Platelet-Therapeutics to Improve Tissue Regeneration and Wound Healing-Physiological Background and Methods of Preparation

Platelet-Rich Plasma in Dermatology: New Insights on the Cellular Mechanism of Skin Repair and Regeneration

The skin's recognised functions may undergo physiological alterations due to ageing, manifesting as varying degrees of facial wrinkles, diminished tautness, density, and volume. Additionally, these functions can be disrupted (patho)physiologically through various physical and chemical injuries, including surgical trauma, accidents, or chronic conditions like ulcers associated with diabetes mellitus, venous insufficiency, or obesity. Advancements in therapeutic interventions that boost the skin's innate regenerative abilities could significantly enhance patient care protocols. The application of Platelet-Rich Plasma (PRP) is widely recognized for its aesthetic and functional benefits to the skin. Yet, the endorsement of PRP's advantages often borders on the dogmatic, with its efficacy commonly ascribed solely to the activation of fibroblasts by the factors contained within platelet granules. PRP therapy is a cornerstone of regenerative medicine which involves the autologous delivery of conditioned plasma enriched by platelets. This is achieved by centrifugation, removing erythrocytes while retaining platelets and their granules. Despite its widespread use, the precise sequences of cellular activation, the specific cellular players, and the molecular machinery that drive PRP-facilitated healing are still enigmatic. There is still a paucity of definitive and robust studies elucidating these mechanisms. In recent years, telocytes (TCs)-a unique dermal cell population-have shown promising potential for tissue regeneration in various organs, including the dermis. TCs' participation in neo-angiogenesis, akin to that attributed to PRP, and their role in tissue remodelling and repair processes within the interstitia of several organs (including the dermis), offer intriguing insights. Their potential to contribute to, or possibly orchestrate, the skin regeneration process following PRP treatment has elicited considerable interest. Therefore, pursuing a comprehensive understanding of the cellular and molecular mechanisms at work, particularly those involving TCs, their temporal involvement in structural recovery following injury, and the interconnected biological events in skin wound healing and regeneration represents a compelling field of study.

Comprehensive characterization of pathogenic synovial fluid extracellular vesicles from knee osteoarthritis

Synovial fluid (SF) extracellular vesicles (EVs) play a pathogenic role in osteoarthritis (OA). However, the surface markers, cell and tissue origins, and effectors of these EVs are largely unknown. We found that SF EVs contained 692 peptides that were positively associated with knee radiographic OA severity; 57.4% of these pathogenic peptides were from 46 proteins of the immune system, predominantly the innate immune system. CSPG4, BGN, NRP1, and CD109 are the major surface markers of pathogenic SF EVs. Genes encoding surface marker CSPG4 and CD109 were highly expressed by chondrocytes from damaged cartilage, while VISG4, MARCO, CD163 and NRP1 were enriched in the synovial immune cells. The frequency of CSPG4+ and VSIG4+ EV subpopulations in OA SF was high. We conclude that pathogenic SF EVs carry knee OA severity-associated proteins and specific surface markers, which could be developed as a new source of diagnostic biomarkers or therapeutic targets in OA.

Supernatant of activated platelet-rich plasma rejuvenated aging-induced hyposalivation in mouse

