Extracorporeal shockwave treatment: A novel tool to improve Schwann cell isolation and culture

Emerging role of extracellular vesicles and exogenous stimuli in molecular mechanisms of peripheral nerve regeneration

Peripheral nerve injuries lead to significant morbidity and adversely affect quality of life. The peripheral nervous system harbors the unique trait of autonomous regeneration; however, achieving successful regeneration remains uncertain. Research continues to augment and expedite successful peripheral nerve recovery, offering promising strategies for promoting peripheral nerve regeneration (PNR). These include leveraging extracellular vesicle (EV) communication and harnessing cellular activation through electrical and mechanical stimulation. Small extracellular vesicles (sEVs), 30-150 nm in diameter, play a pivotal role in regulating intercellular communication within the regenerative cascade, specifically among nerve cells, Schwann cells, macrophages, and fibroblasts. Furthermore, the utilization of exogenous stimuli, including electrical stimulation (ES), ultrasound stimulation (US), and extracorporeal shock wave therapy (ESWT), offers remarkable advantages in accelerating and augmenting PNR. Moreover, the application of mechanical and electrical stimuli can potentially affect the biogenesis and secretion of sEVs, consequently leading to potential improvements in PNR. In this review article, we comprehensively delve into the intricacies of cell-to-cell communication facilitated by sEVs and the key regulatory signaling pathways governing PNR. Additionally, we investigated the broad-ranging impacts of ES, US, and ESWT on PNR.

ESWT Diminishes Axonal Regeneration following Repair of the Rat Median Nerve with Muscle-In-Vein Conduits but Not after Autologous Nerve Grafting

Investigations reporting positive effects of extracorporeal shockwave therapy (ESWT) on nerve regeneration are limited to the rat sciatic nerve model. The effects of ESWT on muscle-in-vein conduits (MVCs) have also not been investigated yet. This study aimed to evaluate the effects of ESWT after repair of the rat median nerve with either autografts (ANGs) or MVCs. In male Lewis rats, a 7 mm segment of the right median nerve was reconstructed either with an ANG or an MVC. For each reconstructive technique, one group of animals received one application of ESWT while the other rats served as controls. The animals were observed for 12 weeks, and nerve regeneration was assessed using computerized gait analysis, the grasping test, electrophysiological evaluations and histological quantification of axons, blood vessels and lymphatic vasculature. Here, we provide for the first time a comprehensive analysis of ESWT effects on nerve regeneration in a rat model of median nerve injury. Furthermore, this study is among the first reporting the quantification of lymphatic vessels following peripheral nerve injury and reconstruction in vivo. While we found no significant direct positive effects of ESWT on peripheral nerve regeneration, results following nerve repair with MVCs were significantly inferior to those after ANG repair.

Effects of Extracorporeal Shockwave Therapy on Functional Recovery and Circulating miR-375 and miR-382-5p after Subacute and Chronic Spinal Cord Contusion Injury in Rats

Extracorporeal shockwave therapy (ESWT) can stimulate processes to promote regeneration, including cell proliferation and modulation of inflammation. Specific miRNA expression panels have been established to define correlations with regulatory targets within these pathways. This study aims to investigate the influence of low-energy ESWT—applied within the subacute and chronic phase of SCI (spinal cord injury) on recovery in a rat spinal cord contusion model. Outcomes were evaluated by gait analysis, µCT and histological analysis of spinal cords. A panel of serum-derived miRNAs after SCI and after ESWT was investigated to identify injury-, regeneration- and treatment-associated expression patterns. Rats receiving ESWT showed significant improvement in motor function in both a subacute and a chronic experimental setting. This effect was not reflected in changes in morphology, µCT-parameters or histological markers after ESWT. Expression analysis of various miRNAs, however, revealed changes after SCI and ESWT, with increased miR-375, indicating a neuroprotective effect, and decreased miR-382-5p potentially improving neuroplasticity via its regulatory involvement with BDNF. We were able to demonstrate a functional improvement of ESWT-treated animals after SCI in a subacute and chronic setting. Furthermore, the identification of miR-375 and miR-382-5p could potentially provide new targets for therapeutic intervention in future studies.

The Effects of the Exposure of Musculoskeletal Tissue to Extracorporeal Shock Waves

Extracorporeal shock wave therapy (ESWT) is a safe and effective treatment option for various pathologies of the musculoskeletal system. Many studies address the molecular and cellular mechanisms of action of ESWT. However, to date, no uniform concept could be established on this matter. In the present study, we perform a systematic review of the effects of exposure of musculoskeletal tissue to extracorporeal shock waves (ESWs) reported in the literature. The key results are as follows: (i) compared to the effects of many other forms of therapy, the clinical benefit of ESWT does not appear to be based on a single mechanism; (ii) different tissues respond to the same mechanical stimulus in different ways; (iii) just because a mechanism of action of ESWT is described in a study does not automatically mean that this mechanism is relevant to the observed clinical effect; (iv) focused ESWs and radial ESWs seem to act in a similar way; and (v) even the most sophisticated research into the effects of exposure of musculoskeletal tissue to ESWs cannot substitute clinical research in order to determine the optimum intensity, treatment frequency and localization of ESWT.

