Platelet rich plasma extract promotes angiogenesis through the angiopoietin1-Tie2 pathway

Platelets: A Potential Factor that Offers Strategies for Promoting Bone Regeneration

Bone defects represent a prevalent category of clinical injuries, causing significant pain and escalating health care burdens. Effectively addressing bone defects is thus of paramount importance. Platelets, formed from megakaryocyte lysis, have emerged as pivotal players in bone tissue repair, inflammatory responses, and angiogenesis. Their intracellular storage of various growth factors, cytokines, and membrane protein receptors contributes to these crucial functions. This article provides a comprehensive overview of platelets' roles in hematoma structure, inflammatory responses, and angiogenesis throughout the process of fracture healing. Beyond their application in conjunction with artificial bone substitute materials for treating bone defects, we propose the potential future use of anticoagulants such as heparin in combination with these materials to regulate platelet number and function, thereby promoting bone healing. Ultimately, we contemplate whether manipulating platelet function to modulate bone healing could offer innovative ideas and directions for the clinical treatment of bone defects. Impact statement Given that 5-10% of fracture patients with delayed bone healing or even bone nonunion, this review explores the potential role of platelets in bone healing (directly/indirectly) and proposes ideas and directions for the future as to whether it is possible to promote bone healing and improve fracture healing rates by modulating platelets.

Treatment of Oroantral Communication and Fistulas with the Use of Blood-Derived Platelet-Rich Preparations Rich in Growth Factors: A Systematic Review

The formation of an oroantral communication (OAC) or fistula (OAF) is a rare complication resulting from the presence of processes in the lateral parts of the maxilla or for iatrogenic reasons. The most common causes of OAC or OAF are tooth extraction with periapical lesions. The aims of this systematic review were to assess the use of platelet-derived preparations rich in growth factors in the treatment of OAC or OAF, to determine the success of treating the communication or fistula, as well as impact on postoperative complications and the course of healing. The study was performed following PRISMA guidelines (PROSPERO: CRD42024570758). The inclusion criteria were as follows: at least ten patients, the presence of oroantral communication or oroantral fistula, treatment with platelet-derived preparations rich in growth factors, and information regarding the response to treatment. In order to find relevant studies, international databases, including PubMed, Google Scholar, Web of Science Core Collection, MDPI, Wiley, and Cochrane Library were searched. The last search was performed on 31 August 2024. Seven articles were included in the systematic review. In total, platelet-derived preparations rich in growth factors were used in 164 patients. Only studies in which OAC was treated and with platelet-rich fibrin (PRF) met the inclusion criteria. Only PRF was used as the sole treatment method in three studies. When OAC is greater than 5 mm, platelet-derived preparations rich in growth factors should be considered adjuncts to treatment, not the sole treatment method. The success rate of OAC treatment was 90-100%. The use of blood products to close OAC may be an effective therapeutic alternative. Proper patient qualification and the use of an appropriate protocol are crucial. There is a need for future well-designed case-control or cohort studies as well as randomized controlled trials to provide the required level of evidence.

Insights to Ang/Tie signaling pathway: another rosy dawn for treating retinal and choroidal vascular diseases

Retinal neurovascular unit (NVU) is a multi-cellular structure that consists of the functional coupling between neural tissue and vascular system. Disrupted NVU will result in the occurrence of retinal and choroidal vascular diseases, which are characterized by the development of neovascularization, increased vascular permeability, and inflammation. This pathological entity mainly includes neovascular age-related macular degeneration (neovascular-AMD), diabetic retinopathy (DR) retinal vein occlusion (RVO), and retinopathy of prematurity (ROP). Emerging evidences suggest that the angopoietin/tyrosine kinase with immunoglobulin and epidermal growth factor homology domains (Ang/Tie) signaling pathway is essential for the development of retinal and choroidal vascular. Tie receptors and their downstream pathways play a key role in modulating the vascular development, vascular stability, remodeling and angiogenesis. Angiopoietin 1 (Ang1) is a natural agonist of Tie2 receptor, which can promote vascular stability. On the other hand, angiopoietin 2 (Ang2) is an antagonist of Tie2 receptor that causes vascular instability. Currently, agents targeting the Ang/Tie signaling pathway have been used to inhibit neovascularization and vascular leakage in neovascular-AMD and DR animal models. Particularly, the AKB-9778 and Faricimab have shown promising efficacy in improving visual acuity in patients with neovascular-AMD and DR. These experimental and clinical evidences suggest that activation of Ang/Tie signaling pathway can inhibit the vascular permeability, neovascularization, thereby maintaining the normal function and structure of NVU. This review seeks to introduce the versatile functions and elucidate the modulatory mechanisms of Ang/Tie signaling pathway. Recent pharmacologic therapies targeting this pathway are also elaborated and summarized. Further translation of these findings may afford a new therapeutic strategy from bench to bedside.

Angiogenic factor-driven improvement of refractory thin endometrium with autologous platelet-rich plasma intrauterine infusion in frozen embryo transfer cycles

Objective

A beneficial effect on endometrial thickness (EMT) and improvement of pregnancy outcome after intrauterine infusion of platelet-rich plasma (PRP) has been suggested. This study assessed the effect of intrauterine PRP infusion on live birth rate and obstetrical outcomes and analyzed cytokines that can potentially improve pregnancy outcomes through PRP.

Method

This study was a prospective cohort study conducted in a university hospital fertility center. The study included ninety-one patients who had a history of two or more failed in vitro fertilization (IVF) attempts and refractory thin endometrium that remained unresponsive after at least two conventional treatments for thin endometrium. Patients were treated with an intrauterine infusion of autologous PRP between days 7 and 14 of their hormone replacement therapy-frozen embryo transfer (HRT-FET) cycle. PRP was administered at 3-day intervals until their EMT reached 7mm. After a maximum of three PRP administrations, embryo transfer (ET) was performed. The primary outcome was the live birth rate. Secondary outcomes included the implantation rate and increase in EMT compared to the previous cycle. We compared the cytokines related to angiogenesis in a patient's whole blood (WB) and PRP by utilizing a commercial screening kit.

Results

The live birth rate in the PRP treatment cycle was 20.9% (19 of 91 patients), significantly superior to the previous cycle without PRP infusion (p < 0.001). The implantation rate was also significantly higher during the PRP treatment cycle (16.4%) compared to the previous cycle (3.1%) (p < 0.001). The mean EMT post-PRP treatment was 6.1 mm, showing a significant increase of 0.8 mm (p < 0.001). Nonetheless, an increase in EMT was also observed in the non-pregnancy group. No adverse effects were reported by patients treated with autologous PRP. Cytokine array analysis confirmed marked increases in well-known pro-angiogenic factors such as Ang-1, EGF, LAP (TGF-b1), MMP-8, PDGF-AA, and PDGF-AB/PDGF-BB.

Conclusion

Intrauterine PRP infusion offers a safe and effective treatment for patients with refractory thin endometrium and implantation failures. The angiogenic cytokines present in PRP are the primary drivers of this improvement.

Biomimetic Structure Hydrogel Loaded with Long-Term Storage Platelet-Rich Plasma in Diabetic Wound Repair

Exploring the preparation of multifunctional hydrogels from a bionic perspective is an appealing strategy. Here, a multifunctional hydrogel dressing inspired by the characteristics of porous extracellular matrix produced during Acomys wound healing is prepared. These dressings are printed by digital light processing printing of hydrogels composed of gelatin methacrylate, hyaluronic acid methacrylate, and pretreated platelet-rich plasma (PRP) to shape out triply periodic minimal surface structures, which are freeze-dried for long-term storage. These dressings mimic the porous extracellular matrix of Acomys, while the freeze-drying technique effectively extends the storage duration of PRP viability. Through in vivo and in vitro experiments, the biomimetic dressings developed in this study modulate cell behavior and facilitate wound healing. Consequently, this research offers a novel approach for the advancement of regenerative wound dressings.

Laryngeal Applications of Platelet Rich Plasma and Platelet Poor Plasma: A Systematic Review

BACKGROUND

Platelet rich plasma (PRP) and platelet poor plasma (PPP) are regenerative therapies that offer the potential for improving care for disorders of the larynx. The laryngeal applications of these substances have been examined in both animals and humans. The goal of this systematic review is to examine the various applications of PRP and PPP in laryngology, assess the protocols for preparation and application of these substances and evaluate the outcomes and complications in both humans and animals.