Hyposalivation is a common complaint among the elderly, but no established treatment prevents age-induced hyposalivation. Platelet derivatives such as platelet-rich plasma (PRP), platelet-rich fibrin (PRF), and plasma rich in growth factor (PRGF), are used widely in different areas of regenerative medicine to enhance the wound healing processes. This study examined whether the local injection of the supernatant of activated PRP (saPRP) into the salivary gland (SG) could help prevent aging-induced SG dysfunction and explored the mechanisms responsible for the protective effects on the SG hypofunction. The platelets were separated from the blood of male SD rats (220 ± 20 g). saPRP was manufactured by removing the fibrin clot after activating platelet with calcium ionophore 10 μM (A23187). The total protein and TGF-β1 levels were significantly higher in saPRP than in PRP. Human salivary gland epithelial cell(hSGEC) was treated with saPRP or PRP after senescence through irradiation. The significant proliferation of hSGEC was observed in saPRP treated group compared to irradiation only group and irradiation + PRP group. Cellular senescence, apoptosis, and inflammation significantly reduced in saPRP group. The SG function and structural tissue remodeling by the saPRP were investigated with naturally aged mice. The mice were divided into three groups: 3 months old (3 M), 22 months old (22 M), and 22 months old treated with saPRP (22 M + saPRP). Salivary flow rate and lag time were significantly improved in 22 M + saPRP group compared to 22 M group. The histologic examinations showed the significant proliferation of acinar cell in 22 M + saPRP group. The decrease of senescence, apoptosis, and inflammation observed by western blot in 22 M + saPRP group. The saPRP induced the proliferation of hSGECs, leading to a significant decrease in cellular senescence via decrease inflammation and apoptosis, in vitro. Moreover, the acini cells of the salivary gland were regenerated, and the salivary function increased in aged mice. These results showed that saPRP could be a treatment agent against aging-induced SG dysfunction.

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.

Autologous platelet-rich fibrin promotes wound healing in cats

Street cats commonly present large skin wounds that pose significant challenges in veterinary practice. Platelet-rich fibrin (PRF) is a second-generation platelet concentrate increasingly used in humans to promote wound healing. Ease of use and clinical success in humans has prompted interest in using PRF in veterinary practice. However, until now, there is no reported study on the use of autologous PRF in feline wound management. This study evaluated the effect of application of autologous PRF in cats with naturally occurring cutaneous wounds. 16 cats with full-thickness cutaneous acute/subacute wounds were randomly allocated to PRF or Control (standard care) groups. Each cat was enrolled for 2 weeks. PRF was prepared according to previously described procedures. PRF was applied on Days 1 and 4 in addition to standard wound care. Wound size was measured using tracing planimetry. Wound surface area was calculated using SketchAndCalc^™ software on scanned tracing images. Average wound sizes at enrolment were 8.39 cm² (Control) (standard deviation (SD) 5.08 cm²) and 9.18 cm² (PRF) (SD 3.71 cm²) (range 2.42-15.97 cm²). By Day 14, the mean wound size for the Control group was 2.17 cm² (SD 1.52 cm²) and for the PRF was 0.62 cm² (SD 0.44 cm²) (p = 0.015). At Day 14, the PRF group showed mean 93.85% wound contraction with SD 3.66, while the control group showed mean 76.23% wound contraction with SD 5.30 (p = <0.0001). Based on the results, PRF could be further investigated to promote wound healing in cats as a low-risk and convenient adjunctive therapy.

A case series of autologous platelet-rich plasma injection in treating chronic ulcers conducted in Saudi Arabia

Objective

This is a case series study of 14 cases of chronic unhealed ulcers involving patients of 19-85 years, aimed to demonstrate the positive therapeutic outcomes of using autologous platelet rich plasma (PRP) in diabetic foot ulcer (DFU) and other chronic wound healing.

Methods

This is a formal consecutive clinical case series. Patients with chronic unhealed ulcers were enrolled from the amputation prevention clinic by an interdisciplinary team includes podiatrist, general surgeon, orthopedic, vascular surgeon, and wound care nurses at Kahel Specialized Centre, a specialized center for managing foot and ankle diseases, located in Riyadh, Saudi Arabia. Those patients who presented with chronic wounds and showed no significant wound reduction despite following the standard wound care protocol were included in the study. There were no specific predetermined exclusion criteria when considering patients for treatment with this modality.

Results

In this case series, majority (80%) of the patients were above 50 years of age, and 10 (66.7%) patients were male and 5 (33.3%) were female. Of all the cases presented to the amputation prevention clinic, majority (73.3%) reported suffering from type 2 diabetes mellitus (DM) and also, one reported type 1 DM [6.7%]). All the cases of DFU received a combination of hydrogel and autologous PRP treatment and were put of suitable offloading devices, except one case received a combination of Cadexomer iodine, hydrogel and PRP treatment. In the present case series involving 3-14 weeks of the treatment duration, only 2-3 doses of autologous PRP provided complete healing and or maximum wound closure.

