Role of embedded pure xenogenous bovine platelet gel on experimental tendon healing, modelling and remodelling

Mussel-Derived Bioadaptive Artificial Tendon Facilitates the Cell Proliferation and Tenogenesis to Promote Tendon Functional Reconstruction

Tendon injuries range from acute-related trauma to chronic-related injuries are prevalent and bring substantial pain, functional loss, and even disability to the patients. The management of tendon injuries is tricky due to the innate limited regenerative capability of the tendon. Currently, surgical intervention of tendon injuries with artificial tendons remains the standard of care. However, most of artificial tendons are manufactured with synthetic materials, which possess relatively poor biomimetic characteristics and inadequate inherent biodegradability, hence rendering limited cell proliferation and migration for tendon healing. To address these limitations, this work develops a mussel-derived artificial tendon based on double-cross-linked chitosan modification. In this design, decellularized artificial tendon serves as a natural biomimetic scaffold to facilitate the migration and adhesion of tendon repair cells. Additionally, as the cells proliferate, the artificial tendon can be degraded to facilitate tendon regeneration. Moreover, the chitosan cross-linking further enhances the mechanical strength of artificial tendon and offers a controllable degradation. The in vitro and in vivo experimental results demonstrate that mussel-derived artificial tendon not only accelerate the tendon functional reconstruction but also enable harmless clearance at postimplantation. The finding provides a promising alternative to conventional artificial tendons and spurs a new frontier to explore nature-derived artificial tendons.

The Opportunities and Challenges regarding Induced Platelets from Human Pluripotent Stem Cells

As a standard clinical treatment, platelet transfusion has been employed to prevent hemorrhage in patients with thrombocytopenia or platelet dysfunctions. Platelets also show therapeutic potential for aiding liver regeneration and bone healing and regeneration and for treating dermatological conditions. However, the supply of platelets rarely meets the rising clinical demand. Other issues, including short shelf life, strict storage temperature, and allogeneic immunity caused by frequent platelet transfusions, have become serious challenges that require the development of high-yielding alternative sources of platelets. Human pluripotent stem cells (hPSCs) are an unlimited substitution source for regenerative medicine, and patient-derived iPSCs can provide novel research models to explore the pathogenesis of some diseases. Many studies have focused on establishing and modifying protocols for generating functional induced platelets (iPlatelets) from hPSCs. To reach high efficiency production and eliminate the exogenous antigens, media supplements and matrix have been optimized. In addition, the introduction of some critical transgenes, such as c-MYC, BMI1, and BCL-XL, can also significantly increase hPSC-derived platelet production; however, this may pose some safety concerns. Furthermore, many novel culture systems have been developed to scale up the production of iPlatelets, including 2D flow systems, 3D rotary systems, and vertical reciprocal motion liquid culture bioreactors. The development of new gene-editing techniques, such as CRISPR/Cas9, can be used to solve allogeneic immunity of platelet transfusions by knocking out the expression of B2M. Additionally, the functions of iPlatelets were also evaluated from multiple aspects, including but not limited to morphology, structure, cytoskeletal organization, granule content, DNA content, and gene expression. Although the production and functions of iPlatelets are close to meeting clinical application requirements in both quantity and quality, there is still a long way to go for their large-scale production and clinical application. Here, we summarize the diverse methods of platelet production and update the progresses of iPlatelets. Furthermore, we highlight recent advances in our understanding of key transcription factors or molecules that determine the platelet differentiation direction.

Healing potentials of polymethylmethacrylate bone cement combined with platelet gel in the critical-sized radial bone defect of rats

