Effects of platelet-derived growth factor-BB on the metabolic function and morphologic features of equine tendon in explant culture

A Promising Candidate in Tendon Healing Events—PDGF-BB

Tendon injuries are one of the most common musculoskeletal disorders for which patients seek medical aid, reducing not only the quality of life of the patient but also imposing a significant economic burden on society. The administration of growth factors at the wound site is a feasible solution for enhancing tendon healing. Platelet-derived growth factor-BB (PDGF-BB) has a well-defined safety profile compared to other growth factors and has been approved by the Food and Drug Administration (FDA). The purpose of this review is to summarize the role of PDGF-BB in tendon healing through a comprehensive review of the published literature. Experimental studies suggest that PDGF-BB has a positive effect on tendon healing by enhancing inflammatory responses, speeding up angiogenesis, stimulating tendon cell proliferation, increasing collagen synthesis and increasing the biomechanics of the repaired tendon. PDGF-BB is regarded as a promising candidate in tendon healing. However, in order to realize its full potential, we still need to carefully consider and study key issues such as dose and application time in the future, so as to explore further applications of PDGF-BB in the tendon healing process.

Growth Factor Roles in Soft Tissue Physiology and Pathophysiology

Repair and healing of injured and diseased tendons has been traditionally fraught with apprehension and difficulties, and often led to rather unsatisfactory results. The burgeoning research field of growth factors has opened new venues for treatment of tendon disorders and injuries, and possibly for treatment of disorders of the aorta and major arteries as well. Several chapters in this volume elucidate the role of transforming growth factor β (TGFß) in pathogenesis of several heritable disorders affecting soft tissues, such as aorta, cardiac valves, and tendons and ligaments. Several members of the bone morphogenetic group either have been approved by the FDA for treatment of non-healing fractures or have been undergoing intensive clinical and experimental testing for use of healing bone fractures and tendon injuries. Because fibroblast growth factors (FGFs) are involved in embryonic development of tendons and muscles among other tissues and organs, the hope is that applied research on FGF biological effects will lead to the development of some new treatment strategies providing that we can control angiogenicity of these growth factors. The problem, or rather question, regarding practical use of imsulin-like growth factor I (IGF-I) in tendon repair is whether IGF-I acts independently or under the guidance of growth hormone. FGF2 or platelet-derived growth factor (PDGF) alone or in combination with IGF-I stimulates regeneration of periodontal ligament: a matter of importance in Marfan patients with periodontitis. In contrast, vascular endothelial growth factor (VEGF) appears to have rather deleterious effects on experimental tendon healing, perhaps because of its angiogenic activity and stimulation of matrix metalloproteinases-proteases whose increased expression has been documented in a variety of ruptured tendons. Other modalities, such as local administration of platelet-rich plasma (PRP) and/or of mesenchymal stem cells have been explored extensively in tendon healing. Though treatment with PRP and mesenchymal stem cells has met with some success in horses (who experience a lot of tendon injuries and other tendon problems), the use of PRP and mesenchymal stem cells in people has been more problematic and requires more studies before PRP and mesenchymal stem cells can become reliable tools in management of soft tissue injuries and disorders.

Evaluation of Blood Clot, Platelet-rich Plasma, Platelet-rich Fibrin, and Platelet Pellet as Scaffolds in Regenerative Endodontic Treatment: A Prospective Randomized Trial

INTRODUCTION

Regenerative endodontic procedures (REPs) using autologous platelet concentrates as scaffolds can improve the biologic outcome of treatment. This prospective, randomized trial compared the clinical and radiographic performance of REPs using platelet-rich plasma (PRP), platelet-rich fibrin (PRF), a platelet pellet (PP), and an induced blot clot (BC).

METHODS

Sixty-seven healthy children (aged 8-11 years) with 88 immature necrotic incisors were included. After the root canal disinfection step, the teeth were randomly assigned into 1 of the following groups (n = 22/group) according to the scaffold used: PRP, PRF, PP, and BC. In the PRP, PRF, and PP groups, the platelet concentrates were introduced into the root canal without prior induction of apical bleeding. Treatment outcomes were assessed using a combined clinical and radiographic scoring system, whereas the changes in root dimensions were compared using linear measurements of root length and width with ImageJ (National Institutes of Health, Bethesda, MD) and Turboreg (Biomedical Imaging Group, Swiss Federal Institute of Technology, Lausanne, Switzerland) and planar measurements using the radiographic root area (RRA) and radiographic canal area (RCA) techniques. One-way analysis of variance, the Duncan multiple range test, the Kruskal-Wallis test, the Mann-Whitney U test, and chi-square dependency tests were used for statistical analysis of data (all P = .05).

