Autologous platelet-rich plasma for wound and osseous healing: a review of the literature and commercially available products

Differences between first- and second-generation autologous platelet concentrates

Autologous platelet concentrates (APCs) applied alone or combined with other biomaterials are popular bioactive factors employed in regenerative medicine. The main biological rationale of using such products is to concentrate blood-derived growth factors and cells into the wound microenvironment to enhance the body's natural healing capacity. First-generation APC is represented by platelet-rich plasma (PRP). While different protocols have been documented for PRP preparation, they overall consist of two cycles of centrifugation and have important limitations related to the use of an anticoagulant first and an activator afterward, which may interfere with the natural healing process and the release of bioactive molecules. The second generation of platelet concentrates is represented by leukocyte and platelet-rich fibrin (L-PRF). L-PRF protocols involve a single centrifugation cycle and do not require the use of anticoagulants and activators, which makes the preparation more straight forward, less expensive, and eliminates potential risks associated with the use of activators. However, since no anticoagulant is employed, blood undergoes rapid clotting within the blood collection tube; hence, a timely management of L-PRF is crucial. This review provides an overview on the most documented protocols for APC preparations and critically discusses the main differences between first- and second-generation APCs in terms of cell content, protein release, and the formation of a 3D fibrin network. It appears evident that the inconsistency in reporting protocol parameters by most studies has contributed to conflicting conclusions regarding the efficacy of different APC formulations and has significantly limited the ability to interpret the results of individual clinical studies. In the future, the use of a standardized classification system, together with a detailed reporting on APC protocol parameters is warranted to make study outcomes comparable. This will also allow to clarify important aspects on the mechanism of action of APCs (like the role of leukocytes and centrifugation parameters) and to optimize the use of APCs in regenerative medicine.

Effects of platelet-rich plasma combined with exercise therapy for one year on knee osteoarthritis: retrospective cohort study

BACKGROUND

Platelet-rich plasma (PRP) is a promising treatment for knee osteoarthritis (OA). However, exercise therapy and activities of daily living (ADL) guidance are recommended as core treatments in the Osteoarthritis Research Society International (OARSI) guidelines. However, the effects of PRP combined with exercise therapy are not fully understood. This study aimed to clarify the effectiveness of this treatment.

METHODS

We assigned patients diagnosed with knee OA and treated between January 2021 and December 2022 to groups who underwent PRP + exercise (PE), PRP (P), or exercise (E) therapy. Outcomes were evaluated using Knee Injury and Osteoarthritis Outcome Scores (KOOS) before, and 1, 3, and 12 months after treatment. Within-group comparisons according to the time of each score were statistically assessed using a one-way analysis of variance, then differences were analyzed using Bonferroni multiple comparisons p < 0.05). Treatment responses were determined using Outcome Measures in Rheumatology (OMERACT)-OARSI Responder criteria.

RESULTS

Pre-treatment KOOS did not significantly differ among the groups. Pain in the PE group improved within 1 month, symptoms, ADL, and quality of life (QOL) improved after 3, months and continued for 12 months. Pain and symptoms improved in the P group within 1 month, but ADLs and the QOL did not significantly change. Pain improved after 3 months in the E group and ADL, and QOL improved by 12 months. The response among the groups was the highest for the PE, with 50.0% at 1 and 3 months, and 65.0% at 12 months.

CONCLUSIONS

Therapy with PRP immediately relieved pain, whereas exercise conferred late, but enduring effects. Combining PRP with exercise conferred synergistic advantages that persisted for up to 12 months.

Percutaneous injection of autologous platelet gel accelerate healing in diabetic tibial non union: On going longitudinal study

INTRODUCTION

In this study the tibial shaft fracture non unions in diabetes mellitus are evaluated with percutaneous autologous platelet gel supplementation to accelerate union are compared with individually matched control group with autologous iliac crest bone marrow aspirate injection.

MATERIAL AND METHODS

This present study was carried out on tibial non unions in diabetic patients recruited in an ongoing longitudinal study over a period of 2006 to 2017, treated by one surgeon at one institute, are included in this report. Each of 18 established tibial atrophic, aseptic non unions treated by percutaneous autologous platelets and iliac crest bone marrow aspirate were followed up on regular basis up till 9 months. The healing of non union was assessed clinically by painless full weight bearing and the radiological union was judged by bridging callus formation observed on at least 3 of 4 cortices in anteroposterior and lateral views.

RESULTS

Union was observed in 17 (94.4 %) patients of the autologous platelet group. The average time to union was 9.2 weeks (range 8 to 18 weeks) after percutaneous autologous platelet injection (P < 0.0517) .In the control group, union was observed in 14 (77.8 %) patients (P = 0.672). The average time to union following percutaneous bone marrow injection was 11.6 weeks (range 9 to 28 weeks). The proximal 1/3 shaft non union healed comparatively faster than the distal 1/3 shaft tibia (P ≤ 0.0612). No correlation was observed between the comminuted and non comminuted fracture non union (P = 0.789). A significant correlation was noted as regards the non union healing time duration in patients who were on insulin and oral hypoglycemic drugs (P ≤ 0.001) and also about the total duration of diabetes mellitus in years (P ≤ 0.003).

CONCLUSION

This investigation showed that percutaneous autologous platelet gel delivery is sufficient method to obtain union in diabetic tibial fracture non unions, which is less invasive procedure than bone marrow injection. The efficacy of this autologous platelets is once again well established and this study reinforced categorically the previously published report by the author.

