Freeze-dried human serum albumin improves the adherence and proliferation of mesenchymal stem cells on mineralized human bone allografts

Composite Remineralization of Bone-Collagen Matrices by Low-Temperature Ceramics and Serum Albumin: A New Approach to the Creation of Highly Effective Osteoplastic Materials

This study examined the effectiveness of coating demineralized bone matrix (DBM) with amorphous calcium phosphate (DBM + CaP), as well as a composite of DBM, calcium phosphate, and serum albumin (DBM + CaP + BSA). The intact structure of DBM promotes the transformation of amorphous calcium phosphate (CaP) into dicalcium phosphate dihydrate (DCPD) with a characteristic plate shape and particle size of 5-35 µm. The inclusion of BSA in the coating resulted in a better and more uniform distribution of CaP on the surface of DBM trabeculae. MG63 cells showed that both the obtained forms of CaP and its complex with BSA did not exhibit cytotoxicity up to a concentration of 10 mg/mL in vitro. Ectopic (subcutaneous) implantation in rats revealed pronounced biocompatibility, as well as strong osteoconductive, osteoinductive, and osteogenic effects for both DBM + CaP and DBM + CaP + BSA, but more pronounced effects for DBM + CaP + BSA. In addition, for the DBM + CaP + BSA samples, there was a pronounced full physiological intrafibrillar biomineralization and proangiogenic effect with the formation of bone-morrow-like niches, accompanied by pronounced processes of intramedullary hematopoiesis, indicating a powerful osteogenic effect of this composite.

Evaluation of Serum Albumin-Coated Bone Allograft for Bone Regeneration: A Seven-Year Follow-Up Study of 26 Cases

We have previously reported that serum albumin-coated bone allograft (BoneAlbumin, BA) is an effective bone substitute. It improves bone regeneration at the patellar and tibial donor sites six months after harvesting bone-patellar tendon-bone (BPTB) autografts for primary anterior cruciate ligament reconstruction (ACLR). In the present study, we examined these donor sites seven years after implantation. The study group (N = 10) received BA-enhanced autologous cancellous bone at the tibial and BA alone at the patellar site. The control group (N = 16) received autologous cancellous bone at the tibial and blood clot at the patellar site. We evaluated subcortical density, cortical thickness, and bone defect volume via CT scans. At the patellar site, subcortical density was significantly higher in the BA group at both time points. There was no significant difference in cortical thickness between the two groups at either donor site. The control group's bone defect significantly improved and reached the BA group's values at both sites by year seven. Meanwhile, the bone defects in the BA group did not change significantly and were comparable to the six-month measurements. No complications were observed. There are two limitations in this study: The number of patients recruited is small, and the randomization of the patients could have improved the quality of the study as the control group patients were older compared to the study group patients. Our 7-year results seem to demonstrate that BA is a safe and effective bone substitute that supports faster regeneration of donor sites and results in good-quality bone tissue at the time of ACLR with BPTB autografts. However, studies with a larger number of patients are required to definitively confirm the preliminary results of our study.

Albumin-Coated Polycaprolactone (PCL)-Decellularized Extracellular Matrix (dECM) Scaffold for Bone Regeneration

With the emphasis on collagen and hydroxyapatite, the main structural components of bone tissue, synthetic grafts fall short of matching the clinical efficacy of autologous bone grafts. Excluded non-collagenous protein (NCPs) and carbohydrates also participate in critical cell signaling cascades and guide mineral deposition during intermediate stages of bone healing. By mimicking the native fracture repair process, polymeric scaffolds that incorporate calcium-binding moieties present in fibrocartilage can potentially enhance their bioactivity, mineralization, and bone growth. Likewise, coating polymeric fibers with serum albumin is an additional strategy that can impart collagen-like biofunctionality and further increase mineral deposition on the fibrous surface. Here, a combination of electrospun polycaprolactone (PCL) fibers with chondrocyte-derived decellularized extracellular matrix (dECM) and albumin coating were investigated as a fibrocartilage-mimetic scaffold that can serve as a woven bone precursor for bone regeneration. PCL fibrous constructs coated with dECM and albumin are shown to synergistically increase calcium concentration and calcium phosphate (CaP) deposition in a simulated body fluid biomineralization assay. Albumin/dECM coating increased osteoblast proliferation and mineral deposition in culture. In contrast, CaP coating transformed osteoblast bone lining morphology into cuboidal phenotype and arrested their proliferation. Cell sheets of osteoblasts cultured on dECM/albumin/CaP-coated constructs exhibited an increase in calcium deposition and secretion of collagen, osteopontin, osteocalcin, and bone morphogenetic protein. These results highlight the potential of biomolecular coatings to enhance bone-mimetic properties of synthetic nanofibrous scaffolds, stimulate critical protein and mineral deposition, and augment the bone's capacity to heal. Thus, mimicking the intermediate stages of bone regeneration by incorporating calcium-binding moieties may prove to be a useful strategy for improving the clinical outcomes of synthetic bone grafts.

Delivery of Bioactive Albumin from Multi-Functional Polyampholyte Hydrogels

Tissue engineered scaffolds are currently being explored to aid in healing and regeneration of non-union fractures in bone. Additionally, albumin has been demonstrated to provide benefits to healing when applied to injury sites. This paper focuses on delivery of calcium modified, bioactive bovine serum albumin (BSA) from a multi-functional polyampholyte polymer scaffold. First, the inherent nonfouling and conjugation properties of the polyampholyte hydrogel were verified to determine the impact of calcium exposure. The polyampholyte hydrogel delivery platform was then assessed with calcium titrations and osteoblast-like cell (MC3T3-E1) adhesion, proliferation, and viability evaluations. Finally, integrin inhibitors were used to identify the binding mechanisms that mediate cell adhesion to the calcium-modified BSA-conjugated hydrogels. An increase in cell adhesion was observed following calcium exposure up to 0.075 M, although this and higher calcium concentrations affected hydrogel stability and cell growth. BSA exposed to 0.05 M calcium and delivered from polyampholyte hydrogels promoted the most promising viable cell adhesion over 7 days. Cell adhesion to the calcium-modified BSA-conjugated hydrogels appeared to be regulated by arginine-glycine-aspartic acid (RGD) and collagen specific integrins. These results demonstrate that the delivery of calcium modified BSA from an implantable polymer scaffold is promising for bone tissue engineering applications.

