Nanofiber Scaffolds by Electrospinning for Rotator Cuff Tissue Engineering

Three-Dimensional Meltblowing as a High-Speed Fabrication Process for Tendon Tissue Engineered Scaffolds

Rotator cuff tears continue to be a critical challenge for successful repair due to the formation of fibrotic scar tissue during healing. Tendon tissue engineering seeks to improve these outcomes using nonwoven fabrication methods to produce biomimetic scaffolds. Meltblowing has several advantages over other nonwoven approaches including non-toxic fabrication processes and being high-throughput and economical, while accurately producing fiber diameters comparable to native tendon microstructure. Recently 3D meltblowing (3DMB) introduced high degrees of tunability to the core process, allowing for production of highly aligned fiber mats at anatomically relevant dimensions. Here, we evaluated 3DMB scaffolds fabricated using poly-L-lactic acid (PLA) and poly-ε-caprolactone (PCL) by characterizing scaffold properties before and after culture with human adipose stem cells (hASCs). Mechanical and fiber characterization of 3DMB scaffolds closely resembled tendon microarchitecture by exhibiting high fiber alignment and mechanical anisotropy. hASC-seeded 3DMB scaffolds after 28 days of culture proliferated and deposited aligned tendon-like extracellular matrix. Furthermore, cell culture enhanced the Young's modulus of PLA 3DMB scaffolds and improved yield stress, yield stretch, and stiffness of both 3DMB scaffolds. The proteome of cultured 3DMB scaffolds increased expression of tendon-related proteins after 28 days of culture, but polymer-dependent differences in glycoprotein composition was observed. Together, 3DMB is a promising method for tendon tissue engineering, by showing improved fiber and mechanical properties compared to meltblown scaffolds. However, while an improvement on prior iterations, continued development of this 3DMB technology is needed to better mimic the mechanical properties and biologic composition of native tendon.

Biological Augmentation Using Electrospun Constructs with Dual Growth Factor Release for Rotator Cuff Repair

Surgical reattachment of tendon to bone is the standard therapy for rotator cuff tear (RCT), but its effectiveness is compromised by retear rates of up to 94%, primarily due to challenges in achieving successful tendon-bone enthesis regeneration under natural conditions. Biological augmentation using biomaterials has emerged as a promising approach to address this challenge. In this study, a bilayer construct incorporates polydopamine (PDA)-mediated bone morphogenetic protein 2 (BMP2) and BMP12 in separate poly(lactic-co-glycolic acid) (PLGA) fiber layers to promote osteoblast and tenocyte growth, respectively, and intermediate fibrocartilage formation, aiming to enhance the regenerative potential of tendon-bone interfaces. The lower layer, consisting of PLGA fibers with BMP2 immobilization through PDA adsorption, significantly accelerated osteoblast growth. Concurrently, the upper BMP12@PLGA-PDA fiber mat facilitated fibrocartilage formation and tendon tissue regeneration, evidenced by significantly elevated tenocyte viability and tenogenic differentiation markers. Therapeutic efficacy assessed through in vivo RCT models demonstrated that the dual-BMP construct augmentation significantly promoted the healing of tendon-bone interfaces, confirmed by biomechanical testing, cartilage immunohistochemistry analysis, and collagen I/II immunohistochemistry analysis. Overall, this combinational strategy, which combines augmentation patches with the controlled release of dual growth factors, shows great promise in improving the overall success rates of rotator cuff repairs.

The Clinical Application of Gel-Based Composite Scaffolds in Rotator Cuff Repair

Rotator cuff tears are a common injury that can be treated with or without surgical intervention. Gel-based scaffolds have gained significant attention in the field of tissue engineering, particularly for applications like rotator cuff repair. Scaffolds can be biological, synthetic, or a mixture of both materials. Collagen, a primary constituent of the extracellular matrix (ECM) in musculoskeletal tissues, is one of the most widely used materials for gel-based scaffolds in rotator cuff repair, but other ECM-based and synthetic-based composite scaffolds have also been utilized. These composite scaffolds can be engineered to mimic the biomechanical and biological properties of natural tissues, supporting the healing process and promoting regeneration. Various clinical studies examined the effectiveness of these composite scaffolds with collagen, ECM and synthetic polymers and provided outstanding results with remarkable improvements in range of motion (ROM), strength, and pain. This review explores the material composition, manufacturing process and material properties of gel-based composite scaffolds as well as their clinical outcomes for the treatment of rotator cuff injuries.