Physical Considerations for In Vitro ESWT Research Design

In vitro investigations, which comprise the bulk of research efforts geared at identifying an underlying biomechanical mechanism for extracorporeal shock wave therapy (ESWT), are commonly hampered by inadequate descriptions of the underlying therapeutic acoustical pressure waves. We demonstrate the necessity of in-situ sound pressure measurements inside the treated samples considering the significant differences associated with available applicator technologies and cell containment. A statistical analysis of pulse-to-pulse variability in an electrohydraulic applicator yields a recommendation for a minimal pulse number of n = 300 for cell pallets and suspensions to achieve reproducible treatments. Non-linear absorption behavior of sample holders and boundary effects are shown for transient peak pressures and applied energies and may serve as a guide when in-situ measurements are not available or can be used as a controllable experimental design factor. For the use in microbiological investigations of ESWT we provide actionable identification of common problems in describing physical shockwave parameters and improving experimental setups by; (1) promoting in-situ sound field measurements, (2) statistical evaluation of applicator variability, and (3) extrapolation of treatment parameters based on focal and treatment volumes.

Effect of Botulinum Toxin Injection and Extracorporeal Shock Wave Therapy on Nerve Regeneration in Rats with Experimentally Induced Sciatic Nerve Injury

This study was designed to compare the roles of botulinum neurotoxin A (BoNT/A) and extracorporeal shock wave therapy (ESWT) in promoting the functional recovery and regeneration of injured peripheral nerves. A total of 45 six-week-old rats with sciatic nerve injury were randomly divided into two experimental groups and one control group. The experimental groups received a single session of intranerve BoNT/A or ESWT immediately after a nerve-crushing injury. The control group was not exposed to any treatment. Differentiation of Schwann cells and axonal sprouting were observed through immunofluorescence staining, ELISA, real-time PCR, and Western blot at 3, 6, and 10 weeks post-nerve injury. For clinical assessment, serial sciatic functional index analysis and electrophysiological studies were performed. A higher expression of GFAP and S100β was detected in injured nerves treated with BoNT/A or ESWT. The levels of GAP43, ATF3, and NF200 associated with axonal regeneration in the experimental groups were also significantly higher than in the control group. The motor functional improvement occurred after 7 weeks of clinical observation following BoNT/A and ESWT. Compared with the control group, the amplitude of the compound muscle action potential in the experimental groups was significantly higher from 6 to 10 weeks. Collectively, these findings indicate that BoNT/A and ESWT similarly induced the activation of Schwann cells with the axonal regeneration of and functional improvement in the injured nerve.

Motor and sensory Schwann cell phenotype commitment is diminished by extracorporeal shockwave treatment in vitro

The gold standard for peripheral nerve regeneration uses a sensory autograft to bridge a motor/sensory defect site. For motor nerves to regenerate, Schwann cells (SC) myelinate the newly grown axon. Sensory SCs have a reduced ability to produce myelin, partially explaining low success rates of autografts. This issue is masked in pre-clinical research by the excessive use of the rat sciatic nerve defect model, utilizing a mixed nerve with motor and sensory SCs. Aim of this study was to utilize extracorporeal shockwave treatment as a novel tool to influence SC phenotype. SCs were isolated from motor, sensory and mixed rat nerves and in vitro differences between them were assessed concerning initial cell number, proliferation rate, neurite outgrowth as well as ability to express myelin. We verified the inferior capacity of sensory SCs to promote neurite outgrowth and express myelin-associated proteins. Motor Schwann cells demonstrated low proliferation rates, but strongly reacted to pro-myelination stimuli. It is noteworthy for pre-clinical research that sciatic SCs are a strongly mixed culture, not representing one or the other. Extracorporeal shockwave treatment (ESWT), induced in motor SCs an increased proliferation profile, while sensory SCs gained the ability to promote neurite outgrowth and express myelin-associated markers. We demonstrate a strong phenotype commitment of sciatic, motor, and sensory SCs in vitro, proposing the experimental use of SCs from pure cultures to better mimic clinical situations. Furthermore we provide arguments for using ESWT on autografts to improve the regenerative capacity of sensory SCs.

Secretome Conveys the Protective Effects of ASCs: Therapeutic Potential Following Hemorrhagic Shock?