METHODS

A search of PUBMED was conducted in April 2021 using combinations of keywords of "platelet rich plasma" and "platelet poor plasma" with keywords such as "larynx," "vocal folds," "laryngology," and others. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRIMSA) guidelines were followed. Articles were reviewed by two independent coauthors and included based on selection criteria pertinent to the goals of this study. The risk of bias in the included studies was assessed by two independent co-authors using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Randomized Controlled Trials and JBI Critical Appraisal Checklist for Quasi-Experimental Studies. Data regarding the pathologies treated using PRP and PPP, PRP, and PPP preparation protocols, application protocols, human voice outcomes, histopathological animal outcomes, and complications were extracted from each of the studies and presented in tables.

RESULTS

Seven studies were included based on the selection criteria. PRP or PPP were used for vocal fold scar, sulcus, atrophy and palsy; acute vocal fold injury; glottic insufficiency, and graft healing. PRP or PPP were derived from autologous blood in a one- or two-step centrifugation process and administered via injection, soaking of cartilage grafts or topical application. Mean and median voice handicap index-10 (VHI-10) and voice handicap index (VHI) scores decreased following PRP or PPP injections in two human studies and one human study showed a similar VHI-10 score before and after PRP treatment. Videostroboscopy showed the absence of injection site reactions and at least temporary improvement in glottic gap or vibratory function following treatment in some patients. Other objective measures of voice outcomes in human studies showed improved phonatory function in the one-to-four-month period following PRP or PPP injections, with some patients experiencing a subjective decrease or return to baseline in phonatory function following the initial improvement period. Animal studies found elevated levels of growth factors, organized collagen deposition, decreased granulation tissue, increased vascularization, and increased cartilage proliferation in PRP treated laryngeal tissue.

DISCUSSION

PRP and PPP might have the potential to be safely used in the larynx and at least temporarily influence wound healing and vocal function. Further study using comparable outcome measurement tools is required to assess their role and efficacy in treating acute vocal fold injury, chronic vocal fold pathologies, graft healing, and other laryngeal applications.

Advances and prospects of platelet-rich plasma therapy in veterinary ophthalmology

In the recent decades, there has been a significant uptick on the use of platelet-rich plasma (PRP) as a better alternative for ophthalmologic therapies in pathologies, primarily of the ocular surface. PRP is a class of liquid platelet concentrate containing a supra-physiological concentration of platelets in a relatively small amount of plasma. Its potential to heal various tissues has piqued interest in its therapeutic application as a biomaterial in regenerative medicine. It is currently a popular therapeutic agent in plastic surgery, cardiothoracic surgery, reconstructive surgery, and even oral and maxillofacial surgery. Based on the data from in vitro and in vivo studies, it can be concluded that PRP possesses adequate therapeutic potential in ocular pathologies, especially those involving cornea. In addition, the high concentrations of growth factors (TGF-β, VEGF, EGF) present in the PRP accelerate the healing of the corneal epithelium. PRP has great therapeutic prospects in veterinary ophthalmology as a regenerative therapeutic modality. However, several variables are yet to be defined and standardized that can directly affect the efficacy of PRP application in different ophthalmic conditions. There is a shortage of research on the use of PRP in ocular surface defects compared to the number of studies and reports on the use of autologous and allogeneic serum eye drops. Therefore, a data-driven approach is required to generate consensus/guidelines for the preparation, characterization, and therapeutic use of PRP in veterinary ophthalmology. This review aims to inform readers of the latest research on PRP, including its preparation methods, physiological and biochemical properties, clinical applications in veterinary ophthalmology, and their safety and efficacy.

A Clinical Study of Platelet-Rich Fibrin Combined With Autologous High-Density Fat Transplantation in Augmentation Rhinoplasty

OBJECTIVE

This study was designed to analyze the clinical effect of autologous fat-granule transplantation in augmentation rhinoplasty and explore methods to improve the fat retention rate.

METHODS

A total of 70 enrolled patients were randomly divided into 2 groups: the platelet-rich fibrin (PRF) combined with high-density fat transplantation group (combined group) and the conventional fat-granule transplantation group (control group; n = 35 in each group). In the combined group, an appropriate amount of autologous fat was extracted and centrifuged, and the lower layer of high-density fat was taken and mixed with PRF isolated from whole blood for autotransplantation. In the control group, only fat was extracted and centrifuged for transplantation. The patients were followed up with for more than one year to observe the short- and long-term effects, complications, safety, and patient satisfaction.

RESULTS

Six months after the operation, the nasal shape was stable, the contour was higher and more stereoscopic than before, the average increase of nasal height was 3.0 mm in the combined group and 2.0 mm in the control group. No complications, such as fat embolism, infection, or necrosis occurred during the 1-year follow-up. The satisfaction rate between the 2 groups has statistical significance (P < .05).

CONCLUSION

Overall, PRF combined with autologous high-density fat transplantation is simple to perform, has a significantly increased fat-retention rate than the control group, and has stable long-term effects without obvious adverse reactions. A sufficient amount of fat and PRF transplantation can achieve a good orthopedic effect. Thus, this method can be widely used in clinical augmentation rhinoplasty.

Angiopoietin-1 promotes triple-negative breast cancer cell proliferation by upregulating carboxypeptidase A4

Angiopoietin-1 (ANG1) is a pro-angiogenic regulator that contributes to the progression of solid tumors by stimulating the proliferation, migration and tube formation of vascular endothelial cells, as well as the renewal and stability of blood vessels. However, the functions and mechanisms of ANG1 in triple-negative breast cancer (TNBC) are unclear. The clinical sample database shows that a higher level of ANG1 in TNBC is associated with poor prognosis compared to non-TNBC. In addition, knockdown of ANG1 inhibits TNBC cell proliferation and induces cell cycle G1 phase arrest and apoptosis. Overexpression of ANG1 promotes tumor growth in nude mice. Mechanistically, ANG1 promotes TNBC by upregulating carboxypeptidase A4 (CPA4) expression. Overall, the ANG1-CPA4 axis can be a therapeutic target for TNBC.

Strategies to Improve AFT Volume Retention After Fat Grafting

BACKGROUND

Autologous fat grafting has gained increasing popularity used in plastic surgery as a strategy to improve functional and aesthetic outcome. However, variable augmentation results have concerned surgeons in that volume loss of grafted fat reported fluctuates unsteadily.

AIM

An optimal technique that clinically maximizes the long-term survival rate of transplantation is in urgent need to be identified.

METHOD

The PubMed/MEDLINE database was queried to search for animal and human studies published through March of 2022 with search terms related to adipose grafting encompassing liposuction, adipose graft viability, processing technique, adipose-derived stem cell, SVF and others.

RESULTS

45 in vivo studies met inclusion criteria. The principal of ideal processing technique is effective purification of fat and protection of tissue viability, such as gauze rolling and washing-filtration devices. Cell-assisted lipotransfer including SVF, SVF-gel and ADSCs significantly promotes graft retention via differentiation potential and paracrine manner. ADSCs induce polarization of macrophages to regulate inflammatory response, mediate extracellular matrix remodeling and promote endothelial cell migration and sprouting, and differentiate into adipocytes to replace necrotic cells, providing powerful evidence for the benefits and efficacy of cell-assisted lipotransfer.

CONCLUSION

Based on the current evidence, the best strategy can not be decided. Cell-assisted lipotransfer has great potential for use in regenerative medicine. But so far mechanically prepared SVF-gel is conducive to clinical promotion. PRP as endogenous growth factor sustained-release material shows great feasibility.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Skin and Bone Regeneration of Solid Bone Marrow Aspirate Concentrate Versus Platelet-Rich Fibrin

Solid bone marrow aspirate concentrate (sBMAC) is harvested from bone marrow aspirate without anticoagulants by a centrifugation protocol similar to that for platelet-rich fibrin (PRF) prepared from peripheral blood. It was hypothesized that sBMAC could accelerate not only wound healing but also bone regeneration because of the abundant growth factor (GF) releases from enriched bone marrow cells. The purpose of the present study was to investigate skin wound healing and bone regenerative potential of sBMAC compared with arterial blood-derived PRF (Ar-PRF) and venous blood-derived PRF (Ve-PRF) in a skin defect and calvarial bone defect model in rabbits. GF release assays revealed significantly higher release of transforming growth factor-β (TGF-β), alkaline phosphatase (ALP), and osteocalcin (OCN) from sBMAC compared with PRFs for 24 h. In the skin defect animal model, sBMAC and PRFs promoted wound bed angiogenesis and re-epithelization in skin defect sites with higher collagen 1 synthesis, cytokeratin AE1/AE3, vascular endothelial growth factor (VEGF) expressions on week 1. Furthermore, a calvarial defect assay revealed that sBMAC promoted new bone formation with a sufficient bone marrow structure similar to that of intact bone in the bone defects. Ar-PRF achieved the second highest bone closure and new bone volume but yielded new bone that was thinner than the intact bone. In conclusion, sBMAC treatment might be a good option instead of PRF as an adjuvant therapy for both skin and bone tissue regeneration therapies in certain clinical situations. Impact statement Solid bone marrow aspirate concentrate (sBMAC) is new type of clot material prepared from bone marrow aspirate. The present study for the first time showed that sBMAC significantly accelerated both skin wound healing and bone formation in the defects, compared with conventional platelet-rich fibrin in rabbit experiment models.

