Recombinant human platelet-derived growth factor: biology and clinical applications

A rhPDGF-BB/bovine type I collagen/β-TCP mixture for the treatment of critically sized non-union tibial defects: An in vivo study in rabbits

Non-union during healing of bone fractures affects up to ~5% of patients worldwide. Given the success of recombinant human platelet-derived growth factor-B chain homodimer (rhPDGF-BB) in promoting angiogenesis and bone fusion in the hindfoot and ankle, rhPDGF-BB combined with bovine type I collagen/β-TCP matrix (AIBG) could serve as a viable alternative to autografts in the treatment of non-unions. Defects (~2 mm gaps) were surgically induced in tibiae of skeletally mature New Zealand white rabbits. Animals were allocated to one of four groups-(1) negative control (empty defect, healing for 8 weeks), (2 and 3) acute treatment with AIBG (healing for 4 or 8 weeks), and (4) chronic treatment with AIBG (injection 4 weeks post defect creation and then healing for 8 weeks). Bone formation was analyzed qualitatively and semi-quantitatively through histology. Samples were imaged using dual-energy X-ray absorptiometry and computed tomography for defect visualization and volumetric reconstruction, respectively. Delayed healing or non-healing was observed in the negative control group, whereas defects treated with AIBG in an acute setting yielded bone formation as early as 4 weeks with bone growth appearing discontinuous. At 8 weeks (acute setting), substantial remodeling was observed with higher degrees of bone organization characterized by appositional bone growth. The chronic healing, experimental, group yielded bone formation and remodeling, with no indication of non-union after treatment with AIBG. Furthermore, bone growth in the chronic healing group was accompanied by an increased presence of osteons, osteonal canals, and interstitial lamellae. Qualitatively and semiquantitatively, chronic application of AI facilitated complete bridging of the induced non-union defects, while untreated defects or defects treated acutely with AIBG demonstrated a lack of complete bridging at 8 weeks.

A comprehensive review and advanced biomolecule-based therapies for osteoporosis

BACKGROUND

The prevalence of osteoporosis (OP) on a global scale is significantly elevated that causes life threatening issues. The potential of groundbreaking biomolecular therapeutics in the field of OP is highly encouraging. The administration of biomolecular agents has the potential to mitigate the process of bone demineralization while concurrently augmenting the regenerative capacity of bone tissue, thereby facilitating a personalized therapeutic approach. Biomolecules-based therapies showed promising results in term of bone mass protection and restoration in OP.

AIM OF REVIEW

We summarized the recent biomolecular therapies with notable progress in clinical, demonstrating the potential to transform illness management. These treatments frequently utilize different biomolecule based strategies. Biomolecular therapeutics has a targeted character, which results in heightened specificity and less off-target effects, ultimately leading to increased patient outcomes. These aspects have the capacity to greatly enhance the management of OP, thus resulting in a major enhancement in the quality of life encountered by individuals affected by this condition.

Angiogenesis in bone tissue engineering via ceramic scaffolds: A review of concepts and recent advancements

Due to organ donor shortages, long transplant waitlists, and the complications/limitations associated with auto and allotransplantation, biomaterials and tissue-engineered models are gaining attention as feasible alternatives for replacing and reconstructing damaged organs and tissues. Among various tissue engineering applications, bone tissue engineering has become a promising strategy to replace or repair damaged bone. We aimed to provide an overview of bioactive ceramic scaffolds in bone tissue engineering, focusing on angiogenesis and the effect of different biofunctionalization strategies. Different routes to angiogenesis, including chemical induction through signaling molecules immobilized covalently or non-covalently, in situ secretion of angiogenic growth factors, and the degradation of inorganic scaffolds, are described. Physical induction mechanisms are also discussed, followed by a review of methods for fabricating bioactive ceramic scaffolds via microfabrication methods, such as photolithography and 3D printing. Finally, the strengths and weaknesses of the commonly used methodologies and future directions are discussed.

The Effect of a Rotating Magnetic Field on the Regenerative Potential of Platelets

Platelets are actively involved in tissue injury site regeneration by producing a wide spectrum of platelet-derived growth factors such as PDGF (platelet-derived growth factor), IGF-1 (insulin-like growth factor), TGF-β1 (transforming growth factor β), FGF (fibroblast growth factor), etc. A rotating magnetic field (RMF) can regulate biological functions, including reduction or induction regarding inflammatory processes, cell differentiation, and gene expression, to determine the effect of an RMF on the regenerative potential of platelets. The study group consisted of 30 healthy female and male volunteers (n = 15), from which plasma was collected. A portion of the plasma was extracted and treated as an internal control group. Subsequent doses of plasma were exposed to RMF at different frequencies (25 and 50 Hz) for 1 and 3 h. Then, the concentrations of growth factors (IGF-1, PDGF-BB, TGF-β1, and FGF-1) were determined in the obtained material by the ELISA method. There were statistically significant differences in the PDGF-BB, TGF-β1, IGF-1, and FGF-1 concentrations between the analyzed groups. The highest concentration of PDGF-BB was observed in the samples placed in RMF for 1 h at 25 Hz. For TGF-β1, the highest concentrations were obtained in the samples exposed to RMF for 3 h at 25 Hz and 1 h at 50 Hz. The highest concentrations of IGF-1 and FGF-1 were shown in plasma placed in RMF for 3 h at 25 Hz. An RMF may increase the regenerative potential of platelets. It was noted that female platelets may respond more strongly to RMF than male platelets.

Exosomes derived from platelet-rich plasma promote diabetic wound healing via the JAK2/STAT3 pathway

Diabetic non-healing wounds are bringing a heavy burden on patients and society. Platelet-rich plasma (PRP) has been widely applied in tissue regenerating for containing various growth factors. Recently, PRP-derived exosomes (PRP-Exos) have been proved to be more effective than PRP in tissue regeneration. However, few studies have investigated the therapeutic potential of PRP-Exos in diabetic wound healing to date. Therefore, we extracted and identified exosomes derived from PRP and tested its promoting effect on diabetic wound healing in vivo and in vitro. We found that high glucose (HG) inhibited cell proliferation and migration and induced apoptosis through ROS-dependent activation of the JNK and p38 MAPK signaling pathways. PRP-Exos can stimulate fibroblast functions and accelerate diabetic wound healing. The benefits of PRP-Exos may be attributed to its capability to prevent HG-induced ROS-dependent apoptosis via the PDGF-BB/JAK2/STAT3/Bcl-2 signaling pathway. This illustrates the therapeutic potential of PRP-Exos in diabetic wounds.

Mesenchymal Stem/Stromal Cells: Immunomodulatory and Bone Regeneration Potential after Tumor Excision in Osteosarcoma Patients

Osteosarcoma (OS) is a type of bone cancer that is derived from primitive mesenchymal cells typically affecting children and young adults. The current standard of treatment is a combination of neoadjuvant chemotherapy and surgical resection of the cancerous bone. Post-resection challenges in bone regeneration arise. To determine the appropriate amount of bone to be removed, preoperative imaging techniques such as bone and CT scans are employed. To prevent local recurrence, the current standard of care suggests maintaining bony and soft tissue margins from 3 to 7 cm beyond the tumor. The amount of bone removed in an OS patient leaves too large of a deficit for bone to form on its own and requires reconstruction with metal implants or allografts. Both methods require the bone to heal, either to the implant or across the allograft junction, often in the setting of marrow-killing chemotherapy. Therefore, the issue of bone regeneration within the surgically resected margins remains an important challenge for the patient, family, and treating providers. Mesenchymal stem/stromal cells (MSCs) are potential agents for enhancing bone regeneration post tumor resection. MSCs, used with scaffolds and growth factors, show promise in fostering bone regeneration in OS cases. We spotlight two MSC types-bone marrow-derived (BM-MSCs) and adipose tissue-derived (ASCs)-highlighting their bone regrowth facilitation and immunomodulatory effects on immune cells like macrophages and T cells, enhancing therapeutic outcomes. The objective of this review is two-fold: review work demonstrating any ability of MSCs to target the deranged immune system in the OS microenvironment, and synthesize the available literature on the use of MSCs as a therapeutic option for stimulating bone regrowth in OS patients post bone resection. When it comes to repairing bone defects, both MB-MSCs and ASCs hold great potential for stimulating bone regeneration. Research has showcased their effectiveness in reconstructing bone defects while maintaining a non-tumorigenic role following wide resection of bone tumors, underscoring their capability to enhance bone healing and regeneration following tumor excisions.