Albumin as a Biomaterial and Therapeutic Agent in Regenerative Medicine

Albumin is a constitutional plasma protein, with well-known biological functions, e.g., a nutrient for stem cells in culture. However, albumin is underutilized as a biomaterial in regenerative medicine. This review summarizes the advanced therapeutic uses of albumin, focusing on novel compositions that take advantage of the excellent regenerative potential of this protein. Albumin coating can be used for enhancing the biocompatibility of various types of implants, such as bone grafts or sutures. Albumin is mainly known as an anti-attachment protein; however, using it on implantable surfaces is just the opposite: it enhances stem cell adhesion and proliferation. The anticoagulant, antimicrobial and anti-inflammatory properties of albumin allow fine-tuning of the biological reaction to implantable tissue-engineering constructs. Another potential use is combining albumin with natural or synthetic materials that results in novel composites suitable for cardiac, neural, hard and soft tissue engineering. Recent advances in materials have made it possible to electrospin the globular albumin protein, opening up new possibilities for albumin-based scaffolds for cell therapy. Several described technologies have already entered the clinical phase, making good use of the excellent biological, but also regulatory, manufacturing and clinical features of serum albumin.

Nanohydroxyapatite-Protein Interface in Composite Sintered Scaffold Influences Bone Regeneration in Rabbit Ulnar Segmental Defect

The healing physiology of bone repair and remodeling that occurs after normal fracture is well orchestrated. However, it fails in complex clinical conditions and hence requires augmentation by grafts. In this study, composite nanohydroxyapatite (nHA), poly(hydroxybutyrate) (PHB) and poly(ɛ-caprolactone) (PCL) constituted microspheres sintered three-dimensional scaffold were evaluated in rabbit ulnar segmental defect. A composite scaffold using PHB-PCL-nHA microspheres was developed with protein interface by solvent/non-solvent sintering to provide multiple cues such as biocomposition, cancellous bone equivalent meso-micro multi-scale porosity, and compressive strength. In vitro DNA quantification and alkaline phosphatase (ALP) assays revealed that the protein interfaced composite scaffolds supported osteoblast proliferation and mineralization significantly higher than scaffolds without protein and TCPS (p < 0.05). Scanning electron micrographs of osteoblasts cultured scaffolds demonstrated cell-matrix interaction, cell spreading, colonization and filopodial extension across the porous voids. Cylindrical scaffolds (5 × 10 mm) were implanted following segmental defect (10 mm) in rabbit ulnar bone and compared with untreated control. Radiography (4, 8 and 12 weeks) and µ-computed tomography (12 weeks) analysis showed directional bone tissue formation by bridging defective site in both scaffolds with and without protein interface. Whereas, undesired sclerotic-like tissue formation was observed in control groups from 8 weeks. Histology by hot Stevenel's blue and van Gieson's picrofuchsin staining has confirmed enhanced bone maturation in scaffold groups while presence of osteoids was observed in control after 12 weeks. Thus, the developed composite matrices exhibits osteoinductive, osteoconductive properties and demonstrates its bone regenerative potential owing to its compositional, micro & macro structural and mechanical properties. Graphical abstract.

Paired Simulations and Experimental Investigations into the Calcium-Dependent Conformation of Albumin

Serum albumin is the most abundant protein in blood plasma, and it is involved in multiple biological processes. Serum albumin has recently been adapted for improving biomaterial integration with bone tissue, and studies have shown the importance of this protein in bone repair and regeneration. However, the mechanism of action is not yet clear. In stark contrast, other studies have demonstrated that albumin blocks cell adhesion to surfaces, which is seen as a limitation to its bone healing role. These apparent contradictions suggest that the conformation of albumin facilitates its bioactivity, leading to enhanced bone repair. Serum albumin is known to play a major role in maintaining the calcium ion concentration in blood plasma. Due to the prevalence of calcium at bone repair and regeneration sites, it has been hypothesized that calcium binding to serum albumin triggers a conformational change, leading to bioactivity. In the current study, molecular modeling approaches including molecular docking, atomic molecular dynamics (MD) simulation, and coarse-grained MD simulation were used to test this hypothesis by investigating the conformational changes induced in bovine serum albumin by interaction with calcium ions. The computational results were qualitatively validated with experimental Fourier-transform infrared spectroscopy analysis. We find that free calcium ions in solution transiently bind with the three major loops in albumin, triggering a conformational change where N-terminal and C-terminal domains separate from each other in a partial unfolding process. The separation distance between these domains was found to correlate with the calcium ion concentration. The experimental data support the simulation results showing that albumin has enhanced conformational heterogeneity upon exposure to intermediate levels of calcium, without any significant secondary structure changes.

Perfused Platforms to Mimic Bone Microenvironment at the Macro/Milli/Microscale: Pros and Cons

As life expectancy increases, the population experiences progressive ageing. Ageing, in turn, is connected to an increase in bone-related diseases (i.e., osteoporosis and increased risk of fractures). Hence, the search for new approaches to study the occurrence of bone-related diseases and to develop new drugs for their prevention and treatment becomes more pressing. However, to date, a reliable in vitro model that can fully recapitulate the characteristics of bone tissue, either in physiological or altered conditions, is not available. Indeed, current methods for modelling normal and pathological bone are poor predictors of treatment outcomes in humans, as they fail to mimic the in vivo cellular microenvironment and tissue complexity. Bone, in fact, is a dynamic network including differently specialized cells and the extracellular matrix, constantly subjected to external and internal stimuli. To this regard, perfused vascularized models are a novel field of investigation that can offer a new technological approach to overcome the limitations of traditional cell culture methods. It allows the combination of perfusion, mechanical and biochemical stimuli, biological cues, biomaterials (mimicking the extracellular matrix of bone), and multiple cell types. This review will discuss macro, milli, and microscale perfused devices designed to model bone structure and microenvironment, focusing on the role of perfusion and encompassing different degrees of complexity. These devices are a very first, though promising, step for the development of 3D in vitro platforms for preclinical screening of novel anabolic or anti-catabolic therapeutic approaches to improve bone health.