Optimizing Tissue Engineering for Clinical Relevance in Rotator Cuff Repair

Rotator cuff tear (RCT) is the most common cause of disability in the upper extremity. It results in 4.5 million physician visits in the United States every year and is the most common etiology of shoulder conditions evaluated by orthopedic surgeons. Over 460,000 RCT repair surgeries are performed in the United States annually. Rotator cuff (RC) retear and failure to heal remain significant postoperative complications. Literature suggests that the retear rates can range from 29.5% to as high as 94%. Weakened and irregular enthesis regeneration is a crucial factor in postsurgical failure. Although commercially available RC repair grafts have been introduced to augment RC enthesis repair, they have been associated with mixed clinical outcomes. These grafts lack appropriate biological cues such as stem cells and signaling molecules at the bone-tendon interface. In addition, they do little to prevent fibrovascular scar tissue formation, which causes the RC to be susceptible to retear. Advances in tissue engineering have demonstrated that mesenchymal stem cells (MSCs) and growth factors (GFs) enhance RC enthesis regeneration in animal models. These models show that delivering MSCs and GFs to the site of RCT enhances native enthesis repair and leads to greater mechanical strength. In addition, these models demonstrate that MSCs and GFs may be delivered through a variety of methods including direct injection, saturation of repair materials, and loaded microspheres. Grafts that incorporate MSCs and GFs enhance anti-inflammation, osteogenesis, angiogenesis, and chondrogenesis in the RC repair process. It is crucial that the techniques that have shown success in animal models are incorporated into the clinical setting. A gap currently exists between the promising biological factors that have been investigated in animal models and the RC repair grafts that can be used in the clinical setting. Future RC repair grafts must allow for stable implantation and fixation, be compatible with current arthroscopic techniques, and have the capability to deliver MSCs and/or GFs.

Cutting-Edge Hydrogel Technologies in Tissue Engineering and Biosensing: An Updated Review

Hydrogels, known for their unique ability to retain large amounts of water, have emerged as pivotal materials in both tissue engineering and biosensing applications. This review provides an updated and comprehensive examination of cutting-edge hydrogel technologies and their multifaceted roles in these fields. Initially, the chemical composition and intrinsic properties of both natural and synthetic hydrogels are discussed, highlighting their biocompatibility and biodegradability. The manuscript then probes into innovative scaffold designs and fabrication techniques such as 3D printing, electrospinning, and self-assembly methods, emphasizing their applications in regenerating bone, cartilage, skin, and neural tissues. In the realm of biosensing, hydrogels' responsive nature is explored through their integration into optical, electrochemical, and piezoelectric sensors. These sensors are instrumental in medical diagnostics for glucose monitoring, pathogen detection, and biomarker identification, as well as in environmental and industrial applications like pollution and food quality monitoring. Furthermore, the review explores cross-disciplinary innovations, including the use of hydrogels in wearable devices, and hybrid systems, and their potential in personalized medicine. By addressing current challenges and future directions, this review aims to underscore the transformative impact of hydrogel technologies in advancing healthcare and industrial practices, thereby providing a vital resource for researchers and practitioners in the field.

Nanofiber Graft Therapy to Prevent Shoulder Stiffness and Adhesions after Rotator Cuff Tendon Repair: A Comprehensive Review

Stiffness and adhesions following rotator cuff tears (RCTs) are common complications that negatively affect surgical outcomes and impede healing, thereby increasing the risk of morbidity and failure of surgical interventions. Tissue engineering, particularly through the use of nanofiber scaffolds, has emerged as a promising regenerative medicine strategy to address these complications. This review critically assesses the efficacy and limitations of nanofiber-based methods in promoting rotator cuff (RC) regeneration and managing postrepair stiffness and adhesions. It also discusses the need for a multidisciplinary approach to advance this field and highlights important considerations for future clinical trials.

Semi-Bone Tunnel Technique Using Double-Row Suture Bridge Combined With Platelet-Rich Plasma Hydrogel for Rotator Cuff Repair in a Rabbit Model

BACKGROUND

The approach to managing the footprint area and reconstructing the tendon-bone interface (TBI) is critical for optimal healing.