Growth Factor Delivery Using a Collagen Membrane for Bone Tissue Regeneration

The use of biomaterials and bioactive agents has shown promise in bone defect repair, leading to the development of strategies for bone regeneration. Various artificial membranes, especially collagen membranes (CMs) that are widely used for periodontal therapy and provide an extracellular matrix-simulating environment, play a significant role in promoting bone regeneration. In addition, numerous growth factors (GFs) have been used as clinical applications in regenerative therapy. However, it has been established that the unregulated administration of these factors may not work to their full regenerative potential and could also trigger unfavorable side effects. The utilization of these factors in clinical settings is still restricted due to the lack of effective delivery systems and biomaterial carriers. Hence, considering the efficiency of bone regeneration, both spaces maintained using CMs and GFs can synergistically create successful outcomes in bone tissue engineering. Therefore, recent studies have demonstrated a significant interest in the potential of combining CMs and GFs to effectively promote bone repair. This approach holds great promise and has become a focal point in our research. The purpose of this review is to highlight the role of CMs containing GFs in the regeneration of bone tissue, and to discuss their use in preclinical animal models of regeneration. Additionally, the review addresses potential concerns and suggests future research directions for growth factor therapy in the field of regenerative science.

PDGFR in PDGF-BB/PDGFR Signaling Pathway Does Orchestrates Osteogenesis in a Temporal Manner

Platelet-derived growth factor-BB (PDGF-BB)/platelet-derived growth factor receptor-β (PDGFR-β) pathway is conventionally considered as an important pathway to promote osteogenesis; however, recent study suggested its role during osteogenesis to be controversial. Regarding the differential functions of this pathway during 3 stages of bone healing, we hypothesized that temporal inhibition of PDGF-BB/PDGFR-β pathway could shift the proliferation/differentiation balance of skeletal stem and progenitor cells, toward osteogenic lineage, which leads to improved bone regeneration. We first validated that inhibition of PDGFR-β at late stage of osteogenic induction effectively enhanced differentiation toward osteoblasts. This effect was also replicated in vivo by showing accelerated bone formation when block PDGFR-β pathway at late stage of critical bone defect healing mediated using biomaterials. Further, we found that such PDGFR-β inhibitor-initiated bone healing was also effective in the absence of scaffold implantation when administrated intraperitoneally. Mechanistically, timely inhibition of PDGFR-β blocked extracellular regulated protein kinase 1/2 pathway, which shift proliferation/differentiation balance of skeletal stem and progenitor cell to osteogenic lineage by upregulating osteogenesis-related products of Smad to induce osteogenesis. This study offered updated understanding of the use of PDGFR-β pathway and provides new insight routes of action and novel therapeutic methods in the field of bone repair.

The Delivery and Activation of Growth Factors Using Nanomaterials for Bone Repair

Bone regeneration is a comprehensive process that involves different stages, and various growth factors (GFs) play crucial roles in the entire process. GFs are currently widely used in clinical settings to promote bone repair; however, the direct application of GFs is often limited by their fast degradation and short local residual time. Additionally, GFs are expensive, and their use may carry risks of ectopic osteogenesis and potential tumor formation. Nanomaterials have recently shown great promise in delivering GFs for bone regeneration, as they can protect fragile GFs and control their release. Moreover, functional nanomaterials can directly activate endogenous GFs, modulating the regeneration process. This review provides a summary of the latest advances in using nanomaterials to deliver exogenous GFs and activate endogenous GFs to promote bone regeneration. We also discuss the potential for synergistic applications of nanomaterials and GFs in bone regeneration, along with the challenges and future directions that need to be addressed.

An Update on the Clinical Efficacy and Safety of Collagen Injectables for Aesthetic and Regenerative Medicine Applications

Soft tissues diseases significantly affect patients quality of life and usually require targeted, costly and sometimes constant interventions. With the average lifetime increase, a proportional increase of age-related soft tissues diseases has been witnessed. Due to this, the last two decades have seen a tremendous demand for minimally invasive one-step resolutive procedures. Intensive scientific and industrial research has led to the recognition of injectable formulations as a new advantageous approach in the management of complex diseases that are challenging to treat with conventional strategies. Among them, collagen-based products are revealed to be one of the most promising among bioactive biomaterials-based formulations. Collagen is the most abundant structural protein of vertebrate connective tissues and, because of its structural and non-structural role, is one of the most widely used multifunctional biomaterials in the health-related sectors, including medical care and cosmetics. Indeed, collagen-based formulations are historically considered as the "gold standard" and from 1981 have been paving the way for the development of a new generation of fillers. A huge number of collagen-based injectable products have been approved worldwide for clinical use and have routinely been introduced in many clinical settings for both aesthetic and regenerative surgery. In this context, this review article aims to be an update on the clinical outcomes of approved collagen-based injectables for both aesthetic and regenerative medicine of the last 20 years with an in-depth focus on their safety and effectiveness for the treatment of diseases of the integumental, gastrointestinal, musculoskeletal, and urogenital apparatus.

Genipin modified lyophilized platelet-rich fibrin scaffold for sustained release of growth factors to promote bone regeneration

Lyophilized platelet-rich fibrin (L-PRF) was shown to further activate resident platelets in platelet-rich fibrin causing a higher amount of growth factors release. However, it still required further experimental studies to resolve the uncontrolled degradation and burst release problem. In this study, the nature crosslinker genipin is introduced to improve the performance of L-PRF scaffold. We used a series of gradient concentration genipin solutions to react with L-PRF. The crosslinking degree, micro morphology, mean pore size, water absorption and mechanical properties of the crosslinked scaffold were evaluated. In order to study the effect of genipin modification on the release kinetics of growth factors from L-PRF, we detected the release of platelet-derived growth factor, vascular endothelial growth factor and transforming growth factor in vitro by ELISA. To investigate the biodegradability of the crosslinked L-PRF in vivo, the scaffolds were transplanted subcutaneously into backs of rats, and the materials were recovered at 1, 2 and 4 weeks after implantation. The biodegradation, inflammatory reaction and biocompatibility of the scaffolds were examined by histological staining. Finally, the genipin crosslinked/uncrosslinked L- Platelet-rich fibrin scaffolds were implanted with freshly prepared SHED cell sheets into rat critical size calvarial defects and the skull samples were recovered to examine the treatment efficacy of genipin crosslinked L-PRF by histologic and radiographic approaches. Results of this study indicated that genipin can be used to modify L-PRF at room temperature at a very low concentration. Genipin-modified L-PRF shows better biomechanical performance, slower biodegradation, good bioavailable and sustained release of growth factors. The 0.01% w/v and 0.1% w/v genipin crosslinked L-PRF have good porous structure and significantly promote cell proliferation and enhance the expression of key genes in osteogenesis in vitro, and work best in promoting bone regeneration in vivo.

