Fabrication of tissue replacements with minimal harvest of autologous tissues from patients is a key challenge in the field of tissue engineering. Despite the innate potential of bone tissue to spontaneously heal, excessive tissue loss necessitates the harvest of patient-derived autografts. This, in turn, leads to major post-operative complications. Moreover, insufficient vascularization of implanted constructs and lack of proper connectivity with the host circulatory system hampers the engraftment process. To overcome these limitations, tissue-engineered constructs have been designed to provide a suitable environment for bone tissue development, by integrating biocompatible osteoinductive materials, as well as elements that promote vascularization and nutrient supply for cells and regenerative tissues. In the current work, a 3D micro-osteo tubular scaffold was fabricated by incorporating an electrospun vessel-mimic within a highly porous osteoconductive core. These constructs enable the flow of nutrients throughout the entirety of the construct, through a hierarchical structure extending from inlet and outlet and diverging into micro-scaled synthetic vessels. Both in vitro and in vivo cellular adherence, proliferation and biocompatibility were assessed, confirming that the constructs were biocompatible, and a sub-cutaneous ectopic model exhibited the construct integration with host tissues. Eventually, the MOT construct was anastomosed with hosts’ common femoral vessels leading to cellular adhesion, recruitment, and penetration of vasculature, and the formation of de novo osteoids within the MOT scaffold core. The proposed methodology supported the formation of highly perfused bone constructs as an alternative for autologous tissue harvest. The study aimed to create a de novo vascularized bone by combining electrospun polycaprolactone (PCL) with mineralized bone graft (Pro-Osteon) and human cells. The constructs fabricated here termed micro-osteo tubular scaffolds (MOT) can be connected directly with the circulatory system of a live host. Based on the results of the current study, the construct was successfully integrated and vascularized upon implantation and formation of both microvasculature and newly formed bone tissue were observed. Based on the current findings, creating a live de novo bone graft for implantation may be within our reach.

Purpose: The gold standard for bone regeneration of bone deficiencies is still an autologous bone graft, which has considerable disadvantages; namely, the need for a second major surgery and the limited volume of bone available for harvesting. BonoFill (BF) is a novel, tissue-engineered, bone graft with intrinsic osteoinductive, osteoconductive, and osteogenic properties, consisting of the patient's own adipose tissue-derived mesenchymal stem cells, attached to hydroxyapatite particles. Here, we present the safety and efficacy results of BF first-in-human clinical study for maxillofacial bone tissue regeneration. Materials and Methods: Eleven eligible male and female subjects, aged 49-65 years, were enrolled into the clinical study in 2 clinical indications: Bone augmentation and bone void grafting in the jaws. Clinical follow-up was performed throughout a period of 6 months after BF treatment and included clinical examination, blood tests, CT scans, and biopsies collected from the transplantation site to assess chronic bone infection, changes in complete blood count, and adequate bone augmentation for implant placement. Results: The study results demonstrated that BF promoted adequate bone tissue regeneration without complications. Per our evaluation, there were no incidents of chronic bone infection, or significant changes in complete blood count, and the patients reported overall good health for the duration of the study. At trial end, in the sinus augmentation indication, the BF treated sites residual bone was augmented at an average of 6.36 mm(Delta new bone, n = 10) and the total bone height at the treated area was on average 11.44 mm (n = 10). In the indication of filling of bone voids, the patient's average residual bone height of 2.91 mm was 15.76 mm (n = 1) at trial end. Conclusions: BF treatment was shown to be safe and resulted in newly generated bone, which provided adequate bone height for placement of dental implants. Thus, BF is a promising novel autologous bone graft for bone tissue repair. (C) 2020 American Association of Oral and Maxillofacial Surgeons

Mesenchymal stromal cells (MSC) are widely investigated for treating ARDS in Covid-19. Nonetheless, these efforts are overshadowed by studies predating the pandemic that mostly failed to show MSC efficacy in ARDS and recent disappointments with repurposed MSC products. Relying on years of MSC-related experience, Bonus BioGroup developed MesenCure: An enhanced allogeneic MSC therapy for Covid-19, professionalized by a unique combination of culture conditions and optimized in ARDS-relevant models.