Polymethylmethacrylate (PMMA) is the most commonly used filler material that lacks biological properties and osteoconductivity or osteoinductivity. Platelet gel (PG) is a typical source of growth factors, cytokines and molecules efficient for bone formation and remodeling. The aim of this study was to evaluate bone healing and regeneration of bone defect in rat model by combining PMMA with PG. A total of 50 defects were created in the diaphysis of the radii of 25 male Sprague-Dawley rats. These defects were randomly divided into five groups (n = 10 defects for each group) and treated by autograft, plain PMMA, PG and PMMA-PG or left untreated. The rats were examined clinically and radiologically during the experiment and also after euthanasia at the 8^th post-operative week, the healed defects were evaluated by gross morphology, histopathology, histomorphometry, computed tomography, scanning electron microscopy and biomechanical testing. PG could function as efficiently as autograft in promoting bone healing of the radial bones. Additionally, bone formation, and densities of cartilaginous and osseous tissues in the defects treated with autograft, PG and PMMA-PG were more satisfactory than the untreated and PMMA treated defects. Compared with the PMMA-PG implant, more PMMA residuals remained in the defect area and induced more intense inflammatory reaction. In conclusion, addition of PG could improve the bone regenerative properties of PMMA bone cement compared with PMMA alone in vivo. Therefore, the PG-PMMA can be proposed as a promising option to increase regenerative potential of PMMA, particularly when it is used as fixator, filler or adhesive in the dentistry, neurosurgery and bone tissue engineering applications.

An overview of platelet products (PRP, PRGF, PRF, etc.) in the Iranian studies

Aim

The aim of the study was to carry out a review of published studies on various platelet products in Iranian studies.

Materials & methods

Electronic databases were searched for relevant articles. Two review authors independently extracted data via a tested extraction sheet, and disagreements were resolved by a meeting with a third review author.

Results

Bone disorders (25%), wound and fistula (16%), dental and gingival disorders (14%) and osteoarthritis (11%) have more relative frequency based on different fields.

Conclusion

The necessity of pursuing standard protocols in the preparation of platelet products, stating the precise content of platelets and growth factors, and long-term follow-up of study subjects were the most important points in Iranian studies.

Role of Simvastatin on fracture healing and osteoporosis: a systematic review on in vivo investigations

Simvastatin is a lipid lowering drug whose beneficial role on bone metabolism was discovered in 1999. Several in vivo studies evaluated its role on osteoporosis and fracture healing, however, controversial results are seen in the literature. For this reason, Simvastatin has not been the focus of any clinical trials as yet. This systematic review clears the mechanisms of action of Simvastatin on bone metabolism and focuses on in vivo investigations that have evaluated its role on osteoporosis and fracture repair to find out (i) whether Simvastatin is effective on treatment of osteoporosis and fracture repair, and (ii) which of the many available protocols may have the ability to be translated in the clinical setting. Simvastatin induces osteoinduction by increasing osteoblast activity and differentiation and inhibiting their apoptosis. It also reduces osteoclastogenesis by decreasing both the number and activity of osteoclasts and their differentiation. Controversial results between the in vivo studies are mostly due to the differences in the route of administration, dose, dosage and carrier type. Local delivery of Simvastatin through controlled drug delivery systems with much lower doses and dosages than the systemic route seems to be the most valuable option in fracture healing. However, systemic delivery of Simvastatin with much higher doses and dosages than the clinical ones seems to be effective in managing osteoporosis. Simvastatin, in a particular range of doses and dosages, may be beneficial in managing osteoporosis and fracture injuries. This review showed that Simvastatin is effective in the treatment of osteoporosis and fracture healing.

The role of three-dimensional pure bovine gelatin scaffolds in tendon healing, modeling, and remodeling: an in vivo investigation with potential clinical value

AIM OF THE STUDY

Large tendon defects involving extensive tissue loss present complex clinical problems. Surgical reconstruction of such injuries is normally performed by transplanting autogenous and allogenous soft tissues that are expected to remodel to mimic a normal tendon. However, the use of grafts has always been associated with significant limitations. Tissue engineering employing artificial scaffolds may provide acceptable alternatives. Gelatin is a hydrolyzed form of collagen that is bioactive, biodegradable, and biocompatible. The present study has investigated the suitability of gelatin scaffold for promoting healing of a large tendon-defect model in rabbits.