RESULTS

Except for 2 teeth in the PRF and BC groups, all teeth showed similar and high success scores (periapical healing, radiographic root development, and positive response to sensitivity tests) after an average follow-up time of 28.25 ± 1.2 months. Of all teeth, 73.9% showed complete apical closure with similar closure rates among groups (P > .05) and a greater tendency for conical-shaped apical closure than a blunt apex. Although linear measurements indicated a similar increase in root length and width among all groups (P > .05), the RRA of the BC group was significantly greater than those of the PRF and PP groups, and the RCA of the BC group was significantly greater than PRP, PRF, and PP (all P < .05) when the follow-up time was not used as a factor. Eighty-six percent of the teeth showed a positive response to sensitivity tests with similar initial response times (P > .05).

CONCLUSIONS

PRP, PRF, and PP can yield similar clinical and radiographic outcomes to BC without the need for prior apical bleeding and with significantly less tendency for root canal obliteration. RRA and RCA may reveal minor differences that cannot be determined by linear measurements.

Platelet concentrate in bovine reproduction: effects on in vitro embryo production and after intrauterine administration in repeat breeder cows

BACKGROUND

A repeat breeder cow (RBC) can be defined as an animal that after 3 or more inseminations cannot get pregnant because of fertilization failure or early embryonic death. If no cause is identified precisely, inadequate uterine receptivity is responsible for implantation failures. Since a large number of identified molecular mediators, such as cytokines, growth factors and lipids have been postulated to be involved in early feto-maternal interaction, in this study a different approach to the treatment of RBC syndrome has been employed using a platelet concentrate (PC) that contains a significant amount of growth factors accumulated in its α-granules.

METHODS

Three explorative studies were performed. Initially, PC was supplemented in the in vitro embryo culture medium to study its effect on embryo-development. After the pilot study, 4 RBCs were treated with intrauterine administration of PC to evaluate proliferative potential of endometrium by immunohistochemical expression of the antigen Ki-67. Lastly, the effect of intrauterine administration of PC at 48 hrs after artificial insemination in RBCs was evaluated.

RESULTS

The in vitro results show that 5 % of PC and 5 % of fetal calf serum (FCS) increase the rate of blastocysts compared with the control containing 10 % FCS only (43.04 % vs 35.00 % respectively). The immunohistochemical study shows more proliferating nuclei in the treated uterine horn compared to the control one. After intrauterine insemination in RBCs, the percentage of pregnant cows in the control group was 33.33 % compared to 70 % of the treated animals.

CONCLUSION

We suppose that when embryo descends in uterus could find a more appropriate environment for nesting and subsequent pregnancy.

Progress in cell-based therapies for tendon repair

The last decade has seen significant developments in cell therapies, based on permanently differentiated, reprogrammed or engineered stem cells, for tendon injuries and degenerative conditions. In vitro studies assess the influence of biophysical, biochemical and biological signals on tenogenic phenotype maintenance and/or differentiation towards tenogenic lineage. However, the ideal culture environment has yet to be identified due to the lack of standardised experimental setup and readout system. Bone marrow mesenchymal stem cells and tenocytes/dermal fibroblasts appear to be the cell populations of choice for clinical translation in equine and human patients respectively based on circumstantial, rather than on hard evidence. Collaborative, inter- and multi-disciplinary efforts are expected to provide clinically relevant and commercially viable cell-based therapies for tendon repair and regeneration in the years to come.

A comparative evaluation of the blood clot, platelet-rich plasma, and platelet-rich fibrin in regeneration of necrotic immature permanent teeth: A clinical study

INTRODUCTION

This study was designed as a clinical trial to evaluate and compare the regenerative potential of platelet-rich fibrin (PRF), platelet-rich plasma (PRP), and blood clot in immature necrotic permanent teeth with or without associated apical periodontitis.

METHODS

Access preparation was done under rubber dam isolation. Copious irrigation was done with 2.5% NaOCl and triple antibiotic paste was placed as an intracanal medicament. After 4 weeks, the cases were divided into four groups with five patients in each group. The study design had three test arms and one control arm. Group I in which mineral trioxide aggregate apexification was carried out and it was kept as control group to evaluate the regenerative potential of blood clot and platelet concentrates, Group II in which blood clot was used as scaffold in the canal, Group III in PRF was used as scaffold, and Group IV in which PRP carried on collagen was used as a scaffold.