Adipose tissue-derived mesenchymal stem cells (AT-MSCs) are one of the most potent adult stem cells, capable of differentiating into bone, cartilage, adipose, muscle, and others. An innovative autologous AT-MSC-derived cell-based product (BonoFill-II) for bone tissue regeneration was developed to be suited as a bone graft for segmental bone defects. BonoFill-II was transplanted into 8 sheep with 3.2-cm full cortex segmental defect formed in the tibia. Bone regeneration was followed by X-ray radiographs for 12 weeks. At experiment termination, the healed tibia bones were analyzed by computed tomography, histology, and mechanical tests. Our results indicate that one dose of BonoFill-II injectable formula led to an extensive bone growth within the transplantation site and to a complete closure of the critical gap in the sheep’s tibia in a relatively short time (8–12 weeks), with no inflammation and no other signs of graft rejection. This new and innovative product opens new prospects for the treatment of long bone defects. Injection of BonoFill-II (an innovative autologous cell therapy product for bone tissue regeneration) into a critical size segmental defect model (3.2 cm), generated in the sheep tibia, achieved full bridging of the gap in an extremely short period (8–12 weeks).

Human adipose-derived microvascular endothelial cells (HAMEC) and mesenchymal stem cells (MSC) have been shown to bear angiogenic and vasculogenic capabilities. We hypothesize that co-culturing HAMEC:MSC on a porous biodegradable scaffold in vitro, later implanted as a graft around femoral blood vessels in a rat, will result in its vascularization by host vessels, creating a functional vascular flap that can effectively treat a range of large full-thickness soft tissue defects. HAMEC were co-cultured with MSC on polymeric three-dimensional porous constructs. Grafts were then implanted around the femoral vessels of a rat. To ensure vessel sprouting from the main femoral vessels, grafts were pre-isolated from the surrounding tissue. Graft vascularization was monitored to confirm full vascularization before flap transfer. Flaps were then transferred to treat both abdominal wall and exposed bone and tendon of an ankle defects. Flaps were analysed to determine vascular properties in terms of maturity, functionality and survival of implanted cells. Findings show that pre-isolated grafts bearing the HAMEC:MSC combination promoted formation of highly vascularized flaps, which were better integrated in both defect models. The results of this study show the essentiality of a specific adipose-derived cell combination in successful graft vascularization and integration, two processes crucial for flap survival. Copyright © 2017 John Wiley & Sons, Ltd.

Abstract Human adipose-derived microvascular endothelial cells (HAMEC) and mesenchymal stem cells (MSC) have been shown to bear angiogenic and vasculogenic capabilities. We hypothesize that co-culturing HAMEC:MSC on a porous biodegradable scaffold in vitro, later implanted as a graft around femoral blood vessels in a rat, will result in its vascularization by host vessels, creating a functional vascular flap that can effectively treat a range of large full-thickness soft tissue defects. HAMEC were co-cultured with MSC on polymeric 3D porous constructs. Grafts were then implanted around the femoral vessels of a rat. To ensure vessel-sprouting from the main femoral vessels, grafts were pre-isolated from the surrounding tissue. Graft vascularization was monitored to confirm full vascularization before flap transfer. Flaps were then transferred to treat both abdominal wall and exposed bone and tendon of an ankle defects. Flaps were analyzed to determine vascular properties in terms of maturity, functionality and survival of implanted cells. Findings show that pre-isolated grafts bearing the HAMEC:MSC combination, promoted formation of highly vascularized flaps, which were better integrated in both defect-models. The results of this study show the essentiality of specific adipose-derived cell-combination in successful graft vascularization and integration, two processes crucial for flap survival.