Single Cell Sequencing Reveals Mechanisms of Persistent Truncus Arteriosus Formation after PDGFRα and PDGFRβ Double Knockout in Cardiac Neural Crest Cells

Persistent truncus arteriosus (PTA) is an uncommon and complex congenital cardiac malformation accounting for about 1.2% of all congenital heart diseases (CHDs), which is caused by a deficiency in the embryonic heart outflow tract’s (OFT) septation and remodeling. PDGFRα and PDGFRβ double knockout (DKO) in cardiac neural crest cells (CNCCs) has been reported to cause PTA, but the underlying mechanisms remain unclear. Here, we constructed a PTA mouse model with PDGFRα and PDGFRβ double knockout in Pax3+ CNCCs and described the condensation failure into OFT septum of CNCC-derived cells due to disturbance of cell polarity in the DKO group. In addition, we further explored the mechanism with single-cell RNA sequencing. We found that two main cell differentiation trajectories into vascular smooth muscle cells (VSMCs) from cardiomyocytes (CMs) and mesenchymal cells (MSs), respectively, were interrupted in the DKO group. The process of CM differentiation into VSMC stagnated in a transitional CM I-like state, which contributed to the failure of OFT remodeling and muscular septum formation. On the other hand, a Penk+ transitional MS II cluster closely related to cell condensation into the OFT septum disappeared, which led to the OFT’s septation absence directly. In conclusion, the disturbance of CNCC-derived cells caused by PDGFRα and PDGFRβ knockout can lead to the OFT septation disorder and the occurrence of PTA.

Nervous System-Driven Osseointegration

Implants are essential therapeutic tools for treating bone fractures and joint replacements. Despite the in-depth study of osseointegration for more than fifty years, poor osseointegration caused by aseptic loosening remains one of the leading causes of late implant failures. Osseointegration is a highly sophisticated and spatiotemporal process in vivo involving the immune response, angiogenesis, and osteogenesis. It has been unraveled that the nervous system plays a pivotal role in skeletal health via manipulating neurotrophins, neuropeptides, and nerve cells. Herein, the research related to nervous system-driven osseointegration was systematically analyzed and reviewed, aiming to demonstrate the prominent role of neuromodulation in osseointegration. Additionally, it is indicated that the implant design considering the role of neuromodulation might be a promising way to prevent aseptic loosening.

Human SMILE-Derived Stromal Lenticule Scaffold for Regenerative Therapy: Review and Perspectives

A transparent cornea is paramount for vision. Corneal opacity is one of the leading causes of blindness. Although conventional corneal transplantation has been successful in recovering patients’ vision, the outcomes are challenged by a global lack of donor tissue availability. Bioengineered corneal tissues are gaining momentum as a new source for corneal wound healing and scar management. Extracellular matrix (ECM)-scaffold-based engineering offers a new perspective on corneal regenerative medicine. Ultrathin stromal laminar tissues obtained from lenticule-based refractive correction procedures, such as SMall Incision Lenticule Extraction (SMILE), are an accessible and novel source of collagen-rich ECM scaffolds with high mechanical strength, biocompatibility, and transparency. After customization (including decellularization), these lenticules can serve as an acellular scaffold niche to repopulate cells, including stromal keratocytes and stem cells, with functional phenotypes. The intrastromal transplantation of these cell/tissue composites can regenerate native-like corneal stromal tissue and restore corneal transparency. This review highlights the current status of ECM-scaffold-based engineering with cells, along with the development of drug and growth factor delivery systems, and elucidates the potential uses of stromal lenticule scaffolds in regenerative therapeutics.

Controlled Co-delivery of pPDGF-B and pBMP-2 from intraoperatively bioprinted bone constructs improves the repair of calvarial defects in rats

Intraoperative bioprinting (IOB), which refers to the bioprinting process performed on a live subject in a surgical setting, has made it feasible to directly deliver gene-activated matrices into craniomaxillofacial (CMF) defect sites. In this study, we demonstrated a novel approach to overcome the current limitations of traditionally fabricated non-viral gene delivery systems through direct IOB of bone constructs into defect sites. We used a controlled co-delivery release of growth factors from a gene-activated matrix (an osteogenic bioink loaded with plasmid-DNAs (pDNA)) to promote bone repair. The controlled co-delivery approach was achieved from the combination of platelet-derived growth factor-B encoded plasmid-DNA (pPDGF-B) and chitosan-nanoparticle encapsulating pDNA encoded with bone morphogenetic protein-2 (CS-NPs(pBMP2)), which facilitated a burst release of pPDGF-B in 10 days, and a sustained release of pBMP-2 for 5 weeks in vitro. The controlled co-delivery approach was tested for its potential to repair critical-sized rat calvarial defects. The controlled-released pDNAs from the intraoperatively bioprinted bone constructs resulted in ∼40% bone tissue formation and ∼90% bone coverage area at 6 weeks compared to ∼10% new bone tissue and ∼25% total bone coverage area in empty defects. The delivery of growth factors incorporated within the intraoperatively bioprinted constructs could pose as an effective way to enhance bone regeneration in patients with cranial injuries in the future.

Tissue Engineered Neurovascularization Strategies for Craniofacial Tissue Regeneration

Craniofacial tissue injuries, diseases, and defects, including those within bone, dental, and periodontal tissues and salivary glands, impact an estimated 1 billion patients globally. Craniofacial tissue dysfunction significantly reduces quality of life, and successful repair of damaged tissues remains a significant challenge. Blood vessels and nerves are colocalized within craniofacial tissues and act synergistically during tissue regeneration. Therefore, the success of craniofacial regenerative approaches is predicated on successful recruitment, regeneration, or integration of both vascularization and innervation. Tissue engineering strategies have been widely used to encourage vascularization and, more recently, to improve innervation through host tissue recruitment or prevascularization/innervation of engineered tissues. However, current scaffold designs and cell or growth factor delivery approaches often fail to synergistically coordinate both vascularization and innervation to orchestrate successful tissue regeneration. Additionally, tissue engineering approaches are typically investigated separately for vascularization and innervation. Since both tissues act in concert to improve craniofacial tissue regeneration outcomes, a revised approach for development of engineered materials is required. This review aims to provide an overview of neurovascularization in craniofacial tissues and strategies to target either process thus far. Finally, key design principles are described for engineering approaches that will support both vascularization and innervation for successful craniofacial tissue regeneration.

Characterizing the host response to rhPDGF-BB in a rat spinal arthrodesis model

BACKGROUND

Due to the constraints surrounding autograft bone, surgeons have turned to osteoinductive agents to augment spinal fusion. Reports of complications and questionable efficacy slowed the adoption of these alternatives. Recombinant human platelet-derived growth factor B homodimer (rhPDGF-BB) has been Food and Drug Administration (FDA)-approved (Augment) to promote fusion in other areas of orthopedics, but its characterization in spine fusion has not yet been tested. The purpose of this study is to characterize the host response to PDGF-BB in vivo.

METHODS

Eighty female Fischer rats underwent L4-5 posterolateral fusion using one of four implant types: (a) iliac crest syngeneic allograft harvested from syngeneic donors, (b) β-TCP/bovine collagen matrix (β-TCP/Col) with sodium acetate buffer, (c) β-TCP/Col with 0.3 mg/mL "low dose," or (d) β-TCP/Col with 3.0 mg/mL "high dose" of rhPDGF-BB. Animals underwent magnetic resonance imaging (MRI) and serum cytokine quantification at 4, 7, 10, and 21 days, postoperatively. Tissues were processed for immunofluorescence staining for Ki67 and von Willebrand factor (vWF) to assess neovascularization.

RESULTS

MRI demonstrated no differences in fluid accumulation among the four treatment groups at any of the time points. Serum cytokine analysis showed no clinically significant differences between treatment groups in 20 of the 27 cytokines. Inflammatory cytokines IFN-γ, IL-1β, IL-18, MCP-1, MIP-1α, TNF-α were not induced by rhPDGF-BB. Histology showed no differences in cell infiltration, and Ki67 and vWF immunofluorescence staining was similar among groups.