MATERIALS AND METHODS

An experimental model of a large tendon defect was produced by partial excision of the Achilles tendon of the left hind leg in adult rabbits. To standardize and stabilize the length of the tendon defect a modified Kessler core suture was anchored in the sectioned tendon ends. The defects were either left untreated or filled with three-dimensional gelatin scaffold. Before euthanasia 60 days after injury, the progress of healing was evaluated clinically. Samples of healing tendon were harvested at autopsy and evaluated by gross, histopathologic, scanning, and transmission electron microscopy, and by biomechanical testing.

RESULTS

The treated animals showed superior weight-bearing and physical activity compared with those untreated, while frequency of peritendinous adhesions around the healing site was reduced. The gelatin scaffold itself was totally degraded and replaced by neo-tendon that morphologically had significantly greater numbers, diameters, density, and maturation of collagen fibrils, fibers, and fiber bundles than untreated tendon scar tissue. It also had mechanically higher ultimate load, yield load, stiffness, maximum stress and elastic modulus, when compared to the untreated tendons.

CONCLUSION

Gelatin scaffold may be a valuable option in surgical reconstruction of large tendon defects.

Effectiveness of tissue engineered based platelet gel embedded chitosan scaffold on experimentally induced critical sized segmental bone defect model in rat

BACKGROUND

Healing and regeneration of large bone defects are a challenging problem for reconstructive orthopedic surgeons.

PURPOSE

This study investigated the effectiveness of chitosan scaffold (CS), platelet gel (PG) and their combination (CS-PG) on healing process of an experimentally induced critical sized segmental bone defect model in rat.

METHODS

Fifty bilateral defects were created in the mid diaphysis of the radial bones of 25 Sprague-Dawley rats. The animals were randomly divided into five equal groups. The bone defects were either left untreated or treated with corticomedullary autograft, CS, PG or CS-PG. Plain radiographs were provided from the radial bones on weeks 2, 5, and 8 after injury. In addition, clinical examinations were done for the healing radial bones. The animals were euthanized after 8 weeks of injury, and their harvested samples were evaluated by gross morphology, histopathology, scanning electron microscopy, CT-scan, and biomechanical testing.

RESULTS

Compared with the defect group, the PG and autograft treated bone defects had significantly superior radiological scored values, bone volume and biomechanical performance which had positive correlation with their superior gross pathological, histopathological and ultra-structural features. Compared with the untreated defects, the PG and CS-PG treated defects showed significantly superior structural and functional properties so that PG had the highest value. In addition, CS had low value in bone regeneration. Although combination of CS and PG improved the healing efficacy of the CS, this strategy reduced the ability of PG to increase osteoconduction and osteoinduction during bone regeneration.

CONCLUSION

Application of PG alone enhanced bone healing and can be regarded as a promising option for bone tissue engineering in clinical settings. Chitosan was not effective in bone reconstruction surgery and further investigations should be conducted to find a suitable carrier for PG.

Freeze-Dried Platelet-Rich Plasma Accelerates Bone Union with Adequate Rigidity in Posterolateral Lumbar Fusion Surgery Model in Rats

Fresh platelet-rich plasma (PRP) accelerates bone union in rat model. However, fresh PRP has a short half-life. We suggested freeze-dried PRP (FD-PRP) prepared in advance and investigated its efficacy in vivo. Spinal posterolateral fusion was performed on 8-week-old male Sprague-Dawley rats divided into six groups based on the graft materials (n = 10 per group): sham control, artificial bone (A hydroxyapatite-collagen composite) -alone, autologous bone, artificial bone + fresh-PRP, artificial bone + FD-PRP preserved 8 weeks, and artificial bone + human recombinant bone morphogenetic protein 2 (BMP) as a positive control. At 4 and 8 weeks after the surgery, we investigated their bone union-related characteristics including amount of bone formation, histological characteristics of trabecular bone at remodeling site, and biomechanical strength on 3-point bending. Comparable radiological bone union was confirmed at 4 weeks after surgery in 80% of the FD-PRP groups, which was earlier than in other groups (p < 0.05). Histologically, the trabecular bone had thinner and more branches in the FD-PRP. Moreover, the biomechanical strength was comparable to that of autologous bone. FD-PRP accelerated bone union at a rate comparable to that of fresh PRP and BMP by remodeling the bone with thinner, more tangled, and rigid trabecular bone.