BACKGROUND:Adipose-derived mesenchymal stem cells (MSCs) have been gaining fame mainly due to their vast clinical potential, simple isolation methods and minimal donor site morbidity. Adipose-derived MSCs and microvascular endothelial cells have been shown to bear angiogenic and vasculogenic capabilities. We hypothesized that co-culture of human adipose-derived MSCs with human adipose-derived microvascular endothelial cells (HAMECs) will serve as an effective cell pair to induce angiogenesis and vessel-like network formation in three-dimensional scaffolds in vitro.METHODS:HAMECs or human umbilical vein endothelial cells (HUVECs) were co-cultured on scaffolds with either MSCs or human neonatal dermal fibroblasts. Cells were immunofluorescently stained within the scaffolds at different time points post-seeding. Various analyses were performed to determine vessel length, complexity and degree of maturity.RESULTS:The HAMEC:MSC combination yielded the most organized and complex vascular elements within scaffolds, and in the shortest period of time, when compared to the other tested cell combinations. These differences were manifested by higher network complexity, more tube alignment and higher α-smooth muscle actin expression. Moreover, these generated microvessels further matured and developed during the 14-day incubation period within the three-dimensional microenvironment.CONCLUSIONS:These data demonstrate optimal vascular network formation upon co-culture of microvascular endothelial cells and adipose-derived MSCs in vitro and constitute a significant step in appreciation of the potential of microvascular endothelial cells and MSCs in different tissue engineering applications that can also be advantageous in in vivo studies.

Bone tissue regeneration in load-bearing regions of the body requires high-strength porous scaffolds capable of supporting angiogenesis and osteogenesis. 70% porous Nitinol (NiTi) scaffolds with a regular 3-D architecture resembling trabecular bone were produced from Ni foams using an original reactive vapor infiltration technique. The "trabecular Nitinol" scaffolds possessed a high compressive strength of 79 MPa and high permeability of 6.9 × 10−6 cm2. The scaffolds were further modified to produce a near Ni-free surface layer and evaluated in terms of Ni ion release and human mesenchymal stem cell (hMSC) proliferation (AlamarBlue), differentiation (alkaline phosphatase activity, ALP) and mineralization (Alizarin Red S staining). Scanning electron microscopy was employed to qualitatively corroborate the results. hMSCs were able to adhere and proliferate on both as-produced and surface-modified trabecular NiTi scaffolds, to acquire an osteoblastic phenotype and produce a mineralized extracellular matrix. Both ALP activity and mineralization were increased on porous scaffolds compared to control polystyrene plates. Experiments in a model coculture system of microvascular endothelial cells and hMSCs demonstrated the formation of prevascular structures in trabecular NiTi scaffolds. These data suggest that load-bearing trabecular Nitinol scaffolds could be effective in regenerating damaged or lost bone tissue.

Bone repair strategies utilizing resorbable biomaterial implants aim to stimulate endogenous cells in order to gradually replace the implant with functional repair tissue. These biomaterials should therefore be biodegradable, osteoconductive, osteoinductive, and maintain their integrity until the newly formed host tissue can contribute proper function. In recent years there has been impressive clinical outcomes for this strategy when using osteoconductive hydrogel biomaterials in combination with osteoinductive growth factors such as human recombinant bone morphogenic protein (hrBMP-2). However, the success of hrBMP-2 treatments is not without risks if the factor is delivered too rapidly and at very high doses because of a suboptimal biomaterial. Therefore, the aim of this study was to evaluate the use of a PEGylated fibrinogen (PF) provisional matrix as a delivery system for low-dose hrBMP-2 treatment in a critical size maxillofacial bone defect model. PF is a semi-synthetic hydrogel material that can regulate the release of physiological doses of hrBMP-2 based on its controllable physical properties and biodegradation. hrBMP-2 release from the PF material and hrBMP-2 bioactivity were validated using in vitro assays and a subcutaneous implantation model in rats. Critical size calvarial defects in mice were treated orthotopically with PF containing 8 μg/ml hrBMP-2 to demonstrate the capacity of these bioactive implants to induce enhanced bone formation in as little as 6 weeks. Control defects treated with PF alone or left empty resulted in far less bone formation when compared to the PF/hrBMP-2 treated defects. These results demonstrate the feasibility of using a semi-synthetic biomaterial containing small doses of osteoinductive hrBMP-2 as an effective treatment for maxillofacial bone defects.