Network meta-analysis of platelet-rich fibrin in periodontal intrabony defects

OBJECTIVES

To evaluate the effect of platelet-rich fibrin alone or in combination with different biomaterials for the treatment of periodontal intra-bony defect.

METHODS

Up to April 2022, Cochrane library, Medline, EMBASE, and Web of Science databases were searched for randomized clinical trials. The outcomes of interest were probing pocket depth reduction, clinical attachment level gain, bone gain, and bone defect depth reduction. Bayesian network meta-analysis with 95% credible intervals was calculated.

RESULTS

Thirty-eight studies with 1157 participants were included. Platelet-rich fibrin alone or platelet-rich fibrin +biomaterials showed a statistically significant difference when compared with open flap debridement (p < 0.05, low to high certainty evidence). Neither biomaterials alone nor platelet-rich fibrin +biomaterials showed a statistically significant difference when compared to platelet-rich fibrin alone (p > 0.05, very low to high certainty evidence). Platelet-rich fibrin +biomaterials showed insignificant differences as compared to biomaterials alone (p > 0.05, very low to high certainty evidence). Allograft +collagen membrane ranked the best in probing pocket depth reduction while platelet-rich fibrin +hydroxyapatite ranked the best in bone gain.

CONCLUSION

It seems that (1) platelet-rich fibrin with/without biomaterials were more effective than open flap debridement. (2) Platelet-rich fibrin alone provides a comparable effect to biomaterials alone and platelet-rich fibrin +biomaterials. (3) Platelet-rich fibrin +biomaterials provide a comparable effect to biomaterials alone. Although allograft +collagen membrane and platelet-rich fibrin +hydroxyapatite ranked the best in terms of probing pocket depth reduction and bone gain respectively, the difference between different regenerative therapies remains insignificant, and therefore, further studies are still needed to confirm these results.

Platelets and (Lymph)angiogenesis

The formation of new blood and lymphatic vessels is essential for both the development of multicellular organisms and (patho)physiological processes like wound repair and tumor growth. In the 1990s, circulating blood platelets were first postulated to regulate tumor angiogenesis by interacting with the endothelium and releasing angiogenic regulators from specialized α granules. Since then, many studies have validated the contributions of platelets to tumor angiogenesis, while uncovering novel roles for platelets in other angiogenic processes like wound resolution and retinal vascular disease. Although the majority of (lymph)angiogenesis occurs during development, platelets appear necessary for lymphatic but not vascular growth, implying their particular importance in pathological cases of adult angiogenesis. Future work is required to determine whether drugs targeting platelet production or function offer a clinically relevant tool to limit detrimental angiogenesis.

Regeneration potential of bone marrow derived mesenchymal stem cells and platelet rich plasma (PRP) on irradiation-induced damage of submandibular salivary gland in albino rats

Radiation-induced damage to salivary glands (SG) is a consequence of radiotherapy for head and neck cancers. Recovery of the irradiated SG has been studied using various regenerative approaches. This study aims to compare the regenerative potentials of platelet-rich plasma (PRP) and bone marrow mononuclear cells (BMMCs) on irradiated rat submandibular salivary glands (SMD). 32 healthy male albino rats were irradiated with a single dose of 6 Gy then classified into four groups. Group A received no treatment while the other 3 groups were injected 24 h post-radiation with a single dose of either; BMMCs (Group B), PRP (Group C), or BMMCs suspended in PRP (Group D). SMD regeneration was assessed in terms of histological changes and TGF- β1 gene expression. The results showed that compared to the untreated group all groups showed successful regeneration with group D showing the best results. A statistically significant increase in the surface area of acini and TGF- β1 gene expression was observed in group D, followed by group C, then B. Our results prove that using PRP and BMMCs could be promising in decreasing irradiation side effects on SG. Moreover, combining PRP and BMMCs gives better effects compared to each therapy alone.

Platelet-derived concentrates influence human keratinocyte proliferation in vitro and induce wound healing in a prospective case series of chronic wounds of different entities in vivo

Objectives

Soft tissues defects can extend into the fat layer or even deeper and can cause significant clinical disadvantages like pain, infections, and loss of function. In particular, chronic wounds are difficult to treat, as split-thickness skin grafts (STSGs) have varying success rates. To improve wound healing in chronic wounds, the authors have studied the application of platelet-mediator concentrate (PMC) in a human keratinocyte culture model in vitro and of autologous platelet concentrates (PRP) in a combination with surgical procedures in vivo as second line therapy in patients with initially failed wound closure.

Methods

For in vitro testing on keratinocytes, a PMC was processed with a commercially available bedside system (ATR^®, Curasan, Germany). In a clinical, nonrandomized study, five in-house patients with chronic wounds were treated using a combination of surgical debridement and autologous PRP. Time of healing as determined by epithelization as well as laser Doppler imaging to visualize blood flow was analyzed. Additionally, changes in ease of surgical wound closure were determined. Finally, the quality of life of patients was assessed using a validated questionnaire (clinicaltrials.gov # NCT03667638).

Results

In vitro testing shows a significant effect of PMC on keratinocyte proliferation in cell culture. Clinical studies showed that patients treated with PRP had initiation of wound closure, higher blood flow after PRP injection, and easier wound closure as well as improved quality of life.

Conclusions

The injection of platelet concentrates to treat chronic wound defects presents a favorable addition to treatment where single surgical procedures have failed and may improve current therapy options.

Matrine inhibits synovial angiogenesis in collagen-induced arthritis rats by regulating HIF-VEGF-Ang and inhibiting the PI3K/Akt signaling pathway

Matrine (Mat) is an alkaloid of tetracycline quinazine, and previous studies have demonstrated its specific effect on relieving rheumatoid arthritis (RA). However, the effect of Mat on joint synovial angiogenesis in the pathogenesis of RA has not been elucidated. In this study, body weight, joint swelling, arthritis index (AI) score, histopathological changes, immunohistochemical, and western blot- were used in collagen-induced arthritis (CIA) rats to detect pro-inflammatory factors and, - expression levels of key cytokines and proteins along the hypoxia-inducible factor (HIF)-endothelial growth factor (VEGF)-angiopoietin (Ang) axis and VEGF-phosphoinositide 3-kinase (PI3K) / protein kinase B (Akt) pathway. In vitro experiments were conducted to observe the effect of Mat on the proliferation, migration and lumen formation of RA-fibroblast-like synovial cells (FLS) and human umbilical vein endothelial cells (HUVECs). Results showed that Mat reduced the degree of paw swelling and AI score in CIA rats, joint synovial tissue proliferation, inflammatory cell infiltration, and neovascularization; moreover, it down-regulated the expression levels of inflammatory factors interleukin-1β, interferon-γ, and pro-angiogenic factors VEGF, placental growth factor, HIF-α, Ang-1, Ang-2, Tie-2, and phosphorylation-Akt in the ankle joint of CIA rats. In addition, the in vitro experiments showed that Mat inhibited the proliferation and migration of RA-FLS and inhibited the proliferation and lumen formation of HUVECs. Therefore, Mat exerts an anti-angiogenesis effect by regulating the HIF-VEGF-Ang axis and inhibiting the PI3K/Akt signaling pathway. This inhibits the pathogenesis and improve the symptoms of RA, and may be offered as a candidate drug for the treatment of RA.

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.

Treatment of atrophic acne scars: Topical or intralesional plasma gel?

BACKGROUND

Atrophic post-acne scarring is considered to be a therapeutic challenge.

OBJECTIVES

The aim was to compare the safety and efficacy of (A) FCL combined with intradermal injection of plasma gel, (B) FCL combined with topical application of plasma gel, and (C) FCL monotherapy in the treatment of atrophic post-acne scars.