In Vitro Biological Evaluation of a Fabricated Polycaprolactone/Pomegranate Electrospun Scaffold for Bone Regeneration

Different scaffold biomaterials are being investigated as a solution for bone loss due to disease or trauma. The aim of this study is the fabrication, characterization, and in vitro biological evaluation of a novel polycaprolactone (PCL) nanoscaffold incorporating pomegranate peel extract (PG) for bone regeneration. Using electrospinning, three groups of scaffolds were prepared: the control group PCL and two groups of PCL with PG concentrations (11 and 18 weight %). The antioxidant activity and the total phenolic content (TPC) of the fabricated nanoscaffolds were evaluated, in addition to the porosity and degradation measurement. Cultured osteoblasts derived from rabbit bone marrow mesenchymal stem cells were used for the assessment of cell proliferation and attachment on the scaffold's surface. Scaffolds' characterization showed uniform nanofibers (NFs) with a fiber diameter range of 149-168 nm. Meanwhile, higher antioxidant activity and TPC of the PG groups were detected. Furthermore, total porosities of 59 and 62% were determined for the PCL-PG scaffolds. An increased degradation rate and significant improvement in cell proliferation and cell attachment were revealed for the PCL-PG fabricated scaffolds. Such incorporation of natural food waste, PG, in PCL NFs offered novel PCL-PG scaffolds as a promising candidate for bone regeneration applications.

Evaluation of the Histomorphometric and Micromorphometric Performance of a Serum Albumin-Coated Bone Allograft Combined with A-PRF for Early and Conventional Healing Protocols after Maxillary Sinus Augmentation: A Randomized Clinical Trial

The aim of this study was to compare the microarchitecture of augmented bone following maxillary sinus augmentation (MSA) after healing periods of 3 (test) and 6 (control) months using the combination of advanced platelet-rich fibrin (A-PRF) and a serum albumin-coated bone allograft (SACBA). Twenty-six patients with 30 surgical sites who required two-stage MSA were enrolled and grafted with the combination of A-PRF and SACBAs. The surgical sites were randomly allocated to the test or control group. During implant site preparation, 17 bone core biopsy samples were collected from each study group for histological, histomorphometric and micromorphometric analysis. Resonance frequency analysis was performed at the time of implant placement and 6, 8, 10, and 12 weeks postoperatively. The percentage of newly formed bone was 44.89 ± 9.49% in the test group and 39.75 ± 8.15% in the control group (p = 0.100). The results of the µCT analysis showed no significant differences in morphometric parameters between the study groups. The implant stability quotient was not significantly different between the two groups at 10 and 12 weeks postoperatively. Based on these findings, the total treatment time may be reduced by 3 months with the use of A-PRF and SACBAs for two-stage MSA.

Enhancement and mechanisms of MC3T3-E1 osteoblast-like cell adhesion to albumin through calcium exposure

Serum albumin is the most prominent protein in blood, and it aids in bone fracture healing, though the manner through which enhanced healing occurs is not well understood. This study investigates the influence of calcium on the bioactivity of albumin due to the prevalence of calcium at bone injury sites. Bovine serum albumin (BSA) was exposed to varying concentrations of calcium, adsorbed to tissue culture polystyrene, and the subsequent BSA-coated surfaces were evaluated with calcium titration, and cell adhesion, viability, and binding inhibition studies. Calcium-modified BSA improved overall MC3T3-E1 osteoblast-like cell adhesion, although high calcium concentrations induced cell death. Inhibiting specific integrins revealed that without calcium exposure, cell binding to BSA was primarily mediated by integrins that typically bind to the GFOGER sequence of collagen. As calcium exposure increases, the primary binding interaction transitioned to integrins known to bind RGD. However, cell binding to calcium-modified BSA was not completely eliminated during the inhibition studies indicating additional unidentified binding interactions occur. Overall, these results suggest that the exposure to calcium induces conformational changes that affect the cell-binding bioactivity of BSA, which may explain the beneficial impact of albumin in bone tissue.

Biomaterials Regulating Bone Hematoma for Osteogenesis

Blood coagulation in tissue healing not only prevents blood loss, but also forms a natural scaffold for tissue repair and regeneration. As blood clot formation is the initial and foremost phase upon bone injury, and the quality of blood clot (hematoma) orchestrates the following inflammatory and cellular processes as well as the subsequent callus formation and bone remodeling process. Inspired by the natural healing hematoma, tissue-engineered biomimic scaffold/hydrogels and blood prefabrication strategies attract significant interests in developing functional bone substitutes. The alteration of the fracture hematoma ca significantly accelerate or impair the overall bone healing process. This review summarizes the impact of biomaterials on blood coagulation and provides evidence on fibrin network structure, growth factors, and biomolecules that contribute to bone healing within the hematoma. The aim is to provide insights into the development of novel implant and bone biomaterials for enhanced osteogenesis. Advances in the understanding of biomaterial characteristics (e.g., morphology, chemistry, wettability, and protein adsorption) and their effect on hematoma properties are highlighted. Emphasizing the importance of the initial healing phase of the hematoma endows the design of advanced biomaterials with the desired regulatory properties for optimal coagulation and hematoma properties, thereby facilitating enhanced osteogenesis and ideal therapeutic effects.

The Viability of Human Testis-Derived Cells on Human Serum Albumin-Based Scaffold as An Artificial Male Germ Cell Niche

Azoospermia is one of the challenging disorders affecting couples who are afflicted with infertility. Human testisderived cells (hTCs) are suitable candidates for the initiation of in-vitro spermatogenesis for these types of patients. The current study aimed to assess the proliferation of hTCs through the cell culture on the three-dimensional (3D) porous scaffolds. Cells harvested from the testicular sperm extraction (TESE) samples of the azoospermic patients were cultured on the 3D porous scaffolds containing human serum albumin (HSA)/tri calcium phosphate nanoparticles (TCP NPs) for two weeks. The proliferation/viability of the cells was assessed using the MTT assay, along with H&E histological staining method. The MTT assay showed that hTCs could stay alive on this scaffold with 50 and 66.66% viability after 7 and 14 days, respectively. Such viability was not significantly different when compared with cells grown on monolayer flask culture (P>0.05). Therefore, 3D HSA/TCP NPs scaffolds could be used for the reconstitu- tion of the artificial human somatic testicular niche for future applications in regenerative medicine for male infertility.

