Osteoinductive Bone Morphogenic Protein, Collagen Scaffold, Calcium Phosphate Cement, and Magnesium-Based Fixation Enhance Anterior Cruciate Ligament Tendon Graft to Bone Healing In Animal Models: A Systematic Review

Biomass bilayer membranes with an asymmetric structure to promote a tendon-bone interface healing mechanism

Biologically, tendon-bone interface healing needs to overcome two problems: tendon dislocation and scar tissue proliferation at the interface. Because of the above problems, we proposed a bone tunnel membrane to aid tendon-bone interface healing. This study aims to explore the effects of absorbable membranes with different surface morphologies on tendon-bone interface healing. At the tendon-bone interface, the tendon graft was wrapped with a bilayer flexible absorbable membrane and implanted into the bone tunnel. Using the micron topological structure on the surface of the membrane to accelerate tendon healing and osteogenic differentiation provides environmental support for the healing of the two tissue interfaces. The different topological structures on the surface of the material can promote the oriented differentiation of cells. The micron groove structure can arrange fibroblasts according to orientation, promote tendon bundle healing, change cell morphology, and secrete tendon specific proteins to promote tendon repair. The porous structure can promote cell osteogenic differentiation and accelerate bone integration. After in vivo experimental analysis, the material is suitable for the adjuvant treatment of tendon-bone healing. Therefore, this study provides a new treatment idea for accelerating tendon-to-bone healing.

Hypermagnesemia- and Hyperphosphatemia-Associated Cardiac Arrest after Injection of a Novel Magnesium-Based Bone Cement in Spinal Surgery

We report a case of pulseless electrical activity (PEA) associated with profound hypermagnesemia immediately after cementation of a novel magnesium-based cement in spine surgery. During T8 to T12 posterior instrumentation and decompression laminectomy for vertebral metastasis secondary to lung cancer, a 61-year-old Chinese woman developed sudden hypotension and went into PEA immediately after injection of a novel magnesium-based cement. Intraoperative fluoroscopic imaging did not show any notable cement extravasation. Resuscitation using intravenous epinephrine with five doses of 1-mg epinephrine in 1:10,000 dilution was instituted, and the patient had return of spontaneous circulation after 5 minutes. After successful resuscitation, surgery was expedited and completed. Intraoperative and postoperative investigations were notable for profound hypermagnesemia and hyperphosphatemia requiring diuresis. No echocardiographic or computerized tomographic evidence of pulmonary embolism was found. The patient was transferred to the surgical intensive care unit and remained on dual inotropic support over the next few days. She subsequently weaned off inotropic support and electrolyte imbalances resolved before making a full recovery. This case report demonstrates the severe magnesium toxicity and PEA related to the use of novel magnesium-based cement in spine surgery. Further studies need to be conducted to understand the potential complications related to its use and compare them to the standard bone cement implantation syndrome.

Silk fibroin-based scaffolds for tissue engineering

Silk fibroin is an important natural fibrous protein with excellent prospects for tissue engineering applications. With profound studies in recent years, its potential in tissue repair has been developed. A growing body of literature has investigated various fabricating methods of silk fibroin and their application in tissue repair. The purpose of this paper is to trace the latest developments of SF-based scaffolds for tissue engineering. In this review, we first presented the primary and secondary structures of silk fibroin. The processing methods of SF scaffolds were then summarized. Lastly, we examined the contribution of new studies applying SF as scaffolds in tissue regeneration applications. Overall, this review showed the latest progress in the fabrication and utilization of silk fibroin-based scaffolds.

Biomimetic Intrafibrillar Mineralization of Native Tendon for Soft-Hard Interface Integration by Infiltration of Amorphous Calcium Phosphate Precursors

Soft and hard tissues possess distinct biological properties. Integrating the soft-hard interface is difficult due to the inherent non-osteogenesis of soft tissue, especially of anterior cruciate ligament and rotator cuff reconstruction. This property makes it difficult for tendons to be mineralized and integrated with bone in vivo. To overcome this challenge, a biomimetic mineralization strategy is employed to engineer mineralized tendons. The strategy involved infiltrating amorphous calcium phosphate precursors into collagen fibrils, resulting in hydroxyapatite deposition along the c-axis. The mineralized tendon presented characteristics similar to bone tissue and induced osteogenic differentiation of mesenchymal stem cells. Additionally, the interface between the newly formed bone and tendon is serrated, suggesting a superb integration between the two tissues. This strategy allows for biomineralization of tendon collagen and replicating the hallmarks of the bone matrix and extracellular niche, including nanostructure and inherent osteoinductive properties, ultimately facilitating the integration of soft and hard tissues.

Strategies for promoting tendon-bone healing: Current status and prospects

Tendon-bone insertion (TBI) injuries are common, primarily involving the rotator cuff (RC) and anterior cruciate ligament (ACL). At present, repair surgery and reconstructive surgery are the main treatments, and the main factor determining the curative effect of surgery is postoperative tendon-bone healing, which requires the stable combination of the transplanted tendon and the bone tunnel to ensure the stability of the joint. Fibrocartilage and bone formation are the main physiological processes in the bone marrow tract. Therefore, therapeutic measures conducive to these processes are likely to be applied clinically to promote tendon-bone healing. In recent years, biomaterials and compounds, stem cells, cell factors, platelet-rich plasma, exosomes, physical therapy, and other technologies have been widely used in the study of promoting tendon-bone healing. This review provides a comprehensive summary of strategies used to promote tendon-bone healing and analyses relevant preclinical and clinical studies. The potential application value of these strategies in promoting tendon-bone healing was also discussed.

BMP-2/TGF-β1 gene insertion into ligament-derived stem cells sheet promotes tendon-bone healing in a mouse

Bone morphogenetic protein-2 (BMP-2) and transforming growth factor-β1 (TGF-β1) reportedly induce the osteogenic and tenogenic differentiation of anterior cruciate ligament (ACL)-derived stem cells (LDSCs), respectively. However, few studies have investigated the effect of BMP-2/TGF-β1 on the differentiation of LDSC. We developed a BMP-2/TGF-β1 gene insertion into an LDSC cell sheet that promotes tendon-bone healing in a mouse ACL reconstruction (ACLR) model. CD34⁺ LDSCs were isolated from human ACL stump tissues, virally transduced to express BMP-2 or TGF-β1, and then embedded within cell sheets. All mice underwent ACLR using an autograft wrapped with a cell sheet and were randomly divided into three groups: BMP-2-, TGF-β1-, and BMP-2/TGF-β1-transduced. At 4 and 8 weeks, tendon-bone healing was evaluated by micro-CT, biomechanical test, and histological analysis. BMP-2 and TGF-β1 promoted the osteogenic and tenogenic differentiation of LDSC in vitro. BMP-2/TGF-β1-transduced LDSC sheet application contributed to early improvement in mean failure load and graft stiffness, accelerated maturation of the tendon-bone junction, and inhibited bone tunnel widening. Furthermore, reduced M1 macrophage infiltration and a higher M2 macrophage percentage were observed in the BMP-2/TGF-β1-transduced LDSC group. This work demonstrated that BMP-2 and TGF-β1 promoted CD34⁺ LDSCs osteogenic and tenogenic differentiation in vitro and in vivo, which accelerated the tendon-bone healing after ACLR using autografts wrapped with cell sheets in a mouse model.