Abstract Bone morphogenetic proteins (BMPs) are increasingly being used clinically to enhance fracture repair and healing of non-unions. However, the potential efficacy of supraphysiological dosing ...for clinical results warrants further clarification of the BMP signaling pathway in human fracture healing. As BMP signaling can be fine-tuned at numerous levels, the role of BMP-inhibitors has become a major focus. The aim of the present study was to document co-expression of BMPs, pSmad 1/5/8, and BMP-inhibitors in human fracture callus and human non-unions. Using human tissue of fracture callus (n = 14) and non-unions (n = 4) we documented expression of BMPs (BMP2, BMP3 and BMP7), pSmad 1/5/8 and the BMP-inhibitors noggin, gremlin, chordin, Smad-6, Smad-7 and BAMBI. Co-expression of pSmad 1/5/8, BMPs and BMP-inhibitors was noted in the osteoblasts of fracture callus as well as of non-unions. Expression of BMP-inhibitors was generally stronger in non-unions than in fracture callus. The most pertinent differences were noted in the cartilaginous tissue components. Expression of BMP2 in chondrocytes was markedly decreased in non-unions compared to fracture callus and that of BMP7 was almost completely absent. Expression of BMP-inhibitors was almost the same in osteoblasts, chondrocytes and fibroblasts of fracture callus and well as in non-unions. Interestingly, although BMP ligands were present in the chondrocytes and fibroblasts of non-unions, they did not co-express pSmad 1/5/8 suggesting that BMP signaling may have been inhibited at some point before Smad 1/5/8 phosphorylation. These results suggest co-expression of BMP, pSmad 1/5/8 and BMP-inhibitors occurs in human fracture callus as well as non-unions but the relative expression of BMPs vs. BMP-inhibitors was different between these two tissue types. In contrast to our expectations, the expression of BMP inhibitors was comparable between fracture callus and non-unions, whereas the expression of BMPs was notably lower in the cartilaginous component of the non-unions in comparison to fracture callus. Based on these results, we believe that aberrations in the BMP-signaling pathway in the cartilaginous component of fracture healing could influence clinical fracture healing. An imbalance between the local presence of BMP and BMP-inhibitors may switch the direction towards healing or non-healing of a fracture.
Recombinant human bone morphogenetic proteins (rhBMPs) have been extensively investigated for developing therapeutic strategies aimed at the restoration and treatment of orthopaedic as well as ...craniofacial conditions. In this first part of the review, we discuss the rationale for the necessary use of carrier systems to deliver rhBMP-2 and rhBMP-7 to sites of bone tissue regeneration and repair. General requirements for growth factor delivery systems emphasizing the distinction between localized and release-controlled delivery strategies are presented highlighting the current limitations in the development of an effective rhBMP delivery system applicable in clinical bone tissue engineering.
Abstract The present work is focused on the formulation of core–shell nanoparticles via the layer-by-layer (L-b-L) self-assembly technique for delivery of biomacromolecules such as bone growth ...factors. The drug encapsulation efficiency of liposomes is enhanced with the increased stability of polyelectrolyte systems achieved through the alternate adsorption of several layers of natural polymers: anionic alginate and cationic chitosan on cationic nanosized phospholipid vesicles. The resulting particles were characterized for their size, surface charge, morphology, encapsulation efficiency, loading capacity and release kinetics over an extended period of 30 days. The L-b-L deposition technique succeeded in building a spherical, monodisperse and stable hybrid nanoparticulate protein delivery system with a cumulative size of 383 ± 11.5 nm and zeta potential surface charge of 44.61 ± 3.31 mV for five bilayered liposomes. The system offers numerous compartments for encapsulation including the aqueous core and within the polyelectrolyte shell demonstrating good entrapment and sustained linear release of a model protein, bovine serum albumin, in vitro . Our results demonstrate that this delivery system features an extended shelf life and can be loaded immediately prior to administration, thus preventing any loss of the protein.
The aim of this study is to describe the technique of retrograde application of Fassier-Duval (FD) rod for the humerus in patients with osteogenesis imperfecta (OI). This technique was developed to ...overcome the downsides of the previously used techniques of humerus rodding.
The study was done at a tertiary care pediatric orthopaedic hospital from April 2014 to August 2021. Skeletally immature patients with OI who underwent retrograde FD rodding were included. This surgery was performed for humeral shaft fractures/bowing limited to the distal half of the bone to ensure appropriate stability of the fixation. Surgical technique of the procedure is described in detail.
Six patients with OI, of which 2 (33.3%) had FD rodding bilaterally, were included. The mean age at rodding was 7.6±3.5 (range: 3 to 14) years. The mean duration of postoperative follow-up was 45.5±18.0 (range: 24 to 75) months. All patients had full healing of the fracture/osteotomy, with functional alignment of their humeri. No surgical complications were observed; however, 1 (12.5%) segment only had a traumatic humerus fracture following a fall that was associated with rod migration, occurring 60 months postoperatively. This was treated with a retrograde FD rodding again, with fracture augmentation with plate and screws.