Sustained and controlled delivery of growth factors, such as bone morphogenetic protein 2 (BMP-2), from polymer scaffolds has excellent potential for enhancing bone regeneration. The present study investigated the use of novel sintered polymer scaffolds prepared using temperature-sensitive PLGA/PEG particles. Growth factors can be incorporated into these scaffolds by mixing the reconstituted growth factor with the particles prior to sintering. The ability of the PLGA/PEG scaffolds to deliver BMP-2 in a controlled and sustained manner was assessed and the osteogenic potential of these scaffolds was determined in a mouse calvarial defect model. BMP-2 was released from the scaffolds in vitro over 3 weeks. On average, ca. 70% of the BMP-2 loaded into the scaffolds was released by the end of this time period. The released BMP-2 was shown to be active and to induce osteogenesis when used in a cell culture assay. A substantial increase in new bone volume of 55% was observed in a mouse calvarial defect model for BMP-2-loaded PLGA/PEG scaffolds compared to empty defect controls. An increase in new bone volume of 31% was observed for PLGA/PEG scaffolds without BMP-2, compared to empty defect controls. These results demonstrate the potential of novel PLGA/PEG scaffolds for sustained BMP-2 delivery for bone-regeneration applications.

AIMSinus augmentation procedures commonly employ osteoconductive scaffolding materials to stimulate and support bone formation. The aim of this study was to develop a simple screening methodology for the evaluation of the osteoconductive potential of various bone graft materials prior to clinical use.MATERIALS AND METHODSMaterials tested were Bio-Oss, Bi-Ostetic, OraGraft, and ProOsteon. These Simple and composite bone substitutes were embedded with osteoprogenitor cells derived from either the human maxillary sinus schneiderian membrane (hMSSM) or from maxillary tuberosity bone marrow and then monitored both in vitro and in vivo.RESULTSCell adherence and proliferation was most pronounced in OraGraft, followed by ProOsteon. In vivo bone formation, within the bone graft, was also observed, with most marked results in OraGraft and ProOsteon grafts.CONCLUSIONSThe proposed osteoconductivity testing method proved simple, informative, and reliable for the purpose of screening candidate biomaterials for sinus lifting or sinus augmentation.

OBJECTIVE AND DESIGN:The activity of immune cells affects the balance between bone mineralization and resorption carried out by the opposing actions of osteoblasts and osteoclasts, respectively. This study was aimed at determining the possible interaction between inflammatory conditions and collagen type I degrading MMP (mainly MMP-2 and MMP-9) synthesis and secretion in rat osteoprogenitors.MATERIALS AND METHODS:The study was performed using primary rat bone marrow-derived osteoprogenitors during their advanced osteogenesis. Biochemical, immunohistochemical, and molecular biology techniques were used to investigate the influence of pro-inflammatory cytokines on MMP-2 and MMP-9 synthesis and secretion in osteoprogenitors.RESULTS:Results indicated that both synthesis and secretion of MMPs (MMP-1, -2, -8, -9, and -13) were significantly induced after pro-inflammatory cytokine treatments, except MMP-2, whose levels remained unchanged. NF-κB (nuclear factor kappa-light chain enhancer of activated B cells) inhibition assays showed that induced MMP-9 secretion by inflammatory cytokines was mediated by activation of NF-κB via the classical pathway and that oxidants play a significant role in this signal transduction pathway. In contrast, no such effect was observed for synthesis of MMP-2.CONCLUSIONS:These results indicate the possibility that inflammatory processes may trigger osteoblasts to absorb bone by secreting elevated levels of MMPs capable of degrading collagen type I, especially MMP-9 which is upregulated due to increased NF-κB transcription activity.