CONCLUSIONS

rhPDGF-BB delivered with a β-TCP/Col matrix exerts no exaggerated systemic or local host inflammatory response when compared to iliac crest syngeneic allograft bone or the control carrier. rhPDGF-BB mixed with a β-TCP/Col matrix could be a viable and safe biologic alternative to syngeneic allograft in spine fusion. Further studies need to be performed to evaluate efficacy in this setting.

The effects of lyophilised platelet-rich plasma in third molar extraction sockets and its surrounding tissues

Objective

To determine the effects of repeated placement of quantified lyophilised platelet-rich plasma (LPRP) on the soft and hard tissue components.

Methods

Lyophilised platelet-rich plasma was topically placed, and later injected, into fresh sockets using the third molar surgical model, randomised according to the split-mouth approach. The control site received placebo. The application of LPRP was done intraoperatively, one month and two months postoperatively. The measured endpoints included post-operative pain, swelling, trismus, pocket depth at mid-distal adjacent second molar, soft tissue healing, and bone formation (which was assessed radiographically). Fifteen healthy young adults, aged between 21 and 35 years, visiting the Oral and Maxillofacial Surgery Clinic at the University of Malaya were recruited for this study.

Results

There was no significant difference in post-operative pain, swelling size, trismus, and bone healing within their specific timelines during this study. However, the LPRP group showed significant reduction in pocket depth at the two-month post-operative period, suggesting that LPRP improves soft tissue healing.

Conclusion

Soft tissue healing, measured as the change of periodontal pocket depth, showed significant reduction, suggesting the benefit of LPRP for soft tissue healing. However, bone regeneration and reduction of post-operative sequelae showed no improvement even after quantification and repeated LPRP application.

Craniofacial Bone Tissue Engineering: Current Approaches and Potential Therapy

Craniofacial bone defects can result from various disorders, including congenital malformations, tumor resection, infection, severe trauma, and accidents. Successfully regenerating cranial defects is an integral step to restore craniofacial function. However, challenges managing and controlling new bone tissue formation remain. Current advances in tissue engineering and regenerative medicine use innovative techniques to address these challenges. The use of biomaterials, stromal cells, and growth factors have demonstrated promising outcomes in vitro and in vivo. Natural and synthetic bone grafts combined with Mesenchymal Stromal Cells (MSCs) and growth factors have shown encouraging results in regenerating critical-size cranial defects. One of prevalent growth factors is Bone Morphogenetic Protein-2 (BMP-2). BMP-2 is defined as a gold standard growth factor that enhances new bone formation in vitro and in vivo. Recently, emerging evidence suggested that Megakaryocytes (MKs), induced by Thrombopoietin (TPO), show an increase in osteoblast proliferation in vitro and bone mass in vivo. Furthermore, a co-culture study shows mature MKs enhance MSC survival rate while maintaining their phenotype. Therefore, MKs can provide an insight as a potential therapy offering a safe and effective approach to regenerating critical-size cranial defects.

Medical gas plasma-stimulated wound healing: Evidence and mechanisms

Defective wound healing poses a significant burden on patients and healthcare systems. In recent years, a novel reactive oxygen and nitrogen species (ROS/RNS) based therapy has received considerable attention among dermatologists for targeting chronic wounds. The multifaceted ROS/RNS are generated using gas plasma technology, a partially ionized gas operated at body temperature. This review integrates preclinical and clinical evidence into a set of working hypotheses mainly based on redox processes aiding in elucidating the mechanisms of action and optimizing gas plasmas for therapeutic purposes. These hypotheses include increased wound tissue oxygenation and vascularization, amplified apoptosis of senescent cells, redox signaling, and augmented microbial inactivation. Instead of a dominant role of a single effector, it is proposed that all mechanisms act in concert in gas plasma-stimulated healing, rationalizing the use of this technology in therapy-resistant wounds. Finally, addressable current challenges and future concepts are outlined, which may further promote the clinical utilization, efficacy, and safety of gas plasma technology in wound care in the future.

Recombinant factors for periodontal intrabony defects: A systematic review and network meta-analysis of preclinical studies

The use of bioactive agents combined with osteoconductive scaffolds for the regeneration of periodontal intrabony defects has been the subject of intensive research in the past 20 years. Most studies reported that such agents, used in different concentrations, doses and combined with various scaffolds, might promote periodontal tissue regeneration, but evidence for the most effective combination of such agents is lacking. The objective of this study 13 was to rank the different combinations of recombinant human-derived growth and differentiation factors with/without scaffold biomaterial in the treatment of periodontal intrabony defects, through network meta-analysis of pre-clinical studies. The systematic review and network meta-analysis protocol was registered on the PROSPERO Systematic Review database with reference number: CRD42021213673. Relevant published articles were obtained after searching five electronic databases. A specific search strategy was followed by using keywords related to intrabony defects, regenerative materials, scaffolds and recombinant factors, and animal studies. All pre-clinical studies used for periodontal regeneration were included. The primary outcomes were: regeneration of junctional epithelium (mm), new cementum, connective tissue attachment, percentage of new bone formation (%), bone area (mm² ), bone volume density (g/cm³ ) and bone height (mm) data was extracted. The analysis was carried out using network meta-analysis methods, that is illustrating network plots, contribution plots, predictive and confidence interval plot, surface under the cumulative ranking (SUCRA), multidimensional scale ranking and net funnel plots using STATA IC statistical software. An SYRCLE's tool for assessing risk of bias was used for reporting risk of bias among individual studies. A total of N = 24 for qualitative and N = 21 studies for quantitative analysis published till 2020 were included. The cumulative total number of animals included in the control and test groups were N = 162 and N = 339, respectively. The duration of the study was between 3 and 102 weeks rhBMP-2 ranked higher in SUCRA as the agent associated with the best performance for bone volume density. rhGDF-5/TCP ranked best in the bone area (mm2), rhPDGF-BB/Equine ranked best in bone height (mm), rhBMP-2 ranked best in the percentage of new bone fill, rhBMP-2/ACS ranked best in new cementum formation, and rhGDF-5/b- TCP/PLGA ranked best in connective tissue attachment and junctional epithelium. There were no adverse effects identified in the literature that could affect the different outcomes for regeneration in intrabony defects. Various recombinant factors are effective in promoting the regeneration of both soft and hard tissue supporting structures of the periodontium. However, when considering different outcomes, different agents, associated or not with biomaterials, ranked best. Keeping into account the limited transferability of results from animal studies to the clinical setting, the choice of the most appropriate formulation of bioactive agents may depend on clinical needs and purpose.

TIPE2 inhibits PDGF-BB-induced phenotype switching in airway smooth muscle cells through the PI3K/Akt signaling pathway

Background

Childhood asthma is a common respiratory disease characterized by airway inflammation. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) has been found to be involved in the progression of asthma. This study aimed to explore the role of TIPE2 in the regulation of airway smooth muscle cells (ASMCs), which are one of the main effector cells in the development of asthma.

Materials and methods

ASMCs were transfected with pcDNA3.0-TIPE2 or si-TIPE2 for 48 h and then treated with platelet-derived growth factor (PDGF)-BB. Cell proliferation of ASMCs was measured using the MTT assay. Cell migration of ASMCs was determined by a transwell assay. The mRNA expression levels of calponin and smooth muscle protein 22α (SM22α) were measured using qRT-PCR. The levels of TIPE2, calponin, SM22α, PI3K, p-PI3K, Akt, and p-Akt were detected by Western blotting.

Results

Our results showed that PDGF-BB treatment significantly reduced TIPE2 expression at both the mRNA and protein levels in ASMCs. Overexpression of TIPE2 inhibited PDGF-BB-induced ASMC proliferation and migration. In addition, overexpression of TIPE2 increased the expression of calponin and SM22α in PDGF-BB-stimulated ASMCs. However, an opposite effect was observed with TIPE2 knockdown. Furthermore, TIPE2 overexpression blocked PDGF-BB-induced phosphorylation of PI3K and Akt, whereas the expression of p-PI3K and p-Akt were aggravated by TIPE2 knockdown. Additionally, the effects of TIPE2 overexpression and TIPE2 knockdown were altered by IGF-1 and LY294002 treatments, respectively.