Albumin-impregnated bone granules modulate the interactions between mesenchymal stem cells and monocytes under in vitro inflammatory conditions

Bone regeneration around newly implanted biomaterials is a complex process, which in its early phases involves the interactions between Mesenchymal Stem Cells (MSCs) and immune cells. The response of these cells to the biomaterial depends both on the local microenvironment and on the characteristics of the inserted bone substitute. In this work, bone allografts impregnated with albumin are loaded with a co-culture of human MSCs and monocytes; bone granules without albumin are used for comparison. Co-cultures are contextually treated with pro-inflammatory cytokines to simulate the inflammatory milieu naturally present during the bone regeneration process. As revealed by microscopic images, albumin-impregnated bone granules promote adhesion and interactions between cells populations. Compared to control granules, albumin coating diminishes reactive species production by cells. This reduced oxidative stress may be attributable to antioxidant properties of albumin, and it is also reflected in the mitigated gene expression of mitochondrial electron transport chain complexes, where most intracellular reactive molecules are generated. MSCs-monocytes co-cultured onto albumin-impregnated bone granules additionally release higher amounts of immunomodulatory cytokines and growth factors. In summary, this work demonstrates that impregnation of bone granules with albumin positively modulates the interactions between MSCs and immune cells, consequently influencing their mutual activities and immunomodulatory functions.

Albumin-Enriched Fibrin Hydrogel Embedded in Active Ferromagnetic Networks Improves Osteoblast Differentiation and Vascular Self-Organisation

Porous coatings on prosthetic implants encourage implant fixation. Enhanced fixation may be achieved using a magneto-active porous coating that can deform elastically in vivo on the application of an external magnetic field, straining in-growing bone. Such a coating, made of 444 ferritic stainless steel fibres, was previously characterised in terms of its mechanical and cellular responses. In this work, co-cultures of human osteoblasts and endothelial cells were seeded into a novel fibrin-based hydrogel embedded in a 444 ferritic stainless steel fibre network. Albumin was successfully incorporated into fibrin hydrogels improving the specific permeability and the diffusion of fluorescently tagged dextrans without affecting their Young’s modulus. The beneficial effect of albumin was demonstrated by the upregulation of osteogenic and angiogenic gene expression. Furthermore, mineralisation, extracellular matrix production, and formation of vessel-like structures were enhanced in albumin-enriched fibrin hydrogels compared to fibrin hydrogels. Collectively, the results indicate that the albumin-enriched fibrin hydrogel is a promising bio-matrix for bone tissue engineering and orthopaedic applications.

Serum albumin-coated bone allograft (BoneAlbumin) results in faster bone formation and mechanically stronger bone in aging rats

Serum albumin-coated bone allografts (BoneAlbumin) have successfully supported bone regeneration in various experimental models by activating endogenous progenitors. However, the effect of tissue aging, linked to declining stem cell function, has yet to be explicitly examined within the context of BoneAlbumin's regenerative capacity. Stem cell function was tested with an in vitro attachment assay, which showed that albumin coating increases stem cell attachment on demineralized bone surfaces in an aging cell population. Bone regeneration was investigated in vivo by creating critical size bone defects on the parietal bones of aging female rats. Demineralized bone matrices with and without serum albumin coating were used to fill the defects. Bone regeneration was determined by measuring the density and the size of the remaining bone defect with computed tomography (CT). Microcomputed tomography (MicroCT) and mechanical testing were performed on the parietal bone explants. In vivo CT and ex vivo microCT measurements showed better regeneration with albumin-coated grafts. Additionally, the albumin-coated group showed a twofold increase in peak fracture force compared with uncoated allografts. In the present study, serum albumin-coated demineralized bone matrices successfully supported faster and functionally superior bone regeneration in aging rats. Because stem cell function, a key contributor of bone remodelling, decreases with age and serum albumin is an effective activator of endogenous progenitor cells, this method could be an effective and safe adjuvant in bone regeneration of aging adult and osteo-compromised populations.

Albumin conjugates and assemblies as versatile bio-functional additives and carriers for biomedical applications

As the most abundant plasma protein, serum albumin has been extensively studied and employed for therapeutic applications. Despite its direct clinical use for the maintenance of blood homeostasis in various medical conditions, this review exclusively summarizes and discusses albumin-based bio-conjugates and assemblies as versatile bio-functional additives and carriers in biomedical applications. As one of the smallest-sized proteins in the human body, albumin is physiochemically stable and biochemically inert. Moreover, albumin is also endowed with abundant specific binding sites for numerous therapeutic compounds, which also endow it with superior bioactivities. Firstly, due to its small size and binding specificity, albumin alone or its derived assemblies can be utilized as competent drug carriers, which can deliver drugs through the enhanced permeability and retention (EPR) effect or actively target lesion sites through binding with gp60 and secreted protein acidic and rich in cysteine (SPARC) in tumor sites. Furthermore, its biochemical stability and inertness make it a safe and biocompatible coating material for use in biomedical applications. Albumin-based surface modifying additives can be used to functionalize both macro substrates (e.g. surfaces of medical devices or implants) and nanoparticle surfaces (e.g. drug carriers and imaging contrast agents). In this review, we elaborate on the synthesis and applications of albumin-based bio-functional coatings and drug carriers, respectively.

Biological and Mechanical Properties of Platelet-Rich Fibrin Membranes after Thermal Manipulation and Preparation in a Single-Syringe Closed System

Platelet-rich fibrin (PRF) membrane is a three-dimensional biodegradable biopolymer, which consists of platelet derived growth factors enhancing cell adhesion and proliferation. It is widely used in soft and hard tissue regeneration, however, there are unresolved problems with its clinical application. Its preparation needs open handling of the membranes, it degrades easily, and it has a low tensile strength which does not hold a suture blocking wider clinical applications of PRF. Our aim was to produce a sterile, suturable, reproducible PRF membrane suitable for surgical intervention. We compared the biological and mechanical properties of PRF membranes created by the classical glass-tube and those that were created in a single-syringe closed system (hypACT Inject), which allowed aseptic preparation. HypACT Inject device produces a PRF membrane with better handling characteristics without compromising biological properties. Freeze-thawing resulted in significantly higher tensile strength and higher cell adhesion at a lower degradation rate of the membranes. Mesenchymal stem cells seeded onto PRF membranes readily proliferated on the surface of fresh, but even better on freeze/thawed or freeze-dried membranes. These data show that PRF membranes can be made sterile, more uniform and significantly stronger which makes it possible to use them as suturable surgical membranes.