Conclusion

Autologous PRP therapy is efficacious in facilitating, enhancing wound healing and aids in complete wound closure. This case series was limited in term of the sample size which is the number patients enrolled for the study, hence, the study finding remain inconclusive to some extent and hence, further study is required with greater number of sample size. The strength of this study is that it is the first study in Saudi Arabia and gulf region, to report the beneficial effect of PRP in chronic unhealed ulcers including diabetic ulcers.

Skin cell-derived extracellular vesicles: a promising therapeutic strategy for cutaneous injury

Wound healing refers to the healing process that occurs after the skin and other tissues are separated or damaged by internal or external forces. It is a complex combination of tissue regeneration, granulation tissue hyperplasia, and scar formation, and shows the synergistic effects of these processes. After skin damage, the environment around the wound and the cells at site of the damage respond immediately, and a range of cytokines and growth factors are released. In cutaneous injury, extracellular vesicle (EV) signaling plays a vital role in the healing process via paracrine and endocrine mechanisms. EVs are natural intercellular and inter-organ communication tools that carry various bioactive substances for message exchange. Stem cells and stem cell EVs facilitate tissue repair, showing promising potential in regenerative medicine. Nevertheless, EVs derived from specific skin tissue cells, such as epidermal cells, fibroblasts, vascular endothelial cells and inflammatory cells, also play important roles in cutaneous tissue repair. Here, we describe the characteristics of wound healing, concentrating on the production and functions of EVs derived from specific skin cells, and provide new ideas for wound therapy using EVs.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2021 dental literature in restorative dentistry to inform busy dentists regarding noteworthy scientific and clinical progress over the past year. Each member of the committee brings discipline-specific expertise to coverage of this broad topical area. Specific subject areas addressed, in order of the appearance in this report, include COVID-19 and the dental profession (new); prosthodontics; periodontics, alveolar bone, and peri-implant tissues; implant dentistry; dental materials and therapeutics; occlusion and temporomandibular disorders; sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence daily dental treatment decisions with an emphasis on future trends in dentistry. With the tremendous volume of dentistry and related literature being published daily, this review cannot possibly be comprehensive. Rather, its purpose is to update interested readers and provide important resource material for those interested in pursuing greater details on their own. It remains our intent to assist colleagues in negotiating the extensive volume of important information being published annually. It is our hope that readers find this work useful in successfully managing the patients and dental problems they encounter.

Elevated Pre- and Postoperative ROTEM™ Clot Lysis Indices Indicate Reduced Clot Retraction and Increased Mortality in Patients Undergoing Liver Transplantation

Background: The ROTEM™ clot lysis index, describing the decrease in firmness of a clot with time, predicts mortality in various settings. The variability of the clot lysis index in surgical procedures and the involved pathophysiological mechanisms are unknown. We therefore compared pre- and postoperative clot lysis indices in liver transplantation (LTX) procedures, determined the eventual association with mortality, and investigated the mechanisms underlying decreased clot lysis index using inhibitors of fibrinolysis and clot retraction, respectively. Methods: In this retrospective cohort study, data on pre- and post-transplant ROTEM™ findings as obtained with EXTEM (tissue factor activation), INTEM (intrinsic system activation), FIBTEM (extrinsic system activation and inhibition of clot retraction), APTEM (extrinsic system activation and fibrinolysis inhibition), conventional laboratory coagulation tests, blood loss, transfusion of blood products, and outcome were registered. Results: Pre-transplant clot lysis indices showed a broad distribution ranging from 75% to 99% independent of the activator used (EXTEM, INTEM). During the surgical procedure, median clot lysis index values markedly increased from 92% to 97% (EXTEM) and 93% to 98% (INTEM), respectively (p < 0.0001 each). Aprotinin had no effect on either pre- or postsurgical clot lysis indices. Inhibition of platelet clot retraction with cytochalasin D (FIBTEM) markedly increased the preoperative clot lysis index. High pre- and post-transplantation clot lysis indices were associated with increased mortality irrespective of the activator used (EXTEM, INTEM) and the inhibition of fibrinolysis (APTEM). Inhibition of clot retraction (FIBTEM) abolished the association of clot lysis index with mortality in both pre- and post-transplantation samples. Conclusion: Both pre- and postoperative ROTEM™ clot lysis indices predict mortality in patients following liver transplantation. Inhibitor experiments reveal that the clot lysis index is not an indicator of fibrinolysis, but indicates platelet clot retraction. The marked increase of clot lysis index during liver transplantation is caused by a decrease in clot retraction with eventual consequences for clot stability, retraction of wound margins, and reperfusion of vessels in case of thrombosis.

