Autologous fibrin scaffolds: When platelet- and plasma-derived biomolecules meet fibrin

Advances in meniscus tissue engineering: Towards bridging the gaps from bench to bedside

Meniscus is vital for maintaining the anatomical and functional integrity of knee. Injuries to meniscus, commonly caused by trauma or degenerative processes, can result in knee joint dysfunction and secondary osteoarthritis, while current conservative and surgical interventions for meniscus injuries bear suboptimal outcomes. In the past decade, there has been a significant focus on advancing meniscus tissue engineering, encompassing isolated scaffold strategies, biological augmentation, physical stimulus, and meniscus organoids, to improve the prognosis of meniscus injuries. Despite noteworthy promising preclinical results, translational gaps and inconsistencies in the therapeutic efficiency between preclinical and clinical studies exist. This review comprehensively outlines the developments in meniscus tissue engineering over the past decade (Scheme 1). Reasons for the discordant results between preclinical and clinical trials, as well as potential strategies to expedite the translation of bench-to-bedside approaches are analyzed and discussed.

Mesoporous silica thin film as effective coating for enhancing osteogenesis through selective protein adsorption and blood clotting

The role of blood clots in tissue repair has been identified for a long time; however, its participation in the integration between implants and host tissues has attracted attention only in recent years. In this work, a mesoporous silica thin film (MSTF) with either vertical or parallel orientation was deposited on titania nanotubes surface, resulting in superhydrophilic nanoporous surfaces. A proteomic analysis of blood plasma adsorption revealed that the MSTF coating could significantly increase the abundance of acidic proteins and the adsorption of coagulation factors (XII and XI), with the help of cations (Na+, Ca2+) binding. As a result, both the activation of platelets and the formation of blood clots were significantly enhanced on the MSTF surface with more condensed fibrin networks. The two classical growth factors of platelets-derived growth factors-AB and transformed growth factors-βwere enriched in blood clots from the MSTF surface, which accounted for robust osteogenesis bothin vitroandin vivo. This study demonstrates that MSTF may be a promising coating to enhance osteogenesis by modulating blood clot formation.

Profound Properties of Protein-Rich, Platelet-Rich Plasma Matrices as Novel, Multi-Purpose Biological Platforms in Tissue Repair, Regeneration, and Wound Healing

Autologous platelet-rich plasma (PRP) preparations are prepared at the point of care. Centrifugation cellular density separation sequesters a fresh unit of blood into three main fractions: a platelet-poor plasma (PPP) fraction, a stratum rich in platelets (platelet concentrate), and variable leukocyte bioformulation and erythrocyte fractions. The employment of autologous platelet concentrates facilitates the biological potential to accelerate and support numerous cellular activities that can lead to tissue repair, tissue regeneration, wound healing, and, ultimately, functional and structural repair. Normally, after PRP preparation, the PPP fraction is discarded. One of the less well-known but equally important features of PPP is that particular growth factors (GFs) are not abundantly present in PRP, as they reside outside of the platelet alpha granules. Precisely, insulin-like growth factor-1 (IGF-1) and hepatocyte growth factor (HGF) are mainly present in the PPP fraction. In addition to their roles as angiogenesis activators, these plasma-based GFs are also known to inhibit inflammation and fibrosis, and they promote keratinocyte migration and support tissue repair and wound healing. Additionally, PPP is known for the presence of exosomes and other macrovesicles, exerting cell-cell communication and cell signaling. Newly developed ultrafiltration technologies incorporate PPP processing methods by eliminating, in a fast and efficient manner, plasma water, cytokines, molecules, and plasma proteins with a molecular mass (weight) less than the pore size of the fibers. Consequently, a viable and viscous protein concentrate of functional total proteins, like fibrinogen, albumin, and alpha-2-macroglobulin is created. Consolidating a small volume of high platelet concentrate with a small volume of highly concentrated protein-rich PPP creates a protein-rich, platelet-rich plasma (PR-PRP) biological preparation. After the activation of proteins, mainly fibrinogen, the PR-PRP matrix retains and facilitates interactions between invading resident cells, like macrophages, fibroblast, and mesenchymal stem cells (MSCs), as well as the embedded concentrated PRP cells and molecules. The administered PR-PRP biologic will ultimately undergo fibrinolysis, leading to a sustained release of concentrated cells and molecules that have been retained in the PR-PRP matrix until the matrix is dissolved. We will discuss the unique biological and tissue reparative and regenerative properties of the PR-PRP matrix.

Platelet-Rich Plasma in Young and Elderly Humans Exhibits a Different Proteomic Profile

As people age, their ability to resist injury and repair damage decreases significantly. Platelet-rich plasma (PRP) has demonstrated diverse therapeutic effects on tissue repair. However, the inconsistency of patient outcomes poses a challenge to the practical application of PRP in clinical practice. Furthermore, a comprehensive understanding of the specific impact of aging on PRP requires a systematic investigation. We derived PRP from 6 young volunteers and 6 elderly volunteers, respectively. Subsequently, 95% of high-abundance proteins were removed, followed by mass spectrometry analysis. Data are available via ProteomeXchange with the identifier PXD050061. We detected a total of 739 proteins and selected 311 proteins that showed significant differences, including 76 upregulated proteins in the young group and 235 upregulated proteins in the elderly group. Functional annotation and enrichment analysis unveiled upregulation of proteins associated with cell apoptosis, angiogenesis, and complement and coagulation cascades in the elderly. Conversely, IGF1 was found to be upregulated in the young group, potentially serving as the central source of enhanced cell proliferation ability. Our investigation not only provides insights into standardizing PRP preparation but also offers novel strategies for augmenting the functionality of aging cells or tissues.

Platelet Power: Revitalizing Endodontics With Scaffolds

This article provides an overview of a biologically based method for restoring damaged tooth structures and pulp tissues known as regenerative endodontics. It explores the concept of regenerative endodontics, its tissue engineering approach, and its application in maintaining vitality. The article discusses the significance of the factors affecting growth, scaffolds, and stem cells being the three tissue engineering components involved in the regeneration of pulp tissues. It also delves into the classification of scaffolds and the role of platelet-rich fibrin (PRF) and platelet-rich plasma (PRP) as biological scaffolds. The methodology section details the search process for relevant studies, and the review section presents research findings associated with PRF and its application in regeneration and repair of tissue. The article concludes by highlighting the potential of advanced PRF and injectable PRF in regenerative endodontics, with a focus on their impact on tissue regeneration and healing.

Slow-sculpting graphene oxide/alginate gel loaded with platelet-rich plasma to promote wound healing in rats

Wounds, especially chronic wounds, have become an important problem that endangers human health. At present, there are many repair methods, and among them combines materials science and biology is one of the important repair methods. This study explored the preparation method, physicochemical properties, biological activity and safety of Platelet-Rich plasma (PRP)-loaded slow-sculpting graphene oxide (GO)/alginate gel, and applied it to acute full-thickness skin defect wounds in rats to observe its role in wound healing. The results show that the slow-sculpting GO/alginate gel has excellent plasticity and is suitable for a variety of irregularly shaped wounds. At the same time, its porous structure and water content can maintain the activity of platelets and their released growth factors in PRP, thereby promoting wound collagen synthesis and angiogenesis to accelerate wound healing. This indicates that the slow-sculpting GO/alginate gel is an excellent loading material for PRP, and the combination of the two may become one of the methods to promote wound repair.

Injection of autologous conditioned plasma combined with a collagen scaffold may improve the clinical outcome in shoulder impingement syndrome: a prospective study

BACKGROUND

Shoulder impingement syndrome (SIS) is one of the most common diseases of the shoulder and can be addressed with various therapeutic concepts. Orthobiological agents such as platelet rich plasma with a low side effect rate gain importance in the conservative treatment of SIS. Currently, the knowledge about success rate influencing factors, such as the growth factors (GF) concentration or acromion type, is limited. The aim of this study was to analyze the clinical outcome in the therapy of external SIS using autologous conditioned plasma combined with recombinant human collagen scaffold (ACP/STR) injection in comparison with a corticosteroid-local anesthetic (CSA) injection. Additionally, the influence of potential limiting factors such as GF concentration, age and acromial morphology was proved.