Novel radiomics evaluation of bone formation utilizing multimodal (SPECT/X-ray CT) in vivo imaging

Although an extensive research is being undertaken, the ideal bone graft and evaluation method of the bone formation draw still a warranted attention. The purpose of this study was to develop a novel multimodal radiomics evaluation method, utilizing X-ray computed tomography (CT) and single photon emission computed tomography (SPECT) with Tc-99m-Methyl diphosphonate (Tc-99m-MDP) tracer. These modalities are intended to provide quantitative data concerning the mineral bone density (after evaluation it is referred to as opacity) and the osteoblast activity, at the same time. The properties of bone formation process within poly (methyl methacrylate)-based bone cement graft (PMMA) was compared to that of albumin coated, sterilized, antigen-extracted freeze-dried human bone grafts (HLBC), in caudal vertebrae (C5) of rats. The animals were scanned at 3 and 8 weeks after surgery. In both groups, the mean opacity increased, while the mean Tc-99m-MDP activity decreased. The later parameter was significant (n = 4, p = 0.002) only in HLBC group. The linear regression analysis of PMMA-treated group variables (mean opacity increase; mean Tc-99m-MDP activity decrease), revealed a negative correlation with the medium strength (r = 0.395, p = 0.605). Whereas, it showed strong positive correlation when HLBC group variables were analyzed (r = 0.772, p = 0.012). These results indicate that using HLBC grafts is advantageous in terms of the osteoblast activity and bone vascularization over PMMA cement. Using this regression analysis method, we were able to distinguish characteristics that otherwise could not be distinguished by a regular data analysis. Hence, we propose utilizing this novel method in preclinical tests, and in clinical monitoring of bone healing, in order to improve diagnosis of bone-related diseases.

Hyperacute serum has markedly better regenerative efficacy than platelet-rich plasma in a human bone oxygen-glucose deprivation model

AIM

Platelet-rich plasma (PRP) and hyperacute serum (HAS) were compared in a novel human model of ex vivo bone damage induced by oxygen-glucose deprivation (OGD).

MATERIALS & METHODS

Osteoarthritic subchondral bone pieces were harvested from discarded femoral heads during hip replacement surgery and subjected to transient OGD.

RESULTS

Proteome profiling revealed that PRP is more angiopoietic, whereas HAS is more antiangiopoietic in composition. However, treatment of OGD-exposed bone with multiple PRP preparations had no effect on cell counts, whereas HAS restored cell proliferation capacity and rescued viable cell number following OGD.

CONCLUSION

A similar pro-proliferation effect was observed with recombinant growth factors, indicating that HAS may be an alternative agent for enhancing the regeneration of damaged bone cells.

Microarchitecture of the Augmented Bone Following Sinus Elevation with an Albumin Impregnated Demineralized Freeze-Dried Bone Allograft (BoneAlbumin) versus Anorganic Bovine Bone Mineral: A Randomized Prospective Clinical, Histomorphometric, and Micro-Computed Tomography Study

Serum albumin has been identified as an endogenous protein that is integral to early bone regeneration. We hypothesized that albumin addition to allografts may result in better bone remodeling than what can be achieved with anorganic xenografts. Sinus elevations were performed at 32 sites of 18 patients with the lateral window technique. Sites either received filling with an anorganic bovine bone mineral (ABBM, BioOss, Geistlich, CH) or albumin impregnated allograft (BoneAlbumin, OrthoSera, AT). After 6-months patients received dental implants and 16 bone core biopsy samples were obtained from the ABBM filled, and 16 from the BoneAlbumin augmented sites. The biopsies were examined by histomorphometry and µCT. Percentage of the residual graft in the BoneAlbumin group was 0–12.7%, median 5.4% vs. ABBM 6.3–35.9%, median 16.9%, p < 0.05. Results of the µCT analysis showed that the microarchitecture of the augmented bone in the BoneAlbumin group resembles that of the native maxilla in morphometric parameters Trabecular Pattern Factor and Connectivity. Our data show that while ABBM successfully integrates into the newly formed bone tissue as persisting particles, BoneAlbumin is underway towards complete remodeling with new bone closely resembling that of the intact maxilla.

Serum albumin as a local therapeutic agent in cell therapy and tissue engineering

Albumin is a major plasma protein that has become ubiquitous in regenerative medicine research. As such, many studies have examined its structure and advantageous properties. However, a systematic and comprehensive understanding of albumin's role, capabilities and therapeutic potential still eludes the field. In the present work, we review how albumin is applied in tissue engineering, including cell culture and storage, in vitro fertilization and transplantation. Furthermore, we discuss how albumin's physiological role extends beyond a carrier for metal ions, fatty acids, pharmacons and growth factors. Albumin acts as a bacteriostatic coating that simultaneously promotes attachment and proliferation of eukaryotic cells. These properties with the combination of free radical scavenging, neutrophil activation and as a buffer molecule already make the albumin protein beneficial in healing processes supporting functional tissue remodeling. Nevertheless, recent data revealed that albumin can be synthesized by osteoblasts and its local concentration is raised after bone trauma. Interestingly, by increasing the local albumin concentration in vivo, faster bone healing is achieved, possibly because albumin recruits endogenous stem cells and promotes the growth of new bone. These data also suggest an active role of albumin, even though a specific receptor has not yet been identified. Together, this discussion sheds light on why the extravascular use of the albumin molecule is in the scope of scientific investigations and why it should be considered as a local therapeutic agent in regenerative medicine. © 2016 BioFactors, 43(3):315-330, 2017.