Evaluation of Survival of Subdermal Plexus Skin Flaps in 8 Cats After Injection of Platelet Rich Plasma

The aim of the present study was to evaluate the effect of platelet-rich plasma injection on the survival of experimentally developed subdermal plexus skin flaps in cats. Two flaps, 2 cm wide and 6 cm long were created bilaterally in the dorsal midline in 8 cats. Each flap was randomized to 1 of 2 groups: platelet-rich plasma injection and control. After flap development, the flaps were immediately placed back on the recipient bed. Then 1.8 mL of platelet-rich plasma was equally injected into 6 different parts of the treatment flap. All flaps were evaluated macroscopically daily and on days 0, 7, 14, and 25 by planimetry, Laser Doppler flowmetry, and histology. Mean flap survival on day 14 was 80.437 % (±22.745) for the treatment group and 66.516 % (±24,12) for the control group with no statistically significant difference between the 2 groups (P = .158). Histologically, a significant difference was found between the base of the PRP and the control flap in edema score on day 25 (P = .034). In conclusion, there is no evidence to support the use of platelet-rich plasma in subdermal plexus flaps in cats. However, the use of platelet-rich plasma may aid in reducing edema of subdermal plexus flaps.

Locally Injected Autologous Platelet-Rich Plasma Improves Cutaneous Wound Healing in Cats

Cutaneous defects in cats are commonly encountered in clinical practice, and healing can be accomplished by first or second intention. Platelet-rich plasma (PRP) is characterized by a plasma concentration containing a large number of platelets in a small volume of plasma. The objective of the present study was to record the efficacy of PRP infiltration in open wounds in laboratory cats. Six wounds were created in the dorsal midline of eight laboratory cats, with the wounds of one side designated as the PRP group and the wounds of the other side as the control group. Wound healing was evaluated by daily clinical examination, planimetry, laser Doppler flowmetry, and histologic examination on days 0, 7, 14, and 25, and by measurement of metalloproteinases (MMPs)-2 and -9 and tissue inhibitor metalloproteinase (TIMP)-1 on days 0, 14, and 25. Based on the results of the present study, the mean time for full coverage with granulation tissue was shorter in the PRP group, the mean contraction and total wound healing percentage were increased compared to the control group, and finally, the perfusion measured with laser Doppler flowmetry was higher in the PRP group during all examination days. In conclusion, this is the first study focusing on the topical application of PRP in the treatment of open wounds in laboratory cats, and our results are encouraging—showing a more rapid healing in the PRP group.

Nanocarrier-Mediated Topical Insulin Delivery for Wound Healing

Wound care has been clinically demanding due to inefficacious treatment that represents an economic burden for healthcare systems. In Europe, approximately 7 million people are diagnosed with untreated wounds, leading to a cost between 6.000€ and 10.000€ per patient/year. In the United States of America, 1.5 million people over 65 years old suffer from chronic wounds. A promising therapeutic strategy is the use of exogenous growth factors because they are decreased at the wound site, limiting the recovery of the skin. Insulin is one of the cheapest growth factors in the market able to accelerate the re-epithelialization and stimulate angiogenesis and cell migration. However, the effectiveness of topical insulin in wound healing is hampered by the proteases in the wound bed. The encapsulation into nanoparticles improves its stability in the wound, providing adhesion to the mucosal surface and allowing its sustained release. The aim of this review is to perform a standing point about a promising strategy to treat different types of wounds by the topical delivery of insulin-loaded nanocarriers.

Effect of platelet-rich plasma on fracture healing

Bone has the ability to completely regenerate under normal healing conditions. Although fractures generally heal uneventfully, healing problems such as delayed union or nonunion still occur in approximately 10% of patients. Optimal healing potential involves an interplay of biomechanical and biological factors. Orthopedic implants are commonly used for providing the necessary biomechanical support. In situations where the biological factors that are needed for fracture healing are deemed inadequate, additional biological enhancement is needed. With platelets being packed with granules that contain growth factors and other proteins that have osteoinductive capacity, local application of platelet concentrates, also called platelet-rich plasma (PRP) seems an attractive biological to enhance fracture healing. This review shows an overview of the use PRP and its effect in enhancing fracture healing. PRP is extracted from the patient's own blood, supporting that its use is considered safe. Although PRP showed effective in some studies, other studies showed controversial results. Conflicts in the literature may be explained by the absence of consensus about the preparation of PRP, differences in platelet counts, low number of patients, and absence of a standard application technique. More studies addressing these issues are needed in order to determine the true effect of PRP on fracture healing.

Wound dressings as growth factor delivery platforms for chronic wound healing

Introduction: Years of tissue engineering research have clearly demonstrated the potential of integrating growth factors (GFs) into scaffolds for tissue regeneration, a concept that has recently been applied to wound dressings. The old concept of wound dressings that only take a passive role in wound healing has now been overtaken, and advanced dressings which can take an active part in wound healing, are of current research interest.Areas covered: In this review we will focus on the recent strategies for the delivery of GFs to wound sites with an emphasis on the different approaches used to achieve fine tuning of spatial and temporal concentrations to achieve therapeutic efficacy.Expert opinion: The use of GFs to accelerate wound healing and reduce scar formation is now considered a feasible therapeutic approach in patients with a high risk of infections and complications. The integration of micro - and nanotechnologies into wound dressings could be the key to overcome the inherent instability of GFs and offer adequate control over the release rate. Many investigations have led to encouraging outcomes in various in vitro and in vivo wound models, and it is expected that some of these technologies will satisfy clinical needs and will enter commercialization.

Platelet-rich fibrin can accelerate the healing of common bile duct anastomosis in a rat

Objectives

This study aimed to evaluate the effect of platelet-rich fibrin (PRF) concentrate on the bile duct anastomosis healing process in rats.

Material and Methods

Thirty male Sprague Dawley (SD) rats were used for the study. The animals were allocated into three groups: Group I Control Group (n=10): Anastomosis to the common bile duct (CBD) with a stent. Group II PRF Group (n=10): Anastomosis to the CBD with a stent and covered with PRF. Group III Sham Group (n=10): Preparation of the common bile duct, no anastomosis. The animals were followed up for 1 month, then sacrificed. Study parameters were adhesions around the anastomosis, thickness of the bridging bile duct tissue over the stent, and histopathologic examination of the bridging bile duct tissue.

Results

CBD anastomosis using a stent caused severe adhesion around the anastomosis, bridging bile duct tissues were weak and histopathologically, healing was incomplete in most of the control animals. However, PRF application significantly reduced the adhesions, increased the quality of the bridging bile duct tissues, and caused complete healing histologically.