MATERIALS AND METHODS

This prospective pseudo-randomized trial recruited 58 patients with external SIS who received an ultrasound-guided subacromial injection either an ACP/STR or a CSA followed by physical therapy. Follow-up (FU) was performed at 6 weeks, 3 and 6 months. The outcome was assessed with Constant-Murley score, disability of arm, shoulder and hand score and simple shoulder test. The concentration of GF was measured using ELISA.

RESULTS

During the FU, the improvement of outcome measures was observed with no differences between both groups. Shoulder force was significantly increased in the ACP/STR group (p < 0.01). We found no correlation between the amount of GF and age or gender in the ACP/STR patients. An acromion Bigliani type III predisposes for therapy failure (p < 0.001, OR = 56) in both treatment groups.

CONCLUSIONS

Patients with SIS benefit regarding to PROMs after both ACP/STR and CSA injection and physical therapy. Patients who received ACP/STR obtained superior improvement in force. The quantity of GF did not vary depending on the age, so that ACP/STR can be a treatment option for SIS in elderly patients with multimorbidity. The presence of an acromion type III seems to be a predictive factor for limited effectivity of injections in the clinical management of SIS.

Molecular basis of clot retraction and its role in wound healing

Clot retraction is important for the prevention of bleeding, in the manifestations of thrombosis and for tissue repair. The molecular mechanisms behind clot formation are complex. Platelet involvement begins with adhesion at sites of vessel injury followed by platelet aggregation, thrombin generation and fibrin production. Other blood cells incorporate into a fibrin mesh that is consolidated by FXIIIa-mediated crosslinking and platelet contractile activity. The latter results in the asymmetric redistribution of erythrocytes into a tighter central mass providing the clot with stability and resistance to fibrinolysis. Integrin αIIbβ3 on platelets is the key player in these events, bridging fibrin and the platelet cytoskeleton. Glycoprotein VI participates in thrombus formation but not in the retraction. Rheological and environmental factors influence clot construction with retraction driven by the platelet cytoskeleton with actomyosin acting as the motor. Activated platelets provide procoagulant activity stimulating thrombin generation together with the release of a plethora of biologically active proteins and substances from storage pools; many form chemotactic gradients within the fibrin or the underlying matrix. Also released are newly synthesized metabolites and lipid-rich vesicles that circulate within the vasculature and mimic platelet functions. Platelets and their released elements play key roles in wound healing. This includes promoting stem cell and mesenchymal stromal cell recruitment, fibroblast and endothelial cell migration, angiogenesis and matrix formation. These properties have led to the use of autologous clots in therapies designed to accelerate tissue repair while offering the potential for genetic manipulation in both inherited and acquired diseases.

Cellular composition modifies the biological properties and stability of platelet rich plasma membranes for tissue engineering

Scaffolds should provide structural support for tissue regeneration, allowing their gradual biodegradation and interacting with cells and bioactive molecules to promote remodeling. Thus, the scaffold's intrinsic properties affect cellular processes involved in tissue regeneration, including migration, proliferation, differentiation, and protein synthesis. In this sense, due to its biological effect and clinical potential, Platelet Rich Plasma (PRP) fibrin could be considered a successful scaffold. Given the high variability in commercial PRPs formulations, this research focused on assessing the influence of cellular composition on fibrin membrane stability and remodeling cell activity. The stability and biological effect were evaluated at different time points via D-dimer, type I collagen and elastase quantification in culture media conditioned by Plasma Rich in Growth Factors - Fraction 1 (PRGF-F1), Plasma Rich in Growth Factors - Whole Plasma (PRGF-WP) and Leukocyte-rich Platelet Rich Plasma (L-PRP) membranes, and by gingival fibroblast cells seeded on them, respectively. Ultrastructure of PRP membranes was also evaluated. Histological analyses were performed after 5 and 18 days. Additionally, the effect of fibrin membranes on cell proliferation was determined. According to the results, L-PRP fibrin membranes degradation was complete at the end of the study, while PRGF membranes remained practically unchanged. Considering fibroblast behavior, PRGF membranes, in contrast to L-PRP ones, promoted extracellular matrix biosynthesis at the same time as fibrinolysis and enhanced cell proliferation. In conclusion, leukocytes in PRP fibrin membranes drastically reduce scaffold stability and induce behavioral changes in fibroblasts by reducing their proliferation rate and remodeling ability.

Biomaterials derived from hard palate mucosa for tissue engineering and regenerative medicine

Autologous materials have superior biosafety and are widely used in clinical practice. Due to its excellent trauma-healing ability, the hard palate mucosa (HPM) has become a hot spot for autologous donor area research. Multiple studies have conducted an in-depth analysis of the healing ability of the HPM at the cellular and molecular levels. In addition, the HPM has good maneuverability as a donor area for soft tissue grafts, and researchers have isolated various specific mesenchymal stem cells (MSCs) from HPM. Free soft tissue grafts obtained from the HPM have been widely used in the clinic and have played an essential role in dentistry, eyelid reconstruction, and the repair of other specific soft tissue defects. This article reviews the advantages of HPM as a donor area and its related mechanisms, classes of HPM-derived biomaterials, the current status of clinical applications, challenges, and future development directions.

Progress in Regenerative Medicine: Exploring Autologous Platelet Concentrates and Their Clinical Applications

The goal of regenerative medicine is to achieve tissue regeneration. In the past, commonly used techniques included autologous or allogeneic transplantation and stem cell therapy, which have limitations, such as a lack of donor sites in the case of autologous transplantation and the invasiveness of stem cell harvesting. In recent years, research has, therefore, focused on new and less invasive strategies to achieve tissue regeneration. A step forward in this direction has been made with the development of autologous platelet concentrates (APCs), which are derived from the patient's own blood. They can be classified into three generations: platelet-rich plasma (PRP), platelet-rich fibrin (PRF), and concentrated growth factors (CGFs). These APCs have different structural characteristics, depending on the distinctive preparation method, and contain platelets, leukocytes, and multiple growth factors, including those most involved in regenerative processes. The purpose of this review is to clarify the most used techniques in the field of regenerative medicine in recent years, comparing the different types of APCs and analyzing the preparation protocols, the composition of the growth factors, the level of characterization achieved, and their clinical applications to date.

Engineering a platelet-rich plasma-based multifunctional injectable hydrogel with photothermal, antibacterial, and antioxidant properties for skin regeneration

Wound healing remains a significant challenge worldwide, necessitating the development of new wound dressings to aid in the healing process. This study presents a novel photothermally active hydrogel that contains platelet-rich plasma (PRP) for infected wound healing. The hydrogel was formed in a one pot synthesis approach by mixing alginate (Alg), gelatin (GT), polydopamine (PDA), and PRP, followed by the addition of CaCl2 as a cross-linker to prepare a multifunctional hydrogel (AGC-PRP-PDA). The hydrogel exhibited improved strength and good swelling properties. PDA nanoparticles (NPs) within the hydrogel endowed them with high photothermal properties and excellent antibacterial and antioxidant activities. Moreover, the hydrogels sustained the release of growth factors due to their ability to protect PRP. The hydrogels also exhibited good hemocompatibility and cytocompatibility, as well as high hemostatic properties. In animal experiments, the injectable hydrogels effectively filled irregular wounds and promoted infected wound healing by accelerating re-epithelialization, facilitating collagen deposition, and enhancing angiogenesis. The study also indicated that near-infrared light improved the healing process. Overall, these hydrogels with antibacterial, antioxidant, and hemostatic properties, as well as sustained growth factor release, show significant potential for skin regeneration in full-thickness, bacteria-infected wounds.