The Growth Factor Release from a Platelet-Rich Plasma Preparation Is Influenced by the Onset of Guttate Psoriasis: A Case Report

The involvement of platelets in immune and inflammatory processes is generally recognized; nevertheless, in psoriasis, their role is not clearly understood. We studied the in vitro growth factor release from a platelet-rich plasma preparation, the concentrated growth factors (CGF), in a case of a psoriasis subject three days before the onset of the papule. The CGF clots were incubated in a cell culture medium without growth supplements for 5 h and 1, 3, 6, 7, and 8 days, and the release kinetics of PDGF-AB, VEGF, TNF-α, and TGF-β1 were evaluated. The data, based on the results obtained during the case study, report a general increase in growth factor release in the psoriasis subject with respect to the healthy control, indicating an imbalance of growth factor production from blood cells. Although the results should be validated in the future, they show new aspects of this dermatological pathology, opening new possibilities both as the method of study, using CGF, and the involvement of platelets and growth factors in its development and maintenance.

Low-dose Indonesian Aloe vera Increases Viability and Migration of the Fibroblast: An In Vitro Study

BACKGROUND: Important stages in wound healing involve homeostasis, inflammation, proliferation, and remodeling phases. Fibroblasts are essential factors in the healing pathway through the process of cell proliferation and migration. Aloe vera contains various active compounds used for anti-inflammatory, antimicrobial, immunomodulatory, anticancer, and wound healing. AIM: This study aimed to evaluate the effect of A. vera on the viability and migration of fibroblast cells. MATERIALS AND METHODS: Fibroblasts were cultured in a monolayer with Dulbecco’s Modified Eagle Medium containing 10% fetal bovine serum, 1% pinstripe, and 0.5% fungizone. We use fresh A. vera leaves extracted with 95% ethanol. Cell viability will be evaluated using the MTT test and microscopic evaluation. Cell migration was tested using an in vitro wound scratch assay and analyzed with ImageJ software. RESULTS: A. vera stimulated cell viability compared to control (p < 0.05). Administration of A. vera does not change shape and is not toxic to fibroblasts. A. vera stimulated cell migration at doses of 250, 125, 50, and 5 μg/mL compared to control after 24 h of intervention. At 48 h incubation, migration doses of 250, 50, and 5 μg/mL were higher than control (p < 0.05). CONCLUSIONS: A. vera extract may effectively wound healing by increasing viability and migration of fibroblast cells.

Synergy of Human Platelet-Derived Extracellular Vesicles with Secretome Proteins Promotes Regenerative Functions