Conclusion

PRF is an autologous, easily prepared membrane. The present study findings show that PRF prevents local complications and increases the healing capacity of the bile duct after CBD anastomosis. Therefore, it might be a new treatment option for preventing complications following common bile duct anastomosis in liver transplantation patients.

The effect of platelet-rich plasma on fracture healing in long-bone pseudoarthrosis

PURPOSE

The aim of this study was to investigate the effects of platelet-rich plasma (PRP) on fracture union rate and fracture union time in pseudoarthrosis surgery and to evaluate the clinical and functional results of the patients.

METHODS

The patients who were undergone pseudoarthrosis surgery between 2011 and 2014 were evaluated retrospectively. Twenty-four patients were included in the study. Patients were divided into two groups with used PRP and not used PRP during surgery. There were 14 patients in the PRP group and 10 patients in the control group. The two groups were compared in terms of demographic characteristics, fracture union time, and functional scores of the Lower Extremity Functional Scale and Upper Extremity Functional Index.

RESULTS

Fractures were healed in both groups, and no complications were encountered. A statistically significant difference was found between the two groups in terms of fracture union time. The mean time of union was 5.3 months in the PRP group and 11.3 months in the control group (p: 0.000). There was no statistically significant difference between the two groups in terms of functional scores (p: 0.250).

CONCLUSION

As a result of our study, we concluded that PRP is an effective and safe method in pseudoarthrosis surgery that reduces fracture union time. Controlled studies with more patient numbers are needed.

Leukocyte- and platelet-rich fibrin as an adjuvant to the surgical approach for osteoradionecrosis: a case report

We present a case of osteoradionecrosis treated with leukocyte- and platelet-rich fibrin (LPRF) and surgery and followed up with clinical and tomographic investigations. A 65-year-old woman presented with pain in the posterior region of the right palate. Her medical history included cardiovascular disease and squamous cell carcinoma in the anterior region of the floor of the mouth that had been treated with intensity-modulated radiation therapy. Measurements of isodose curves showed a full dosage of 6,462.6 cGy in the anterior mandibular region, whereas that in the posterior region on the right side of the maxilla reached 5,708.1 cGy. Osteotomy was performed using rotary instruments, and debridement and placement of two LPRF membranes were also carried out. New gum tissue with no bone exposure was noted 14 days postoperatively. Tissue repair was complete, and the patient had no further complaints. During a 39-month follow-up period, the oral mucosa remained intact, and the patient was rehabilitated with a new upper denture. Since there is no consensus regarding the best protocol to treat osteoradionecrosis, LPRF might be an interesting adjuvant to a surgical approach. The use of LPRF is simple and reduces operational costs, time of handling, probability of technical failure, and associated morbidities for patients with osteoradionecrosis.

The Effectiveness of Autologous Platelet Rich Plasma Application in the Wound Bed Prior to Resurfacing with Split Thickness Skin Graft vs. Conventional Mechanical Fixation Using Sutures and Staples

BACKGROUND

Autologous platelet rich plasma (PRP) has significant benefits facilitating improved graft take on wound beds due to hemostasis, adhesive and healing properties. This study aimed at effective use of PRP in wound beds on graft take irrespective of etiology as compared to conventional methods of mechanical fixation using sutures and staples.

METHODS

Forty cases including 20 in control and 20 in PRP groups admitted to the Department of Plastic Surgery at Vydehi Institute of Medical Sciences and Research Centre, Bangalore were enrolled between October 2015 and September 2017. Freshly prepared autologous PRP was applied on wound beds in the treated group, while conventional mechanical fixation methods like staples and sutures were used in the control group for the fixation of the skin grafts.

RESULTS

Most significant result was the instant graft take to the wound bed irrespective of the etiology besides hemostasis and healing properties in the PRP treated group which resulted in considerable reduction of surgeon’s time required for the removal of sutures and staples at the final stages. Also, only 10% with graft edema were noted in the PRP treated patients as compared to 68% in the control group. The inner dressings and skin graft were dry in the PRP group and the post-operative etching, weeping and pain at the graft site reduced.

CONCLUSION

The cosmetic appearance of this scar was better in the PRP group besides post-operative edema and graft loss. The study recommends use of PRP at the recipient site of split thickness skin graft.

Cytoplasmic Interactions between the Glucocorticoid Receptor and HDAC2 Regulate Osteocalcin Expression in VPA-Treated MSCs

Epigenetic regulation has been considered an important mechanism for influencing stem cell differentiation. In particular, histone deacetylases (HDACs) have been shown to play a role in the osteoblast differentiation of mesenchymal stem cells (MSCs). In this study, the effect of the HDAC inhibitor, valproic acid (VPA), on bone formation in vivo by MSCs was determined. Surprisingly, VPA treatment, unlike other HDAC inhibitors, produced a well-organized lamellar bone tissue when MSCs–collagen sponge constructs were implanted subcutaneously into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice, although a decrease of osteocalcin (OC) expression was observed. Consequently, we decided to investigate the molecular mechanisms by which VPA exerts such effects on MSCs. We identified the glucocorticoid receptor (GR) as being responsible for that downregulation, and suggested a correlation between GR and HDAC2 inhibition after VPA treatment, as evidenced by HDAC2 knockdown. Furthermore, using co-immunoprecipitation analysis, we showed for the first time in the cytoplasm, binding between GR and HDAC2. Additionally, chromatin immunoprecipitation (ChIP) assays confirmed the role of GR in OC downregulation, showing recruitment of GR to the nGRE element in the OC promoter. In conclusion, our results highlight the existence of a cross-talk between GR and HDAC2, providing a mechanistic explanation for the influence of the HDAC inhibitor (namely VPA) on osteogenic differentiation in MSCs. Our findings open new directions in targeted therapies, and offer new insights into the regulation of MSC fate determination.