Conclusions

Our findings demonstrate that TIPE2 inhibits PDGF-BB-induced ASMC proliferation, migration, and phenotype switching via the PI3K/Akt signaling pathway. Thus, TIPE2 may be a potential therapeutic target for the treatment of asthma.

The Mechanistic Effects and Clinical Applications of Various Derived Mesenchymal Stem Cells in Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by persistent thrombocytopenia resulting from increased platelet destruction and a loss of autoimmune tolerance. The pathogenesis of ITP is highly complex. Although ITP may be effectively controlled with currently available medications in some patients, a subset of cases remain refractory. The application of mesenchymal stem cells (MSCs) for human hematopoietic stem cell transplantation has increasingly demonstrated that MSCs modulate innate or adaptive immunity, thus resulting in a tolerant microenvironment. Functional defects and immunomodulatory disorders have been observed after the use of bone marrow mesenchymal stem cells (BM-MSCs) from patients with ITP. Here, we summarize the underlying mechanisms and clinical applications of various derived MSCs for ITP treatment, focusing on the main mechanisms underlying the functional defects and immune dysfunction of BM-MSCs from patients with ITP. Functional effects associated with the activation of the p53 pathway include decreased activity of the phosphatidylinositol 3 kinase/Akt pathway and activation of the TNFAIP3/NF-κB/SMAD7 pathway. Immune dysfunction appears to be associated with an impaired ability of BM-MSCs to induce various types of immune cells in ITP. At present, research focusing on MSCs in ITP remains in preliminary stages. The application of autologous or exogenous MSCs in the clinical treatment of ITP has been attempted in only a small case study and must be validated in larger-scale clinical trials.

Recombinant Human Derived Growth and Differentiating Factors in treatment of periodontal intrabony defects: Systematic review and network meta-analysis

The introduction of recombinant human growth and differentiation factors (rhGFs) for intrabony defects regeneration has represented a considerable breakthrough in recent years. However, they have been used in different concentrations, doses and combined with various scaffolds, and there is no evidence on which the most effective formulation for periodontal regeneration is. Therefore, we aimed to evaluate and rank the various formulations of such bioactive agents through network meta-analysis of clinical studies. The protocol registration was done on PROSPERO with registration ID CRD42020213753. To report NMA, we followed PRISMA guidelines and searched PUBMED, Embase, Web of Science and Cochrane Central electronic databases. Studies were screened based on specific inclusion criteria. Primary outcomes extracted from included studies were the most common indexes for periodontal regeneration (PPD, CAL, %bone filling). The NMA analysis included network plots, contribution plots, inconsistency plots (if eligible to form the loop), predictive interval plots, SUCRA rankings and multidimensional scale ranking (MDS) plots. SUCRA would demonstrate the rankings of multiple competing bioactive agents based on their best performance. Twelve clinical studies for qualitative and quantitative analysis were considered. Network meta-analysis found that rhFGF + hydroxyapatite was ranked highest in PPD and CAL outcome. rhPDGF-BB+β-tricalcium phosphate was ranked highest in the percentage of bone filling. In addition, all bioactive agents performed better than control groups without rhGFs. Despite clear benefits deriving from rhGFs for periodontal regeneration, the present results should be interpreted with caution due to several confounding factors affecting the outcome. Nevertheless, further well designed randomized clinical trials will allow establishing guidelines for an appropriate indication of the use of rhGFs.

In ovariectomy-induced osteoporotic rat models, BMP-2 substantially reversed an impaired alveolar bone regeneration whereas PDGF-BB failed

OBJECTIVES

We previously suggested an ovariectomy (OVX)-induced osteoporotic rat model showing an impaired alveolar bone defect healing. This study aimed to evaluate and compare the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human platelet-derived growth factor-BB (rhPDGF-BB) on alveolar bone defect healing in OVX-induced osteoporotic rats.

MATERIALS AND METHODS

A total of forty-one female rats were divided into four groups: a collagen group (n=10), a PDGF-BB group (n=11), a BMP-2 group (n=10), and a control group (n=10). Four months after OVX, alveolar bone drill-hole defects were created and grafted with collagen gel, rhPDGF-BB/collagen gel, or rhBMP-2/collagen gel. The defects in the control group were not grafted with any material. Defect healing was evaluated by histological, histomorphometric, and microcomputed tomographic (micro-CT) analyses at 2 and 4 weeks.

RESULTS

According to the micro-CT analysis, the BMP-2 group exhibited the greatest bone volume fraction among all groups, while the PDGF-BB group did not show significant differences compared with the collagen group. The histomorphometric analysis showed a significantly larger amount of new bone area in the BMP-2 group than in the control and collagen groups at 4 weeks; however, the PDGF-BB group did not reach significant superiority compared with the other groups.

CONCLUSIONS

Alveolar bone regeneration was significantly enhanced by the local use of rhBMP-2/collagen gel compared with the use of rhPDGF-BB/collagen gel in OVX-induced osteoporotic rats.

CLINICAL RELEVANCE

A treatment modality using rhBMP-2 may be a promising approach to promote alveolar bone regeneration in patients suffering from postmenopausal osteoporosis.

The Potential of FGF-2 in Craniofacial Bone Tissue Engineering: A Review

Bone is a hard-vascularized tissue, which renews itself continuously to adapt to the mechanical and metabolic demands of the body. The craniofacial area is prone to trauma and pathologies that often result in large bone damage, these leading to both aesthetic and functional complications for patients. The "gold standard" for treating these large defects is autologous bone grafting, which has some drawbacks including the requirement for a second surgical site with quantity of bone limitations, pain and other surgical complications. Indeed, tissue engineering combining a biomaterial with the appropriate cells and molecules of interest would allow a new therapeutic approach to treat large bone defects while avoiding complications associated with a second surgical site. This review first outlines the current knowledge of bone remodeling and the different signaling pathways involved seeking to improve our understanding of the roles of each to be able to stimulate or inhibit them. Secondly, it highlights the interesting characteristics of one growth factor in particular, FGF-2, and its role in bone homeostasis, before then analyzing its potential usefulness in craniofacial bone tissue engineering because of its proliferative, pro-angiogenic and pro-osteogenic effects depending on its spatial-temporal use, dose and mode of administration.

Guided bone regeneration with osteoconductive grafts and PDGF: A tissue engineering option for segmental bone defect reconstruction

Regeneration and reconstruction of segmental bone defects (SBD) is a clinical challenge in maxillofacial surgery and orthopedics. The present study evaluated efficacy of guided bone-regeneration (GBR) of rat femoral SBD using osteoconductive equine-bone (EB) and beta-tricalcium phosphate (beta-TCP) grafts, either with or without platelet-derived growth-factor (PDGF). Following ethical-approval, 50 male Wistar-Albino rats (aged ~12-15 months and weighing ~450-500 g) were included. A 5 mm femoral critical-size SBD was created and animals were divided into five groups depending on the graft material used for GBR (EB, EB + PDGF, Autograft, beta-TCP, beta-TCP + PDGF; n = 10/group). Following 12-weeks of healing, animals were sacrificed and femur specimens were analyzed through qualitative histology and quantitative histomorphometry. There was new bone bridging femoral SBD in all groups and qualitatively, better bone formation was seen in autograft and EB + PDGF groups. Histomorphometric bone-area (BA %) was significantly high in autograft group, followed by EB + PDGF, beta-TCP + PDGF, EB, and beta-TCP groups. Addition of PDGF to EB and beta-TCP during GBR resulted in significantly higher BA%. After 12-weeks of healing, EB + PDGF for GBR of rat femoral segmental defects resulted in new bone formation similar to that of autograft. Based on this study, GBR with EB and adjunct PDGF could be a potential clinical alternative for reconstruction and regeneration of segmental bone defects.