Abstract Adult human mesenchymal stromal cells (hMSCs) are an important source for tissue repair in regenerative medicine. Notably, targeted gene therapy in hMSCs to promote osteogenic differentiation may help in the development of novel therapeutic approaches for bone repair. We recently showed that α5 integrin (ITGA5) promotes osteoblast differentiation in bone marrow-derived hMSCs. Here, we determined whether lentiviral (LV)-mediated expression of ITGA5 in hMSCs derived from the bone-marrow stroma of healthy individuals may promote bone repair in vivo in two relevant critical-size bone defects in the mouse. In a first series of experiments, control or LV-ITGA5-transduced hMSCs were seeded on collagen-based gelatin sponge and transplanted in a cranial critical-size defect (5 mm) in Nude-Foxn1nu mice. Microcomputed tomography and quantitative histological analyses after 8 weeks showed no or little de novo bone formation in defects implanted with collagen sponge alone or with hMSCs, respectively. In contrast, implantation of collagen sponge with LV-ITGA5-transduced hMSCs showed greater bone formation compared with control hMSCs. We also tested the bone-repair potential of LV-mediated ITGA5 expression in hMSCs in a critical-size long-bone defect (2 mm) in femur in Nude-Foxn1nu mice. Bone remnants were stabilized with external fixation, and control or LV-ITGA5-transduced hMSCs mixed with coral/hydroxyapatite particles were transplanted into the critical-size long-bone defect. Histological analysis after 8 weeks showed that LV-ITGA5-transduced hMSCs implanted with particles induced 85% bone regeneration and repair. These results demonstrate that repair of critical-size mouse cranial and long-bone defects can be induced using LV-mediated ITGA5 gene expression in hMSCs, which provides a novel gene therapy for bone regeneration.

A multifunctional fibronectin fragment enhances the regenerative effects of growth factors in vivo in animal models of chronic wounds and critical-size bone defects.

Human mesenchymal stem cells (hMSCs) are able to generate mesodermal derivatives, such as bone, cartilage, tendon, muscle, ligament and fat tissue; furthermore, they can differentiate to specific cell types, such as cardiomyocyte progenitors under defined conditions. Recently, their paracrine, pro-angiogenic, pro-myogenic, anti-apoptotic, anti-inflammatory and anti-fibrotic properties have been emphasized. These cells actively secrete a large number of bioactive molecules, peptides, hormones, and long non-coding RNAs. This may promote the regeneration of injured, ischemic tissues upon in vivo delivery. Human MSCs can be isolated from bone marrow, peripheral tissues such as adipose tissue, dental pulp, umbilical cord blood and matrix and potentially from peripheral blood. They have been widely used without the ethical issues implicated with pluripotent stem cell derivatives. Large randomized clinical trials underway with hMSCs show good safety and tolerability. In order to reach the number required for clinical use, efficient isolation and expansion of hMSCs are required. A variety of technologies are applied for hMSC expansion: static tissue culture flasks, cell factory and gas-permeable blood bags; or using dynamic culture by spinner flasks, stirred or rotary bioreactors with/without three-dimensional cell carriers. Routine quality controls are essential to maintain sterile culture conditions, ensure stable phenotype and monitor potential mutations before clinical applications. Human MSCs have recently been tested in large randomized clinical trials for cardiac regeneration. Although in vivo application was safe, clinical endpoints showed only neutral effects so far. In order to enhance regenerative capacity of hMSCs, cells may be boosted in vitro prior to implantation and delivery strategies and patient selection must also be improved.

Animal models for preclinical functionality assays lie midway between in vitro systems such as cell culture and actual clinical trials. We have developed a novel external fixation device for femoral critical size defect (CSD) in the femurs of immunodeficient mice as an experimental model for studying bone regeneration and bone tissue engineering. The external fixation device comprises four pointed rods and dental acrylic paste. A segmental bone defect (2 mm) was created in the midshaft of the mouse femur. The CSD in the femur of the mice were either left untreated or treated with a bone allograft, a cell-scaffold construct, or a scaffold-only construct. The repair and healing processes of the CSD were monitored by digital x-ray radiography, microcomputed tomography, and histology. Repair of the femoral CSD was achieved with the bone allografts, and partial repair of the femoral CSD was achieved with the cell scaffold and the scaffold-only constructs. No repair of the nongrafted femoral CSD was observed. Our results establish the feasibility of this new mouse femoral model for CSD repair of segmental bone using a simple stabilized external fixation device. The model should prove especially useful for in vivo preclinical proof-of-concept studies that involve cell therapy-based technologies for bone tissue engineering applications in humans.

