Adhesion Prevention after Laminectomy Using Silk-Polyethylene Glycol Hydrogels

Enhanced Biodegradation of Silk Fibroin Hydrogel for Preventing Postoperative Adhesion

An absorbable adhesion barrier is a medical device that prevents postoperative adhesion and matches its biodegradation time with the regeneration period of its target tissues, which is important for antiadhesion effects. Physical hydrogels of Bombyx mori silk fibroin (SF) proteins are degradable in vivo. However, their biodegradation time is too long to exert antiadhesion effects. To shorten the biodegradation time of the SF hydrogels, we decreased the molecular weight (MW) of the SF proteins by alkaline treatment and prepared low-MW (LMW) SF hydrogels. The hydrogels contained less β-sheet crystalline and more amorphous structures than conventional, high-MW (HMW) SF hydrogels. Because of the potential loosened SF molecular structures in the hydrogel networks, the LMW SF hydrogels showed enhanced biodegradation (i.e., shorter in vitro enzymatic biodegradation time and faster in vivo biodegradation rate) as well as a lower affinity for plasma proteins and fibroblasts, which are involved in postoperative adhesion formation. An antiadhesion test using a rat abdominal adhesion model demonstrated that the LMW SF hydrogel applied to the abraded cecum was almost completely degraded within two weeks postimplantation, with a significantly lower adhesion severity score than that in the untreated model rat group. Conversely, the HMW SF hydrogel remained between the cecum and abdominal wall, with the same adhesion severity as that of the untreated model rat group. Therefore, we concluded that the antiadhesion effects of SF hydrogels were induced by enhanced biodegradation. The results of this study indicate the potential of LMW SF hydrogels as absorbable adhesion barriers.

The current status and development trend of hydrogel application in spinal surgery

Spinal diseases often result in compromised mobility and diminished quality of life due to the intricate anatomy surrounding the nervous system. Medication and surgical interventions remain the primary treatment methods for spinal conditions. However, currently available medications have limited efficacy in treating spinal surgical diseases and cannot achieve a complete cure. Furthermore, surgical intervention frequently results in inevitable alterations and impairments to the initial anatomical integrity of the spinal structure, accompanied by the consequential loss of certain physiological functionalities. Changes in spine surgery treatment concepts and modalities in the last decade have led to a deepening of minimally invasive treatment, with treatment strategies focusing more on repairing and reconstructing the patient's spine and preserving physiological functions. Therefore, developing novel and more efficient treatment strategies to reduce spinal lesions and iatrogenic injuries is essential. In recent years, significant advancements in biomedical research have led to the discovery that hydrogels possess excellent biocompatibility, biodegradability, and adjustable mechanical properties. The application of hydrogel-based biotechnology in spinal surgery has demonstrated remarkable therapeutic potential. This review presents the therapeutic strategies for spinal diseases based on hydrogel tissue engineering technology.

Silk Fibroin-Based Tough Hydrogels with Strong Underwater Adhesion for Fast Hemostasis and Wound Sealing

Rapid and strong adhesion of hydrogel adhesives is required for instant wound closure and hemostasis. However, in situ hydrogel formation and sufficient adhesion at target tissue sites in biological environments are severely compromised by the presence of blood and body fluids. In this work, an underwater adhesive hydrogel (named SHCa) is fabricated with rapid in situ gelation, enhanced mechanical toughness, and robust underwater adhesion. The SHCa can undergo rapid UV irradiation-induced gelation under water within 5 s and adhere firmly to underwater surfaces for 6 months. The synergistic effects of crystalline β-sheet structures and dynamic energy-dissipating mechanisms enhance the mechanical toughness and cohesion, supporting the balance between adhesion and cohesion in wet environments. Importantly, the SHCa can achieve rapid in situ gelation and robust underwater adhesion at various tissue surfaces in highly dynamic fluid environments, substantially outperforming the commercially available tissue adhesives. The lap shear adhesion strength and wound closure strength of SHCa on blood-covered substrates are 7.24 and 12.68 times higher than those of cyanoacrylate glue, respectively. Its fast hemostasis and wound sealing performance are further demonstrated in in vivo animal models. The proposed hydrogel with strong underwater adhesion provides an effective tool for fast wound closure and hemostasis.