Albumin-mediated deposition of bone-like apatite onto nano-sized surfaces: Effect of surface reactivity and interfacial hydration

The bioactivity of an implant is displayed on its ability to induce heterogeneous nucleation of biogenic apatite onto its surface upon immersion in body fluids; forming, through this layer, a stable bond with the host tissue. The present article evaluates the bioactivity of different nanostructured substrates based on synthetic hydroxyapatite (HA) and titania (TiO₂) nanoparticles, where we extend the debate regarding the selective roles played by the presence of albumin on the biogenic apatite coating evolution. The substrates bone-bonding potential was evaluated by keeping the materials in contact with Simulated Body Fluid, while the influence of the presence of Bovine Serum Albumin in bioactivity was analyzed by a spectrophotometric technique. Our results show that materials' surface reactivity and their interfacial hydration are responsible for the bonding-site alteration and surface charge density distribution, which in turn, regulate the protein adsorption process. As a matter of fact, variations on the protein adsorbed density have a directly proportional impact on calcium binding sites, which should be responsible for the initiation of the mineralization process, disturbing the deposition of the interfacial calcium phosphate (Ca-P) mineralized coating.

Effect of Blood Component Coatings of Enosseal Implants on Proliferation and Synthetic Activity of Human Osteoblasts and Cytokine Production of Peripheral Blood Mononuclear Cells

The study monitored in vitro early response of connective tissue cells and immunocompetent cells to enosseal implant materials coated by different blood components (serum, activated plasma, and plasma/platelets) to evaluate human osteoblast proliferation and synthetic activity and inflammatory response presented as a cytokine profile of peripheral blood mononuclear cells (PBMCs) under conditions imitating the situation upon implantation. The cells were cultivated on coated Ti-plasma-sprayed (Ti-PS), Ti-etched (Ti-Etch), Ti-hydroxyapatite (Ti-HA), and ZrO₂ surfaces. The plasma/platelets coating supported osteoblast proliferation only on osteoconductive Ti-HA and Ti-Etch whereas activated plasma enhanced proliferation on all surfaces. Differentiation (BAP) and IL-8 production remained unchanged or decreased irrespective of the coating and surface; only the serum and plasma/platelets-coated ZrO₂ exhibited higher BAP and IL-8 expression. RANKL production increased on serum and activated plasma coatings. PBMCs produced especially cytokines playing role in inflammatory phase of wound healing, that is, IL-6, GRO-α, GRO, ENA-78, IL-8, GM-CSF, EGF, and MCP-1. Cytokine profiles were comparable for all tested surfaces; only ENA-78, IL-8, GM-CSF, and MCP-1 expression depended on materials and coatings. The activated plasma coating led to uniformed surfaces and represented a favorable treatment especially for bioinert Ti-PS and ZrO₂ whereas all coatings had no distinctive effect on bioactive Ti-HA and Ti-Etch.

The effect of polyurethane scaffold surface treatments on the adhesion of chondrocytes subjected to interstitial perfusion culture

The purpose of this study was to measure chondrocytes detachment from cellularized constructs cultured in a perfusion bioreactor, and to evaluate the effect of different scaffold coatings on cell adhesion under a fixed flow rate. The scaffolds were polyurethane foams, treated to promote cell attachment and seeded with human chondrocytes. In a preliminary static culture experiment, the scaffolds were imbibed with fetal bovine serum (FBS) and then cultured for 4 weeks. To quantify cell detachment, the number of detached cells from the scaffold treated with FBS was estimated under different interstitial perfusion flow rates and shear stress levels (0.005 mL/min equivalent to 0.05 mPa, 0.023 mL/min equivalent to 0.23 mPa, and 0.045 mL/min equivalent to 0.45 mPa). Finally, groups of scaffolds differently treated (FBS, plasma plus FBS, plasma plus collagen type I) were cultured under a fixed perfusion rate of 0.009 mL/min, equivalent to a shear stress of 0.09 mPa, and the detached cells were counted. Static cultivation showed that cell proliferation increased with time and matrix biosynthesis decreased after the first week of culture. Perfused culture showed that the number of detached cells increased with the perfusion rate on FBS-treated constructs. The plasma-treated/collagen-coated scaffolds showed the highest resistance to cell detachment. To minimize cell detachment, the perfusion rate must be maintained in the order of 0.02 mL/min, giving a shear stress of 0.2 mPa. Our set-up allowed estimating the resistance to cell detachment under interstitial perfusion in a repeatable manner, to test other scaffold coatings and cell types.

Bone-Albumin filling decreases donor site morbidity and enhances bone formation after anterior cruciate ligament reconstruction with bone-patellar tendon-bone autografts

PURPOSE

Donor site pain affects 32-43 % of patients after anterior cruciate ligament surgery when the autograft is freshly harvested bone-patellar tendon-bone tissue. Our aim was to compare functional and morphological differences between donor sites with and without serum albumin-coated bone allograft filling.

METHODS

After harvesting and implanting the graft, the tibia site was filled with either fresh autologous cancellous bone enhanced with albumin-coated allograft or autologous bone alone. The patella site was filled either with albumin-coated allograft or with blood clot. Knee function was evaluated by the VISA, Lysholm and IKDC scores and a visual analog scale of pain during standing, kneeling and crouching after six weeks and six months. Computed tomography was performed at six months for morphological evaluation.

RESULTS

At six weeks, both groups were still recovering from surgery and the overall knee function was still impaired but the functional scores were significantly higher in the Bone-Albumin group. The pain with crouching and kneeling was also lower as compared to controls. At six months, the knee function scores were close to normal, with a slight decrease in the controls. Pain at kneeling was still prominent in the controls, but significantly lower in the Bone-Albumin group. Computed tomography showed significantly smaller bone defects and higher bone density in the Bone-Albumin group.

CONCLUSIONS

Results from the present study indicate that donor site pain, a disturbing long-term side effect of bone-patellar tendon-bone surgery, is significantly reduced if bone buildup in the patella and the tibia is augmented by serum albumin-coated bone allografts.

Does Serum Albumin Level Affect the Healing Outcomes of Simple Diaphyseal Tibial Fractures?

Aims:

To quantify the serum albumin level and its correlation with fracture healing progression and outcomes in adult patients.

Settings and Design:

A prospective cohort study at an institutional trauma center.