Advanced Growth Factor Delivery Systems in Wound Management and Skin Regeneration

Growth factors are endogenous signaling molecules that regulate cellular responses required for wound healing processes such as migration, proliferation, and differentiation. However, exogenous application of growth factors has limited effectiveness in clinical settings due to their low in vivo stability, restricted absorption through skin around wound lesions, elimination by exudation prior to reaching the wound area, and other unwanted side effects. Sophisticated systems to control the spatio-temporal delivery of growth factors are required for the effective and safe use of growth factors as regenerative treatments in clinical practice, such as biomaterial-based drug delivery systems (DDSs). The current review describes the roles of growth factors in wound healing, their clinical applications for the treatment of chronic wounds, and advances in growth factor-loaded DDSs for enhanced wound healing, focusing on micro- and nano-particulate systems, scaffolds, hydrogels, and other miscellaneous systems.

Use of autologous platelet-rich plasma for a delayed consolidation of a tibial fracture in a young donkey

A 9-month-old filly donkey was referred for a comminuted diaphyseal fracture of the right tibia. Surgical osteosynthesis, with multiple lag screws and a neutralization plate, was performed for anatomical reconstruction. Despite a good gait condition, delayed bone consolidation and a bone gap were evident on follow up radiographic evaluations. Due to delayed healing, autologous platelet-rich plasma (PRP) was injected on the surface of the tibia. Increased bone consolidation was evident on radiographs one month after the PRP injection. Progressive filling of both the fracture lines and bone gap continued during the six-month follow up. Clinical outcome was excellent. Autologous PRP should be considered as a practical adjuvant therapy in bone healing process in donkeys.

The Biology of Bone and Ligament Healing

This review describes the normal healing process for bone, ligaments, and tendons, including primary and secondary healing as well as bone-to-bone fusion. It depicts the important mediators and cell types involved in the inflammatory, reparative, and remodeling stages of each healing process. It also describes the main challenges for clinicians when trying to repair bone, ligaments, and tendons with a specific emphasis on Charcot neuropathy, fifth metatarsal fractures, arthrodesis, and tendon sheath and adhesions. Current treatment options and research areas are also reviewed.

Osteogenic differentiation of human mesenchymal stem cells promotes mineralization within a biodegradable peptide hydrogel

An attractive strategy for the regeneration of tissues has been the use of extracellular matrix analogous biomaterials. Peptide-based fibrillar hydrogels have been shown to mimic the structure of extracellular matrix offering cells a niche to undertake their physiological functions. In this study, the capability of an ionic-complementary peptide FEFEFKFK (F, E, and K are phenylalanine, glutamic acid, and lysine, respectively) hydrogel to host human mesenchymal stem cells in three dimensions and induce their osteogenic differentiation is demonstrated. Assays showed sustained cell viability and proliferation throughout the hydrogel over 12 days of culture and these human mesenchymal stem cells differentiated into osteoblasts simply upon addition of osteogenic stimulation. Differentiated osteoblasts synthesized key bone proteins, including collagen-1 (Col-1), osteocalcin, and alkaline phosphatase. Moreover, mineralization occurred within the hydrogel. The peptide hydrogel is a naturally biodegradable material as shown by oscillatory rheology and reversed-phase high-performance liquid chromatography, where both viscoelastic properties and the degradation of the hydrogel were monitored over time, respectively. These findings demonstrate that a biodegradable octapeptide hydrogel can host and induce the differentiation of stem cells and has the potential for the regeneration of hard tissues such as alveolar bone.

Prospective Randomized Evaluation of Intraoperative Application of Autologous Platelet-Rich Plasma on Surgical Site Infection or Delayed Wound Healing

BACKGROUND

Prevention of surgical site infections and the reduction of wound-related complication rates have become increasingly emphasized by hospital task groups and government agencies given the degree of economic burden it places on the health care system. Platelet-rich plasma (PRP) contains growth factors and other biomolecules that promote endogenous microbicidal activity. We hypothesized that PRP would help prevent postoperative infection and delayed wound healing (DWH).

METHODS

We randomized patients having foot or ankle surgery to the treatment group receiving intraoperative PRP (applied to operative field) and platelet-poor plasma at closing (PPP, on the sutured skin) or the control group (no PRP/PPP). The incidence of deep surgical site infection and DWH (collectively called endpoints) was compared between groups (n = 250/group). PRP had a mean 5.3-fold platelet concentration compared to whole blood, with concentrated white blood cells. Mean age (±SD) of patients was 52 years (±15), 65% were women. Minor and major operative procedures were included. Patients were followed for 60 days. Seventy controls had PRP prepared for assay of growth factors. Procedure mix, ASA scores, mean operative times, and comorbidity mix were similar between groups.

RESULTS

The primary result was no difference in number of endpoints between groups: 19 patients in the PRP group (7.6%) versus 18 controls (7.2%). Endpoints were deep surgical site infections in 2 PRP/PPP patients and 1 control, and DWH in 17 PRP/PPP patients and 17 controls. Analysis of PRP samples revealed a large variation in growth factor concentrations between patients.

CONCLUSIONS

Intraoperative application of PRP/PPP did not reduce the incidence of postoperative infection or DWH. Growth factor profiles varied greatly between patients, suggesting that the potentially therapeutic treatment delivered was not consistent from patient-to-patient.

LEVEL OF EVIDENCE

Level I, prospective randomized trial.

Tendinopathies and platelet-rich plasma (PRP): from pre-clinical experiments to therapeutic use

OBJECTIVES

The restorative properties of platelets, through the local release of growth factors, are used in various medical areas. This article reviews fundamental and clinical research relating to platelet-rich plasma applied to tendinous lesions.

MATERIALS AND METHOD

Articles in French and English, published between 1 January 2012 and 31 December 2014. dealing with PRP and tendons were searched for using the Medline and Scopus data bases.

RESULTS

Forty-seven articles were identified which addressed pre-clinical and clinical studies: 27 relating to in vitro and in vivo animal studies and 20 relating to human studies. Of these, five addressed lateral epicondylitis, two addressed rotator cuff tendinopathies, ten dealt with patellar tendinopathies and three looked at Achilles tendinopathies.

CONCLUSIONS

The majority of pre-clinical studies show that PRP stimulates the tendon's healing process. However, clinical series remain more controversial and level 1, controlled, randomised studies are still needed.