Multifunctional Supramolecular Hydrogel for Prevention of Epidural Adhesion after Laminectomy

Postoperative epidural adhesion remains a clinically challenging problem in spine surgery. Currently there are no effective and safe antifibrotic and antiadhesion biomaterials that have been specifically developed for this complication in clinical practice. Herein we designed and engineered an advanced antiadhesion hydrogel with multiple functionalities, including temperature-responsive gelation, self-healing, tissue adhesiveness, antioxidation, anti-inflammation, and antifibrosis. This multifunctional supramolecular hydrogel can be facilely constructed by integrating three functional modules, i.e., a thermosensitive triblock copolymer, poloxamer 407 (PX); a reactive oxygen species-eliminating and anti-inflammatory nanoparticle (TPCD NP); and an adhesion-enhancing compound, tannic acid (TA). The optimal formulation (PXNT) was hierarchically screened based on in vitro properties and in vivo activities. Therapeutically, local treatment with PXNT hydrogel effectively prevented epidural fibrosis and adhesion after laminectomy in both rats and rabbits. Of note, PXNT hydrogel showed more beneficial efficacy than different control thermosensitive hydrogels and a commercially available barrier product, Interceed. Mechanistically, PXNT hydrogel significantly attenuated local oxidative stress, inhibited inflammatory responses, and reduced fibrotic tissue formation. Moreover, treatment with PXNT hydrogel did not cause systemic adverse effects and neurological symptoms. Consequently, PXNT hydrogel is a highly promising biomaterial for preventing postlaminectomy epidural adhesion and adhesions after other surgeries.

Gellable silk fibroin-polyethylene sponge for hemostasis

Traditional haemostatic materials generally have slow hemostasis rate and poor biocompatibility. This paper reports on the haemostatic properties and mechanism of silk fibroin (SF). SF-PEG sponge that could be solubilised and changed to gel form by blood was fabricated through mixing SF and polyethylene glycol (PEG, 1500 Da) followed by lyophilisation of the mixed solution. SF-PEG sponge, together with control samples of SF sponge (no PEG) and a commercially available haemostatic material, gelatine sponge, were subjected to the hemostasis tests using a liver trauma model of rabbit. The results showed that SF was superior to gelatine sponge in hemostasis time (136.17 ± 62.27 s and 249.83 ± 29.18 s) and blood loss (2.16 ± 1.27 g vs. 4.97 ± 1.44 g). Furthermore, in vitro experiments indicated SF-PEG sol-gel transition promoted platelet adhesion and aggregation, as well as platelet-fibrinogen interaction. Therefore, except for the physical blocking of bleeding port due to PEG-induced SF fast gelation, SF might also have an impact on blood coagulation process, a phenomenon that has not been reported before. In conclusion, SF is a new type of haemostatic material that might be able to meet the requirements of speed, efficiency and biosafety in a variety of clinical applications.

The therapeutic effect of secretome from human umbilical cord-derived mesenchymal stem cells in age-related osteoporosis

Senile osteoporosis is closely related to the loss of function of stem cells. In this study, we tried to investigate the potential of secretome from human umbilical cord-derived mesenchymal stem cells (hUCMSCs) in recovering stem cell ability from senescence and then delaying bone loss. We first harvested bone marrow-derived mesenchymal stem cells (BMSCs) from young and old rats and then compared their cellular characteristics such as cell growth, anti-senescence and differentiation. The results showed that these abilities were negatively affected by animal aging. Subsequently, aged BMSCs were exposed to secretome from hUCMSCs, and we found that this loss of cell potential can be modified by secretome treatment. Thereafter, the secretome was loaded into silk fibroin-based hydrogels and used for an in vivo animal study. The results showed that compared to the old untreated group, the bone formation capacity of aged rats was improved by local treatment of secretome-loaded silk fibroin hydrogels. In conclusion, these findings demonstrated that secretome from hUCMSCs has the capacity to recover stem cell potential and delay local bone loss in age-related osteoporosis, which could potentially be applied in osteoporosis therapy in the future.