METHODS

Thirty patients with facial atrophic post-acne scars were enrolled in this study and randomly assigned into one of three groups. All of them underwent four treatment sessions at 4-weeks intervals. They were assessed objectively by the quantitative global scarring grading system (GSGS). This system was applied at baseline, and after 1- and 6-month follow-up (FU). Subjective assessments were performed through the global esthetic improvement scale (GAIS) and level of patient satisfaction. The DLQI questionnaire was employed at the baseline and 6-month FU.

RESULTS

According to the quantitative GSGS scores, the reductions in group A (68.4%) and group B (63%) scores were comparable, and both were significantly higher than that in group C (41.2%) in all steps of evaluation. At 6-month FU, both groups A and B showed further significant improvement, while group C did not. Based on the GAIS and patients' satisfaction, there were no significant differences between all groups. The reductions in DLQI scores in groups A and B were comparable; however, both were significantly higher than group C (P < .001).

CONCLUSIONS

The combination of plasma gel and FCL resurfacing was noticeably outstanding in their efficacy and impact on the patients' quality of life.

The Effects of Inactive Platelet-rich Plasma at Different Injection Time on Prefabricated Flap Viability in Rabbits

PURPOSE

To evaluate the effect of inactive form of platelet-rich plasma (PRP) at different injection time on the prefabricated flap viability in rabbits.

METHODS

A thoracodorsal artery vascular bundle prefabricated flap was established on the back of 30 healthy male New Zealand white rabbits by 2 phases of operations. A total of 60 sides were randomly divided into the experimental side and the control side. The experimental side was injected with autologous inactive PRP around the thoracodorsal vascular bundle, and the control side was injected with the same amount of normal saline. According to preoperative (group A), intraoperative (group B), and postoperative (group C) injection of PRP, 30 rabbits were divided into 3 groups of 10 each. Histological and immunohistochemical observation, vascular density measurement, and lead oxide angiography were used to compare the differences in the survival of prefabricated flaps between the 3 groups of rabbits injected with inactive PRP at different injection time.

RESULTS

The flap survival ratio, microvessels density, vascular endothelial growth factor and vascular endothelial growth factor receptor 2 expression of PRP injection side were significantly improved compared with the control side. In the comparison of 3 injection time groups, we found that group A and group B could achieve better results, and especially group B had the most significant effect on the revascularization and flap viability.

CONCLUSION

Autologous inactive PRP can promote the survival of the prefabricated flap, and the intraoperative injection can significantly improve the survival rate of the prefabricated flap. It provides a theoretical guidance for obtaining a larger area of prefabricated axial flap in clinical practice.

Angiogenesis Is Differentially Modulated by Platelet-Derived Products

Platelet-derived preparations are being used in clinic for their role in tissue repair and regenerative processes. The release of platelet-derived products such as autologous growth factors, cytokines and chemokines can trigger therapeutic angiogenesis. In this in vitro study, we evaluated and compared the ability of three platelet-derived preparations: platelet-rich-plasma (PRP), PRP-hyaluronic acid (PRP-HA) and platelet lysates (PL) at various concentrations (5–40%) to modulate human umbilical vein endothelial cells (HUVEC) biological effects on metabolism, viability, senescence, angiogenic factors secretion and angiogenic capacities in 2D (endothelial tube formation assay or EFTA) and in 3D (fibrin bead assay or FBA). HUVEC exocytosis was stimulated with PRP and PRP-HA. Cell viability was strongly increased by PRP and PRP-HA but mildly by PL. The three preparations inhibit HUVEC tube formation on Matrigel, while PRP enhanced the complexity of the network. In the fibrin bead assay (FBA), PRP and PRP-HA stimulated all steps of the angiogenic process resulting in massive sprouting of a branched microvessel network, while PL showed a weaker angiogenic response. Secretome profiling revealed modulation of 26 human angiogenic proteins upon treatment with the platelet derived preparations. These in vitro experiments suggest that PRP and PRP-HA are effective biological therapeutic tools when sustained therapeutic angiogenesis is needed.

FTY720 Improves the Survival of Autologous Fat Grafting by Modulating Macrophages Toward M2 Polarization Via STAT3 Pathway

Autologous fat grafting (AFG) is widely regarded as an important method for breast reconstruction after mastectomy among breast cancer (BC) patients. FTY720 has been proved to affect macrophage polarization and improve the sensitivity of postoperative BC treatment. This study aimed to explore FTY720 function and underlying mechanism in fat transplantation. The C57BL/6 J mice that received AFG were randomly divided into two groups treated with saline and FTY720, respectively. The fat graft samples were obtained at week 1, 2, 4, and 12 post-transplantation. Graft volumes, graft structures, M2 macrophages, and STAT3 protein expression were estimated by histological examination, immunofluorescence, flow cytometry, and western blot, respectively. In vitro, mouse preadipocytes were stimulated with FTY720 treated-M2 macrophages conditioned medium (FTY720-M2-CM) to evaluate the adipogenesis effect. The level of adipogenic mRNA expression in preadipocytes was detected by RT-PCR. The in vivo results showed that FTY720 treatment significantly enhanced the fat graft retention, structure integrity, and neovascularization, indicating the potential of FTY720 in improving graft survival. The histology results showed more polarized M2 macrophage presented in the FTY720 group. In the in vitro assay, after FTY720-M2-CM treatment, the 3T3-L1 preadipocytes showed the increased triglyceride content and adipogenic mRNA expression, including FABP4, C/EBP-α, Adipoq, and PPARγ. Furthermore, FTY720 treatment up-regulated the expression level of M2 biomarker CD206, Arg-1, Fizz-1, which could be weakened by the STAT3 inhibitor. Together, this study confirmed the potential efficacy of FTY720 in improving graft survival in the AFG model, possibly mediated by polarizing macrophages to M2 type through activating the STAT3 pathway.

Combined Use of Autologous Bone Marrow-derived Stem Cells and Platelet-rich Plasma for Ovarian Rejuvenation in Poor Responders

Background:

The management of poor responders is still a challenge in modern-assisted reproductive technology. Several researches are showing encouraging results with autologous bone marrow-derived stem cells (ABMDSCs) and platelet-rich plasma (PRP) individually. Hence, we decided to study the synergistic effect of ABMDSCs with PRP.

Aims and Objective:

The aim of the study was to assess the safety and efficacy of intraovarian instillation of ABMDSCs combined with PRP in poor responders.

Design:

This was an interventional pilot study. Study Period: January 2017 to January 2019.

Materials and Methods:

We designed a pilot study using Patient-oriented Strategies Encompassing IndividualizeD Oocyte Number (POSEIDON) Group 3 and 4 poor responder patients (n = 20). The study group underwent laparoscopic/transvaginal intraovarian instillation of ABMDSCs combined with PRP and the outcome was analyzed – primary outcome – antral follicular count (AFC) and mature MII oocytes and secondary outcome – Anti-Mullerian hormone (AMH) levels and number of Grade A and B embryos frozen on day 3. The Wilcoxon signed-rank test and Pearson correlation were used for the statistical analysis and P < 0.05 was considered statistically significant.

Results:

After 6 weeks of intraovarian instillation ABMDSCs mixed with PRP, patients were reassessed for AFC and AMH and their response to subsequent controlled ovarian stimulation (COS) cycle was observed. Statistically significant improvement was seen in AFC, MII oocytes, and Grade A and Grade B embryos. AMH was also increased in some patients, but the result was not statistically significant.

Conclusion:

Our results suggest that intraovarian instillation of ABMDSCs combined with PRP is safe and it optimized the recruitment of existing dormant primordial follicles to improve oocyte yield and hence the number and quality of embryos after COS in POSEIDON Group 3 and 4 poor responders.

PRP in wound healing applications

Platelets play a crucial role in hemostasis, tissue regeneration and host defense. Based on these settings, platelet-rich plasma (PRP) and its derivatives are therapeutically used to promote wound healing in several scenarios. This review summarizes the biological mechanisms underlying the most traditional as well as innovative applications of PRP in wound healing. These mechanisms involve the combined action of platelet-derived growth factors and cytokines, together with the role of plasma-derived fibrillar, antioxidant and homeostatic factors. In addition, regenerative treatments with PRP consist of personalized and non-standardized methods. Thus, the quality of PRP varies depending on endogenous factors (e.g., age; gender; concomitant medication; disease-associated systemic factors; nutrition) and exogenous factors (anticoagulants and cellular composition). This review also analyses whether these factors affect the biological mechanisms of PRP in wound healing applications.