RESULTS

The clinical and radiographic evaluation after 6 and 18 months was done by two independent observers who were blinded from the groups. The scoring was done as: None score was denoted by, Fair by 1, Good by 2, and Excellent by 3. The data were then analyzed statistically by Fisher's exact test using Statistics and Data 11.1(PRP Using harvest Smart PReP2) which showed statistically significant values in Group III as compared to other Groups.

CONCLUSION

PRF has huge potential to accelerate the growth characteristics in immature necrotic permanent teeth as compared to PRP and blood clot.

Intramammary administration of platelet concentrate as an unconventional therapy in bovine mastitis: first clinical application

Bovine udder infections induce a variety of changes in gene expression of different growth factors that may suggest their possible role in glandular tissue protection or repair processes. Growth factors and also chemokines and cytokines may act synergistically to increase the infiltration of neutrophils and macrophages to promote angiogenesis, fibroplasia, matrix deposition, and, ultimately, re-epithelialization. Considering the vast applications, typically in human medicine, of platelet concentrate (PC) and its ease of preparation, the aim of our study was to evaluate an alternative therapy to stimulate the regeneration of glandular tissue, administering a concentration in excess of the growth factors contained in the PC. In each one of the 3 farms examined in the trial, PC was prepared from donor cows in good health, free from infections, and with no records of medications administered during the previous 2 mo. The platelet produced in one farm was used only for treating the cows of the same farm in a heterologous way. A total of 229 mastitic quarters were divided in 3 groups: antibiotic group (treated with intramammary antibiotic), antibiotic and PC group (treated intramammarily with antibiotics in association with PC), and PC group (treated with intramammary PC alone). The diagnosis of mastitis was based on somatic cell count and bacteriological evaluation of the milk from the affected quarter. Platelet concentrate, alone or in association with antibiotic, was used for 3 consecutive days as an unconventional therapy in bovine acute and chronic mastitis. Our data show that the associated action of antibiotic and PC performed significantly better than the antibiotic alone, either for the recovery of the affected mammary quarters or for somatic cell count reduction. In the same way, the association antibiotic plus PC showed significantly fewer relapses compared with the antibiotic alone, either for acute or chronic mastitis. The treatment with only PC did not show statistically significant differences compared with both antibiotic alone or associated treatment for acute mastitis, and it was better than the use of only antibiotic for chronic mastitis. Our results show that PC alone may be useful for a quick resolution of the inflammatory response, playing a role in limiting the tissue damage to the mammary gland parenchyma and reducing the recurrence rates.

The growth factors involved in flexor tendon repair and adhesion formation

Flexor tendon injuries remain a significant clinical problem, owing to the formation of adhesions or tendon rupture. A number of strategies have been tried to improve outcomes, but as yet none are routinely used in clinical practice. Understanding the role that growth factors play in tendon repair should enable a more targeted approach to be developed to improve the results of flexor tendon repair. This review describes the main growth factors in tendon wound healing, and the role they play in both repair and adhesion formation.

Platelet-rich fibrin-mediated revitalization of immature necrotic tooth

Contemporary studies have shown that the regeneration of tissues and root elongation is possible in necrotic immature permanent teeth. The purpose of this case report is to add a new vista in regenerative endodontic therapy by using platelet rich fibrin for revitalization of immature non vital tooth. An 11year old boy with the history of trauma was diagnosed with the pulpal necrosis and symptomatic apical periodontitis in tooth #21. Intra oral periapical radiograph showed open apex and associated immature supernumerary tooth with respect to tooth #21. Access preparation and minimal instrumentation was done to remove necrotic debris under copious irrigation with 2.5% sodium hypochlorite. Triple antibiotic paste was packed in the canal for four weeks. During second visit, 5 mL of whole blood was drawn from the medial cubital vein of the patient and blood was then subjected to centrifugation at 2400 rpm for 12 minutes for the preparation of Platelet rich fibrin (PRF) utilizing Choukroun's method. Triple antibiotic paste was removed and canal was dried. PRF clot was pushed to the apical region of tooth #21 using hand pluggers. Three milimetres of Mineral trioxide (MTA) was placed in cervical part of the root canal and permanent restoration was done three days later. Clinical examination at 6 and 12 months revealed no sensitivity to percussion and palpation in tooth #21and it responded positively to both electric pulp and cold tests. Radiographic examination showed resolution of periapical rarefaction, further root development and apical closure of the tooth #21 and its associated supernumerary tooth. On the basis of successful outcome of the present case it can be stated that PRF clot may serve as a scaffold for regeneration of necrotic immature teeth.