Prospective application of stem cells to prevent post-operative skeletal fibrosis

Post-operative skeletal fibrosis is considered one of the major complications causing dysfunction of the skeletal system and compromising the outcomes of clinical treatment. Limited success has been achieved using current therapies; more effective therapies to reduce post-operative skeletal fibrosis are needed. Stem cells possess the ability to repair and regenerate damaged tissue. Numerous studies show that stem cells serve as a promising therapeutic approach for fibrotic diseases in tissues other than the skeletal system by inhibiting the inflammatory response and secreting favorable cytokines through activating specific signaling pathways, acting as so-called medicinal signaling cells. In this review, current therapies are summarized for post-operative skeletal fibrosis. Given that stem cells are used as a promising therapeutic approach for fibrotic diseases, little effort has been undertaken to use stem cells to prevent post-operative skeletal fibrosis. This review aims at providing useful information for the potential application of stem cells in preventing post-operative skeletal fibrosis in the near future. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1236-1245, 2019.

Effect of surface microstructure on the anti-fibrosis/adhesion of hydroxyapatite ceramics in spinal repair of rabbits

Epidural adhesion is a great clinical challenge after laminectomy. In the present study, two types of hydroxyapatite (HA) laminas with distinct surface microstructures were prepared by cold isostatic pressing (CIP) and slip casting (SC) techniques, and investigated to their anti-fibrosis/adhesion effects by in vitro and in vivo evaluations. In contrast with the dense HA-CIP, HA-SC had a large number of micropores on the surface. After cultured on both HA ceramics, human skin fibroblasts presented the obvious senescent feature, and CCN1 gene expression was significantly up-regulated. HA-SC induced higher CCN1 gene expression than HA-CIP. After used for closing the lost vertebral after laminectomy in rabbits, both HA laminas promoted the recovery of the bony structure as well as prevented the hyperplastic fibrous tissue from penetration into the spinal canal area and inhibited the formation of scar-like tissue in laminectomy sites to some extent. Besides, thinner layer of fibrous tissue and smaller gap between the implant surface and paravertebral muscles were found in HA-CIP than HA-SC. Therefore, HA ceramics could have good anti-fibrosis/adhesion effect when used in spinal repair, and the dense HA-CIP could be an ideal choice. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2629-2637, 2019.

Effects of silk solution against laminectomy-induced dural adhesion formation and inflammation in a rat model

The authors investigated the effects of a silk solution against laminectomy-induced dural adhesion formation and inflammation in a rat model. They found that it significantly reduced postlaminectomy dural adhesion formation and inflammation. Dural adhesion formation, thought to be an inevitable consequence of laminectomy, is one of the most common complications following spinal surgery, and the authors' results indicate that the silk solution might be a potential novel therapeutic agent for dural adhesion formation.

Preoperative Mechanical Bowel Evacuation Reduces Intraoperative Bleeding and Operation Time in Spinal Surgery

Study Design

Randomized clinical trial.

Purpose

In this study, we evaluated the effect of mechanical evacuation of the bowels prior to operation on intraoperative bleeding.

Overview of Literature

Bleeding is the most significant complication in patients undergoing spinal surgery.

Methods

We randomly divided 108 individuals planned to undergo spinal surgery into two age-, sex-, and co-morbidity (especially preoperative hemoglobin [Hb])-matched groups of 54. The treatment group was administered polyethylene glycol (PEG) before the operation, whereas the control group was not. The exact amount (mL) of bleeding during operation, operative time, and approximate amount of blood transfused were recorded. The volume of bleeding and Hb level were also recorded 24 and 48 hours postoperatively.