Biologic therapies for foot and ankle injuries

Introduction: The use of orthobiologics as supplemental treatment for foot and ankle pathologies have increased in the past decades. They have been used to improve the healing of bone and soft tissue injuries. There have been several studies that examined the use of biologics for knee and hip pathologies but the foot and ankle construct has unique features that must be considered.Areas covered: The biologics for foot and ankle injuries that are covered in this review are platelet-rich plasma (PRP), stem cells, growth factors, hyaluronic acid, bone grafts, bone substitutes, and scaffolds. These modalities are used in the treatment of pathologies related to tendon and soft tissue as well as cartilage.Expert opinion: The utilization of biological adjuncts for improved repair and regeneration of ankle injuries represents a promising future in our efforts to address difficult clinical problems. The application of concentrated bone marrow and PRP each represents the most widely studied and commonly used injection therapies with early clinical studies demonstrating promising results, research is also being done using other potential therapies such as stem cells and growth factors; further investigation and outcome data are still needed.

Growth Factors, Carrier Materials, and Bone Repair

This chapter provides an overview of the growth factors active in bone regeneration and healing. Both normal and impaired bone healing are discussed, with a focus on the spatiotemporal activity of the various growth factors known to be involved in the healing response. The review highlights the activities of most important growth factors impacting bone regeneration, with a particular emphasis on those being pursued for clinical translation or which have already been marketed as components of bone regenerative materials. Current approaches the use of bone grafts in clinical settings of bone repair (including bone grafts) are summarized, and carrier systems (scaffolds) for bone tissue engineering via localized growth factor delivery are reviewed. The chapter concludes with a consideration of how bone repair might be improved in the future.

Progress and Prospects of Polymer-Based Drug Delivery Systems for Bone Tissue Regeneration

Despite the high regenerative capacity of bone tissue, there are some cases where bone repair is insufficient for a complete functional and structural recovery after damage. Current surgical techniques utilize natural and synthetic bone grafts for bone healing, as well as collagen sponges loaded with drugs. However, there are certain disadvantages associated with these techniques in clinical usage. To improve the therapeutic efficacy of bone tissue regeneration, a number of drug delivery systems based on biodegradable natural and synthetic polymers were developed and examined in in vitro and in vivo studies. Recent studies have demonstrated that biodegradable polymers play a key role in the development of innovative drug delivery systems and tissue engineered constructs, which improve the treatment and regeneration of damaged bone tissue. In this review, we discuss the most recent advances in the field of polymer-based drug delivery systems for the promotion of bone tissue regeneration and the physical-chemical modifications of polymers for controlled and sustained release of one or more drugs. In addition, special attention is given to recent developments on polymer nano- and microparticle-based drug delivery systems for bone regeneration.

Effect of biologic materials on the outcomes of horizontal alveolar ridge augmentation: A retrospective study

PURPOSE

The purpose of this study was to investigate if the addition of biologic agents to a particulate bone graft enhances horizontal ridge augmentation outcomes in terms of bone dimensions, bone density, and successful implant placement.

MATERIALS AND METHODS

A retrospective chart review was done to assess the clinical and radiographic outcomes in 52 horizontal ridge augmentation sites in 43 patients. Information was gathered regarding surgical technique, type of graft material, biologic agents used (PRP or rhPDGF-BB), method of space maintenance, and achieved alveolar ridge width and bone density changes as quantified on CBCT scans.

RESULTS

The use of tenting screws, a resorbable membrane, and a combination of particulate allogenic and xenogenic bone graft material provided an average horizontal bone gain of 3.6 mm in the 52 augmented sites. There was no statistically significant difference observed in the amount of horizontal bone gain between sites treated with the addition of biologic agents (n = 21), or with a particulate bone graft alone (n = 31). A marginally statistically significant difference was found in the density of the grafted bone with the addition of biologics (p value = .0653).

CONCLUSION

The addition of biologic agents to the graft materials did not have a significant effect on the amount of horizontal bone gain or successful implant placement; however, it marginally enhanced the bone density of the grafted area.

Oral Soft Tissue Grafting

The presence of healthy soft tissue at the tooth and implant interface correlates to long-term success and stability in function and esthetics. Grafting procedures utilizing various techniques can be performed during any stage of the implant or restorative therapy. Materials of autogenous, allogeneic, and xenogeneic sources are available for oral soft tissue grafting. This article describes the classifications of soft tissue defects, treatment modalities, and materials used to enhance soft tissue quality and quantity and to achieve optimal esthetics and function around teeth and implants.

Dual delivery of platelet-derived growth factor and bone morphogenetic factor-6 on titanium surface to enhance the early period of implant osseointegration

OBJECTIVE

To test the surface properties and in vitro effects of a new sequential release system on MC3T3-E1 cells for improved osseointegration.

BACKGROUND

BMP6-loaded anodized titanium coated with PDGF containing silk fibroin (SF) may improve osseointegration.

METHODS

Titanium surfaces were electrochemically anodized, and SF layer was covered via electrospinning. Five experimental groups (unanodized Ti (Ti), anodized Ti (AnTi), anodized + BMP6-loaded Ti (AnTi-BMP6), anodized + BMP6 loaded + silk fibroin-coated Ti (AnTi-BMP6-SF), and anodized + BMP6-loaded + silk fibroin with PDGF-coated Ti (AnTi-BMP6-PDGF-SF)) were tested. After SEM characterization, contact angle analysis, and FTIR analysis, the amount of released PDGF and BMP6 was detected using ELISA. Cell proliferation (XTT), mineralization, and gene expression (RUNX2 and ALPL) were also evaluated.

RESULTS

After successful anodization and loading of PDGF and BMP6, contact angle measurements showed hydrophobicity for TiO₂ and hydrophilicity for protein-adsorbed surfaces. In FTIR, protein-containing surfaces exhibited amide-I, amide-II, and amide-III bands at 1600 cm^-1 -1700 cm^-1 , 1520 cm^-1 -1540 cm^-1 , and 1220 cm^-1 -1300 cm^-1 spectrum levels with a significant peak in BMP6- and/or SF-loaded groups at 1100 cm^-1 . PDGF release and BMP6 release were delayed, and relatively slower release was detected in SF-coated surfaces. Higher MC3T3-E1 proliferation and mineralization and lower gene expression of RUNX2 and ALPL were detected in AnTi-BMP6-PDGF-SF toward day 28.

CONCLUSION

The new system revealed a high potential for an improved early osseointegration period by means of a better factor release curve and contribution to the osteoblastic cell proliferation, mineralization, and associated gene expression.

Approaches to promoting bone marrow mesenchymal stem cell osteogenesis on orthopedic implant surface

Bone marrow-derived mesenchymal stem cells (BMSCs) play a critical role in the osseointegration of bone and orthopedic implant. However, osseointegration between the Ti-based implants and the surrounding bone tissue must be improved due to titanium’s inherent defects. Surface modification stands out as a versatile technique to create instructive biomaterials that can actively direct stem cell fate. Here, we summarize the current approaches to promoting BMSC osteogenesis on the surface of titanium and its alloys. We will highlight the utilization of the unique properties of titanium and its alloys in promoting tissue regeneration, and discuss recent advances in understanding their role in regenerative medicine. We aim to provide a systematic and comprehensive review of approaches to promoting BMSC osteogenesis on the orthopedic implant surface.

A novel experimental approach to evaluate guided bone regeneration (GBR) in the rat femur using a 3D-printed CAD/CAM zirconia space-maintaining barrier

Introduction

Obtaining a certain bone volume is an important goal in implantology or orthopedics. Thus, after tooth extraction, quite a lot of horizontal and vertical alveolar bone is lost in time and can be detrimental to the implant treatment outcome, while the treatment of critical bone defects is a considerable challenge for surgery.