Antioxidant and Biological Properties of Mesenchymal Cells Used for Therapy in Retinitis Pigmentosa

Both tissue repair and regeneration are a priority in regenerative medicine. Retinitis pigmentosa (RP), a complex retinal disease characterized by the progressive loss of impaired photoreceptors, is currently lacking effective therapies: this represents one of the greatest challenges in the field of ophthalmological research. Although this inherited retinal dystrophy is still an incurable genetic disease, the oxidative damage is an important pathogenetic element that may represent a viable target of therapy. In this review, we summarize the current neuroscientific evidence regarding the effectiveness of cell therapies in RP, especially those based on mesenchymal cells, and we focus on their therapeutic action: limitation of both oxidative stress and apoptotic processes triggered by the disease and promotion of cell survival. Cell therapy could therefore represent a feasible therapeutic option in RP.

Mesenchymal stem cell surgery, rescue and regeneration in retinitis pigmentosa: clinical and rehabilitative prognostic aspects

Purpose:

To assess whether treatment with the Limoli Retinal Restoration Technique (LRRT) can be performed in patients with retinitis pigmentosa (RP), grafting the autologous cells in a deep scleral pocket above the choroid of each eye to exert their beneficial effect on the residual retinal cells.

Methods:

The patients were subjected to a complete ophthalmological examination, including best corrected visual acuity (BCVA), close-up visus measurements, spectral domain-optical coherence tomography (SD-OCT), microperimetry (MY), and electroretinography (ERG). Furthermore, the complete ophthalmological examination was carried out at baseline (T0) and at 6 months (T180) after surgery. The Shapiro–Wilk test was used to assess the normality of distribution of the investigated parameters. A mixed linear regression model was used to analyse the difference in all the studied parameters at T0 and T180, and to compare the mean change between the two groups. All statistical analyses were performed with STATA 14.0 (Collage Station, Texas, USA).

Results:

LRRT treatment was performed in 34 eyes of 25 RP patients recruited for the study. The eyes were classified in two groups on the basis of foveal thickness (FT) assessed by SD-OCT: 14 eyes in Group A (FT≤190μm) and the remaining 20 ones in Group B (FT > 190μm). Although it had not reached the statistical significance, Group B showed a better improvement in BCVA, residual close-up visus and sensitivity than Group A.

Conclusions:

Previous studies have described the role of LRRT in slowing down retinal degenerative diseases. Consequently, this surgical procedure could improve the clinical and rehabilitative prognostic parameters in RP patients. On the other hand, further clinical research and studies with longer follow-up will be needed to evaluate its efficacy.

In vivo behavior of untreated and compressed concentrated growth factors as biomaterials in rabbits

To characterize concentrated growth factors (CGFs) in vivo, we examined the degradation of implanted CGF in rabbits. Untreated CGF (U-CGF) and compressed CGF (C-CGF) were subcutaneously implanted into the dorsum. Histological analyses showed that the U-CGF and C-CGF induced very few inflammatory cells and that the U-CGF and C-CGF were subsequently degraded with dendritic invasion of granulation tissue. The C-CGF histopathologically remained for longer term than the U-CGF. Aggregated CD31+ and RAM11+ cells appeared in and around the implanted CGF. The number of macrophages and blood vessels in the CGF-implanted groups was greater than that in the sham group. There were more blood vessels in the U-CGF group than that in the C-CGF and sham group. We showed that CGF was degraded by macrophages in 4 weeks and enhanced angiogenesis with dendritically branching new capillaries. Therefore, the U-CGF and C-CGF can be clinically applied as a biomaterial inducing angiogenesis.

Endothelial Twist1-PDGFB signaling mediates hypoxia-induced proliferation and migration of αSMA-positive cells

Remodeling of distal pulmonary arterioles (PAs) associated with marked accumulation of pulmonary artery smooth muscle cells (PASMCs) represents one of the major pathologic features of pulmonary hypertension (PH). We have reported that the transcription factor Twist1 mediates hypoxia-induced PH. However, the mechanism by which endothelial Twist1 stimulates SMC accumulation to distal PAs in PH remains unclear. Here, we have demonstrated that Twist1 overexpression increases the expression of platelet-derived growth factor (PDGFB) in human pulmonary arterial endothelial (HPAE) cells. Hypoxia upregulates the levels of Twist1 and PDGFB in HPAE cells. When we implant hydrogel supplemented with endothelial cells (ECs) on the mouse lung, these ECs form vascular lumen structures and hypoxia upregulates PDGFB expression and stimulates accumulation of αSMA–positive cells in the gel, while knockdown of endothelial Twist1 suppresses the effects. The levels of Twist1 and PDGFB are higher in PAE cells isolated from idiopathic pulmonary arterial hypertension (IPAH) patients compared to those from healthy controls. IPAH patient-derived PAE cells stimulate accumulation of αSMA–positive cells in the implanted gel, while Twist1 knockdown in PAE cells inhibits the effects. Endothelial Twist1-PDGFB signaling plays a key role in αSMA–positive cell proliferation and migration in PH.

Platelet-Rich Plasma Enhances Distal Flap Viability and Underlying Vascularity in a Radiated Rotational Flap Rodent Model

Importance: Autologous platelet-rich plasma (PRP) has received widespread attention due to its physiologic healing properties, augmenting the body's natural healing process through platelet activation and release of growth factors. The effects of PRP on radiated tissue have been inadequately studied in vivo. Objective: To determine whether PRP can be used to improve viability of radiated tissue subjected to a clinically meaningful stressor, in this case a rotational skin flap. Design, Setting, Participants: This is a prospective trial using a radiated rat abdominal rotational flap model in the laboratory. Male Sprague-Daley rats were used in this study. Harvested PRP or saline control was injected into rotational flaps immediately after surgery. Progression of necrosis was documented with photo analysis. After 1 week, animals were sacrificed and flap tissue was stained and analyzed for presence of vascular tissue. Intervention: PRP versus control injection into radiated skin tissue. Main Outcomes and Measures: Percentage necrosis of rotational flap and number of vascular channels stained with CD31 present in flap tissue. Results: PRP administration helped rescue the distal flap from necrosis, achieving viability similar to nonradiated controls. Superficial vascularity was similarly increased fivefold in radiated tissue if PRP was given postoperatively, mirroring the vascular density of nonradiated tissue. Conclusions and Relevance: PRP may enhance distal rotational flap viability after radiation, possibly by protecting superficial vessels from tissue necrosis when administered at the time of surgery.

Characterization of Naturally Occurring Bioactive Factor Mixtures for Bone Regeneration

In this study, the bone-regenerative potential of bioactive factors derived from adipose tissue, platelet-rich plasma (PRP) and conditioned medium from hypoxia-treated human telomerase immortalized bone-marrow-derived mesenchymal stem cells (hTERT-MSC) was investigated in vitro with the aim to develop cost-effective and efficient bone substitutes for optimized regeneration of bone defects. Adipose tissue was harvested from human donors undergoing reconstructive surgery, and adipose tissue extract (ATE) was prepared. Platelet lysates (PL) were produced by repeated freeze-thaw cycles of PRP, and hypoxia-conditioned medium (HCM) was obtained by culturing human telomerase immortalized bone-marrow-derived mesenchymal stromal cells for 5 days with 1% O2. Besides analysis by cytokine and angiogenesis arrays, ELISA was performed. Angiogenic potential was investigated in cocultures of bone-marrow-derived (BM)-MSC and human umbilical vein endothelial cells. Multiple angiogenic proteins and cytokines were detected in all growth factor mixtures. HCM and ATE contained high amounts of angiogenin and CCL2/MCP-1, whereas PL contained high amounts of IGFBP-1. Culturing cells with HCM and ATE significantly increased specific ALP activity of BM-MSC as well as tubule length and junctions of endothelial networks, indicating osteogenic and angiogenic stimulation. To achieve a synergism between chemoattractive potential and osteogenic and angiogenic differentiation capacity, a combination of different growth factors appears promising for potential clinical applications.

The Angiopoietin-Tie2 Pathway in Critical Illness

Lethal features of sepsis and acute respiratory distress syndrome (ARDS) relate to the health of small blood vessels. For example, alveolar infiltration with proteinaceous fluid is often driven by breach of the microvascular barrier. Spontaneous thrombus formation within inflamed microvessels exacerbates organ ischemia, and in its final stages, erupts into overt disseminated intravascular coagulation. Disruption of an endothelial signaling axis, the Angiopoietin-Tie2 pathway, may mediate the abrupt transition from microvascular integrity to pathologic disruption. This review summarizes preclinical and clinical results that implicate the Tie2 pathway as a promising target to restore microvascular health in sepsis and ARDS.