The retrograde FD rodding technique of the humerus in OI patients is relatively simple and preserves the soft tissue surrounding the shoulder joint, with favorable outcomes. Studies with larger sample size and long-term follow-up duration are needed.
Level IV-case series.
Localized and release-controlled delivery systems for the sustained expression of the biologic potency of rhBMPs are essential. A substantial number of biomaterials have been investigated thus far. ...Most fail after implantation or administration mainly due to either being too soft, difficult to control and/or stabilize mechanically. In the second part of this review, we review a representative selection of rhBMP-2 and rhBMP-7 carrier materials and delivery systems ranging from simple nano/microparticles to complex 3-D scaffolds in sites of orthopaedic and craniofacial bone regeneration and repair.
Pediatric patients with Osteogenesis Imperfecta (OI), a heritable connective tissue disorder, frequently suffer from long bone deformations. Surgical correction often results in bone non-unions, ...necessitating revision surgery with autogenous bone grafting using bone-marrow-derived stem cells (BM-SC) to regenerate bone. BM-SC harvest is generally invasive and limited in supply; thus, adipose tissue's stromal vascular fraction (SVF) has been introduced as an alternative stem cell reservoir. To elucidate if OI patients' surgical site dissected adipose tissue could be used as autologous bone graft in future, we investigated whether the underlying genetic condition alters SVF's cell populations and in vitro differentiation capacity. After optimizing SVF isolation, we demonstrate successful isolation of SVF of pediatric OI patients and non-OI controls. The number of viable cells was comparable between OI and controls, with about 450,000 per gram tissue. Age, sex, type of OI, disease-causing collagen mutation, or anatomical site of harvest did not affect cell outcome. Further, SVF-containing cell populations were similar between OI and controls, and all isolated SVF's demonstrated chondrogenic, adipogenic, and osteogenic differentiation capacity in vitro. These results indicate that SVF from pediatric OI patients could be used as a source of stem cells for autologous stem cell therapy in OI.
Bone morphogenetic proteins (BMPs) are recognized for their ability to induce bone formation in vivo and in vitro. Their osteogenic and osteoinductive properties are tightly regulated by the ...secretion of specific BMP antagonists, which have been shown to physically bind and sometimes be blocked by the extracellular proteoglycan heparan sulphate side chains (from hereon referred to as HS). The purpose of this study was to investigate if local application of 5 µg of HS proteoglycan to a bone regenerate site in a mouse model of distraction osteogenesis (DO) can accelerate bone healing and affect the expression of key members of the BMP signaling pathway. DO was performed on the right tibia of 115 adult male wild-type mice. At mid-distraction (day 11), half the group was injected locally with 5 µg of HS, while the other half was injected with saline. The mice were sacrificed at 2 time-points: mid-consolidation (34 days) and full consolidation (51 days). The distracted tibial zone was then collected for analysis by μCT, radiology, biomechanical testing, immunohistochemistry, and histology. While μCT data showed no statistically significant difference in bone formation, the results of biomechanical testing in stiffness and ultimate force were significantly lower in the HS-injected bones at 51 days, compared to controls. Immunohistochemistry results also suggested a decrease in expression of several key members of the BMP signaling pathway at 34 days. Furthermore, wound dehiscence and infection rates were significantly elevated in the HS group compared to the controls, which resulted in a higher rate of euthanasia in the treatment group. Our findings demonstrate that exogenous application of 5 µg of HS in the distracted gap of a murine model had a negative impact on bone and wound healing.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background
Sclerostin is a secreted glycoprotein that inhibits the intracellular Wnt signaling pathway, which, when inactivated, stimulates bone formation. This has been seen in fracture studies, ...which have shown larger and stronger calluses with accelerated fracture healing in sclerostin knockout and sclerostin antibody injection models. However, the effects of these two mechanisms have not been compared in the context of fracture healing.
Questions/purposes
We sought to determine the degree to which sclerostin inhibition (Scl-Ab injection) and complete sclerostin depletion inhibit fracture healing in a mouse model as evaluated by (1) morphometric trabecular bone measures at the fracture site, and (2) fracture site structural strength.