Impact of a Novel Hydrogel with Injectable Platelet-Rich Fibrin in Diabetic Wound Healing

Diabetic wounds are serious complications caused by diabetes mellitus (DM), which are further exacerbated by angiogenesis disorders and prolonged inflammation. Injectable platelet-rich fibrin (i-PRF) is rich in growth factors (GFs) and has been used for the repair and regeneration of diabetic wounds; however, direct application of i-PRF has certain disadvantages, including the instability of the bioactive molecules. Sericin hydrogel, fabricated by silkworm-derived sericin, is a biocompatible material that has anti-inflammatory and healing-promoting properties. Therefore, in this study, we developed a novel hydrogel (named sericin/i-PRF hydrogel) using a simple one-step activation method. The in vitro studies showed that the rapid injectability of the sericin/i-PRF hydrogel allows it to adapt to the irregular shape of the wounds. Additionally, sericin hydrogel could prolong the release of i-PRF-derived bioactive GFs in the sericin/i-PRF hydrogel. Furthermore, sericin/i-PRF hydrogel effectively repaired diabetic wounds, promoted angiogenesis, and reduced inflammation levels in the diabetic wounds of nude mice. These results demonstrate that the sericin/i-PRF hydrogel is a promising agent for diabetic wound healing.

The Dual-Responsive Interaction of Particulated Hyaline Cartilage and Plasma Rich in Growth Factors (PRGF) in the Repair of Cartilage Defects: An In Vitro Study

The treatment of chondral and osteochondral defects is challenging. These types of lesions are painful and progress to osteoarthritis over time. Tissue engineering offers tools to address this unmet medical need. The use of an autologous cartilage construct consisting of hyaline cartilage chips embedded in plasma rich in growth factors (PRGF) has been proposed as a therapeutic alternative. The purpose of this study was to dig into the potential mechanisms behind the in vitro remodelling process that might explain the clinical success of this technique and facilitate its optimisation. Chondrocyte viability and cellular behaviour over eight weeks of in vitro culture, type II collagen synthesis, the dual delivery of growth factors by hyaline cartilage and PRGF matrix, and the ultrastructure of the construct and its remodelling were characterised. The main finding of this research is that the cartilage fragments embedded in the three-dimensional PRGF scaffold contain viable chondrocytes that are able to migrate into the fibrin network, proliferate and synthesise extracellular matrix after the second week of in vitro culture. The characterization of this three-dimensional matrix is key to unravelling the molecular kinetics responsible for its efficacy.

Office-Based Intraosseous Infiltrations of PRGF as an Effective Treatment for Knee Osteoarthritis: A Retrospective Observational Clinical Study

The aim of this study was to explore and assess office-based ultrasound-guided intraosseous and intra-articular infiltrations of plasma rich in growth factors (PRGF) in patients with moderate and severe knee osteoarthritis (KOA). Seventy-nine patients (30 women and 49 men) with grade 3-4 KOA according to the Kellgren-Lawrence classification participated in the study. All patients were treated with a minimally invasive technique using local anesthesia WALANT (wide-awake local anesthesia no tourniquet) in the ambulatory setting. A PRGF intra-articular infiltration and two intraosseous infiltrations in the tibial plateau and femoral condyle were performed weekly for a total of three sessions. The evaluation of the results was carried out using knee injury and osteoarthritis outcome score (KOOS) at baseline and post-treatment. After a follow-up period of 11 months (median) [interquartile range, 7-14], all the KOOS domains showed statistically significant improvement (p < 0.001). Moreover, 88% of the patients showed a pain reduction of at least 10 points (minimally clinically important improvement) from pre- to post-treatment. Our retrospective study using the in-office procedure of ultrasound-guided combination of intra-articular and intraosseous infiltrations of PRGF is a safe and efficacious approach for the treatment of grade 3-4 knee osteoarthritis.

Treatment of Aneurysmal Bone Cyst with Endoscopic Resection and Bone Allograft with Platelet-Rich Plasma: A Case Report

An aneurysmal bone cyst (ABC) is a rare bone tumor usually observed in long bones. The surgical treatment of this pathology is often related to high recurrence rates, so novel biological techniques can help to enhance tissue regeneration and bone consolidation. We present a case of a patient with ABC of the calcaneus treated with an endoscopic resection followed by grafting with an autologous-based matrix composed of allograft bone chips and autologous platelet-rich plasma (PRP) in semisolid and liquid states. Patient demonstrated excellent defect filling in both magnetic resonance imaging and radiologic exams and returned to pre-injury activity with no recurrence at 2 years follow-up. Endoscopic curettage together with allograft bone and autologous PRP is effective in treating ABC patients and could be a good adjuvant treatment to prevent reinjury and enhance consolidation.

Characterization of the Protein Corona of Three Chairside Hemoderivatives on Melt Electrowritten Polycaprolactone Scaffolds

In tissue engineering, the relationship between a biomaterial surface and the host's immune response during wound healing is crucial for tissue regeneration. Despite hemoderivative functionalization of biomaterials becoming a common tissue-engineering strategy for enhanced regeneration, the characteristics of the protein-biomaterial interface have not been fully elucidated. This study characterized the interface formed by the adsorbed proteins from various hemoderivatives with pristine and calcium phosphate (CaP)-coated polycaprolactone (PCL) melt electrowritten scaffolds. PCL scaffolds were fabricated by using melt electrospinning writing (MEW). Three hemoderivatives (pure platelet-rich plasma (P-PRP), leucocyte platelet-rich plasma (L-PRP) and injectable platelet-rich fibrin (i-PRF)) and total blood PLASMA (control) were prepared from ovine blood. Hemoderivatives were characterized via SEM/EDX, cross-linking assay, weight loss, pH and protein quantification. The interface between PCL/CaP and hemoderivative was examined via FTIR, XPS and electrophoresis. i-PRF/PCL-CaP (1653 cm^-1), PLASMA/PCL-CaP (1652 cm^-1) and i-PRF/PCL (1651 cm^-1) demonstrated a strong signal at the Amide I region. PLASMA and i-PRF presented similar N1s spectra, with most of the nitrogen involved in N-C=O bonds (≈400 eV). i-PRF resulted in higher adsorption of low molecular weight (LMW) proteins at 60 min, while PLASMA exhibited the lowest adsorption. L-PRP and P-PRP had a similar pattern of protein adsorption. The characteristics of biomaterial interfaces can be customized, thus creating a specific hemoderivative-defined layer on the PCL surface. i-PRF demonstrated a predominant adsorption of LMW proteins. Further investigation of hemoderivative functionalized biomaterials is required to identify the differential protein corona composition, and the resultant immune response and regenerative capacity.

Plasma rich in growth factors versus corticosteroid injections for management of chronic rotator cuff tendinopathy: a prospective double-blind randomized controlled trial with 1 year of follow-up

BACKGROUND

Rotator cuff tendinopathy (RCT) is a painful and dysfunctional shoulder condition traditionally considered as a degenerative pathology. However, evidence is pointing to immunocompetent cells and activated stromal fibroblasts as the drivers of a nonresolved inflammatory condition in RCT. As potent anti-inflammatory agents, corticosteroid injections have been among the first-line and the most common therapeutic strategies. Recently, another adjuvant therapy to treat musculoskeletal inflammation-driven painful conditions, namely, platelet-rich plasma (PRP), has emerged as safe and effective. The aim of this study was to compare the clinical efficacy of intratendinous injections of plasma rich in growth factors (PRGF) with conventional intratendinous corticosteroid injections on patients with chronic RCT using patient-reported outcome measures.

METHODS

A total of 39 patients received PRGF treatment (3 infiltrations, 1 every other week), whereas 40 patients, as a control group, received corticosteroid (3 infiltrations, 1 every other week). Patients were evaluated before treatment and at 3, 6, and 12 months of follow-up using the University of California Los Angeles (UCLA) scale, Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH), and Constant test. The primary outcome of the study was a 15% superior improvement of the PRGF group compared with the corticosteroid group in the UCLA scale and QuickDASH test at 6 months of follow-up, considering this difference to be clinically relevant.