Platelet-rich plasma is a promising regenerative therapeutic with controversial efficacy. We and others have previously demonstrated regenerative functions of human platelet lysate (HPL) as an alternative platelet-derived product. Here we separated extracellular vesicles (EVs) from soluble factors of HPL to understand the mode of action during skin-organoid formation and immune modulation as model systems for tissue regeneration. HPL-EVs were isolated by tangential-flow filtration (TFF) and further purified by size-exclusion chromatography (SEC) separating EVs from (lipo)protein-enriched soluble fractions. We characterized samples by tunable resistive pulse sensing, western blot, tandem mass-tag proteomics and super-resolution microscopy. We evaluated EV function during angiogenesis, wound healing, organoid formation and immune modulation. We characterized EV enrichment by TFF and SEC according to MISEV2018 guidelines. Proteomics showed three major clusters of protein composition separating TSEC-EVs from HPL clustering with TFF soluble fractions and TFF-EVs clustering with TSEC soluble fractions, respectively. HPL-derived TFF-EVs promoted skin-organoid formation and inhibited T-cell proliferation more efficiently than TSEC-EVs or TSEC-soluble fractions. Recombining TSEC-EVs with TSEC soluble fractions re-capitulated TFF-EV effects. Zeta potential and super-resolution imaging further evidenced protein corona formation on TFF-EVs. Corona depletion on SEC-EVs could be artificially reconstituted by TSEC late fraction add-back. In contrast to synthetic nanoparticles, which commonly experience reduced function after corona formation, the corona-bearing EVs displayed improved functionality. We conclude that permissive isolation technology, such as TFF, and better understanding of the mechanism of EV corona function are required to realize the complete potential of platelet-based regenerative therapies.

Combined Antiplatelet Therapy Reduces the Proinflammatory Properties of Activated Platelets

The cause of atherothrombosis is rupture or erosion of atherosclerotic lesions, leading to an increased risk of myocardial infarction or stroke. Here, platelet activation plays a major role, leading to the release of bioactive molecules, for example, chemokines and coagulation factors, and to platelet clot formation. Several antiplatelet therapies have been developed for secondary prevention of cardiovascular events, in which anticoagulant drugs are often combined. Besides playing a role in hemostasis, platelets are also involved in inflammation. However, it is unclear whether current antiplatelet therapies also affect platelet immune functions. In this study, the possible anti-inflammatory effects of antiplatelet medications on chemokine release were investigated using enzyme-linked immunosorbent assay and on the chemotaxis of THP-1 cells toward platelet releasates. We found that antiplatelet medication acetylsalicylic acid (ASA) led to reduced chemokine (CC motif) ligand 5 (CCL5) and chemokine (CXC motif) ligand 4 (CXCL4) release from platelets, while leukocyte chemotaxis was not affected. Depending on the agonist, α _IIb β ₃ and P2Y ₁₂ inhibitors also affected CCL5 or CXCL4 release. The combination of ASA with a P2Y ₁₂ inhibitor or a phosphodiesterase (PDE) inhibitor did not lead to an additive reduction in CCL5 or CXCL4 release. Interestingly, these combinations did reduce leukocyte chemotaxis. This study provides evidence that combined therapy of ASA and a P2Y ₁₂ or PDE3 inhibitor can decrease the inflammatory leukocyte recruiting potential of the releasate of activated platelets.

Clot Retraction: Cellular Mechanisms and Inhibitors, Measuring Methods, and Clinical Implications

Platelets have important functions in hemostasis. Best investigated is the aggregation of platelets for primary hemostasis and their role as the surface for coagulation leading to fibrin- and clot-formation. Importantly, the function of platelets does not end with clot formation. Instead, platelets are responsible for clot retraction through the concerted action of the activated αIIbβ3 receptors on the surface of filopodia and the platelet's contractile apparatus binding and pulling at the fibrin strands. Meanwhile, the signal transduction events leading to clot retraction have been investigated thoroughly, and several targets to inhibit clot retraction have been demonstrated. Clot retraction is a physiologically important mechanism allowing: (1) the close contact of platelets in primary hemostasis, easing platelet aggregation and intercellular communication, (2) the reduction of wound size, (3) the compaction of red blood cells to a polyhedrocyte infection-barrier, and (4) reperfusion in case of thrombosis. Several methods have been developed to measure clot retraction that have been based on either the measurement of clot volume or platelet forces. Concerning the importance of clot retraction in inborn diseases, the failure of clot retraction in Glanzmann thrombasthenia is characterized by a bleeding phenotype. Concerning acquired diseases, altered clot retraction has been demonstrated in patients with coronary heart disease, stroke, bronchial asthma, uremia, lupus erythematodes, and other diseases. However, more studies on the diagnostic and prognostic value of clot retraction with methods that have to be standardized are necessary.