A literature-based guide to the conservative and surgical management of the acute Charcot foot and ankle

Acute Charcot neuroarthropathy of the foot and ankle presents with the insidious onset of a unilateral acutely edematous, erythematous, and warm lower extremity. The acute stages are typically defined as Eichenholtz Stage 1, or Stage 0, which was first described by Shibata et al. in 1990. The ultimate goal of treatment is maintenance of a stable, plantigrade foot which can be easily shod, minimizing the risk of callus, ulceration, infection, and amputation. The gold standard of treatment is non-weight-bearing immobilization in a total contact cast. Surgical intervention remains controversial. A review of the literature was performed to provide an evidenced-based approach to the conservative and surgical management of acute Charcot neuroarthropathy of the foot and ankle.

Formation of blood clot on biomaterial implants influences bone healing

The first step in bone healing is forming a blood clot at injured bones. During bone implantation, biomaterials unavoidably come into direct contact with blood, leading to a blood clot formation on its surface prior to bone regeneration. Despite both situations being similar in forming a blood clot at the defect site, most research in bone tissue engineering virtually ignores the important role of a blood clot in supporting healing. Dental implantology has long demonstrated that the fibrin structure and cellular content of a peri-implant clot can greatly affect osteoconduction and de novo bone formation on implant surfaces. This article reviews the formation of a blood clot during bone healing in relation to the use of platelet-rich plasma (PRP) gels. It is implicated that PRP gels are dramatically altered from a normal clot in healing, resulting in conflicting effect on bone regeneration. These results indicate that the effect of clots on bone regeneration depends on how the clots are formed. Factors that influence blood clot structure and properties in relation to bone healing are also highlighted. Such knowledge is essential for developing strategies to optimally control blood clot formation, which ultimately alter the healing microenvironment of bone. Of particular interest are modification of surface chemistry of biomaterials, which displays functional groups at varied composition for the purpose of tailoring blood coagulation activation, resultant clot fibrin architecture, rigidity, susceptibility to lysis, and growth factor release. This opens new scope of in situ blood clot modification as a promising approach in accelerating and controlling bone regeneration.

Updating on understanding and managing chronic wound

The art of healing wounds is quite complex. It requires the patient's local condition in conjunction with their systemic condition to provide the most ideal wound environment. As wound care is expanding with advances in technology, we are facing a variety of different wound care products based on an assortment of bioengineered skin substances, growth factors, oxygen therapies, low frequency ultrasound and even low energy light. While these emerging evidence-based treatments prove to be promising in improving clinical outcomes and quality of life, it challenges providers to provide cost-effective treatment plans. The goal of this paper is to introduce a discussion regarding practical clinical application of various forms of advanced wound technologies in order to optimize the art of wound healing.

Unique antimicrobial effects of platelet-rich plasma and its efficacy as a prophylaxis to prevent implant-associated spinal infection

Platelet-rich-plasma (PRP) has attracted great attention and has been increasingly used for a variety of clinical applications including orthopedic surgeries, periodontal and oral surgeries, maxillofacial surgeries, plastic surgeries, and sports medicine. However, very little is known about the antimicrobial activities of PRP. PRP is found to have antimicrobial properties both in vitro and in vivo. In vitro, the antimicrobial properties of PRP are bacterial-strain-specific and time-specific: PRP significantly (80-100 fold reduction in colony-forming units) inhibits the growth of methicillin-sensitive and methicillin-resistant Staphylococcus aureus, Group A streptococcus, and Neisseria gonorrhoeae within the first few hours but it has no significant antimicrobial properties against E. coli and Pseudomonas. The antimicrobial properties of PRP also depend on the concentration of thrombin. In vivo, an implant-associated spinal infection rabbit model is established and used to evaluate the antimicrobial and wound-healing properties of PRP. Compared to the infection controls, PRP treatment results in significant reduction in bacterial colonies in bone samples at all time points studied (i.e. 1, 2, and 3 weeks) and significant increase in mineralized tissues (thereby better bone healing) at postoperative weeks 2 and 3. PRP therefore may be a useful adjunct strategy against postoperative implant-associated infections.

An improved freeze-dried PRP-coated biodegradable material suitable for connective tissue regenerative therapy

We previously published an investigation indicating freeze-dried platelet-rich plasma (PRP)-coated polyglactin mesh was a promising wound-dressing material. However, one of its disadvantages was the inflammatory nature due to degradation of the polyglactin. Therefore, in this study, we investigated the use of a collagen sponge as the carrier for PRP. When implanted subcutaneously in nude mice, the PRP-coated sponge alone rapidly induced angiogenesis and infiltration of surrounding connective tissue without inducing appreciable inflammation. Moreover, addition of periosteal fibroblastic cells substantially augmented the angiogenic response. With in vitro studies, the PRP-coated sponge provided various major growth factors at high levels to stimulate the proliferation of cells cultured on plastic dishes, but did not stimulate the proliferation of cells inoculated into the PRP-coated sponge. Cells were embedded in the fibrin mesh and maintained their spherical shape without stretching. The atomic force microscopic analysis demonstrated that the fibrin gel formed on the PRP-coated sponge was much softer (approx. 22 kPa) than the cross-linked collagen that formed the sponge base (appox. 1.9 MPa). Because insoluble matrices have recently and increasingly been considered important regulatory factors of cellular behavior, as are soluble growth factors, it is suggested that this soft fibrin mesh possibly suppresses cell survival. Overall, our investigation has successfully demonstrated improved wound-healing and regenerative potential of the PRP-coated mesh by combining it with the collagen sponge. In the clinical setting, this PRP-coated collagen sponge is a promising material for connective tissue regenerative therapy, such as periodontal therapy, burn victim treatment and in cosmetic or plastic surgery.