Stem Cell Surgery and Growth Factors in Retinitis Pigmentosa Patients: Pilot Study after Literature Review

To evaluate whether grafting of autologous mesenchymal cells, adipose-derived stem cells, and platelet-rich plasma into the supracoroideal space by surgical treatment with the Limoli retinal restoration technique (LRRT) can exert a beneficial effect in retinitis pigmentosa (RP) patients. Twenty-one eyes underwent surgery and were divided based on retinal foveal thickness (FT) ≤ 190 or > 190 µm into group A-FT and group B-FT, respectively. The specific LRRT triad was grafted in a deep scleral pocket above the choroid of each eye. At 6-month follow-up, group B showed a non-significant improvement in residual close-up visus and sensitivity at microperimetry compared to group A. After an in-depth review of molecular biology studies concerning degenerative phenomena underlying the etiopathogenesis of retinitis pigmentosa (RP), it was concluded that further research is needed on tapeto-retinal degenerations, both from a clinical and molecular point of view, to obtain better functional results. In particular, it is necessary to increase the number of patients, extend observation timeframes, and treat subjects in the presence of still trophic retinal tissue to allow adequate biochemical and functional catering.

The Role of Platelet Concentrates in Facial Fat Grafting

Autologous fat grafting is increasingly being used as a method for the repair of facial soft tissue defects and facial rejuvenation, given its low risk of adverse effects and high efficacy. However, the unpredictability of graft retention is a limitation of this procedure. In addition, there is no standard procedure to date for autologous fat grafting. Different methods have been developed to increase the retention of grafted fat. For instance, platelet concentrates have been used to directly deliver bioactive factors to grafted fat. Platelet concentrates also provide incidental therapeutic benefits by enhancing the persistence of fat grafted in the face via the release of growth factors and cytokines. In this review, we describe current strategies for improving the survival of facial fat grafts, mainly focusing on the application of growth factors/cytokines and platelet concentrates to fat grafting.

The influence of leukocyte-platelet-rich plasma on accelerated orthodontic tooth movement in rabbits

Objective

To determine the effects of a local injection of leukocyte-platelet-rich plasma (L-PRP) on orthodontic tooth movement in rabbits.

Methods

Twenty-three male New Zealand white rabbits were included in a split-mouth design. Tooth movement with a 100-g nickel-titanium closed-coil spring was performed on the maxillary first premolars. L-PRP was injected submucosally at the buccal and lingual areas of the first premolar in one random side of the maxilla and the other side served as the control and received normal saline. The amount of tooth movement was assessed on three-dimensional digital models on days 0, 3, 7, 14, 21, and 28. Histological findings and osteoclast numbers were examined on day 0 as the baseline and on days 7, 14, and 28.

Results

The L-PRP group showed significantly greater cumulative tooth movement at all observed periods. However, a significantly higher rate of tooth movement was observed only on days 0–7 and 7–14. The osteoclast numbers were significantly increased in the L-PRP group on days 7 and 14.

Conclusions

Local injection of L-PRP resulted in a transient increase in the rate of tooth movement and higher osteoclast numbers.

Histological Evidence for Therapeutic Induction of Angiogenesis Using Mast Cells and Platelet-Rich Plasma within A Bioengineered Scaffold following Rat Hindlimb Ischemia

Objective

Peripheral arterial disease results from obstructed blood flow in arteries and increases the risk of amputation in acute cases. Therapeutic angiogenesis using bioengineered tissues composed of a chitosan scaffold that was enriched with mast cells (MCs) and/or platelet-rich plasma (PRP) was used to assess the formation of vascular networks and subsequently improved the functional recovery following hindlimb ischemia. This study aimed to find an optimal approach for restoring local vascularization.

Materials and Methods

In this experimental study, thirty rats were randomly divided into six experimental groups: a. Ischemic control group with right femoral artery transection, b. Ischemia with phosphate-buffered saline (PBS) control group, c. Ischemia with chitosan scaffold, d. Ischemia with chitosan and MCs, e. Ischemia with chitosan and PRP, and f. Ischemia with chitosan, PRP, and MCs. The left hind limbs served as non-ischemic controls. The analysis of capillary density, arterial diameter, histomorphometric analysis and immunohistochemistry at the transected locations and in gastrocnemius muscles was performed.

Results

The group treated with chitosan/MC significantly increased capillary density and the mean number of large blood vessels at the site of femoral artery transection compared with other experimental groups (P<0.05). The treatment with chitosan/MC also significantly increased the muscle fiber diameter and the capillary-to-muscle fiber ratio in gastrocnemius muscles compared with all other ischemic groups (P<0.05).

Conclusion

These findings suggested that chitosan and MCs together could offer a new approach for the therapeutic induction of angiogenesis in cases of peripheral arterial diseases.

PEGylated Platelet-Free Blood Plasma-Based Hydrogels for Full-Thickness Wound Regeneration

Objective: To develop a cost-effective and clinically usable therapy to treat full-thickness skin injuries. We accomplished this by preparing a viscoelastic hydrogel using polyethylene glycol (PEG)-modified platelet-free plasma (PEGylated PFP) combined with human adipose-derived stem cells (ASCs). Approach: PEGylated PFP hydrogels were prepared by polymerizing the liquid mixture of PEG and PFP±ASCs and gelled either by adding calcium chloride (CaCl₂) or thrombin. Rheological and in vitro studies were performed to assess viscoelasticity and the ability of hydrogels to direct ASCs toward a vasculogenic phenotype, respectively. Finally, a pilot study evaluated the efficacy of hydrogels±ASCs using an athymic rat full-thickness skin wound model. Results: Hydrogels prepared within the range of 11 to 27 mM for CaCl₂ or 5 to 12.5 U/mL for thrombin exhibited a storage modulus of ∼62 to 87 Pa and ∼47 to 92 Pa, respectively. The PEGylated PFP hydrogels directed ASCs to form network-like structures resembling vasculature, with a fourfold increase in perivascular specific genes that were confirmed by immunofluorescent staining. Hydrogels combined with ASCs exhibited an increase in blood vessel density when applied to excisional rat wounds compared with those treated with hydrogels (110.3 vs. 95.6 BV/mm²; p < 0.05). Furthermore, ASCs were identified in the perivascular region associated with newly forming blood vessels. Innovation: This study demonstrates that PFP modified with PEG along with ASCs can be used to prepare cost-effective stable hydrogels, at the bed-side, to treat extensive skin wounds. Conclusion: These results indicate that PEGylated plasma-based hydrogels combined with ASCs may be a potential regenerative therapy for full-thickness skin wounds.

Local pharmacological induction of angiogenesis: Drugs for cells and cells as drugs

The past decades have seen significant advances in pro-angiogenic strategies based on delivery of molecules and cells for conditions such as coronary artery disease, critical limb ischemia and stroke. Currently, three major strategies are evolving. Firstly, various pharmacological agents (growth factors, interleukins, small molecules, DNA/RNA) are locally applied at the ischemic region. Secondly, preparations of living cells with considerable bandwidth of tissue origin, differentiation state and preconditioning are delivered locally, rarely systemically. Thirdly, based on the notion, that cellular effects can be attributed mostly to factors secreted in situ, the cellular secretome (conditioned media, exosomes) has come into the spotlight. We review these three strategies to achieve (neo)angiogenesis in ischemic tissue with focus on the angiogenic mechanisms they tackle, such as transcription cascades, specific signalling steps and cellular gases. We also include cancer-therapy relevant lymphangiogenesis, and shall seek to explain why there are often conflicting data between in vitro and in vivo. The lion's share of data encompassing all three approaches comes from experimental animal work and we shall highlight common technical obstacles in the delivery of therapeutic molecules, cells, and secretome. This plethora of preclinical data contrasts with a dearth of clinical studies. A lack of adequate delivery vehicles and standardised assessment of clinical outcomes might play a role here, as well as regulatory, IP, and manufacturing constraints of candidate compounds; in addition, completed clinical trials have yet to reveal a successful and efficacious strategy. As the biology of angiogenesis is understood well enough for clinical purposes, it will be a matter of time to achieve success for well-stratified patients, and most probably with a combination of compounds.