PURPOSE

To evaluate the outcomes of the semi-bone tunnel (SBT) technique using a double-row suture bridge combined with platelet-rich plasma (PRP) hydrogel for rotator cuff repair in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 48 New Zealand White rabbits were divided into 4 groups. The supraspinatus tendons were severed at the footprint to create a rotator cuff tear model in the surgical groups. Rabbits were treated with the traditional onto-surface repair (control group), SBT technique (SBT group), and SBT technique combined with PRP hydrogel implantation (SBT+PRP group). The rabbits without surgery were the normal group. At 8 weeks after surgery, macroscopic observation, magnetic resonance imaging (MRI) and micro-computed tomography (μCT) examinations, histological evaluations, and biomechanical tests were performed to assess the curative effects of the given treatments.

RESULTS

The MRI results showed that the repaired supraspinatus tendon presented a uniform signal, minimal inflammatory response, and the lowest signal-to-noise quotient value in the SBT+PRP group. The μCT results suggested that the SBT technique did not reduce the local bone mineral density in the TBI area compared with the onto-surface repair technique. The histological staining results showed that the regenerated TBI in the SBT+PRP group had a 4-layer structure similar to the natural tissue. The highest values for biomechanical properties were observed in the SBT+PRP group, and there was no significant difference between the SBT+PRP group and normal group.

CONCLUSION

The SBT technique presented a better tendon-bone healing effect for rotator cuff tear in the rabbit model compared with the traditional onto-surface repair technique. The specimens in the SBT+PRP group had a similar TBI structure and biomechanical properties to the natural tissue.

CLINICAL RELEVANCE

The SBT technique can be an alternative surgical approach for rotator cuff repair, especially for moderate to large tears and cases requiring scaffold implantation.

Co-Culture of Mesenchymal Stem Cells and Ligamentocytes on Triphasic Embroidered Poly(L-lactide-co-ε-caprolactone) and Polylactic Acid Scaffolds for Anterior Cruciate Ligament Enthesis Tissue Engineering

Successful anterior cruciate ligament (ACL) reconstructions strive for a firm bone-ligament integration. With the aim to establish an enthesis-like construct, embroidered functionalized scaffolds were colonized with spheroids of osteogenically differentiated human mesenchymal stem cells (hMSCs) and lapine (l) ACL fibroblasts in this study. These triphasic poly(L-lactide-co-ε-caprolactone) and polylactic acid (P(LA-CL)/PLA) scaffolds with a bone-, a fibrocartilage transition- and a ligament zone were colonized with spheroids directly after assembly (DC) or with 14-day pre-cultured lACL fibroblast and 14-day osteogenically differentiated hMSCs spheroids (=longer pre-cultivation, LC). The scaffolds with co-cultures were cultured for 14 days. Cell vitality, DNA and sulfated glycosaminoglycan (sGAG) contents were determined. The relative gene expressions of collagen types I and X, Mohawk, Tenascin C and runt-related protein (RUNX) 2 were analyzed. Compared to the lACL spheroids, those with hMSCs adhered more rapidly. Vimentin and collagen type I immunoreactivity were mainly detected in the hMSCs colonizing the bone zone. The DNA content was higher in the DC than in LC whereas the sGAG content was higher in LC. The gene expression of ECM components and transcription factors depended on cell type and pre-culturing condition. Zonal colonization of triphasic scaffolds using spheroids is possible, offering a novel approach for enthesis tissue engineering.

Scaffold-based tissue engineering strategies for soft-hard interface regeneration

Repairing injured tendon or ligament attachments to bones (enthesis) remains costly and challenging. Despite superb surgical management, the disorganized enthesis newly formed after surgery accounts for high recurrence rates after operations. Tissue engineering offers efficient alternatives to promote healing and regeneration of the specialized enthesis tissue. Load-transmitting functions thus can be restored with appropriate biomaterials and engineering strategies. Interestingly, recent studies have focused more on microstructure especially the arrangement of fibers since Rossetti successfully demonstrated the variability of fiber underspecific external force. In this review, we provide an important update on the current strategies for scaffold-based tissue engineering of enthesis when natural structure and properties are equally emphasized. We firstly described compositions, structures and features of natural enthesis with their special mechanical properties highlighted. Stimuli for growth, development and healing of enthesis widely used in popular strategies are systematically summarized. We discuss the fabrication of engineering scaffolds from the aspects of biomaterials, techniques and design strategies and comprehensively evaluate the advantages and disadvantages of each strategy. At last, this review pinpoints the remaining challenges and research directions to make breakthroughs in further studies.