RESULTS

Both PRGF and corticosteroid groups showed significant clinical improvement in the 3 scores at all time points of the study compared with baseline. However, at 6 and 12 months of follow-up, the PRGF group had 22.1% and 21.2% superior improvement of the UCLA test, 14.3% and 13.5% for QuickDASH, and 16.4% and 20.2% for the Constant-Murley test, respectively, compared to the corticosteroid group.

CONCLUSIONS

Three PRGF intratendinous injections every other week in patients with chronic rotator cuff tendinopathy show significantly superior and sustained pain-relieving and functional improvements compared with corticosteroid intratendinous injections assessed by 3 patient-reported outcome scales at 6 and 12 months of follow-up.

Polymeric biomaterials-based tissue engineering for wound healing: a systemic review

Background

Biomaterials are vital products used in clinical sectors as alternatives to several biological macromolecules for tissue engineering techniques owing to their numerous beneficial properties, including wound healing. The healing pattern generally depends upon the type of wounds, and restoration of the skin on damaged areas is greatly dependent on the depth and severity of the injury. The rate of wound healing relies on the type of biomaterials being incorporated for the fabrication of skin substitutes and their stability in in vivo conditions. In this review, a systematic literature search was performed on several databases to identify the most frequently used biomaterials for the development of successful wound healing agents against skin damage, along with their mechanisms of action.

Method

The relevant research articles of the last 5 years were identified, analysed and reviewed in this paper. The meta-analysis was carried out using PRISMA and the search was conducted in major scientific databases. The research of the most recent 5 years, from 2017-2021 was taken into consideration. The collected research papers were inspected thoroughly for further analysis. Recent advances in the utilization of natural and synthetic biomaterials (alone/in combination) to speed up the regeneration rate of injured cells in skin wounds were summarised. Finally, 23 papers were critically reviewed and discussed.

Results

In total, 2022 scholarly articles were retrieved from databases utilizing the aforementioned input methods. After eliminating duplicates and articles published before 2017, ~520 articles remained that were relevant to the topic at hand (biomaterials for wound healing) and could be evaluated for quality. Following different procedures, 23 publications were selected as best fitting for data extraction. Preferred Reporting Items for Systematic Reviews and Meta-Analyses for this review illustrates the selection criteria, such as exclusion and inclusion parameters. The 23 recent publications pointed to the use of both natural and synthetic polymers in wound healing applications. Information related to wound type and the mechanism of action has also been reviewed carefully. The selected publication showed that composites of natural and synthetic polymers were used extensively for both surgical and burn wounds. Extensive research revealed the effects of polymer-based biomaterials in wound healing and their recent advancement.

Conclusions

The effects of biomaterials in wound healing are critically examined in this review. Different biomaterials have been tried to speed up the healing process, however, their success varies with the severity of the wound. However, some of the biomaterials raise questions when applied on a wide scale because of their scarcity, high transportation costs and processing challenges. Therefore, even if a biomaterial has good wound healing qualities, it may be technically unsuitable for use in actual medical scenarios. All of these restrictions have been examined closely in this review.

Advances in the Clinical Application of Platelet-Rich Plasma in the Foot and Ankle: A Review

Autologous and recombinant biologic substances have been generated as a result of the research into the cellular features of the healing process. Orthobiologics are increasingly being used in sports medicine and musculoskeletal surgery. Nevertheless, clinical data are limited; consequently, further studies are required, particularly in foot and ankle pathologies. This review aims to provide evidence of the most recent literature results and ignite the interest of orthopedic specialists eager for an update about the most current discussion on platelet-rich plasma (PRP) clinical applications in the foot and ankle fields. Previous studies have shown that platelet-rich plasma can be beneficial in treating various conditions, such as chronic foot ulcers, osteoarthritis, Achilles tendinopathy, etc. Despite the positive effects of PRP on various musculoskeletal conditions, more prospective studies are needed to confirm its effectiveness at treating ankle and foot pathologies. In addition to clinical trials, other factors, such as the quality of the research and the procedures involved, must be considered before they can be used in patients. More long-term evaluations are needed to support or oppose its application in treating foot and ankle disorders. We present the most extensive review of PRP's clinical applications in the foot and ankle field.

Pure Platelet and Leukocyte-Platelet-Rich Plasma for Regenerative Medicine in Orthopedics-Time- and Preparation-Dependent Release of Growth Factors and Effects on Synovial Fibroblasts: A Comparative Analysis

Intra-articular injections of autologous platelet concentrates are considered capable to enhance the healing of cartilage lesions, alleviate joint inflammation, and relieve other musculoskeletal pathological conditions. The aim of this study was to analyze the soluble fractions obtained from platelet-rich plasma (pure- and leukocyte-PRP) to compare time- and preparation-dependent modifications of growth factor concentrations and the supporting activity of the two preparations on synovial fibroblast growth and hyaluronic acid (HA) production in vitro. The release kinetics of FGF-2, SDF-1, VEGF, HGF, EGF, PD GF-AB/BB, IGF-1, VCAM-1, and TGF-β isoforms were followed up to 168 h after PRP activation, and their amounts were determined by multiplex-beads immunoassay. Synovial cell growth and supernatant HA production were respectively analyzed by Alamar Blue assay and ELISA. Time-dependent modifications grouped molecules in three peculiar patterns: one reaching the highest concentrations within 18 h and decreasing afterwards, another progressively increasing up to 168 h, and the last peaking at the central time points. Synovial fibroblast growth in response to L-PRP and P-PRP revealed differences over time and among added concentrations. Both preparations displayed a preserved supporting capacity of HA synthesis.

Advances in 3D skin bioprinting for wound healing and disease modeling

Even with many advances in design strategies over the past three decades, an enormous gap remains between existing tissue engineering skin and natural skin. Currently available in vitro skin models still cannot replicate the three-dimensionality and heterogeneity of the dermal microenvironment sufficiently to recapitulate many of the known characteristics of skin disorder or disease in vivo. Three-dimensional (3D) bioprinting enables precise control over multiple compositions, spatial distributions and architectural complexity, therefore offering hope for filling the gap of structure and function between natural and artificial skin. Our understanding of wound healing process and skin disease would thus be boosted by the development of in vitro models that could more completely capture the heterogeneous features of skin biology. Here, we provide an overview of recent advances in 3D skin bioprinting, as well as design concepts of cells and bioinks suitable for the bioprinting process. We focus on the applications of this technology for engineering physiological or pathological skin model, focusing more specifically on the function of skin appendages and vasculature. We conclude with current challenges and the technical perspective for further development of 3D skin bioprinting.

Immunomodulatory Blood-Derived Hybrid Hydrogels as Multichannel Microenvironment Modulators for Augmented Bone Regeneration

Autologous blood-derived protein hydrogels have shown great promise in the field of personalized regenerative medicine. However, the inhospitable regenerative microenvironments, especially the unfavorable immune microenvironment, are closely associated with their limited tissue-healing outcomes. Herein, novel immunomodulatory blood-derived hybrid hydrogels (PnP-iPRF) are rationally designed and constructed for enhanced bone regeneration via multichannel regulation of the osteogenic microenvironment. Such double-network hybrid hydrogels are composed of clinically approved injectable platelet-rich fibrin (i-PRF) and polycaprolactone/hydroxyapatite composite nanofibers by using enriched polydopamine (PDA) as the anchor. The polycaprolactone component in PnP-iPRF provides a reinforced structure to stimulate osteoblast differentiation in a proper biomechanical microenvironment. Most importantly, the versatile PDA component in PnP-iPRF can not only offer high adhesion capacity to the growth factors of i-PRF and create a suitable biochemical microenvironment for sustained osteogenesis but also reprogram the osteoimmune microenvironment via the induction of M2 macrophage polarization to promote bone healing. The present study will provide a new paradigm to realize enhanced osteogenic efficacy by multichannel microenvironment regulations and give new insights into engineering high-efficacy i-PRF hydrogels for regenerative medicine.

Platelet-Rich Plasma in acute Achilles tendon ruptures: A systematic review and meta-analysis

BACKGROUND

Platelet Rich Plasma (PRP) is known to exert multi-directional biological effects favouring tendon healing. However, conclusions drawn by numerous studies on its clinical efficacy for acute Achilles tendon rupture are limited. We performed a systematic review and meta-analysis to investigate this and to compare to those without PRP treatment.