Materials and Methods:

A total of 50 adult patients with simple, fresh traumatic diaphyseal fractures of both bones of the leg managed conservatively were included in the study. Serum albumin was measured initially and at the 6^th week postfracture. The clinico-radiological follow-up was done to analyze the fracture healing progression and their final outcomes, which were correlated with the quantified serum albumin level of the patients.

Statistical Analysis Used:

Student t-test, Mann–Whitney U-test and Pearson correlation coefficient.

Results:

As per the last clinico-radiological follow-up at the 24^th week, patients were grouped into two groups: Group I (normal union n = 38) and Group II (impaired healing n = 12). The mean serum albumin levels were significantly higher in Group I when compared to Group II. The association between the serum albumin level at baseline and at the 6^th week was moderate. The best cut-off measure of serum albumin level was 3.45 g/dL, both at baseline and at the 6^th week after fracture to predict the healing outcome. The correlation of serum albumin levels with fracture healing outcomes was statistically significant.

Conclusion:

Serum albumin is moderately associated with the baseline and 6^th-week values and showed a positive correlation with the bony healing progression and may provide an early predictor of the healing outcomes of simple diaphyseal tibial fractures.

Recent Advances in Hydroxyapatite Scaffolds Containing Mesenchymal Stem Cells

Modern day tissue engineering and cellular therapies have gravitated toward using stem cells with scaffolds as a dynamic modality to aid in differentiation and tissue regeneration. Mesenchymal stem cells (MSCs) are one of the most studied stem cells used in combination with scaffolds. These cells differentiate along the osteogenic lineage when seeded on hydroxyapatite containing scaffolds and can be used as a therapeutic option to regenerate various tissues. In recent years, the combination of hydroxyapatite and natural or synthetic polymers has been studied extensively. Due to the interest in these scaffolds, this review will cover the wide range of hydroxyapatite containing scaffolds used with MSCs for in vitro and in vivo experiments. Further, in order to maintain a progressive scope of the field this review article will only focus on literature utilizing adult human derived MSCs (hMSCs) published in the last three years.

ATR-FTIR measurements of albumin and fibrinogen adsorption: Inert versus calcium phosphate ceramics

Arthritis, bone fracture, bone tumors and other musculoskeletal diseases affect millions of people across the world. Nowadays, inert and bioactive ceramics are used as bone substitutes or for bone regeneration. Their bioactivity is very much dictated by the way proteins adsorb on their surface. In this work, we compared the adsorption of albumin and fibrinogen on inert and calcium phosphates ceramics (CaPs) using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to follow in situ protein adsorption on these materials. To this effect, we developed a sol-gel technique to control the surface chemistry of an ATR-FTIR detector. Hydroxyapatite adsorbed more albumin and β-tricalcium phosphate adsorbed more fibrinogen. Biphasic calcium phosphate presented the lowest adsorption among CaP for both proteins, illustrating the effect of surface heterogeneities. Inert ceramics adsorbed a lower amount of both proteins compared with bioactive ceramics. A significant change was observed in the conformation of the adsorbed protein versus the surface chemistry. Hydroxyapatite produced a larger loss of α-helix structure on albumin and biphasic calcium phosphate reduced β-sheet percentage on fibrinogen. Inert ceramics produced large α-helix loss on albumin and presented weak interaction with fibrinogen. Zirconia did not adsorb albumin and titanium dioxide promoted huge denaturalization of fibrinogen.

[The use of structural proximal tibial allografts coated with human albumin in treating extensive periprosthetic knee-joint bone deficiency and averting late complications. Case report]

The authors report the history of a 74-year-old patient who underwent surgical treatment for segmental knee-joint periprosthetic bone loss using structural proximal tibial allografts coated with serum albumin. Successful treatment of late complications which occurred in the postoperative period is also described. The authors emphasize that bone replacement with allografts is a physiological process that enables the stable positioning of the implant and the reconstruction of the soft tissues, the replacement of extensive bone loss, and also it is a less expensive operation. It has been already confirmed that treatment of lyophilised allografts with albumin improves the ability of bone marrow-derived mesenchymal stem cells to adhere and proliferate the surface of the allografts, penetrate the pores and reach deeper layers of the graft. Earlier studies have shown osteoblast activity on the surface and interior of the graft.

Nanostructured platforms for the sustained and local delivery of antibiotics in the treatment of osteomyelitis

This article provides a critical view of the current state of the development of nanoparticulate and other solid-state carriers for the local delivery of antibiotics in the treatment of osteomyelitis. Mentioned are the downsides of traditional means for treating bone infection, which involve systemic administration of antibiotics and surgical debridement, along with the rather imperfect local delivery options currently available in the clinic. Envisaged are more sophisticated carriers for the local and sustained delivery of antimicrobials, including bioresorbable polymeric, collagenous, liquid crystalline, and bioglass- and nanotube-based carriers, as well as those composed of calcium phosphate, the mineral component of bone and teeth. A special emphasis is placed on composite multifunctional antibiotic carriers of a nanoparticulate nature and on their ability to induce osteogenesis of hard tissues demineralized due to disease. An ideal carrier of this type would prevent the long-term, repetitive, and systemic administration of antibiotics and either minimize or completely eliminate the need for surgical debridement of necrotic tissue. Potential problems faced by even hypothetically "perfect" antibiotic delivery vehicles are mentioned too, including (i) intracellular bacterial colonies involved in recurrent, chronic osteomyelitis; (ii) the need for mechanical and release properties to be adjusted to the area of surgical placement; (iii) different environments in which in vitro and in vivo testings are carried out; (iv) unpredictable synergies between drug delivery system components; and (v) experimental sensitivity issues entailing the increasing subtlety of the design of nanoplatforms for the controlled delivery of therapeutics.

