprogramming through mechanotransduction process and epigenetic changes accompanied by altered occupancy of mechanosensitive genes. This study highlights the strong link between external physical forces with subsequent mechanotransduction process and the epigenetic changes with expression of related genes in cellular reprogramming, holding substantial implications in the field of cell biology, tissue engineering, and regenerative medicine.

Silencing of Nesprin-2 inhibits the differentiation of myofibroblasts from fibroblasts induced by mechanical stretch

Mechanical force plays a pivotal role in the pathogenesis of hypertrophic scar (HTS). Dermal fibroblasts and myofibroblasts are the key cells involved in HTS. Myofibroblasts in HTS possess different biochemical and biophysical characteristics by which myofibroblasts are often distinguished from fibroblasts. The role of mechanotransducers outside the nucleus in the pathogenesis of HTS has been reported in many studies. However, the role of Nesprin‐2 in HTS is not clear. Hence, we aim to construct a cell model of HTS and explore the role of Nesprin‐2 in this process. Myofibroblasts and fibroblasts were isolated from HTS and healthy skin tissues of the same patient. Fibroblasts were exposed to cyclic stretch with 10% magnitude and a frequency of 0.1 Hz for 3 days, 5 days, and 7 days, respectively. After the cell model was confirmed, fibroblasts transfected with siRNA targeting human Nesprin‐2 were exposed to cyclic stretch. The mechanical behaviour and biochemical reaction of the dermal fibroblasts were analysed. The stretched fibroblasts at day 5 showed the same mechanotransductive and biochemical features as unstretched myofibroblasts. Mechanical strain could induce the myofibroblasts differentiation and a cell model of HTS was established successfully at day 5. The expressions of lamin A/C, alpha‐smooth muscle actin, transforming growth factor beta 1, and collagen type I in fibroblasts were reduced by the silencing of Nesprin‐2. Mechanical strain could induce the myofibroblasts differentiation and silencing of Nesprin‐2 could block the mechanical stimulation of terminal myofibroblasts differentiation. Nesprin‐2 might be a potential target to treat the HTS.

Application of ADSCs and their Exosomes in Scar Prevention

Scar is a common way of healing after tissue injury. The poor scar healing will not only cause dysfunction of tissues and organs but also affect the appearance of the patients’ body surface, which causes the pressure of life and spirit to the patients. However, the formation of scar tissue is an extremely complex process and its mechanism is not fully understood. At present, there is no treatment method to eliminate scars completely. Fibroblasts are the most abundant cells in the dermis, which have the ability to synthesize and remodel extracellular matrix (ECM). Myofibroblasts actively participate in the wound healing process and influence the outcome. Therefore, both of them play important roles in wound healing and scar formation. Adipose tissue-derived stem cells (ADSCs) are pluripotent stem cells that can act on target cells by paracrine. Adipose tissue stem cell-derived exosomes (ADSC-Exos) are important secretory substances of ADSCs. They are nanomembrane vesicles that can transport a variety of cellular components and fuse with target cells. In this review, we will discuss the effects of ADSCs and ADSC-Exos on the behavior of fibroblasts and myofibroblasts during wound healing and scarring stage in combination with recent studies.

Inhibition of Notch Intracellular Domain Suppresses Cell Activation and Fibrotic Factors Production in Hypertrophic Scar Fibroblasts Versus Normal Skin Fibroblasts

BACKGROUND

Hypertrophic scar (HS) is the most common complication after skin injury with unknown etiopathogenesis. There is increasing evidence to suggest that aberrant Notch signaling contributes directly to skin pathogenesis and altered expression of the Notch intracellular domain (NICD) identified in HS. Therefore, the aim of this study was to investigate the effects of Notch signaling pathway in HS pathogenesis.

METHODS

Hypertrophic scar and normal skin samples were collected. Notch intracellular domain expression was detected by immunohistochemistry staining and fibroblasts were separated from the samples. We compared fibrotic factors production, cell viability, migration and apoptosis of HS fibroblasts (HFB) versus normal skin fibroblasts (NFB) by real time quantitative polymerase chain reaction, MTS, cell scratch assay and flow cytometry respectively under the impact of inhibition of Notch signaling by NICD-small-interfering RNA (SiRNA).

RESULTS

The results showed that NICD was overexpressed in the dermis of HS tissues. Inhibition of Notch signaling by NICD-SiRNA suppressed the production of the fibrotic factors including collagen 1, collagen 3, α-SMA, and TGF-β1 by HFB and NFB. Cell viability and migration were reduced in NICD-SiRNA-treated NFB and HFB, whereas cell apoptosis was enhanced by NICD-SiRNA.

CONCLUSIONS

Conclusively, the study demonstrates a potential role for Notch signaling in HS progression, and targeting this pathway may provide a novel strategy for treatment of HS.

Effects of cyclic fluid stress at different frequencies on behaviors of cells incubated on titanium alloy

The orthopedic external fixation is always in dynamic mechanical environment with the somatic movement. We used a self-designed mini oscillator to simulate this condition by providing the reciprocating cyclic fluid stress, and observed the behavioral responses of fibroblasts implanted on titanium alloy plane to the stress at different frequencies, including 0.2 Hz, 0.6 Hz, and 1.0 Hz. We found that the cell angle, shape index and expression of vinculin were mostly biphasic-dependent with the increase of frequency, with peaks at 0.6 Hz. Whereas the cell area, expression of Col-I and α-SMA were mainly affected by the 1.0 Hz stress. Interestingly, 1.0 Hz stress also promoted Col-I expression of bone marrow mesenchymal stem cells (BMSCs), although it did not increase α-SMA. These results reveal that 0.6 Hz stress improves the alignment, polarity and adherence of fibroblasts on titanium alloy substrates, thus improving the sealing of implants; the 1.0 Hz force activates the differentiation of fibroblasts into myofibroblasts and increases collagen produced by stem cells, which probably cause the formation of fibrous capsules around implants.