Methods
Ten-week-old male sclerostin knockout (n = 20) and wild type (n = 40) mice underwent insertion of a tibial intramedullary pin after which a midshaft tibial osteotomy was performed. The mice were divided in three groups: sclerostin knockout (n = 20), wild type with sclerostin antibody injection (intravenous dose of 100 mg/kg weekly) (n = 20), and wild type with saline injection (n = 20). The mice for each group where subdivided and euthanized at 14, 21, 28, and 35 days after surgery, at which time the fractured tibias were assessed with microCT (to assess morphometric trabecular bone measures: bone volume to total volume (BV/TV), trabecular thickness, trabecular number, and structural model index at the fracture site. Biomechanical testing in the form of three-point bending also was done to assess fracture site structural strength. A difference greater than 3.7% in our primary outcome (BV/TV) would be required to detect a difference between groups with a power of 80%, as per our power analysis.
Results
The wild type with sclerostin antibody and the sclerostin knockout groups showed increased trabecular BV/TV at the fracture site compared with the wild type group with saline at all times, however no difference was seen between the treatment groups with the numbers available, except at 28 days postoperatively when the sclerostin knockout group showed greater BV/TV than the wild type sclerostin antibody group (47.0 ± 3.5 vs 40.1 ± 2.1; p < 0.05). On biomechanical testing the wild type sclerostin antibody showed increased stiffness at Days 14 and 28 compared with the wild type with saline group (70.9 ± 6.4 vs 14.8 ± 8.1; p = 0.001), (106.8 ± 24.3 vs 74.9 ± 16.0; p = 0.004); respectively. However, with the numbers available, no differences were detected between the wild type with sclerostin antibody and the sclerostin knockout groups in terms of whole-bone structural strength.
Conclusions
Sclerostin antibody injections showed promising results, which were not different with the numbers available, from results achieved with complete depletion of sclerostin, especially at earlier stages of the healing process, and therefore completed the healing process at an earlier time.
Clinical Relevance
Sclerostin antibody injections appear to enhance fracture healing to a degree that is not different than complete sclerostin depletion, but larger animal studies are required to assess the accurate dosage and timing of administration in the fracture healing process to further evaluate its potential clinical utility to enhance fracture healing.
The distraction osteogenesis (DO) technique has been used worldwide to treat many complex orthopedic and craniofacial conditions. One limitation of this technique is the long time of fixator needs to ...be left in place until the bone is completely consolidated. Various biophysical, mechanical, and biological methods have been investigated to accelerate bone regeneration during DO. Several growth factors (GFs) are known to enhance bone regeneration such as bone morphogenic proteins, transforming growth factor beta, fibroblast growth factor, insulin growth factor, vascular endothelial growth factor, and platelet-derived growth factor. These GFs are known to stimulate cellular growth, proliferation, migration, and differentiation. In this review, an extensive overview of these GFs development and applications on acceleration of bone regeneration in the context of DO is discussed. Current challenges and alternative tissue engineering techniques to address the delivery and sustain release of these factors are also discussed. Finally, we highlighted our view regarding the remaining questions and future research directions.
RATIONALE:Mesenchymal stromal cells (MSCs) are promising therapeutic strategies for coronary artery disease; however, donor-related variability in cell quality is a main cause of discrepancies in ...preclinical studies. In vitro, MSCs from individuals with coronary artery disease have reduced ability to suppress activated T-cells. The mechanisms underlying the altered immunomodulatory capacity of MSCs in the context of atherosclerosis remain elusive.
OBJECTIVE:The aim of this study was to assess the role of mitochondrial dysfunction in the impaired immunomodulatory properties of MSCs from patients with atherosclerosis.
METHODS AND RESULTS:Adipose tissue–derived MSCs were isolated from atherosclerotic (n=38) and nonatherosclerotic (n=42) donors. MSCs:CD4T-cell suppression was assessed in allogeneic coculture systems. Compared with nonatherosclerotic-MSCs, atherosclerotic-MSCs displayed higher levels of both intracellular (P=0.006) and mitochondrial (P=0.03) reactive oxygen species reflecting altered mitochondrial function. The increased mitochondrial reactive oxygen species levels of atherosclerotic-MSCs promoted a phenotypic switch characterized by enhanced glycolysis and an altered cytokine secretion (interleukin-6 P<0.0001, interleukin-8/C-X-C motif chemokine ligand 8 P=0.04, and monocyte chemoattractant protein-1/chemokine ligand 2 P=0.01). Furthermore, treatment of atherosclerotic-MSCs with the reactive oxygen species scavenger N-acetyl-L-cysteine reduced the levels of interleukin-6, interleukin-8/C-X-C motif chemokine ligand 8, and monocyte chemoattractant protein-1/chemokine ligand 2 in the MSC secretome and improved MSCs immunosuppressive capacity (P=0.03).
CONCLUSIONS:An impaired mitochondrial function of atherosclerotic-MSCs underlies their altered secretome and reduced immunopotency. Interventions aimed at restoring the mitochondrial function of atherosclerotic-MSCs improve their in vitro immunosuppressive ability and may translate into enhanced therapeutic efficiency.
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