Transportation conditions for prompt use of ex vivo expanded and freshly harvested clinical-grade bone marrow mesenchymal stromal/stem cells for bone regeneration

Successful preliminary studies have encouraged a more translational phase for stem cell research. Nevertheless, advances in the culture of human bone marrow-derived mesenchymal stromal/stem cells (hBM-MSC) and osteoconductive qualities of combined biomaterials can be undermined if necessary cell transportation procedures prove unviable. We aimed at evaluating the effect of transportation conditions on cell function, including the ability to form bone in vivo, using procedures suited to clinical application. hBM-MSC expanded in current Good Manufacturing Practice (cGMP) facilities (cGMP-hBM-MSC) to numbers suitable for therapy were transported overnight within syringes and subsequently tested for viability. Scaled-down experiments mimicking shipment for 18 h at 4°C tested the influence of three different clinical-grade transportation buffers (0.9% saline alone or with 4% human serum albumin [HSA] from two independent sources) compared with cell maintenance medium. Cell viability after shipment was >80% in all cases, enabling evaluation of (1) adhesion to plastic flasks and hydroxyapatite tricalcium phosphate osteoconductive biomaterial (HA/β-TCP 3D scaffold); (2) proliferation rate; (3) ex vivo osteogenic differentiation in contexts of 2D monolayers on plastic and 3D HA/β-TCP scaffolds; and (4) in vivo ectopic bone formation after subcutaneous implantation of cells with HA/β-TCP scaffold into NOD/SCID mice. Von Kossa staining was used to assess ex vivo osteogenic differentiation in 3D cultures, providing a quantifiable test of 3D biomineralization ex vivo as a rapid, cost-effective potency assay. Near-equivalent capacities for cell survival, proliferation, and osteogenic differentiation were found for all transportation buffers. Moreover, cGMP-hBM-MSC transported from a production facility under clinical-grade conditions of 4% HSA in 0.9% saline to a destination 18 h away showed prompt adhesion to HA/β-TCP 3D scaffold and subsequent in vivo bone formation. A successfully validated transportation protocol extends the applicability of fresh stem cells involving multicentric trials for regenerative medicine.

Serum albumin enhances bone healing in a nonunion femoral defect model in rats: a computer tomography micromorphometry study

PURPOSE

Blood-derived proliferative factors such as platelet rich plasma or activated plasma are promising adjuvants for bone grafts. Our earlier studies showed that serum albumin itself can markedly enhance the proliferation of stem cells on bone allograft and postulated that albumin coating alone may improve bone graft integration in vivo.

METHODS

Two femoral defect models were performed in adult male Wistar rats. In the critical size model a six millimetre gap was created in the midshaft of the femur and fixed with plate and screws, while a nonunion model was established by the interposition of a spacer in the osteotomy for four weeks which resulted in compromised healing and nonunion. Albumin coated and uncoated grafts were placed into the defects. Bone healing and morphometry were evaluated by μCT and histology four weeks after implantation of the grafts.

RESULTS

In the critical size model none of the bone grafts were able to bridge the defect, and graft resorption was the typical outcome. In the nonunion model regular uncoated grafts had a low union rate (two out of six), which increased markedly when albumin coating was applied (six out of eight). Trabecular thickness and pattern factor improved significantly in the albumin coated group versus uncoated or empty controls.

CONCLUSIONS

Our results showed that serum albumin coating of bone grafts can enhance the remodelling and efficacy of treatment in a nonunion model.

Bony defect repair in rabbit using hybrid rapid prototyping polylactic-co-glycolic acid/β-tricalciumphosphate collagen I/apatite scaffold and bone marrow mesenchymal stem cells

BACKGROUND

In bone tissue engineering, extracellular matrix exerts critical influence on cellular interaction with porous biomaterial and the apatite playing an important role in the bonding process of biomaterial to bone tissue. The aim of this study was to observe the therapeutic effects of hybrid rapid prototyping (RP) scaffolds comprising polylactic-co-glycolic acid (PLGA), β-tricalciumphosphate (β-TCP), collagen I and apatite (PLGA/β-TCP-collagen I/apatite) on segmental bone defects in conjunction with combination with bone marrow mesenchymal stem cells (BMSCs).

MATERIALS AND METHODS

BMSCs were seeded into the hybrid RP scaffolds to repair 15 mm defect in the radius of rabbits. Radiograph, microcomputed tomography and histology were used to evaluate new bone formation.

RESULTS

Radiographic analysis done from 12 to 36 weeks postoperative period demonstrated that new bone formed at the radial defect site and continues to increase until the medullary cavity is recanalized and remodelling is complete. The bone defect remained unconnected in the original RP scaffolds (PLGA/β-TCP) during the whole study. Histological observations conformed to the radiographic images. In hybrid RP scaffold group, woven bone united the radial defect at 12 weeks and consecutively remodeled into lamellar bone 24 weeks postoperation and finally matured into cortical bone with normal marrow cavity after another 12 weeks. No bone formation but connective tissue has been detected in RP scaffold at the same time.

CONCLUSION

Collagen I/apatite sponge composite coating could improve new bone formation in vivo. The hybrid RP scaffold of PLGA/β-TCP skeleton with collagen I/apatite sponge composite coating is a promising candidate for bone tissue engineering.

Viability and proliferation of rat MSCs on adhesion protein-modified PET and PU scaffolds

In 2011, the first in-man successful transplantation of a tissue engineered trachea-bronchial graft, using a synthetic POSS-PCU nanocomposite construct seeded with autologous stem cells, was performed. To further improve this technology, we investigated the feasibility of using polymers with a three dimensional structure more closely mimicking the morphology and size scale of native extracellular matrix (ECM) fibers. We therefore investigated the in vitro biocompatibility of electrospun polyethylene terephthalate (PET) and polyurethane (PU) scaffolds, and determined the effects on cell attachment by conditioning the fibers with adhesion proteins. Rat mesenchymal stromal cells (MSCs) were seeded on either PET or PU fiber-layered culture plates coated with laminin, collagen I, fibronectin, poly-D-lysine or gelatin. Cell density, proliferation, viability, morphology and mRNA expression were evaluated. MSC cultures on PET and PU resulted in similar cell densities and amounts of proliferating cells, with retained MSC phenotype compared to data obtained from tissue culture plate cultures. Coating the scaffolds with adhesion proteins did not increase cell density or cell proliferation. Our data suggest that both PET and PU mats, matching the dimensions of ECM fibers, are biomimetic scaffolds and, because of their high surface area-to-volume provided by the electrospinning procedure, makes them per se suitable for cell attachment and proliferation without any additional coating.