A novel calcium aluminate-melatonin scaffold enhances bone regeneration within a calvarial defect

Over 500,000 bone graft or bio-implant procedures are performed annually in the United States. It has been reported that osseous autograft procurement may result in donor site complications and bio-implant allografts have been associated with disease transmission. Ceramic scaffolds are only osteoconductive, limiting their clinical use. The objective of this study was to create a bone filler substitute with regenerating properties similar to natural bone. Therefore, melatonin and platelet-rich plasma (PRP) were utilized for their known osteoinductive properties. It was hypothesized that melatonin and/or PRP would enhance the osteoinductive and osteoconductive properties of calcium aluminate (CA) scaffolds to promote bone regeneration in a model of calvarial defects. The biocompatibility of CA and CA-Mel scaffolds was tested in vitro and in vivo. Data show that CA-Mel scaffolds, in comparison with CA scaffolds, enhanced the adhesion, viability, and proliferation of normal human osteoblasts cells but not that of NIH3T3 fibroblasts. Data also showed that human adult mesenchymal stem cells grown on CA or CA-Mel scaffolds showed a time-dependent induction into osteoblasts over 14days revealed through scanning electron microscopy and by alkaline phosphatase analyses. Implantation of CA-Mel scaffolds into critical size calvarial defects in female, ovariectomized rats showed that the CA-Mel scaffolds were biocompatible, allowed for tissue infiltration, and showed evidence of scaffold biodegradation by 3 and 6months. Bone regeneration, assessed using fluorochrome labeling at 3 and 6months, was greatest in animals implanted with the CA-Mel scaffold. Overall, results from this study show that CA-Mel scaffolds were osteoconductive and osteoinductive.

Platelet-rich plasma: the PAW classification system

Platelet-rich plasma (PRP) has been the subject of hundreds of publications in recent years. Reports of its effects in tissue, both positive and negative, have generated great interest in the orthopaedic community. Protocols for PRP preparation vary widely between authors and are often not well documented in the literature, making results difficult to compare or replicate. A classification system is needed to more accurately compare protocols and results and effectively group studies together for meta-analysis. Although some classification systems have been proposed, no single system takes into account the multitude of variables that determine the efficacy of PRP. In this article we propose a simple method for organizing and comparing results in the literature. The PAW classification system is based on 3 components: (1) the absolute number of Platelets, (2) the manner in which platelet Activation occurs, and (3) the presence or absence of White cells. By analyzing these 3 variables, we are able to accurately compare publications.

The effectiveness of intralesional injection of platelet-rich plasma in accelerating the healing of chronic ulcers: an experimental and clinical study

The purpose of this prospective experimental and clinical study is to evaluate the effectiveness of the intralesional injection of platelet-rich plasma (PRP), in the management of non-healing chronic wounds. Skin defects were created in the ears of 20 white New Zealand rabbits. In the study group, autologous PRP was injected intralesionally. The control group was treated conservatively. Nineteen out of 20 cases of the study group healed within a mean time of 24·9 days. In the control group, seven defects healed within a mean period of 26·7 days, seven ulcers did not heal at day 28 and in six cases a full thickness ear defect was recorded. For a 3-year period, 26 patients with chronic ulcers underwent surgical debridement and intralesional injection of PRP. A histological study was performed before and 7 days after PRP injection. Ten patients healed within a mean period of 7 weeks. In 16 cases, PRP prepared the wound bed for the final and simpler reconstructive procedure. Intralesional injection is a newly described method for application of PRP and represents an effective therapeutic option when dealing with non-healing wounds.

Antimicrobial activity of platelet (PLT)-poor plasma, PLT-rich plasma, PLT gel, and solvent/detergent-treated PLT lysate biomaterials against wound bacteria

BACKGROUND

Platelet (PLT) gels exhibit antimicrobial activity useful for wound healing. The nature of the antibacterial component(s) is unknown.

STUDY DESIGN AND METHODS

PLT-poor plasma (PPP), PLT-rich plasma (PRP), PLT gel (PG), and solvent/detergent-treated PLT lysate (S/D-PL) from two donors were evaluated either native or after complement heat inactivation. Materials were spiked at a 10% ratio (vol/vol) with approximately 10(7-8) colony-forming units/mL with four Gram-positive and four Gram-negative bacteria of the wound flora. Bacterial count was determined by plate assays at time of spiking and after 3 and 48 hours at 31°C. Bacteria growth inhibition tests were also performed.

RESULTS

There was no viable Escherichia coli colony for 48 hours after spiking to the plasma and PLT materials from both donors, corresponding to greater than 7.51 to greater than 9.05 log inactivation. Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus were inactivated (approx. 4.7, 7, and 2 log, respectively) 3 hours after spiking to PRP, PPP, or S/D-PL from the first donor but less (1.1, 4.6, and 0.2 log, respectively) in PG, before a regrowth at 48 hours in all materials. Similar data were obtained with the second donor. No plasma and PLT material had antimicrobial activity against Enterobacter cloacae, Bacillus cereus, Bacillus subtilis, and Staphylococcus epidermidis. Complement-inactivated samples had no antimicrobial activity.

CONCLUSION

Plasma complement is mostly responsible for the activity of plasma and PLT biomaterials against E. coli, P. aeruginosa, K. pneumoniae, and S. aureus. Activation of the coagulation to prepare PG may reduce antimicrobial activity. These findings may help optimize the control of wound infections by blood biomaterials.

Continuous separation of microparticles in a microfluidic channel via the elasto-inertial effect of non-Newtonian fluid

Pure separation and sorting of microparticles from complex fluids are essential for biochemical analyses and clinical diagnostics. However, conventional techniques require highly complex and expensive labeling processes for high purity separation. In this study, we present a simple and label-free method for separating microparticles with high purity using the elasto-inertial characteristic of a non-Newtonian fluid in microchannel flow. At the inlet, particle-containing sample flow was pushed toward the side walls by introducing sheath fluid from the center inlet. Particles of 1 μm and 5 μm in diameter, which were suspended in viscoelastic fluid, were successfully separated in the outlet channels: larger particles were notably focused on the centerline of the channel at the outlet, while smaller particles continued flowing along the side walls with minimal lateral migration towards the centerline. The same technique was further applied to separate platelets from diluted whole blood. Through cytometric analysis, we obtained a purity of collected platelets of close to 99.9%. Conclusively, our microparticle separation technique using elasto-inertial forces in non-Newtonian fluid is an effective method for separating and collecting microparticles on the basis of size differences with high purity.