METHODS

The Cochrane Controlled Register of Trials, Pubmed, Medline and Embase were used and assessed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) criteria with the following search terms: ('plasma' OR 'platelet-rich' OR 'platelet-rich plasma' or 'PRP') AND ('Achilles tendon rupture/tear' OR 'calcaneal tendon rupture/tear' OR 'tendo calcaneus rupture/tear'). Data pertaining to biomechanical outcomes (heel endurance test, isokinetic strength, calf-circumference and range of motion), patient-reported outcome measures (PROMs) and incidence of re-ruptures were extracted. Meta-analysis was performed for same outcomes measured in at least three studies. Pooled outcome data were analysed by random- and fixed-effects models.

RESULTS

After abstract and full-text screening, 6 studies were included. In total there were 510 patients of which 256 had local PRP injection and 254 without. The average age was 41.6 years, mean time from injury to treatment 5.9 days and mean follow-up at 61 weeks. Biomechanically, there was similar heel endurance, isokinetic strength, calf circumference and range of motion between both groups. In general, there were no differences in patient reported outcomes from all scoring systems used in the studies. Both groups returned to their pre-injured level at a similar time and there were no differences on the incidence of re-rupture (OR 1.13, 95% CI, 0.46-2.80, p = 0.79).

CONCLUSION

PRP injections for acute Achilles tendon ruptures do not improve medium to long-term biomechanical and clinical outcomes. However, future studies incorporating the ideal application and biological composition of PRP are required to investigate its true clinical efficacy.

Functionalizing multi-component bioink with platelet-rich plasma for customized in-situ bilayer bioprinting for wound healing

In-situ three-dimensional (3D) bioprinting has been emerging as a promising technology designed to rapidly seal cutaneous defects according to their contour. Improvements in the formulations of multi-component bioink are needed to support cytocompatible encapsulation and biological functions. Platelet-rich plasma (PRP), as a source of patient-specific autologous growth factors, exhibits capabilities in tissue repair and rejuvenation. This study aimed to prepare PRP-integrated alginate-gelatin (AG) composite hydrogel bioinks and evaluate the biological effects in vitro and in vivo. 3D bioprinted constructs embedded with dermal fibroblasts and epidermal stem cells were fabricated using extrusion strategy. The integration of PRP not only improved the cellular behavior of seeded cells, but regulate the tube formation of vascular endothelial cells and macrophage polarization in a paracrine manner, which obtained an optimal effect at an incorporation concentration of 5%. For in-situ bioprinting, PRP integration accelerated the high-quality wound closure, modulated the inflammation and initiated the angiogenesis compared with the AG bioink. In conclusion, we revealed the regenerative potential of PRP, readily available at the bedside, as an initial signaling provider in multi-component bioink development. Combined with in-situ printing technology, it is expected to accelerate the clinical translation of rapid individualized wound repair.

Reconstruction of Chronic Proximal Hamstring Tear: A Novel Surgical Technique with Semitendinosus Tendon Allograft Assisted with Autologous Plasma Rich in Growth Factors (PRGF)

The reconstruction of a chronic proximal hamstring tear is a challenging pathology that posits difficulties to surgeons due to the distal retraction of the hamstring tendon stumps and the entrapment of the sciatic nerve within the scar formed around the torn hamstring tendon. We describe a novel surgical technique using a semitendinosus tendon allograft sutured in a “V inversion” manner, thereby avoiding an excess of tension and length of the new reconstructed hamstring tendons. In addition, and in order to speed up the healing process and avoid new sciatic entrapment, we assisted the surgery with liquid plasma rich in growth factors (PRGF) injected intraosseously, intratendinously and within the suture areas, as well as wrapping the sciatic nerve with a PRGF membrane. In conclusion, this novel approach offers mechanical and biological advantages to tackle the large retraction of hamstring stumps and the entrapment of the sciatic nerve within the scar.

Evolutionary Insight into Immunothrombosis as a Healing Mechanism

Both invertebrates and vertebrates possess a cluster of immediate and local wound-sealing, pathogen-killing, and tissue healing responses known as immunoclotting and immunothrombosis, respectively, to cope with two life-threatening emergencies, namely, bleeding and microbial invasion. Despite their convergence in function, immunoclotting and immunothrombosis are deployed by different blood cells and intravascular multidomain proteins. In vertebrates, these proteins share some domains with intrinsic chemical affinities useful in generating cooperative networks such as pathogen and damage pattern recognition molecules. Moreover, many of the proteins involved in coagulation and fibrinolysis in humans are multifunctional molecules playing roles in other processes from inflammation to healing and beyond. In our modern society, however, the interaction of activated intravascular allosteric proteins with one another and with blood cells entails vulnerabilities posing a biological paradox: intravascular proteins that locally operate as tissue repair enhancers can nevertheless generate pathogenic processes by acting systemically. In this manuscript, we contextualize and frame the coagulation system and hemostasis through an evolutionary time scale, illustrating their role as dual players in the defense against exsanguination and pathogens while significantly influencing wound healing.

High-Throughput Proteomic Analysis of Human Dermal Fibroblast Response to Different Blood Derivatives: Autologous Topical Serum Derived from Plasma Rich in Growth Factors (PRGF) versus Leukocyte- and Platelet-Rich Plasma (L-PRP)

Platelet-rich plasma (PRP) is nowadays used in the treatment of different types of cutaneous lesions. However, different compositions can influence clinical outcomes. Among them, the inclusion of leukocytes is controversial. High-throughput proteomics techniques were used to analyze the proteins that are differentially expressed in human dermal fibroblasts (HDFs) after treatment for 24 h with two PRP types, autologous topical serum (Endoret serum—ES) derived from plasma rich in growth factors (PRGF) and leukocyte- and platelet-rich plasma (L-PRP). The identified proteins were then classified by both Gene Ontology and Ingenuity Pathway Analysis. The obtained results show that the compositions of ES and L-PRP differ in such a way that they induce different responses in HDFs. ES-treated HDFs overexpress growth factor-related proteins, leading to protein synthesis, cell proliferation and migration. By contrast, L-PRP treatment induces a response similar to that caused by proinflammatory molecules. These data could explain the contradictory clinical results obtained for the different types of PRP, especially with respect to their leukocyte contents.

Advances in Fibrin-Based Materials in Wound Repair: A Review

The first bioprocess that occurs in response to wounding is the deterrence of local hemorrhage. This is accomplished by platelet aggregation and initiation of the hemostasis cascade. The resulting blood clot immediately enables the cessation of bleeding and then functions as a provisional matrix for wound healing, which begins a few days after injury. Here, fibrinogen and fibrin fibers are the key players, because they literally serve as scaffolds for tissue regeneration and promote the migration of cells, as well as the ingrowth of tissues. Fibrin is also an important modulator of healing and a host defense system against microbes that effectively maintains incoming leukocytes and acts as reservoir for growth factors. This review presents recent advances in the understanding and applications of fibrin and fibrin-fiber-incorporated biomedical materials applied to wound healing and subsequent tissue repair. It also discusses how fibrin-based materials function through several wound healing stages including physical barrier formation, the entrapment of bacteria, drug and cell delivery, and eventual degradation. Pure fibrin is not mechanically strong and stable enough to act as a singular wound repair material. To alleviate this problem, this paper will demonstrate recent advances in the modification of fibrin with next-generation materials exhibiting enhanced stability and medical efficacy, along with a detailed look at the mechanical properties of fibrin and fibrin-laden materials. Specifically, fibrin-based nanocomposites and their role in wound repair, sustained drug release, cell delivery to wound sites, skin reconstruction, and biomedical applications of drug-loaded fibrin-based materials will be demonstrated and discussed.