A Preliminary Clinical Trial Comparing Split Treatments to the Face and Hand With Autologous Fat Grafting and Platelet-Rich Plasma (PRP): A 3D, IRB-Approved Study

BACKGROUND

Numerous methodologies have been suggested to enhance fat graft survival, but few long-term studies are available.

OBJECTIVES

The authors of this institutional review board-approved study investigated the safety and efficacy of utilizing platelet-rich plasma (PRP).

METHODS

Each of 10 patients received equal volumes of syringe-harvested, centrifuged fat to opposing midfaces with a lateral submuscular aponeurotic system-plication or no face lift and hands that were combined with equal volumes of either concentrated PRP or normal saline. Comparable assessments of fat retention/baseline values by 3D Vectra Analysis, VISIA, and Cortex facial skin analyses were performed. Clinical results were judged on a visual analogue scale.

RESULTS

The average percent change in mean volume assessments at the fat/PRP sites from baseline values, as profiled by 3D Vectra Analysis, demonstrated a higher, but statistically nonsignificant value over 1 year than the percent value changes at the fat/normal saline sites in the opposing face or hand. Three independent evaluators were able to assess volume restorations to the malar fat pad, naso-jugal groove, and nasolabial fold as well as to intermetacarpal hollowness with reduction of visible veins and tendons in the anterior midface and hands with both treatments. No adverse events were observed over the year-long study. Perioperative edema, erythema, bruising, and tenderness lasted up to 1 to 2 weeks at most.

CONCLUSIONS

Autologous fat grafting continues to be a safe and effective adjunct in facial and hand aesthetic surgery. This study will require more patients and longer follow-up periods to determine whether PRP has a potential role to increase fat graft retention in aesthetic patients.

LEVEL OF EVIDENCE: 3

Platelet number is positively and independently associated with glycated hemoglobin in non-diabetic overweight and obese subjects

BACKGROUND AND AIMS

A significant increase in platelet count may be a risk factor for atherosclerotic cardiovascular disease. This study investigates the association between platelet number and glucose metabolism, evaluated by glycated hemoglobin (HbA1c) levels, in a apparently healthy population represented by overweight and obese subjects with normal glucose and HbA1c levels.

METHODS AND RESULTS

As many as 240 subjects, 177 women and 63 men, aged 18-70 years, were enrolled. Body mass index (BMI), waist circumference (WC), systolic and diastolic blood pressure levels, platelet count and fasting blood glucose, insulin, insulin resistance, HbA1c, uric acid, triglyceride, total cholesterol, high and low density lipoprotein cholesterol concentrations were evaluated. Concerning the univariate correlation analyses between platelets number and all other variables, platelet count was significantly (and positively) correlated only with HbA1c (P < 0.05) and female sex (P < 0.01). HbA1c (P < 0.05), female sex (P < 0.001), and diastolic blood pressure (P < 0.01), positively, and age (P < 0.05) and systolic blood pressure (P < 0.05), negatively, were significantly and independently associated to platelet count in a final multiple regression analysis.

CONCLUSION

This is the first study showing a strong positive and independent relationship between HbA1c and platelet number in non-diabetic overweight and obese subjects.

Autologous Platelet-Rich Plasma Treatment Enables Pregnancy for a Woman in Premature Menopause

This report presents the case of a woman aged 40 who has experienced premature menopause from the age of 35. Having rejected oocyte donation, she opted for intraovarian injection of autologous platelet-rich plasma with the aim to rejuvenate the ovarian tissue and enable the employment of her own gametes through in-vitro fertilization. Six weeks following the autologous platelet-rich plasma treatment, a significant reduction in the patient’s follicle-stimulating hormone (FSH) levels were noted. A natural in-vitro fertilization cycle led to a biochemical pregnancy, resulting in a spontaneous abortion at the 5th week of pregnancy. This is the first report of a successful autologous platelet-rich plasma application leading to pregnancy in menopause. This report uniquely contributes to the medical knowledge and challenges current practice in the context of infertility. The efficiency and safety of this treatment with regard to the reproductive system merits further investigation.

Platelet number is negatively and independently associated with carotid intima-media thickness in apparently healthy overweight/obese subjects

BACKGROUND AND AIM

A significant change of platelet number may be a risk factor for atherosclerotic cardiovascular disease. The aim of this study was to investigate the association between platelet number and early signs of atherosclerosis, evaluated by carotid intima-media thickness (c-IMT), in a apparently healthy population mainly represented by obese subjects.

METHODS AND RESULTS

As many as 961 subjects, 686 women and 275 men, aged between 18 and 74 years, were enrolled in the study. Of these, 54 individuals (5.6% of all subjects) were normal weight, 259 individuals (27.0% of all subjects) were overweight, and 648 individuals (67.4% of all subjects) were obese. Waist circumference (WC) and blood glucose, insulin, total cholesterol, high and low density lipoprotein cholesterol, triglycerides and platelet count were also detected in all subjects, who underwent carotid echo color doppler ultrasound to measure c-IMT. c-IMT was significantly and positively associated to age (r = 0.204, P < 0.0001), fasting glucose (r = 0.073, P < 0.0240), total cholesterol (r = 0.096, P = 0.0031), and systolic and diastolic blood pressure (r = 0.140, P < 0.0001 and r = 0.119, P < 0.0003 respectively); c-IMT was significantly and negatively correlated with platelet count (r = -0.165, P < 0.0001). Only age (P < 0.0001) and systolic blood pressure (P = 0.0393), positively, and platelet number (P < 0.0001), negatively, were significantly and independently associated to c-IMT in a final multiple regression analysis.

CONCLUSION

Lower platelet number represented an independent determinant of c-IMT in a population, mainly represented by obese patients. These results suggest that a decrease of platelet number may well be an early defensive mechanism in subjects developing the thickening of carotid artery.

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

The healing of vascularized mammalian tissue injuries initiate with hemostasis and clotting as part of biological defense system leading to the formation of a fibrin clot in which activated platelets are trapped to quickly stop bleeding and destroy microbials. In order to harness the therapeutic potential of biomolecules secreted by platelets and stemmed from plasma, blood deconstruction has allowed to yield autologous platelet-and plasma-derived protein fibrin scaffold. The autologous growth factors and microparticles stemmed from platelets and plasma, interact with fibrin, extracellular matrix, and tissue cells in a combinatorial, synergistic, and multidirectional way on mechanisms governing tissue repair. This interplay will induce a wide range of cell specifications during inflammation and repair process including but not limited to fibrogenesis, angiogenesis, and immunomodulation. As biology-as-a-drug approach, autologous platelet-and plasma-derived protein fibrin scaffold is emerging as a safe and efficacious natural human-engineered growth factor delivery system to repair musculoskeletal tissues, and skin and corneal ulcers and burns. In doing so, it acts as therapeutic agent not perfect but close to biological precision. However, this autologous, biocompatible, biodegradable, and long in vivo lasting strategy faces several challenges, including its non-conventional single dose-response effect, the lack of standardization in its preparation and application, and the patient's biological features. In this review, we give an account of the main events of tissue repair. Then, we describe the procedure to prepare autologous platelet-and plasma-derived protein fibrin scaffolds, and the rationale behind these biomaterials, and finally, we highlight the significance of strategic accuracy in their application.

Angiogenic Properties of 'Leukocyte- and Platelet-Rich Fibrin'

Leukocyte- and Platelet-Rich Fibrin (L-PRF) is an autologous platelet concentrate, consisting of a fibrin matrix enriched with platelets, leukocytes and a plethora of cytokines and growth factors. Since L-PRF is produced bedside from whole blood without the use of an anti-coagulant, it is becoming a popular adjuvant in regenerative medicine. While other types of platelet concentrates have been described to stimulate blood vessel formation, little is known about the angiogenic capacities of L-PRF. Therefore, this study aimed to fully characterize the angiogenic potential of L-PRF. With an antibody array, the growth factors released by L-PRF were determined and high levels of CXC chemokine receptor 2 (CXCR-2) ligands and epidermal growth factor (EGF) were found. L-PRF induced in vitro key steps of the angiogenic process: endothelial proliferation, migration and tube formation. In addition, we could clearly demonstrate that L-PRF is able to induce blood vessel formation in vivo, the chorioallantoic membrane assay. In conclusion, we could demonstrate the angiogenic capacity of L-PRF both in vitro and in vivo, underlying the clinical potential of this easy-to-use platelet concentrate.