Results

T-tests revealed that intraoperative bleeding, the volume of transfusion, and operative time were significantly lower in the treatment group than in the control group. Statistically significant correlations of intraoperative bleeding with age, body mass index (BMI), preoperative Hb levels, operative time, the volume of transfusion, hospitalization time, and 24- and 48-hour postoperative bleeding were observed (p =0.001, all). Repeated measures analysis of covariance after adjusting the covariate variables revealed that the volume of bleeding showed a near-significant trend in the treatment group compared with that in the control group (p =0.056). Diabetic females had the highest bleeding amount between the groups (p =0.03). Bleeding was higher in patients with higher BMI (p =0.02) and was related to operative time (p =0.001) in both the groups.

Conclusions

Preoperative gastrointestinal tract evacuation by PEG administration can decrease intraoperative bleeding in spinal surgeries; however, more research is imperative regarding PEG administration in surgical procedures for this purpose.

Update on biomaterials for prevention of epidural adhesion after lumbar laminectomy

Lumbar laminectomy often results in failed back surgery syndrome. Most scholars support the three-dimensional theory of adhesion: Fibrosis surrounding the epidural tissues is based on the injured sacrospinalis behind, fibrous rings and posterior longitudinal ligaments. Approaches including using the minimally invasive technique, drugs, biomaterial and nonbiomaterial barriers to prevent the postoperative epidural adhesion were intensively investigated. Nevertheless, the results are far from satisfactory. Our review is based on various implant biomaterials that are used in clinical applications or are under study. We show the advantages and disadvantages of each method. The summary will help us to figure out ideas towards new techniques. The translational potential of this article: This review summarises recent biomaterials-related clinical and basic research that focuses on prevention of epidural adhesion after lumbar laminectomy. We also propose a novel possible translational method where a soft scaffold acts as a physical barrier in the early stage, engineered adipose tissue acts as a biobarrier in the later stage in the application of biomaterials and adipose-derived mesenchymal stem cells are used for prevention of epidural adhesion.

Immuno-Informed 3D Silk Biomaterials for Tailoring Biological Responses

Macrophages, the key players in immunoregulation, are actively involved in tissue remodelling and vascularization. Recent advances in tissue engineering and regenerative medicine illustrate the importance of "immuno-informed" biomaterials to regulate the microenvironment of biomedical implants. In the current study, silk-based 3D hydrogels were utilized to regulate cytokine delivery for macrophage, a type of immune cell, differentiation and polarization. Three different hydrogel variants, silk-poly(ethylene glycol) (PEG) (SP), silk-horseradish peroxidase (HRP) (SH) and silk-sonicated (SS) hydrogels were studied. Hydrogels were loaded with the M1 and M2 polarizing cytokines interferon-γ (IFN-γ) and interleukin-4 (IL-4), respectively. Functional cytokine release and macrophage polarization studies were conducted using three cytokine exposure approaches: only cytokine encapsulation (macrophage in culture well), only macrophage encapsulation (cytokine in culture media) and cytokine with macrophage encapsulation. The extent of macrophage polarization by cytokine-eluting and macrophage-encapsulating hydrogels was investigated using gene expression analysis for C-C chemokine receptor 7 (CCR7), Interleukin-1 beta (IL-1β), cluster of differentiation 206 (CD206) and cluster of differentiation 209 (CD209). The released cytokines polarized macrophages from an M0 phenotype to an M1/M2 phenotype. Also, lineage committed M1/M2 macrophages could be "switched" to their M2/M1 counterparts (M1-to-M2 or M2-to-M1 transition) exhibiting their well-established plasticity. When macrophages were encapsulated in hydrogels, polarization could be induced to the lineage committed M1 or M2 phenotypes either in polarizing media or when coencapsulated with cytokines. Through this study, silk hydrogels demonstrated utility as a novel system for focal delivery of cytokines and macrophages as "immuno-informed" 3D silk-biomaterials.