Electrospun hydroxyapatite loaded L-polylactic acid aligned nanofibrous membrane patch for rotator cuff repair

Rotator cuff repair remains a challenge clinically due to the high retear rate after surgical intervention. There is a significant need to develop functional biomaterials facilitating tendon-to-bone integration. In this study, hydroxyapatite (HA) incorporated polylactic acid (PLLA) aligned nanofibrous membranes were fabricated by electrospinning as a low-cost sustainable rotator cuff patch. The morphology, physical, mechanical and in vitro cell assays of the nanofibrous membranes were characterized. The results showed that the nanofibrous membrane maintained a rough surface and weakened hydrophobicity. It has excellent cytocompatibility, and the cells were oriented along the direction of fiber arrangement. What's more, the PLLA-HA nanofibrous membrane could increase the alkaline phosphatase (ALP) expression in rat bone marrow mesenchymal stem cells (BMSCs), indicating that the electrospinning PLLA-HA nanofibrous membrane can better induce the bone formation of rat BMSCs cells. When the mass ratio of PLLA to HA exceeds 3: 1, with the increase of the HA content, the patch showed rising induction ability. The results suggested that electrospinning PLLA-HA nanofibrous membranes are an ideal patch for promoting tendon-bone healing and reducing the secondary tear rate. Furthermore, the use of biodegradable polymers and low-cost preparation methods presented the possibility for commercial production of these nanofibrous membranes.

Bipolar Metal Flexible Electrospun Fibrous Membrane Based on Metal-Organic Framework for Gradient Healing of Tendon-to-Bone Interface Regeneration

Metal ions play a significant role in tissue repair, with widely application in clinical treatment. However, the therapeutic effect of metal ions is always limited due to metabolization and narrow repair capability. Here, a bipolar metal flexible electrospun fibrous membrane based on a metal-organic framework (MOF), which is bioinspired by the gradient structure of the tendon-to-bone interface, with a combination of regulating osteoblasts differentiation and angiogenesis properties, is constructed successfully by a continuous electrospinning technique and matching the longitudinal space morphology for synchronous regeneration. Furthermore, the MOF, acting as carriers, can not only achieve the sustainable release of metal ions, but promote the osteogenesis and tenogenesis on the scaffold. The in vitro data show that this novel hierarchical structure can accelerate the tenogenesis, the biomineralization, and angiogenesis. Moreover, in the in vivo experiment, the flexible fibrous membrane can promote tendon and bone tissue repair, and fibrocartilage reconstruction, to realize the multiple tissue synchronous regeneration at the damaged tendon-to-bone interface. Altogether, this newly developed bipolar metal flexible electrospun fibrous membrane based on a MOF, as a new biomimetic flexible scaffold, has great potential in reconstruct the tissue damage, especially gradient tissue damage.

Tissue-Specific Decellularized Extracellular Matrix Bioinks for Musculoskeletal Tissue Regeneration and Modeling Using 3D Bioprinting Technology

The musculoskeletal system is a vital body system that protects internal organs, supports locomotion, and maintains homeostatic function. Unfortunately, musculoskeletal disorders are the leading cause of disability worldwide. Although implant surgeries using autografts, allografts, and xenografts have been conducted, several adverse effects, including donor site morbidity and immunoreaction, exist. To overcome these limitations, various biomedical engineering approaches have been proposed based on an understanding of the complexity of human musculoskeletal tissue. In this review, the leading edge of musculoskeletal tissue engineering using 3D bioprinting technology and musculoskeletal tissue-derived decellularized extracellular matrix bioink is described. In particular, studies on in vivo regeneration and in vitro modeling of musculoskeletal tissue have been focused on. Lastly, the current breakthroughs, limitations, and future perspectives are described.

[Studies On Glutamic Pyruvic- And Oxaloacetic Transaminase Of Different Organs Of Ascaris Lumbricoides Suis]

A Study on glutamic pyruvic and oxaloacetic transaminase of different organs(e.g intestine, seminal vesicle, reticular tissue, uterus, ovary, testes) in Ascaris lumbricoides suis have been investigated. The activity of transaminase were determined on the whole homogenates and subcellular fractions separated by differential centrifugation. The activity of glutamic pyruvic and oxaloacetic were assayed by colorimetric method of Reitman-Frankel. The results were obtained as follows: 1. About ninty percent of the glutamic pyruvic and oxaloacetic transaminase in different organs was found to be localized in the supernatant fraction with the separation of differential centrifugation. And it was found that ten percent of glutamic pyruvic and oxaloacetic transaminase exists in the mitochondrial fraction. 2. The specific activity of glutamic oxaloacetic transnaminase in different organs was relatively higher than the glutamic pyruvic transaminase activity.