Biomaterial scaffolds for clinical procedures in endodontic regeneration

Regenerative endodontic procedures have been rapidly evolving over the past two decades and are employed extensively in clinical endodontics. These procedures have been perceived as valuable adjuvants to conventional strategies in the treatment of necrotic immature permanent teeth that were deemed to have poor prognosis. As a component biological triad of tissue engineering (i.e., stem cells, growth factors and scaffolds), biomaterial scaffolds have demonstrated clinical potential as an armamentarium in regenerative endodontic procedures and achieved remarkable advancements. The aim of the present review is to provide a broad overview of biomaterials employed for scaffolding in regenerative endodontics. The favorable properties and limitations of biomaterials organized in naturally derived, host-derived and synthetic material categories were discussed. Preclinical and clinical studies published over the past five years on the performance of biomaterial scaffolds, as well as current challenges and future perspectives for the application of biomaterials for scaffolding and clinical evaluation of biomaterial scaffolds in regenerative endodontic procedures were addressed in depth.

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Overview of biomaterials for scaffolding in regenerative endodontics are presented.

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Findings of preclinical and clinical studies on the performance of biomaterial scaffolds are summarized.

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Challenges and future prospects in biomaterial scaffolds are discussed.

Reinforced Blood-Derived Protein Hydrogels Enable Dual-Level Regulation of Bio-Physiochemical Microenvironments for Personalized Bone Regeneration with Remarkable Enhanced Efficacy

Physiological microenvironment engineering has shown great promise in combating a variety of diseases. Herein, we present the rational design of reinforced and injectable blood-derived protein hydrogels (PDA@SiO₂-PRF) composed of platelet-rich fibrin (PRF), polydopamine (PDA), and SiO₂ nanofibers that can act as dual-level regulators to engineer the microenvironment for personalized bone regeneration with high efficacy. From the biophysical level, PDA@SiO₂-PRF with high stiffness can withstand the external loading and maintaining the space for bone regeneration in bone defects. Particularly, the reinforced structure of PDA@SiO₂-PRF provides bone extracellular matrix (ECM)-like functions to stimulate osteoblast differentiation via Yes-associated protein (YAP) signaling pathway. From the biochemical level, the PDA component in PDA@SiO₂-PRF hinders the fast degradation of PRF to release autologous growth factors in a sustained manner, providing sustained osteogenesis capacity. Overall, the present study offers a dual-level strategy for personalized bone regeneration by engineering the biophysiochemical microenvironment to realize enhanced osteogenesis efficacy.

Preparation and Characterization of Plasma-Derived Fibrin Hydrogels Modified by Alginate di-Aldehyde

Fibrin hydrogels are one of the most popular scaffolds used in tissue engineering due to their excellent biological properties. Special attention should be paid to the use of human plasma-derived fibrin hydrogels as a 3D scaffold in the production of autologous skin grafts, skeletal muscle regeneration and bone tissue repair. However, mechanical weakness and rapid degradation, which causes plasma-derived fibrin matrices to shrink significantly, prompted us to improve their stability. In our study, plasma-derived fibrin was chemically bonded to oxidized alginate (alginate di-aldehyde, ADA) at 10%, 20%, 50% and 80% oxidation, by Schiff base formation, to produce natural hydrogels for tissue engineering applications. First, gelling time studies showed that the degree of ADA oxidation inhibits fibrin polymerization, which we associate with fiber increment and decreased fiber density; moreover, the storage modulus increased when increasing the final volume of CaCl₂ (1% w/v) from 80 µL to 200 µL per milliliter of hydrogel. The contraction was similar in matrices with and without human primary fibroblasts (hFBs). In addition, proliferation studies with encapsulated hFBs showed an increment in cell viability in hydrogels with ADA at 10% oxidation at days 1 and 3 with 80 µL of CaCl₂; by increasing this compound (CaCl₂), the proliferation does not significantly increase until day 7. In the presence of 10% alginate oxidation, the proliferation results are similar to the control, in contrast to the sample with 20% oxidation whose proliferation decreases. Finally, the viability studies showed that the hFB morphology was maintained regardless of the degree of oxidation used; however, the quantity of CaCl₂ influences the spread of the hFBs.

Fibrin-based factor delivery for therapeutic angiogenesis: friend or foe?

Therapeutic angiogenesis aims at promoting the growth of blood vessels to restore perfusion in ischemic tissues or aid tissue regeneration. Vascular endothelial growth factor (VEGF) is the master regulator of angiogenesis in development, repair, and disease. However, exploiting VEGF for therapeutic purposes has been challenging and needs to take into account some key aspects of VEGF biology. In particular, the spatial localization of angiogenic signals within the extracellular matrix is crucial for physiological assembly and function of new blood vessels. Fibrin is the provisional matrix that is universally deposited immediately after injury and supports the initial steps of tissue regeneration. It provides therefore several ideal features as a substrate to promote therapeutic vascularization, especially through its ability to present growth factors in their physiological matrix-bound state and to modulate their availability for signaling. Here, we provide an overview of fibrin uses as a tissue-engineering scaffold material and as a tunable platform to finely control dose and duration of delivery of recombinant factors in therapeutic angiogenesis. However, in some cases, fibrin has also been associated with undesirable outcomes, namely the promotion of fibrosis and scar formation that actually prevent physiological tissue regeneration. Understanding the mechanisms that tip the balance between the pro- and anti-regenerative functions of fibrin will be the key to fully exploit its therapeutic potential.

Platelets' Role in Dentistry: From Oral Pathology to Regenerative Potential

Platelets are a cellular subgroup of elements circulating in the bloodstream, responsible for the innate immunity and repairing processes. The diseases affecting this cellular population, depending on the degree, can vary from mild to severe conditions, which have to be taken into consideration in cases of minor dental procedures. Their secretion of growth factors made them useful in the regenerative intervention. The aim of this review is to examine the platelets from biological, examining the biogenesis of the platelets and the biological role in the inflammatory and reparative processes and clinical point of view, through the platelets' pathology and their use as platelets concentrates in dental regenerative surgery.

Plasma Rich in Growth Factors in Macular Hole Surgery

The aim of this study was to evaluate the use of PRGF (plasma rich in growth factors) as an adjuvant to PPV (pars plana vitrectomy) in recurrent, persistent, or poor prognosis MH (macular hole). Patients with MH were treated with PPV plus adjuvant therapy (PRGF membrane (mPRGF) and injectable liquid PRGF (iPRGF)). The anatomical closure of MH and postoperative BCVA (best-corrected visual acuity) were evaluated. Eight eyes (eight patients) were evaluated: myopic MH (MMH, n = 4), idiopathic MH (IMH, n = 2), iatrogenic n = 1, traumatic n = 1. The mean age was 53.1 ± 19.3 years. Hence, 66.7% (n = 4) of patients previously had internal limiting membrane peeling. Five patients (62.5%) received mPRGF and iPRGF, and three patients (37.5%) received iPRGF. Gas tamponade (C3F8) was placed in seven cases and one case of silicone oil. Anatomic closure of MH was achieved in seven eyes (87.5%) and BCVA improved in six cases. In the MMH group, visual acuity improved in two lines of vision. Follow-up time was 27.2 ± 9.0 months. No adverse events or MH recurrences were recorded during follow-up. The use of PRGF as an adjuvant therapy to PPV can be useful to improve anatomical closure and visual acuity in MH surgery.

Extracellular Matrix-Based Conductive Interpenetrating Network Hydrogels with Enhanced Neurovascular Regeneration Properties for Diabetic Wounds Repair

The critical effects that impair diabetic wound healing are characterized by poor vascularization and severe peripheral neuropathy. Current management strategies for diabetic wound healing are unsatisfactory, due to the paucity of neurovascular regeneration at the wound site. Importantly, conductivity in skin tissue is reported to be essential for modulating myriad biological processes especially vascular and nerve regeneration. Herein, an extracellular matrix (ECM)-based conductive dressing is synthesized from an interpenetrating polymer network hydrogel composed of gelatin methacryloyl, oxidized chondroitin sulfate (OCS), and OCS-polypyrrole conductive nanoparticles that can promote diabetic wound repairing by enhancing local neurovascular regeneration. The conductive hydrogels combine the advantageous features of water-swollen hydrogels with conductive polymers (CPs) to provide tissue-matching electrical conductivity and mechanical properties for neurovascular regeneration. In vitro and in vivo studies show that the conductive hydrogel can promote neurovascular regeneration by increasing intracellular Ca²⁺ concentration, which subsequently promotes phosphorylation of proteins in the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathways. Furthermore, the conductive hydrogel stimulates full-thickness diabetic wound repair on day 14 by promoting local neurovascular regeneration and collagen deposition. These findings corroborate that the ECM-based conductive interpenetrating network hydrogel dressing significantly promotes wound repairing due to its neurovascular regeneration properties, suggesting that they are suitable candidates for diabetic wound repair.