PRP-fibrinogen gel-like chondrocyte carrier stabilized by TXA-preliminary study

Three dimensional scaffolds are becoming increasingly popular in the treatment of cartilage defects. Platelet-rich plasma (PRP) and fibrinogen can be used potentially as a three dimensional cell delivery vehicle. PRP is a fraction of plasma containing high levels of growth factors such as PDGF, IGF-I and TGF-I, which stimulate chondrocyte to synthesize extracellular matrix. The aim of this study was to prepare grafts based on fibrinogen, and PRP with fibrinogen as a chondrocyte carrier. Another goal was to estimate tranexamic acid as an antifibrynolytic agent in chondrocyte grafts and in monolayer culture for about 3 weeks. 450 ml blood was collected to produce fibrinogen and PRP from a Regional Blood Center voluntary donor. To prepare gel grafts, chondrocytes were mixed with PRP and, fibrinogen and then with thrombin in calcium chloride. Different doses of tranexamic acid or aprotinin were used to stabilize the constructs. Grafts were cultivated for 4 weeks in vitro to evaluate and compare their disintegration. Grafts were stable for the entire observation period and revealed no shrinkage. During graft storage, cells appeared to be viable, and cell migration from the graft to the culture plate was observed. Chondrocyte graft preparation based on PRP and fibrinogen is a promising method. PRP-fibrinogen carrier in combination with cells constitutes highly plastic and adhesive grafts. Tranexamic acid can be used as an anti-fibrinolytic agent in chondrocyte graft preparation instead of aprotinin.

Platelet activation: ultrastructure and morphometry in platelet-rich plasma of horses

This study was conducted to investigate the activation ability of the platelet-rich plasma (PRP) by pharmacological agents, as well as to verify the need or not of this activation for therapeutic use. The PRP was obtained from four healthy crossbred geldings aged 13 to 16 years (15±1years), and was processed for observation and quantification of the platelet morphology by using the transmission electron microscopy. All PRP samples were activated with 10% calcium chloride (CaCl2) solution, pure bovine thrombin or associated with CaCl2. The control (pure PRP) was not pharmacologically activated. In the pure PRP samples, 49% of the platelets were classified as state of activation uncertain, 41% as resting, 9% as fully activated and 1% as irreversibly damaged. Treatment with 10% CaCl2 provided a distribution of 54% platelets in state of activation uncertain, 24% as fully activated, 20% as resting, and 2% as irreversibly damaged. The platelet morphology of the bovine thrombin treated samples did not fit into classification adopted, as showing irregular shape with emission of large filamentous pseudopods, appearance of ruptured and whole granules in the remaining cytoplasm and extracellular environment. There was effect of the treatment on the platelet morphology (P=0.03). The 10% CaCl2 is an adequate platelet-activating agent. However, in cases the use of PRP under its liquid form is necessary, the use of pure PRP is recommended, since besides presenting an adequate percentage of fully activated platelets it also has significant amount of the resting type, which can be activated by substances found in the injured tissue.

Clinical and magnetic resonance imaging outcomes following platelet rich plasma injection for chronic midsubstance Achilles tendinopathy

BACKGROUND

The successful treatment of chronic mid-substance Achilles tendinopathy remains elusive. Approximately 25% to 50% of patients fail conservative treatment modalities. Scientific evidence has supported the use of platelet rich plasma (PRP) in the tendon healing process, however despite initial promise there is a paucity of clinical data to validate a role for PRP in the treatment of tendon disorders including chronic midsubstance Achilles tendinopathy.

METHODS

As an alternative to operative treatment, our practice offers patients with chronic midsubstance Achilles tendinopathy intratendinous injection of PRP. We retrospectively reviewed all patients treated for Achilles tendinopathy with PRP injection over a 2-year period. Baseline and post injection functional scores including the Foot and Ankle Ability Measure (FAAM), Foot and Ankle Ability Measure - Sports (FAAMS), and the Short Form health survey (SF-8) were examined. Patients also underwent post-injection magnetic resonance imaging (MRI), which were compared to available pre-injection MRI data.

RESULTS

Ten patients were identified for this study. Pre- and postinjection functional outcome scores were available for eight of ten patients. The average SF-8 score improved from 24.9 to 30.0, the average FAAM score improved from 55.4 to 65.8, and the average FAAMS score improved from 14.8 to 17.4. Complete MRI data was available for six patients. Only one in six Achilles tendons demonstrated qualitative MRI improvement post-injection.

CONCLUSION

Patients who received PRP injection demonstrated modest improvement in functional outcome measures, however MRI appearance of diseased Achilles tendons remained largely unchanged following PRP injection.

A Pilot Study to Evaluate the Safety and Clinical Performance of Leucopatch, an Autologous, Additive-Free, Platelet-Rich Fibrin for the Treatment of Recalcitrant Chronic Wounds

This prospective, uncontrolled pilot study evaluated the safety and clinical performance of Leucopatch an additive-free, autologous platelet-rich fibrin in the treatment of recalcitrant chronic wounds. Fifteen patients, with 16 lower extremity chronic wounds of varying etiologies were treated weekly with Leucopatch, prepared at the point of care from a donation of the patients’ blood, for 6 weeks, or until healing was complete. The wounds had been present for 2 to 108 months (median 24 months) and ranged in size from 0.4 to 15.7 cm2 (median 2.3 cm2) and had not responded to previous treatments. Of the 13 wounds (12 patients) included in the per-protocol efficacy analysis, 4 healed completely (31%). Mean wound area decreased significantly by 65% (95% confidence interval = 45.6% to 83.8%) resulting in a median wound size of 0.9 cm2 (range = 0-9.6cm2). There were no serious adverse events. Two adverse events, one of noncompliance and one infection, were observed; neither was considered to be related to treatment. The results indicate that Leucopatch is easy to prepare and apply in the clinic, is safe, and may be a clinically effective treatment of recalcitrant chronic wounds.