Objectives

In this study we designed a new in vivo model as an useful experimental tool to assess guided bone regeneration (GBR) using a computer-aided design/manufacturing (CAD-CAM) space-maintaining barrier.

Methods

The barrier was 3D printed with three progressive heights, surgically placed on rat femur, and GBR results were analyzed at 2, 4, and 8 weeks by X-ray and bone mineral density analysis, histology/morphometry and by immunofluorescence and immunohistochemistry for osteogenesis and angiogenesis evaluation.

Results

The obtained results show that the proposed experimental model provides a real-time useful information on progressive bone tissue formation, which depends on the volume of isolated space created for GBR and on molecular events that lead to satisfactory vertical and horizontal bone augmentation and osteointegration.

Conclusion

In conclusion, the proposed customized three-dome space-maintaining barrier is suitable as an experimental tool to assess the potential of using the designed barriers in dentistry and orthopedics to promote the formation of new bone and determine their space- and time-dependent limitations. Meanwhile, guided bone augmentation for dentistry requires subsequent evaluation on an alveolar bone preclinical model followed by clinical implementation.

Tensile force-induced PDGF-BB/PDGFRβ signals in periodontal ligament fibroblasts activate JAK2/STAT3 for orthodontic tooth movement

Orthodontic force-induced osteogenic differentiation and bone formation at tension side play a pivotal role in orthodontic tooth movement (OTM). Platelet-derived growth factor-BB (PDGF-BB) is a clinically proven growth factor during bone regeneration process with unclear mechanisms. Fibroblasts in periodontal ligament (PDL) are considered to be mechanosensitive under orthodontic force. Thus, we established OTM model to investigate the correlation between PDGF-BB and fibroblasts during bone regeneration at tension side. We confirmed that tensile force stimulated PDL cells to induce osteogenic differentiation via Runx-2, OCN up-regulation, and to accelerate new bone deposition along the periodontium and the alveolar bone interface. Interestingly, PDGF-BB level was remarkably enhanced at tension side during OTM in parallel with up-regulated PDGFRβ+/α-SMA+ fibroblasts in PDL by immunohistochemistry. Moreover, orthodontic force-treated primary fibroblasts from PDL were isolated and, cultured in vitro, which showed similar morphology and phenotype with control fibroblasts without OTM treatment. PDGFRβ expression was confirmed to be increased in orthodontic force-treated fibroblasts by immunofluorescence and flow cytometry. Bioinformatics analysis identified that PDGF-BB/PDGFRβ signals were relevant to the activation of JAK/STAT3 signals. The protein expression of JAK2 and STAT3 was elevated in PDL of tension side. Importantly, in vivo, the treatment of the inhibitors (imatinib and AG490) for PDGFRβ and JAK-STAT signals were capable of attenuating the tooth movement. The osteogenic differentiation and bone regeneration in tension side were down-regulated upon the treatment of inhibitors during OTM. Meanwhile, the expressions of PDGFRβ, JAK2 and STAT3 were inhibited by imatinib and AG490. Thus, we concluded that tensile force-induced PDGF-BB activated JAK2/STAT3 signals in PDGFRβ⁺ fibroblasts in bone formation during OTM.

Adsorption and Release of Growth Factors from Four Different Porcine-Derived Collagen Matrices

Xenogeneic acellular collagen matrices represent a safe alternative to autologous soft tissue transplants in periodontology and implant dentistry. Here, we aimed to investigate the adsorption and release of growth factors from four porcine-derived collagen matrices using enzyme-linked immunosorbent assay. Non-crosslinked collagen matrix (NCM), crosslinked collagen matrix (CCM), dried acellular dermal matrix (DADM), and hydrated acellular dermal matrix (HADM) adsorbed each of the following growth factors, TGF-β1, FGF-2, PDGF-BB, GDF-5 and BMP-2, with an efficiency close to 100%. Growth factor release for a 13-day period was in the range of 10-50% of the adsorbed protein, except for the BMP-2 release that was in the range of 5-7%. Generally, protein release occurred in two phases. Phase I was arbitrary defined by the highest release from the matrices, usually within 24 h. Phase II, spanning the period immediately after the peak release until day 13, corresponded to the delayed release of the growth factors from the deeper layers of the matrices. HADM showed significantly (P < 0.001) higher TGF-β1, FGF-2, and PDGF-BB release in phase II, compared to the rest of the matrices. NCM exhibited significantly (P < 0.001) higher FGF-2 release in phase II, compared to CCM and DADM as well as a characteristic second peak in PDGF-BB release towards the middle of the tested period. In contrast to NCM and HADM, CCM and DADM showed a gradual and significantly higher release of GDF-5 in the second phase. Several burst releases of BMP-2 were characteristic for all matrices. The efficient adsorption and sustained protein release in the first 13 days, and the kinetics seen for HADM, with a burst release within hours and high amount of released growth factor within a secondary phase, may be beneficial for the long-term tissue regeneration following reconstructive periodontal surgery.

Topical GDF11 accelerates skin wound healing in both type 1 and 2 diabetic mouse models

This study aimed to investigate the role of truncated growth differentiation factor 11 (GDF11), in which the recognition site of Furin from wild-type GDF11 was deleted to enhance the cellular stability, in skin wound healing in the setting of diabetes mellitus (DM) and the underlying mechanisms. Our study found that both truncated and natural GDF11s effectively accelerated wound healing processes in both T1DM and T2DM mice with a potency compatible to PDGF, bFGF, and EGF, but being much higher than GDF8. At the cellular level, GDF11 stimulated the proliferation and suppressed HG-induced apoptosis of HSFs. Further study revealed that GDF11 activated the YAP-Smad2/3-CTGF fibrotic signaling pathway by reversing HG-induced upregulation of phosphorylated form of YAP (p-YAP), increases p-Smad2/3 levels, and restoring HG-induced repression of CTGF expression by GDF11. Overall, the study shows that both natural and truncated GDF11s promote the healing process of skin wound in mice of both T1DM and T2DM partly via stimulating dermal fibrosis via the YAP-Smad2/3-CTGF pathway, suggesting it a potential agent for treating skin wound in diabetic population.

Adjuvant drug-assisted bone healing: Part III - Further strategies for local and systemic modulation

In this third in a series of reviews on adjuvant drug-assisted bone healing, further approaches aiming at influencing the healing process are discussed. Local and systemic modulation of bone metabolism is pursued with use of a number of drugs with completely different indications, which are characterized by a pleiotropic spectrum of action. These include drugs used to treat lipid disorders (HMG-CoA reductase inhibitors), hypertension (ACE inhibitors), osteoporosis (bisphosphonates), cancer (proteasome inhibitors) and others. Potential applications to enhance bone healing are discussed.

Multi-peptide presentation and hydrogel mechanics jointly enhance therapeutic duo-potential of entrapped stromal cells

The native extracellular matrix (ECM) contains a host of matricellular proteins and bioactive factors that regulate cell behavior, and many ECM components have been leveraged to guide cell fate. However, the large size and chemical characteristics of these constituents complicate their incorporation into biomaterials without interfering with material properties, motivating the need for alternative approaches to regulate cellular responses. Mesenchymal stromal cells (MSCs) can promote osseous regeneration in vivo directly or indirectly through multiple means including (1) secretion of proangiogenic and mitogenic factors to initiate formation of a vascular template and recruit host cells into the tissue site or (2) direct differentiation into osteoblasts. As MSC behavior is influenced by the properties of engineered hydrogels, we hypothesized that the biochemical and biophysical properties of alginate could be manipulated to promote the dual contributions of encapsulated MSCs toward bone formation. We functionalized alginate with QK peptide to enhance proangiogenic factor secretion and RGD to promote adhesion, while biomechanical-mediated osteogenic cues were controlled by modulating viscoelastic properties of the alginate substrate. A 1:1 ratio of QK:RGD resulted in the highest levels of both proangiogenic factor secretion and mineralization in vitro. Viscoelastic alginate outperformed purely elastic gels in both categories, and this effect was enhanced by stiffness up to 20 kPa. Furthermore, viscoelastic constructs promoted vessel infiltration and bone regeneration in a rat calvarial defect over 12 weeks. These data suggest that modulating viscoelastic properties of biomaterials, in conjunction with dual peptide functionalization, can simultaneously enhance multiple aspects of MSC regenerative potential and improve neovascularization of engineered tissues.