Combined delivery of angiopoietin-1 gene and simvastatin mediated by anti-intercellular adhesion molecule-1 antibody-conjugated ternary nanoparticles for acute lung injury therapy

Effective treatment for acute lung injury (ALI) is in high demand. Lung-targeted ternary nanoparticles containing anti-intercellular adhesion molecule-1 (ICAM-1) antibody-conjugated simvastatin-loaded nanostructured lipid carrier (ICAM/NLC), protamine (Pro), and angiopoietin-1 (Ang-1) gene (ICAM-NLC/Pro/Ang) were developed for ALI therapy. The ternary nanoparticles with different weight ratios of ICAM-NLC to Ang-1 gene were prepared via charge interaction. The anti-ICAM-1 antibody-conjugated ternary nanoparticles exhibited higher cellular uptake and transfection efficiency (from 26.7% to 30.9%) in human vascular endothelial cell line EAhy926 than the non-targeted control. The largest size of ICAM-NLC/Pro/Ang (357.1 nm) was employed for further study, which significantly up-regulated in vitro and in vivo Ang-1 protein expression. In vivo i.v. administration of ICAM-NLC/Pro/Ang (357.1 nm) significantly attenuated pulmonary TNF-α and IL-6 levels, inflammatory cell infiltration, and led to positive histological improvements in lipopolysaccharide-induced ALI mice. Collectively, the ICAM-NLC/Pro/Ang that co-delivered simvastatin and Ang-1 gene may represent a potential treatment modality for ALI.

Healing after Resection of Colonic Endometriosis and Growth Factor-enriched Agents: An Experimental Rat Model

STUDY OBJECTIVE

To examine the potential beneficial effect of platelet-rich plasma (PRP) and fibrin sealant (TISSEEL; Baxter Healthcare Corporation, Deerfield, IL) on bowel wound healing after shaving of an experimentally induced endometriotic lesion.

DESIGN

A single-blind, randomized study (Canadian Task Force classification I).

SETTING

A certified animal research facility.

ANIMALS

Thirty female Sprague-Dawley rats.

INTERVENTIONS

Experimental colonic endometriosis was induced by transplanting endometrial tissue to all animals (first surgery). Thirty rats were then randomized to 1 of 3 groups according to treatment; PRP (group 1, n = 10), fibrin sealant (group 2, n = 10), or no agent (group 3, n = 10) was applied after shaving of the endometriotic nodule (second surgery).

MEASUREMENTS AND MAIN RESULTS

Colonic endometriosis was successfully induced in all subjects. Four days after the second surgery, the animals were euthanized, and microscopic evaluation was performed. The pathologist was blinded to the treatment method. Histopathologic analysis revealed that compared with the control group, collagen disposition was found in a significantly higher expression in both the PRP and fibrin sealant groups (p = .011 and p = .011, respectively). Distortion of the integrity of the colon layers was statistically more pronounced in the control group compared with the fibrin sealant group (p = .033), whereas greater new blood vessel formation was observed in the fibrin sealant group compared with the control (p = .023). No histologic evidence of residual or recurrent disease was detected.

CONCLUSION

Both PRP and fibrin sealant appear to be safe and associated with improved tissue healing during shaving for the excision of colonic endometriosis, attributed to the enhanced collagen disposition, neovascularization, and protection of the integrity of colon layers. Clinical trials are warranted to confirm the feasibility of PRP and fibrin sealant in the clinical setting.

Current Trends in Biomaterial Utilization for Cardiopulmonary System Regeneration

The cardiopulmonary system is made up of the heart and the lungs, with the core function of one complementing the other. The unimpeded and optimal cycling of blood between these two systems is pivotal to the overall function of the entire human body. Although the function of the cardiopulmonary system appears uncomplicated, the tissues that make up this system are undoubtedly complex. Hence, damage to this system is undesirable as its capacity to self-regenerate is quite limited. The surge in the incidence and prevalence of cardiopulmonary diseases has reached a critical state for a top-notch response as it currently tops the mortality table. Several therapies currently being utilized can only sustain chronically ailing patients for a short period while they are awaiting a possible transplant, which is also not devoid of complications. Regenerative therapeutic techniques now appear to be a potential approach to solve this conundrum posed by these poorly self-regenerating tissues. Stem cell therapy alone appears not to be sufficient to provide the desired tissue regeneration and hence the drive for biomaterials that can support its transplantation and translation, providing not only physical support to seeded cells but also chemical and physiological cues to the cells to facilitate tissue regeneration. The cardiac and pulmonary systems, although literarily seen as just being functionally and spatially cooperative, as shown by their diverse and dissimilar adult cellular and tissue composition has been proven to share some common embryological codevelopment. However, necessitating their consideration for separate review is the immense adult architectural difference in these systems. This review also looks at details on new biological and synthetic biomaterials, tissue engineering, nanotechnology, and organ decellularization for cardiopulmonary regenerative therapies.

Therapeutic Effect of Platelet-Rich Plasma in Rat Spinal Cord Injuries

Platelet-rich plasma (PRP) is prepared by centrifuging fresh blood in an anticoagulant state, and harvesting the platelet-rich portion or condensing platelets. Studies have consistently demonstrated that PRP concentrates are an abundant source of growth factors, such as platelet-derived growth factor (PDGF), transforming growth factor β (TGF-β), insulin-like growth factor 1 (IGF-1), and epithelial growth factor (EGF). The complex mechanisms underlying spinal cord injury (SCI) diminish intrinsic repair and neuronal regeneration. Several studies have suggested that growth factor-promoted axonal regeneration can occur for an extended period after injury. More importantly, the delivery of exogenous growth factors contained in PRP, such as EGF, IGF-1, and TGF-β, has neurotrophic effects on central nervous system (CNS) injuries and neurodegenerative diseases. However, only a few studies have investigated the effects of PRP on CNS injuries or neurodegenerative diseases. According to our review of relevant literature, no study has investigated the effect of intrathecal (i.t.) PRP injection into the injured spinal cord and activation of intrinsic mechanisms. In the present study, we directly injected i.t. PRP into rat spinal cords and examined the effects of PRP on normal and injured spinal cords. In rats with normal spinal cords, PRP induced microglia and astrocyte activation and PDGF-B and ICAM-1 expression. In rats with SCIs, i.t. PRP enhanced the locomotor recovery and spared white matter, promoted angiogenesis and neuronal regeneration, and modulated blood vessel size. Furthermore, a sustained treatment (a bolus of PRP followed by a 1/3 dose of initial PRP concentration) exerted more favorable therapeutic effects than a single dose of PRP. Our findings suggest by i.t. PRP stimulate angiogenesis, enhancing neuronal regeneration after SCI in rats. Although PRP induces minor inflammation in normal and injured spinal cords, it has many advantages. It is an autologous, biocompatible, nontoxic material that does not result in a major immune response. In addition, based on its safety and ease of preparation, we hypothesize that PRP is a promising therapeutic agent for SCI.

Platelet-rich Plasma Protects HUVECs against oX-LDL-induced Injury

Platelet-rich plasma (PRP) contains a variety of cytokines, some of which ameliorate oX-LDL (oxidized low-density lipoprotein)-induced endothelial cell (EC) injury. Therefore, we hypothesized that PRP might alleviate oX-LDL-induced injury.

METHODOLOGY

Human umbilical vein endothelial cells (HUVECs) were divided into four groups: a PPP (platelet-poor plasma) group, an oX-LDL group, an oX-LDL+PRP group and a PRP group. CCK-8 (Cell Counting Kit) assay, Annexin V-FITC/7-AAD and Hochest 33342 staining were performed to assess cell proliferation and apoptosis. Tube formation and cell migration assays were performed to evaluate HUVEC-mediated vasculogenesis and migration. Expression levels of Bcl-2, Bax, caspase-3, cleaved caspase-3, PI3K, Akt, eNOS p-Akt, p-eNOS, IL-6 and IL-1 were detected by western blotting or immunofluorescence.

PRINCIPAL FINDINGS

PRP promoted HUVEC proliferation in a non-linear pattern, protected HUVECs against oX-LDL-induced apoptosis and attenuated oX-LDL-mediated inhibition of HUVEC migration and vasculogenesis. Additionally, compared to the PPP group, PRP downregulated pro-apoptotic proteins (ratio of Bax/Bcl-2, caspase-3 and cleaved caspase-3) as well as IL-6 and IL-1. Moreover, the PI3K/Akt/eNOS pathway was activated by PRP and inactivated by oX-LDL.

CONCLUSIONS

It was demonstrated that PRP protected HUVECs against oX-LDL-induced injury and that the PI3K/Akt/eNOS pathway was activated in this process.