Membrane of Plasma Rich in Growth Factors in Primary Pterygium Surgery Compared to Amniotic Membrane Transplantation and Conjunctival Autograft

This prospective and comparative study aimed to compare the use of a conjunctival autograft (CAG), plasma rich in growth factors fibrin membrane (mPRGF) or amniotic membrane transplantation (AMT) in primary pterygium surgery. Patients were assigned for surgery with CAG (group A), mPRGF (group B), or AMT (group C). Pterygium recurrence, Best Corrected Visual Acuity (BCVA), graft size (measured with anterior segment optical coherence tomography (AS-OCT)), and ocular surface symptoms (visual analogue scale (VAS) and ocular surface disease index (OSDI)) were evaluated. Thirteen eyes in group A, 26 in group B, and 10 in group C were evaluated. No changes in BCVA (p > 0.05) were found. Recurrence cases for groups A, B, and C were none, two, and two, respectively, and three cases of pyogenic granulomas in group A. The horizontal/vertical graft size was lower in group B vs group A (p < 0.05) from months 1 to 12. The improvement in VAS frequency for groups A, B, and C was: 35.5%, 86.2%, and 39.1%, respectively. The OSDI scale reduction for groups A, B, and C was: 12.7%, 39.0%, and 84.1%. The use of the three surgical techniques as a graft for primary pterygium surgery was safe and effective, showing similar results. The mPRGF graft represents an autologous novel approach for pterygium surgery.

Culture and Differentiation of Human Umbilical Cord-Derived Mesenchymal Stem Cells on Growth Factor-Rich Fibrin Scaffolds to Produce Engineered Cartilages

INTRODUCTION

After injuries, the cartilage healing capacity is limited owing to its nature as a particular connective tissue without blood vessels, lymphatics, or nerves. The creation of artificial cartilage tissue mimics the biological properties of native cartilage and can reduce the need for donated tissue. Fibrin is a type of biodegradable scaffold that has great potential in tissue engineering applications. It can become good material for cell adhesion and proliferation in vitro. Therefore, this study aimed to create a cartilage tissue in vitro using umbilical cord-derived mesenchymal stem cells (UCMSC) and growth factor-rich fibrin (GRF) scaffolds.

METHODS

UCMSCs were isolated and expanded, and platelet-rich plasma (PRP) preparations were performed following previously published protocols. PRP was activated (aPRP) by a 0.45-μm syringe filter to release growth factors inside the platelets. Each 2.105 of the UCMSCs were suspended in 2 ml of aPRP to make the mixture of MSC and PRP (MSC-PRP). Then, Ca2+ solution was added to this mixture to produce the fibril scaffold with UCMSCs inside. UCMSCs' adhesion and proliferation inside the scaffold were evaluated by observation under inverted microscopy, H-E staining, MTT assays, and scanning electron microscopy (SEM). The fibril structure containing UCMSCs was cultured, and chondrogenesis was induced using commercial chondrogenesis media for 21 days (iMSC-GRF). The differentiation in efficacy toward cartilage was evaluated based on the accumulation of aggrecan (acan), glycosaminoglycans (GAGs), and collagen type II (Col II).

RESULTS

The results showed that we successfully created a cartilage tissue with some characteristics that mimic the properties of natural cartilage. The engineered cartilage tissue was positive with some cartilage protein, such as acan, GAG, and Coll II. In vitro cartilage presented some natural chondrocyte-like cells. The artificial cartilage tissue was positive for CD14, CD34, CD90, CD105, and HLA-DR and negative for CD44, CD45, and CD73.

CONCLUSION

These results showed that using UCMSCs and growth factor-rich fibril from platelet-rich plasma was feasible to produce engineered cartilage tissue for further experiments or clinical usage.

Healing through the lens of immunothrombosis: Biology-inspired, evolution-tailored, and human-engineered biomimetic therapies

Evolution, from invertebrates to mammals, has yielded and shaped immunoclotting as a defense and repair response against trauma and infection. This mosaic of immediate and local wound-sealing and pathogen-killing mechanisms results in survival, restoration of homeostasis, and tissue repair. In mammals, immunoclotting has been complemented with the neuroendocrine system, platelets, and contact system among other embellishments, adding layers of complexity through interconnecting blood-born proteolytic cascades, blood cells, and the neuroendocrine system. In doing so, immunothrombosis endows humans with survival advantages, but entails vulnerabilities in the current unprecedented and increasingly challenging environment. Immunothrombosis and tissue repair appear to go hand in hand with common mechanisms mediating both processes, a fact that is underlined by recent advances that are deciphering the mechanisms of the repair process and of the biochemical pathways that underpins coagulation, hemostasis and thrombosis. This review is intended to frame both the universal aspects of tissue repair and the therapeutic use of autologous fibrin matrix as a biology-as-a-drug approach in the context of the evolutionary changes in coagulation and hemostasis. In addition, we will try to shed some light on the molecular mechanisms underlying the use of the autologous fibrin matrix as a biology-inspired, evolution-tailored, and human-engineered biomimetic therapy.

Encapsulation of lyophilized platelet-rich fibrin in alginate-hyaluronic acid hydrogel as a novel vascularized substitution for myocardial infarction

Cardiovascular diseases such as myocardial infarction (MI) are among the major causes of death worldwide. Although intramyocardial injection of hydrogels can effectively enhance the ventricular wall, this approach is limited because of its restriction to the poor vascularization in the infarcted myocardium. Here, we reported a new type of hydrogel composed of alginate (ALG) and hyaluronic acid (HA) with lyophilized platelet-rich fibrin (Ly-PRF) for releasing abundant growth factors to realize their respective functions. The results of in vitro studies demonstrated favorable mechanical property and release ability of ALG-HA with Ly-PRF. When injected into the infarcted myocardium, this composite hydrogel preserved heart function and the Ly-PRF within the hydrogel promoted angiogenesis and increased vascular density in both infarcted and border zone, which rescued the ischemic myocardium. These beneficial effects were also accompanied by macrophage polarization and regulation of myocardial fibrosis. Moreover, the autologous origin of Ly-PRF with ALG-HA hydrogel offers myriad advantages including safety profile, easiness to obtain and cost-effectiveness. Overall, this study demonstrated the versatile therapeutic effects of a novel composite hydrogel ALG-HA with Ly-PRF, which optimizes a promising vascularized substitution strategy for improving cardiac function after MI.

The effectiveness of spatially cross-linked polymer in the postoperative epidural fibrosis prevention: an experimental study

Introduction. Epidural fibrosis is an urgent problem in modern spinal surgery and orthopedics. The formation of connective tissue in the epidural space after performing surgical interventions on the spinal column inevitably leads to adhesion of the latter to the dura mater and compression of neural structures, followed by the formation of clinical and neurological symptoms. The  search for literary sources in domestic and foreign scientific databases has demonstrated the presence of several works studying the effectiveness of barrier methods for preventing the development of epidural fibrosis. It should be noted that the results of these studies are ambiguous and largely contradictory.

The purpose was to study the effectiveness of using a spatially cross-linked polymer in the postoperative lumbar epidural fibrosis prevention in an experiment.