Incretin accelerates platelet-derived growth factor-BB-induced osteoblast migration via protein kinase A: The upregulation of p38 MAP kinase

Incretins, including glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), secreted from enteroendocrine cells after food ingestion, are currently recognized to regulate glucose metabolism through insulin secretion. We previously demonstrated that platelet-derived growth factor-BB (PDGF-BB) induces the migration of osteoblast-like MC3T3-E1 cells through mitogen-activated protein (MAP) kinases, including p38 MAP kinase. In the present study, we investigated whether or not incretins affect the osteoblast migration. The PDGF-BB-induced cell migration was significantly reinforced by GLP-1, GIP or cAMP analogues in MC3T3-E1 cells and normal human osteoblasts. The upregulated migration by GLP-1 or cAMP analogues was suppressed by H89, an inhibitor of protein kinase A. The amplification by GLP-1 of migration induced by PDGF-BB was almost completely reduced by SB203580, a p38 MAP kinase inhibitor in MC3T3-E1 cells and normal human osteoblasts. In addition, GIP markedly strengthened the PDGF-BB-induced phosphorylation of p38 MAP kinase. Exendin-4, a GLP-1 analogue, induced Rho A expression and its translocation from cytoplasm to plasma membranes in osteoblasts at the epiphyseal lines of developing mouse femurs in vivo. These results strongly suggest that incretins accelerates the PDGF-BB-induced migration of osteoblasts via protein kinase A, and the up-regulation of p38 MAP kinase is involved in this acceleration. Our findings may highlight the novel potential of incretins to bone physiology and therapeutic strategy against bone repair.

Key components of engineering vascularized 3-dimensional bioprinted bone constructs

Vascularization has a pivotal role in engineering successful tissue constructs. However, it remains a major hurdle of bone tissue engineering, especially in clinical applications for the treatment of large bone defects. Development of vascularized and clinically-relevant engineered bone substitutes with sufficient blood supply capable of maintaining implant viability and supporting subsequent host tissue integration remains a major challenge. Since only cells that are 100-200 µm from blood vessels can receive oxygen through diffusion, engineered constructs that are thicker than 400 µm face a challenging oxygenation problem. Following implantation in vivo, spontaneous ingrowth of capillaries in thick engineered constructs is too slow. Thus, it is critical to provide optimal conditions to support vascularization in engineered bone constructs. To achieve this, an in-depth understanding of the mechanisms of angiogenesis and bone development is required. In addition, it is also important to mimic the physiological milieu of native bone to fabricate more successful vascularized bone constructs. Numerous applications of engineered vascularization with cell-and/or microfabrication-based approaches seek to meet these aims. Three-dimensional (3D) printing promises to create patient-specific bone constructs in the future. In this review, we discuss the major components of fabricating vascularized 3D bioprinted bone constructs, analyze their related challenges, and highlight promising future trends.

Transgenic PDGF-BB/sericin hydrogel supports for cell proliferation and osteogenic differentiation

The present study demonstrates fabrication of PDGF-BB functionalized sericin hydrogel to explore biomaterials-related utility in bone tissue engineering.

PDGFBB-modified stem cells from apical papilla and thermosensitive hydrogel scaffolds induced bone regeneration

Bone defects caused by cancer surgery or trauma have a strong negative impact on human health. Treatment with cell and material-based complexes provides an alternative strategy for the regeneration of damaged bone tissue. The good physical properties and suitable biodegradability of a thermosensitive hydrogel has been shown to act as a valuable scaffold. Platelet derived growth factor BB (PDGFBB) is mainly secreted by platelets and promotes the migration and angiogenesis of mesenchymal stem cells (MSCs). Although PDGFBB is known to indirectly enhance bone repair in vivo, the effects of PDGFBB on stem cells from apical papilla (SCAPs) require further investigation. In our study, the proliferation of cells was investigated by the cell counting kit-8 and live/dead staining methods. The results indicated that PDGFBB promoted the proliferation of SCAPs. Real-time polymerase chain reaction and Western blot experiments were used to detect osteogenic genes and proteins. Moreover, calvarial defects were created in Sprague-Dawley rats and different complexes implanted. The results shown by micro-CT and hematoxylin and eosin analysis demonstrated that the hydrogel combined with lentiviral supernatant-green fluorescent protein-PDGFBB significantly improved new bone formation and mineralization compared with the other three groups. In summary, our research showed that a thermosensitive hydrogel can be used as a scaffold for 3D cell culture, and PDGFBB gene-modified SCAPs can improve bone formation in calvarial defects.

Mesenchymal stem cells and biologic factors leading to bone formation

BACKGROUND

Physiological bone formation and bone regeneration occurring during bone repair can be considered distinct but similar processes. Mesenchymal stem cells (MSC) and associated biologic factors are crucial to both bone formation and bone regeneration.

AIM

To perform a narrative review of the current literature regarding the role of MSC and biologic factors in bone formation with the aim of discussing the clinical relevance of in vitro and in vivo animal studies.

METHODS

The literature was searched for studies on MSC and biologic factors associated with the formation of bone in the mandible and maxilla. The search specifically targeted studies on key aspects of how stem cells and biologic factors are important in bone formation and how this might be relevant to bone regeneration. The results are summarized in a narrative review format.

RESULTS

Different types of MSC and many biologic factors are associated with bone formation in the maxilla and mandible.

CONCLUSION

Bone formation and regeneration involve very complex and highly regulated cellular and molecular processes. By studying these processes, new clinical opportunities will arise for therapeutic bone regenerative treatments.

Current and Future Concepts for the Treatment of Impaired Fracture Healing

Bone regeneration represents a complex process, of which basic biologic principles have been evolutionarily conserved over a broad range of different species. Bone represents one of few tissues that can heal without forming a fibrous scar and, as such, resembles a unique form of tissue regeneration. Despite a tremendous improvement in surgical techniques in the past decades, impaired bone regeneration including non-unions still affect a significant number of patients with fractures. As impaired bone regeneration is associated with high socio-economic implications, it is an essential clinical need to gain a full understanding of the pathophysiology and identify novel treatment approaches. This review focuses on the clinical implications of impaired bone regeneration, including currently available treatment options. Moreover, recent advances in the understanding of fracture healing are discussed, which have resulted in the identification and development of novel therapeutic approaches for affected patients.

Biomaterials for the Treatment of Tendon Injury

Background

Most tendon injuries are occurring from a gradual wearing and tearing of the tendon tissues from overuse. Such injuries are usually seen in sports, exercising, or daily activities that involve a high mechanical load and weight bearing. However, owing to the lack of both cellularity and blood vessels in tendons, the process of tendon repair is slow and inefficient. Although various conservative (non-surgical) and surgical management options are conducted by the clinicians, a gold standard of these approaches does not exist. In this regard, the treatment of tendon injuries is challenging.

Method

Here, we describe the recent advances of biomaterial-based approaches for the treatment of injured tendons.

Results

Regenerative medicine is an emerging multidisciplinary research that specializes in the repair of damaged tendon tissues through the delivery of regenerative factors by biomaterials.

Conclusion

Although current biomaterial-based treatment strategies have shown their potential for tendon healing, future research and clinical applications should focused on finding the optimum combinations of regenerative factors with ideal biomaterials for the repair of tendons.