Bone repair is a major concern in reconstructive surgery. Transplants containing osteogenically committed mesenchymal stem cells (MSCs) provide an alternative source to the currently used autologous bone transplants which have limited supply and require additional surgery to the patient. A major drawback, however is the lack of a critical mass of cells needed for successful transplantation. The purpose of the present study was to test the effects of FGF2 and FGF9 on expansion and differentiation of MSCs in order to establish an optimal culture protocol resulting in sufficient committed osteogenic cells required for successful in vivo transplantation. Bone marrow-derived MSCs cultured in αMEM medium supplemented with osteogenic supplements for up to three passages (control medium), were additionally treated with FGF2 and FGF9 in various combinations. Cultures were evaluated for viability, calcium deposition and in vivo osteogenic capacity by testing subcutaneous transplants in nude mice. FGF2 had a positive effect on the proliferative capacity of cultured MSCs compared to FGF9 and control medium treated cultures. Cultures treated with FGF2 followed by FGF9 showed an increased amount of extracted Alizarin red indicating greater osteogenic differentiation. Moreover, the osteogenic capacity of cultured cells transplanted in immunodeficient mice revealed that cells that were subjected to treatment with FGF2 in the first two passages and subsequently to FGF9 in the last passage only, were more successful in forming new bone. It is concluded that the protocol using FGF2 prior to FGF9 is beneficial to cell expansion and commitment, resulting in higher in vivo bone formation for successful bone tissue engineering.

Biocompatible and osteoconductive cell-scaffold constructs comprise the first and most important step towards successful in vivo bone repair. This study reports on a new cell-scaffold construct composed of gelatin-based hydrogel and ceramic (CaCO3/beta-TCP) particles loaded with human MSCs producing a tissue-like construct applied as a transplant for in vivo bone formation. Bone marrow-derived human MSCs were cultured in osteogenic induction medium. 5 x 10(5) (P-2) cells were loaded on a mixture of hydrogel microspheres and ceramic particles, cultured in a rotating dynamic culture for up to 3 weeks. Both hydrogel microspheres and ceramic particles coalesced together to form a tissue-like construct, shown by histology to contain elongated spindle-like cells forming the new tissue between the individual particles. Cell proliferation and cell viability were confirmed by Alamar blue assay and by staining with CFDA, respectively. FACS analysis conducted before loading the cells, and after formation of the construct, revealed that the profile of cell surface markers remained unchanged throughout the dynamic culture. The osteogenic potential of the cells composing the tissue-like construct was further validated by subcutaneous transplants in athymic nude mice. After 8 weeks a substantial amount of new bone formation was observed in the cell-construct transplants, whereas no bone formation was observed in transplants containing no cells. This new cell construct provides a system for in vivo bone transplants. It can be tailored for a specific size and shape as needed for various transplant sites and for all aspects of regenerative medicine and biomaterial science. Copyright (C) 2009 John Wiley & Sons, Ltd.

The design of mat-like scaffolds slow-releasing bone morphogenetic protein-2 (BMP-2) retaining bone regeneration functions has been a major challenge in tissue engineering. This study aimed to develop core-shell fiber scaffolds releasing BMP-2 to support bone regeneration. BMP-2 was incorporated in an aqueous core solution of poly(ethylene oxide), whereas the shell solution was made of polycaprolactone blended with poly(ethylene glycol). This blending induced pores in the shell, which pronouncedly affected the movement of proteins out of the fibers. BMP-2 release profiles were monitored. In vitro bioactivity of BMP-2 released from the scaffolds was assessed using human mesenchymal stem cells by measuring alkaline phosphatase activity. Bone regeneration capabilities were demonstrated by implanting the BMP-2-embedded scaffolds in rat cranial defect model followed by micro-computed tomography analysis. The degree of fiber's shell porosity, highly correlative with the slow- and fast-release patterns of BMP-2, were found to be dependent on the relative amount of poly(ethylene glycol) within the shell. In vitro assays of scaffolds manifesting the slow-release pattern have revealed significant (∼9-fold) increase in alkaline phosphatase activity, compared to fast BMP-2 releasing scaffolds. Likewise, in vivo studies have revealed significant bone regeneration in cranial defects of scaffold implants with recombinant human BMP-2 with slow-release pattern.