Separation of platelets from whole blood using standing surface acoustic waves in a microchannel

Platelet separation from blood is essential for biochemical analyses and clinical diagnosis. In this article, we propose a method to separate platelets from undiluted whole blood using standing surface acoustic waves (SSAWs) in a microfluidic device. A polydimethylsiloxane (PDMS) microfluidic channel was fabricated and integrated with interdigitated transducer (IDT) electrodes patterned on a piezoelectric substrate. To avoid shear-induced activation of platelets, the blood sample flow was hydrodynamically focused by introducing sheath flow from two side-inlets and pressure nodes were designed to locate at side walls. By means of flow cytometric analysis, the RBC clearance ratio from whole blood was found to be over 99% and the purity of platelets was close to 98%. Conclusively, the present technique using SSAWs can directly separate platelets from undiluted whole blood with higher purity than other methods.

Comparação entre dois protocolos para obtenção de plasma rico em plaquetas, em cães

Avaliaram-se dois protocolos para a produção de plasma rico em plaquetas (PRP) com o sangue de 20 cães adultos. Foram coletados três frascos de sangue em que um deles foi usado para produção do PRP por meio do protocolo A - centrifugação única a 1200rpm/10min -, o outro para fabricação do PRP pelo protocolo B - primeira centrifugação a 1200rpm/10min e a segunda centrifugação a 1600rpm/10min - e o terceiro para realização da contagem plaquetária no sangue total, que serviu de parâmetro para os valores alcançados no PRP. O protocolo no qual foi possível alcançar maior concentração plaquetária foi testado em outros 20 cães para avaliar sua reprodutibilidade. Constatou-se que o protocolo B resultou em maior plaquetometria em 100% das amostras e concluiu-se ser ele eficiente para a produção do PRP em cães.

Hydrophoretic high-throughput selection of platelets in physiological shear-stress range

A gentle, but fast means for low-stress, high-throughput platelet purification is of significant clinical and biotechnological utility. Current implementations to sort platelets, however, require an external physical field, specialized buffer, or the harsh separation condition of high shear stress that tends to cause platelet stimulation. Here we report the use of hydrophoretic size separation in a wider channel and its parallelization to augment its throughput capability, maintaining physiological shear-stress range. We demonstrate a parallelized device comprising 10 stacks of the wide-channel hydrophoresis device, yielding a throughput of 2.9 million cells s(-1) and a platelet purity of 76.8%. The use of the wide channel for hydrophoresis also facilitates clogging-free separation by sorting blood clots and plaques. The wide-channel hydrophoresis offers the potential for gentle, fast, clogging-free sorting of rare blood cells with extreme throughput capabilities.

Platelet-rich fibrin versus albumin in surgical wound repair: a randomized trial with paired design

OBJECTIVE

To study the effects of autologous platelet-rich fibrin (PRF) versus human albumin on incisional wound breaking strength and subcutaneous collagen deposition in patients undergoing laparoscopic cholecystectomy in a randomized trial.

SUMMARY BACKGROUND DATA

Platelet peptidic growth factors may stimulate collagen synthesis and tissue repair.

METHODS

One expanded polytetrafluoroethylene (ePTFE) tube was inserted subcutaneously from the edge of each of the two 10-mm trocar incisions in 51 patients. Treatment with PRF prepared from the patient's own blood or human albumin was randomized to respective wound site by concealed allocation. On postoperative day 10, breaking strength of the incisional wounds as well as the collagen concentration, type I procollagen mRNA, type III procollagen mRNA, matrix metalloproteinase-1 mRNA, and fibroblast density in the ePTFE tubes were determined. All analyses were assessor-blinded. The trial was registered in the Current Controlled Trials Registry (ISRCTN34481461).

RESULTS

Local PRF had no significant effect on incisional wound-breaking strength. In the ePTFE tubes, PRF treatment decreased collagen concentration by 24% (P=0.046) and type I procollagen mRNA level by 29% (P=0.003), but had no significant impact on type III procollagen mRNA, matrix metalloproteinase-1 mRNA or fibroblast infiltration. The profibrotic transforming growth factor-beta1 level increased (P<0.0001) 2-fold with PRF. Collagen concentration in albumin-treated ePTFE tubes correlated with breaking strength of the skin incisions (rs=0.48, P=0.03).

CONCLUSIONS

PRF did not improve wound strength significantly compared with albumin but suppressed subcutaneous collagen synthesis and deposition during early repair of surgical wounds in humans. Furthermore, deposition of reparative collagen in the subcutaneous ePTFE tube model partly predicted the breaking strength of an incisional skin wound.

Comparison of Achilles tendon repair techniques in a sheep model using a cross-linked acellular porcine dermal patch and platelet-rich plasma fibrin matrix for augmentation

The primary goal of this study was to evaluate a cross-linked acellular porcine dermal patch (APD), as well as platelet-rich plasma fibrin matrix (PRPFM), for repair of acute Achilles tendon rupture in a sheep model. The 2 surgically transected tendon ends were reapproximated in groups 1 and 2, whereas a gap was left between the tendon ends in group 3. APD was used to reinforce the repair in group 2, and autologous PRPFM was used to fill the gap, which was also reinforced with APD, in group 3. All sheep were humanely euthanized at 24 weeks after the repair, and biomechanical and histological testing were performed. Tensile strength testing showed a statistically significant difference in elongation between the operated limb and the unoperated contralateral limb in groups 1 and 3, but not in group 2. All operated tendons appeared healed with no apparent fibrosis under light and polarized microscopy. In group 1, all surgical separation sites were identifiable, and healing occurred via increasing tendon thickness. In group 2, healing occurred with new tendon fibers across the separation, without increasing tendon thickness in 2 out of 6 animals. Group 3 showed complete bridging of the gap, with no change in tendon thickness in 2 out of 6 animals. In groups 2 and 3, peripheral integration of the APD to tendon fibers was observed. These findings support the use of APD, alone or with PRPFM, to augment Achilles tendon repair in a sheep model.