OBJECTIVES

We tested whether resuscitation supplemented with rat adipose-derived stem cells (ASCs) or secretome (conditioned media) of ASCs can ameliorate inflammation, cell/organ injury, and/or improve outcome after hemorrhagic traumatic shock (HTS).

INTERVENTIONS

Rats were subjected to HTS and a resuscitation protocol that mimics prehospital restrictive reperfusion followed by an adequate reperfusion phase. Twenty minutes into the restrictive reperfusion, animals received an intravenous bolus of 2 × 10 cells (ASC group) or the secretome produced by 2 × 10 ASCs/24 h (ASC-Secretome group). Controls received the vehicle (Vehicle group). All rats were observed for 28-day survival.

MEASUREMENTS AND MAIN RESULTS

HTS-induced inflammation represented by IL-6 was inhibited in the ASC (80%, P < 0.001) and in ASC-Secretome (59%, P < 0.01) group at 48 h compared with Vehicle group. At 24 h, HTS-induced liver injury reflected in plasma alanine aminotransferase was ameliorated by 36% (P < 0.001) in both the ASC and ASC-Secretome groups when compared with the Vehicle. There was no effect on kidney function and/or general cell injury markers. HTS induced a moderate 28-day mortality (18%) that was prevented (P = 0.08) in the ASC but not in the ASC-Secretome group (12%).

CONCLUSIONS

Our data suggest that the ASC-secretome supplemented resuscitation following HTS, in the absence of the stem cells, exerts anti-inflammatory and liver protective effects. Given its ease of preparation, storage, availability, and application (in contrast to the stem cells) we believe that the cell-free secretome has a better therapeutic potential in the early phase of an acute hemorrhagic shock scenario.

An Optimized Collagen-Fibrin Blend Engineered Neural Tissue Promotes Peripheral Nerve Repair

Tissue engineering approaches in nerve regeneration often aim to improve results by bridging nerve defects with conduits that mimic key features of the nerve autograft. One such approach uses Schwann cell self-alignment and stabilization within collagen gels to generate engineered neural tissue (EngNT). In this study, we investigated whether a novel blend of fibrin and collagen could be used to form EngNT, as before EngNT design a beneficial effect of fibrin on Schwann cell proliferation was observed. A range of blend formulations was tested in terms of mechanical behavior (gel formation, stabilization, swelling, tensile strength, and stiffness), and lead formulations were assessed in vitro. A 90% collagen 10% fibrin blend was found to promote SCL4.1/F7 Schwann cell viability and supported the formation of aligned EngNT, which enhanced neurite outgrowth in vitro (NG108 cells) compared to formulations with higher and lower fibrin content. Initial in vivo tests in an 8 mm rat sciatic nerve model using rolled collagen-fibrin EngNT rods revealed a significantly enhanced axonal count in the midsection of the repair, as well as in the distal part of the nerve after 4 weeks. This optimized collagen-fibrin blend therefore provides a novel way to improve the capacity of EngNT to promote regeneration following peripheral nerve injury.

Ultrasound and shock-wave stimulation to promote axonal regeneration following nerve surgery: a systematic review and meta-analysis of preclinical studies

Limited regeneration after nerve injury often leads to delayed or incomplete reinnervation and consequently insufficient muscle function. Following nerve surgery, application of low-intensity ultrasound or extracorporeal shock waves may promote nerve regeneration and improve functional outcomes. Because currently clinical data is unavailable, we performed a meta-analysis following the PRISMA-guidelines to investigate the therapeutic effect of ultrasound and shock wave therapies on motor nerve regeneration. Ten ultrasound-studies (N = 445 rats) and three shock-wave studies (N = 110 rats) were identified from multiple databases. We calculated the difference in means or standardized mean difference with 95% confidence intervals for motor function, nerve conduction velocity and histomorphological parameters of treated versus sham or non-treated animals. Ultrasound treatment showed significantly faster nerve conduction, increased axonal regeneration with thicker myelin and improved motor function on sciatic functional index scale (week two: DM[95%CI]: 19,03[13,2 to 25,6], 71 animals; week four: 7,4[5,4 to 9,5], 47 animals). Shock wave induced recovery improvements were temporarily significant. In conclusion, there is significant evidence for low-intensity ultrasound but not for extracorporeal shock wave treatment to improve nerve regeneration. Prospective clinical trials should therefore investigate available FDA-approved ultrasound devices as adjunct postoperative treatment following nerve surgery.