Materials and methods. The study included 26 male Wistar rats (average body weight 338.5±9.07 g), which were divided into two groups: Group I (control, n = 12): animals underwent laminectomy at the level of vertebral bodies LVII – SI  without application of spatially crosslinked polymer; Group II (experimental, n = 14): animals underwent laminectomy at the level of vertebral bodies LVII – SI  followed by application of a spatially cross-linked polymer to the dura mater. The morphological and instrumental parameters were studied.

Results. Significant differences were noted in the severity of epidural fibrosis (χ2 = 14.846, p = 0.003), the number of newly formed vessels (F = 14.371, p<0.001), the number of fibroblasts (F = 11.158, p<0.001), as well as in the severity of vertebral stenosis channe l according to multislice computed tomography (χ2 = 17.207, p=0.002) between the control and experimental groups of animals.

Conclusion. Application of a spatially cross-linked polymer to the dura mater is an effective way to prevent the development of postoperative epidural fibrosis.

Progress in the use of plasma rich in growth factors in ophthalmology: from ocular surface to ocular fundus

Introduction: The use of blood derivatives and especially Plasma rich in growth factors (PRGF), for regenerative purposes has been a common trend along the last decades in the field of oral surgery, dermatology, orthopedics, and more recently in ophthalmology.Areas covered: PRGF is a type of platelet-rich plasma that is being explored for the treatment of ocular injuries. The present review article highlights 50 ophthalmology-related publications about the application of PRGF in the treatment of acute and chronic pathologies in ophthalmology as well as most relevant challenges and future prospects.Expert opinion: PRGF technology provides a wide range of formulations that can be used therapeutically in many different acute and chronic ocular pathologies. In addition to eye drops enriched with autologous growth factors, PRGF enables the preparation of both immunologically safe and fibrin-based formulations. Recent advances in the field have promoted PRGF storage for 12 months under freezing conditions, its daily use for 7 days at room temperature and the freeze-dried formulation. The thermally treated immunosafe formulation has shown promising clinical results for the treatment of several diseases such as Sjögren syndrome, graft versus host disease or cicatrizing conjunctivitis. In addition, several fibrin formulations have been preclinically evaluated and clinically incorporated as an adjuvant to ocular surface or glaucoma surgeries, dermal fat graft procedures, limbal stem cell expansion and retinal surgeries. The present review explores the latest scientific and clinical data, current challenges, and main prospects of this technology for the treatment of several ocular injuries.

Development of Vancomycin Delivery Systems Based on Autologous 3D Platelet-Rich Fibrin Matrices for Bone Tissue Engineering

Autologous platelet-rich fibrin (PRF) is derived from the blood and its use in the bone tissue engineering has emerged as an effective strategy for novel drug and growth factor delivery systems. Studies have approved that combined therapy with PRF ensures higher biological outcomes, but patients still undergo additional treatment with antibiotic drugs before, during, and even after the implantation of biomaterials with PRF. These systematically used drugs spread throughout the blood and lead not only to positive effects but may also induce adverse side effects on healthy tissues. Vancomycin hydrochloride (VANKA) is used to treat severe Staphylococcal infections but its absorption in the target tissue after oral administration is low; therefore, in this study, we have developed and analyzed two kinds of VANKA carriers—liposomes and microparticles in 3D PRF matrices. The adjustment, characterization, and analysis of VANKA carriers in 3D PRF scaffolds is carried out in terms of encapsulation efficiency, drug release kinetics and antibacterial activity; furthermore, we have studied the micro- and macrostructure of the scaffolds with microtomography.

Efficacy and safety of plasma gel versus platelet-rich plasma in periorbital rejuvenation: a comparative split-face clinical and Antera 3D camera study

BACKGROUND

Periorbital skin is the thinnest. That is why, it is the easiest to wrinkle and the most challenging to rejuvenate. Platelet-rich plasma (PRP) as well as plasma gel have been used for skin rejuvenation and considered relatively safe and effective.

METHODS

This split-face study was conducted on forty female patients seeking periorbital rejuvenation where PRP was injected in the right (Rt) side and plasma gel in the left (Lt) side, two treatment sessions 4 weeks apart (week 0 and week 4). Patients were followed up 2 weeks after each treatment session (week 2 and week 6) as well as 12 weeks after the last session (week 16) using both subjective [physician assessment through Global Aesthetic Improvement score (GAIS) and patient's satisfaction (Likert scale)] and objective [Antera 3D camera] assessment methods.

RESULTS

Both modalities yielded a significant improvement of periorbital wrinkles after the 2nd session, with significantly better results on the plasma gel injected side; however, the improvement achieved through both modalities could not be maintained for the following 3 months. Besides, objective assessment could not prove any improvement in periorbital hyperpigmentation.

CONCLUSION

Two sessions of both PRP and plasma gel are effective for periorbital rejuvenation, with plasma gel showing significantly better results. However, improvement was not maintained for 3 months.

Novel applications of platelet concentrates in tissue regeneration (Review)

Numerous studies have explored the suitability of biocompatible materials in regenerative medicine. Platelet concentrates are derived from centrifuged blood and are named according to their biological characteristics, such as platelet-rich plasma, platelet-rich fibrin and concentrated growth factor. Platelet concentrates have gained considerable attention in soft and hard tissue engineering. Indeed, multiple components of autologous platelet concentrates, such as growth factors, fibrin matrix and platelets, serve essential roles in wound healing. Current studies are focused on cutting-edge strategies to meet the requirements for tissue restoration by improving the properties of autologous platelet concentrates. In the present review, applications of platelet concentrates for tissue engineering are discussed, presenting a selection of recent advances and novel protocols. In addition, several aspects of these strategies, such as the advantages of lyophilized platelet concentrates and the combination of platelet concentrates with biomaterials, stem cells or drugs are discussed. The present review aims to summarize novel strategies using platelet concentrates to improve the outcomes of wound healing.

Platelet-Rich Plasma Applications for Achilles Tendon Repair: A Bridge between Biology and Surgery

Achilles tendon ruptures are very common tendon ruptures and their incidence is increasing in modern society, resulting in work incapacity and months off sport, which generate a need for accelerated and successful therapeutic repair strategy. Platelet-rich plasma (PRP) is emerging as adjuvant human blood-derived constructs to assist Achilles tendon rupture treatment. However, myriad PRP preparation methods in conjunction with poor standardization in the modalities of their applications impinge on the consistent effectiveness of clinical and structural outcomes regarding their therapeutic efficacy. The purpose of this review is to provide some light on the application of PRP for Achilles tendon ruptures. PRP has many characteristics that make it an attractive treatment. Elements such as the inclusion of leukocytes and erythrocytes within PRP, the absence of activation and activation ex vivo or in vivo, the modality of application, and the adjustment of PRP pH can influence the biology of the applied product and result in misleading therapeutic conclusions. The weakest points in demonstrating their consistent effectiveness are primarily the result of myriad PRP preparation methods and the poor standardization of modalities for their application. Selecting the right biological scaffold and applying it correctly to restitutio ad integrum of ruptured Achilles tendons remains a daunting and complex task.

Natural-Based Hydrogels for Tissue Engineering Applications

In the field of tissue engineering and regenerative medicine, hydrogels are used as biomaterials to support cell attachment and promote tissue regeneration due to their unique biomimetic characteristics. The use of natural-origin materials significantly influenced the origin and progress of the field due to their ability to mimic the native tissues' extracellular matrix and biocompatibility. However, the majority of these natural materials failed to provide satisfactory cues to guide cell differentiation toward the formation of new tissues. In addition, the integration of technological advances, such as 3D printing, microfluidics and nanotechnology, in tissue engineering has obsoleted the first generation of natural-origin hydrogels. During the last decade, a new generation of hydrogels has emerged to meet the specific tissue necessities, to be used with state-of-the-art techniques and to capitalize the intrinsic characteristics of natural-based materials. In this review, we briefly examine important hydrogel crosslinking mechanisms. Then, the latest developments in engineering natural-based hydrogels are investigated and major applications in the field of tissue engineering and regenerative medicine are highlighted. Finally, the current limitations, future challenges and opportunities in this field are discussed to encourage realistic developments for the clinical translation of tissue engineering strategies.