Morpho-functional implications of myofascial stretching applied to muscle chains: A case study

BACKGROUND

Most lesions of the soft tissues, especially those at the muscle level, are due to the lack of elasticity of the connective tissue and fascia. Stretching is one of the most commonly used methods of treatment for such musculoskeletal issues.

OBJECTIVE

This study tracks the effects of stretching on the electromyographic activity of muscle chains, applied to a 24-year-old athlete diagnosed with the Haglund's disease.

METHOD

For the evaluation, we used visual examination and surface electromyography (maximum volumetric isometric contraction). The therapeutic intervention consisted in the application of the static stretching positions, which intended the elongation of the shortened muscle chains. The treatment program had a duration of 2 months, with a frequency of 2 sessions per week and an average duration of 60 minutes.

RESULTS

The posterior muscle chains recorded an increase in the EMG activity, while the anterior muscle chains tended to diminish their EMG activity. As a result of the applied treatment, all the evaluated muscle chains recorded a rebalancing of the electromyographic activity, demonstrating the efficiency of stretching as a method of global treatment of muscle chains.

CONCLUSIONS

By analysing all the data, we have come to the conclusion that static stretching is an effective treatment method for shortened muscle chains.

Analysis of Mechanical Behavior of Dermal Fibroblasts Obtained From Various Anatomical Sites in Humans

PURPOSE

Facial skin fibroblasts imposed with cyclic stretch at 10% magnitude display considerable mechanotransduction properties and biochemical reactions in our previous study. However, it is poorly understood how these shared traits are fully parallel to the common features across all fibroblasts derived from different skin-based anatomical regions in response to cyclic stretch stimulation. Thus, the purpose of this study was to evaluate the effects of various cyclic stretches on fibroblasts derived from multiple anatomical skin sites of human bodies, and the optimal stretch magnitude was defined based on the changes to cell mechanical behavior.

METHODS

Fibroblasts from skin areas of the scalp, anterior chest, suprapubic, axilla, and planta were cultured and characterized in vitro. Cyclic stretch at 0%, 5%, 10%, 15%, and 20% magnitudes was imposed at a loading frequency of 0.1 Hz for 48 hours, and thereafter, the mechanical behavior and biochemical reaction of the dermal fibroblasts were analyzed.

RESULTS

Dermal fibroblasts from various anatomical sites preconditioned with varying cyclic stretch led to an evident increase in the cell proliferation ability, the expression of integrin β1 and p130 Crk-associated substrate messenger RNA and protein, and the productions of type I collagen and transforming growth factor β1, most importantly in a strain magnitude-dependent manner with the peak appearing in the range of 10% to 15% magnitude cyclic stretch.

CONCLUSIONS

These findings may facilitate the subsequent studies on the conversion of normal skin fibroblasts into hypertrophic scar cells, which should be considered in an interpretation of the mechanisms of hypertrophic scarring and skin mechanics.

Evaluation of inguinal vascular surgical scars treated with closed incisional negative pressure wound therapy using three-dimensional digital imaging-A randomized controlled trial on bilateral incisions

PURPOSE OF THE INVESTIGATION

Scar formation is an important, permanent surrogate marker for wound healing. The main aim of this randomized trial was to evaluate the effects of incisional negative pressure wound therapy (iNPWT) on scar formation in uncomplicated wound healing with 3-dimensional (3D) digital imaging.

BASIC PROCEDURES

Patients undergoing bilateral inguinal incisions after vascular surgery were randomized to receive iNPWT and standard dressing on separate sides. The incisional scars were documented at a median time of 808 days (range 394-1194) after surgery with 3D photography, which were objectively evaluated by two plastic surgeons using the Stony Brook scar evaluation scale (SBSES) and a 10-point graded numeric ranking scale (NRS10). Subjective evaluation was performed with the patient observer scar assessment scale (POSAS). Patients with surgical site infection or other wound complications were excluded to minimize bias. The p-values were calculated using McNemar's and Wilcoxon signed-rank test for paired nominal and paired continuous data, respectively.

MAIN FINDINGS

Among 33 patients, 32 patients had undergone endovascular aortic repair (EVAR) and 31 patients had transverse inguinal incisions. Objective and subjective scar evaluation showed no difference between iNPWT and standard dressing. In objective scorings, 18.8 and 21.9% received the highest possible SBSES total score in the iNPWT and standard dressing groups, while 43.8 and 37.5% received the highest possible NRS10 score, respectively. The inter-rater reliability between the two assessors for SBSES total score and NRS10 showed an intra-class correlation (ICC) of 0.78 and 0.68 for NPWT and 0.70 and 0.77 for traditional dressing, respectively.

PRINCIPAL CONCLUSION

The present randomized trial showed that iNPWT and standard dressings on closed transverse inguinal incisions after EVAR resulted in equal subtle scar formation. Objective scar evaluation with 3D images showed good inter-rater agreement.