Regenerative tendon and ligament healing: opportunities with recombinant human platelet-derived growth factor BB-homodimer

Intrinsic tendon healing in response to injury is a reparative process that often results in formation of scar tissue with functional and mechanical properties inferior to those of the native tendon. Development of therapies that can promote regenerative, rather than reparative, healing hold the promise of improving patient recovery from tendon and ligament injuries by producing tissue that is morphologically and functionally equivalent to the native tissue. One therapeutic approach that has been a frequent topic of investigation in the preclinical literature is the use of recombinant human platelet-derived growth factor-BB (rhPDGF-BB) to augment tendon and ligament repair. The chemotactic, mitogenic, and pro-angiogenic properties of rhPDGF-BB have been shown to result in recruitment and proliferation of tenogenic cells and a commensurate boost in extracellular matrix deposition and organization, improving the morphological and biomechanical properties of healing tendons and ligaments. The outcomes of the preclinical studies reviewed here strongly suggest that rhPDGF-BB will provide a new therapeutic opportunity to improve the treatment of injured tendons and ligaments.

Cell- and gene-based approaches to tendon regeneration

Repair of rotator cuff tears in experimental models has been significantly improved by the use of enhanced biologic approaches, including platelet-rich plasma, bone marrow aspirate, growth factor supplements, and cell- and gene-modified cell therapy. Despite added complexity, cell-based therapies form an important part of enhanced repair, and combinations of carrier vehicles, growth factors, and implanted cells provide the best opportunity for robust repair. Bone marrow-derived mesenchymal stem cells provide a stimulus for repair in flexor tendons, but application in rotator cuff repair has not shown universally positive results. The use of scaffolds such as platelet-rich plasma, fibrin, and synthetic vehicles and the use of gene priming for stem cell differentiation and local anabolic and anti-inflammatory impact have both provided essential components for enhanced tendon and tendon-to-bone repair in rotator cuff disruption. Application of these research techniques in human rotator cuff injury has generally been limited to autologous platelet-rich plasma, bone marrow concentrate, or bone marrow aspirates combined with scaffold materials. Cultured mesenchymal progenitor therapy and gene-enhanced function have not yet reached clinical trials in humans. Research in several animal species indicates that the concept of gene-primed stem cells, particularly embryonic stem cells, combined with effective culture conditions, transduction with long-term integrating vectors carrying anabolic growth factors, and development of cells conditioned by use of RNA interference gene therapy to resist matrix metalloproteinase degradation, may constitute potential advances in rotator cuff repair. This review summarizes cell- and gene-enhanced cell research for tendon repair and provides future directions for rotator cuff repair using biologic composites.

Effects of preparation method, shear force, and exposure to collagen on release of growth factors from equine platelet-rich plasma

OBJECTIVE

To test the hypotheses that preparation method, exposure to shear force, and exposure to collagen affect the release of growth factors from equine platelet-rich plasma (PRP).

SAMPLE POPULATION

PRP obtained from 6 horses.

PROCEDURES

PRP was prepared via 2 preparation methods (tube and automated) and subjected to 6 treatment conditions (resting, detergent, exposure to shear via 21- and 25-gauge needles, and exposure to collagen [10 and 20 μg/mL]). Concentrations of platelet-derived growth factor, isoform BB (PDGF-BB); transforming growth factor β, isoform 1 (TGFβ₁); and insulin-like growth factor, isoform 1 (IGF-1) were quantified by use of ELISAs. Statistical analysis was conducted via repeated-measures ANOVA.

RESULTS

Platelet numbers were significantly higher in tube-prepared PRP than in automated-prepared PRP Growth factor concentrations did not differ significantly between preparation methods. Mean PDGF-BB concentration ranged from 134 to 7,157 pg/mL, mean TGFβ₁ concentration ranged from 1,153 to 22,677 pg/mL, and mean IGF-1 concentration ranged from 150 to 280 ng/mL. Shear force did not affect growth factor concentrations. Dose-dependent increases in PDGF-BB and TGFβ₁ were detected in response to collagen, but equalled only 10% of the estimated total platelet content. Concentrations of IGF-1 were not significantly different among treatments and negative or positive control treatments. Serum concentrations of PDGF-BB and TGFβ₁ exceeded concentrations in PRP for most treatment conditions.