Human Placenta Laminin-111 as a Multifunctional Protein for Tissue Engineering and Regenerative Medicine

Laminins are major components of all basement membranes surrounding nerve or vascular tissues. In particular laminin-111, the prototype of the family, facilitates a large spectrum of fundamental cellular responses in all eukaryotic cells. Laminin-111 is a biomaterial frequently used in research, however it is primarily isolated from non-human origin or produced with time-intensive recombinant techniques at low yield.Here, we describe an effective method for isolating laminin-111 from human placenta, a clinical waste material, for various tissue engineering applications. By extraction with Tris-NaCl buffer combined with non-protein-denaturation ammonium sulfate precipitation and rapid tangential flow filtration steps, we could effectively isolate native laminin-111 within only 4 days. The resulting material was biochemically characterized using a combination of dot blot, SDS-PAGE, Western blot and HPLC-based amino acid analysis. Cytocompatibility studies demonstrated that the isolated laminin-111 promotes rapid and efficient adhesion of primary Schwann cells. In addition, the bioactivity of the isolated laminin-111 was demonstrated by (a) using the material as a substrate for outgrowth of NG 108-15 neuronal cell lines and (b) promoting the formation of interconnected vascular networks by GFP-expressing human umbilical vein endothelial cells.In summary, the isolation procedure of laminin-111 as described here from human placenta tissue, fulfills many demands for various tissue engineering and regenerative medicine approaches and therefore may represent a human alternative to various classically used xenogenic standard materials.

Extracorporeal shock wave therapy in situ - novel approach to obtain an activated fat graft

One of the mainstays of facial rejuvenation strategies is volume restoration, which can be achieved by autologous fat grafting. In our novel approach, we treated the adipose tissue harvest site with extracorporeal shock wave therapy (ESWT) in order to improve the quality of the regenerative cells in situ. The latter was demonstrated by characterizing the cells of the stromal vascular fraction (SVF) in the harvested liposuction material regarding cell yield, adenosine triphosphate (ATP) content, proliferative capacity, surface marker profile, differentiation potential and secretory protein profile. Although the SVF cell yield was only slightly enhanced, viability and ATP concentration of freshly isolated cells as well as proliferation doublings after 3 weeks in culture were significantly increased in the ESWT compared with the untreated group. Likewise, cells expressing mesenchymal and endothelial/pericytic markers were significantly elevated concomitant with an improved differentiation capacity towards the adipogenic lineage and enhancement in specific angiogenic proteins. Hence, in situ ESWT might be applied in the future to promote cell fitness, adipogenesis and angiogenesis within the fat graft for successful facial rejuvenation strategies with potential long-term graft survival.

Potential applications of low-energy shock waves in functional urology

A shock wave, which carries energy and can propagate through a medium, is a type of continuous transmitted sonic wave with a frequency of 16 Hz-20 MHz. It is accompanied by processes involving rapid energy transformations. The energy associated with shock waves has been harnessed and used for various applications in medical science. High-energy extracorporeal shock wave therapy is the most successful application of shock waves, and has been used to disintegrate urolithiasis for 30 years. At lower energy levels, however, shock waves have enhanced expression of vascular endothelial growth factor, endothelial nitric oxide synthase, proliferating cell nuclear antigen, chemoattractant factors and recruitment of progenitor cells; shock waves have also improved tissue regeneration. Low-energy shock wave therapy has been used clinically with musculoskeletal disorders, ischemic cardiovascular disorders and erectile dysfunction, through the mechanisms of neovascularization, anti-inflammation and tissue regeneration. Furthermore, low-energy shock waves have been proposed to temporarily increase tissue permeability and facilitate intravesical drug delivery. The present review article provides information on the basics of shock wave physics, mechanisms of action on the biological system and potential applications in functional urology.

[Basic research in traumatology and its contribution to routine operation]

Basic research in traumatology supports the clinical outcome of patients in trauma care and tries to find science-based solutions for clinical problems. Furthermore, institutions for basic research in traumatology usually offer training in different skills, such as how to write a scientific paper, or practice in microsurgery or intubation. Two examples of clinically significant research topics are presented.

A therapeutic shock propels Schwann cells to proliferate in peripheral nerve injury

Damage to the peripheral nervous system (PNS) is a prevalent issue and represents a great burden to patients. Although the PNS has a good capacity for regeneration, regeneration over long distances poses several difficulties. Several recent studies have addressed Schwann cells’ limited proliferative capacity; however, a solution has yet to be found. Here, we examine the effects of extracorporeal shock wave therapy (ESWT) on Schwann cell isolation, culture, and proliferation rate. The study conducted demonstrated that Schwann cells treated with ESWT had significantly improved isolation, culture, and proliferative capacities. These findings represent a solution to a significant problem that hospitals and health-care providers face every year: how to treat long distance damage to the PNS with the limited proliferative capabilities of Schwann cells. Although these findings are promising, further studies must be conducted to address the molecular mechanisms by which ESWT alters Schwann cells and the potential implications for peripheral nerve damage and other prevalent illnesses. This study is a review article. Referred literature in this paper has been listed in the references part. The datasets supporting the conclusions of this article are available online by searching the PubMed. Some original points in this article come from the laboratory practice in our research centers and the authors’ experiences.