CONCLUSIONS AND CLINICAL RELEVANCE

Release of growth factors from equine PRP was negligible as a result of the injection process alone. Investigation of platelet-activation protocols is warranted to potentially enhance PRP treatment efficacy in horses.

Growth factor-rich plasma increases tendon cell proliferation and matrix synthesis on a synthetic scaffold: an in vitro study

Numerous scaffolds have been proposed for use in connective tissue engineering. Although these scaffolds direct cell migration and attachment, many are biologically inert and thus lack the physiological stimulus to attract cells and induce mitogenesis and matrix synthesis. In the current study, a bioactive scaffold was created by combining a synthetic scaffold with growth factor-rich plasma (GFRP), an autologous concentration of growth factors derived from a platelet-rich plasma preparation. In vitro tendon cell proliferation and matrix synthesis on autologous GFRP-enriched scaffolds, autologous serum-enriched scaffolds, and scaffolds alone were compared. The GFRP preparation was found to have a 4.7-fold greater concentration of a sentinel growth factor (transforming growth factor-beta1) compared with serum. When combined with media containing calcium, the GFRP produced a thin fibrin matrix over and within the GFRP-enriched scaffolds. Cell proliferation assays demonstrated that GFRP-enriched scaffolds significantly enhanced cell proliferation over autologous serum and control groups at both 48 and 72 h. Analysis of the scaffolds at 14, 21, and 28 days revealed that GFRP-enriched scaffolds significantly increased the deposition of a collagen-rich extracellular matrix when compared with the other groups. These results indicate that GFRP can be used to enhance in vitro cellular population and matrix deposition of tissue-engineered scaffolds.

Growth factors as active participants in carcinogenesis: a perspective

Growth factors are low molecular peptides active in the stimulation of cell proliferation and in the regulation of embryonic development and cellular differentiation. Significant progress has been made in developing effective strategies to treat human malignancies with new chemical compounds based on a rationale directed against various components of signaling pathways. Many of these drugs target a growth factor receptor--for instance, in the form of monoclonal antibodies or inhibitors of tyrosine kinases, such as monoclonal antibodies against epidermal growth factor receptors used in treating certain types of breast cancer. Imatinib mesylate [Gleevec]) is an excellent example of mediators of signal transduction, such as tyrosine kinases. Growth factors proper are used to ameliorate various and sometimes fatal side effects of cytotoxic and/or myelosuppressive chemotherapy. Basic characteristics of several growth families are discussed with therapeutic modalities based on growth factor activity or, more often, inhibition of such activity.

Evaluation of early cellular influences of bone morphogenetic proteins 12 and 2 on equine superficial digital flexor tenocytes and bone marrow-derived mesenchymal stem cells in vitro

OBJECTIVE

To evaluate early cellular influences of bone morphogenetic protein (BMP)12 and BMP2 on equine superficial digital flexor tenocytes (SDFTNs) and equine bone marrow-derived mesenchymal stem cells (BMDMSCs).

ANIMALS

9 adult clinically normal horses.

PROCEDURES

BMDMSCs and SDFTNs were cultured in monolayer, either untreated or transduced with adenovirus encoding green fluorescent protein, adenovirus encoding BMP12, or adenovirus encoding BMP2. Cytomorphologic, cytochemical, immunocytochemical, and reverse transcriptase-quantitative PCR (RT-qPCR) analyses were performed on days 3 and 6. Genetic profiling for effects of BMP12 was evaluated by use of an equine gene expression microarray on day 6.

RESULTS

BMDMSCs and SDFTNs had high BMP12 gene expression and remained viable and healthy for at least 6 days. Type l collagen immunocytochemical staining for SDFTNs and tenocyte-like morphology for SDFTNs and BMDMSCs were greatest in BMP12 cells. Cartilage oligomeric matrix protein, as determined via RT-qPCR assay, and chondroitin sulfate, as determined via gene expression microarray analysis, were upregulated relative to control groups in SDFTN-BMP12 cells. The BMDMSCs and SDFTNs became mineralized with BMP2, but not BMP12. Superficial digital flexor tenocytes responded to BMP12 with upregulation of genes relevant to tendon healing and without mineralization as seen with BMP2.

CONCLUSIONS AND CLINICAL RELEVANCE

Targeted equine SDFTNs may respond to BMP12 with improved tenocyte morphology and without mineralization, as seen with BMP2. Bone marrow-derived mesenchymal stem cells may be able to serve as a cell delivery method for BMP12.