Cold to Hot: Tumor Immunotherapy by Promoting Vascular Normalization Based on PDGFB Nanocomposites

Immunotherapy is a promising cancer therapeutic strategy. However, the "cold" tumor immune microenvironment (TIME), characterized by insufficient immune cell infiltration and immunosuppressive status, limits the efficacy of immunotherapy. Tumor vascular abnormalities due to defective pericyte coverage are gradually recognized as a profound determinant in "cold" TIME establishment by hindering immune cell trafficking. Recently, several vascular normalization strategies by improving pericyte coverage have been reported, whereas have unsatisfactory efficacy and high rates of resistance. Herein, a combinatorial strategy to induce tumor vasculature-targeted pericyte recruitment and zinc ion-mediated immune activation with a platelet-derived growth factor B (PDGFB)-loaded, cyclo (Arg-Gly-Asp-D-Phe-Lys)-modified zeolitic imidazolate framework 8 (PDGFB@ZIF8-RGD) nanoplatform is proposed. PDGFB@ZIF8-RGD effectively induced tumor vascular normalization, which facilitated trafficking and infiltration of immune effector cells, including natural killer (NK) cells, M1-like macrophages and CD8+ T cells, into tumor microenvironment. Simultaneously, vascular normalization promoted the accumulation of zinc ions inside tumors to trigger effector cell immune activation and effector molecule production. The synergy between these two effects endowed PDGFB@ZIF8-RGD with superior capabilities in reprogramming the "cold" TIME to a "hot" TIME, thereby initiating robust antitumor immunity and suppressing tumor growth. This combinatorial strategy for improving immune effector cell infiltration and activation is a promising paradigm for solid tumor immunotherapy.

COL1A1::PDGFB fusion-associated uterine fibrosarcoma: A case report and review of the literature

BACKGROUND

Mesenchymal neoplasms of the uterus encompass a diverse group of tumors, with varying characteristics and origins, collectively accounting for 8% of uterine malignancies. The most common variants include uterine leiomyosarcoma, low-grade and high-grade endometrial stromal sarcoma, adenosarcoma, and undifferentiated sarcoma. Clinical presentation is often nonspecific and can lead to delayed diagnosis. Uterine sarcomas are generally aggressive, resulting in poorer prognosis compared to carcinomas. Recent advances in molecular techniques, such as next-generation sequencing (NGS), have led to the identification of new subtypes of uterine sarcomas, including COL1A1::PDGFB fusion-associated fibrosarcoma, which has a specific chromosomal translocation t(17;22)(q22;q13). Imatinib, a tyrosine kinase inhibitor (TKI), is an effective treatment for dermatofibrosarcoma protuberans (DFSP), marked by this translocation.

CASE

We present the case of a 42-year-old woman diagnosed with COL1A1::PDGFB fusion-associated uterine fibrosarcoma. The patient underwent total hysterectomy and excision of the tumor, initially misdiagnosed as a low-grade leiomyosarcoma. Subsequent histological examination, immunohistochemistry, and fluorescence in situ hybridization (FISH) confirmed the diagnosis. After 10 months, disease recurrence was detected, and Imatinib therapy was initiated at a dose of 400 mg daily. An allergic reaction led to a temporary discontinuation, but upon resumption with appropriate medication, a positive radiological response was observed. The patient achieved a complete remission after 2 years and is still on Imatinib treatment.

CONCLUSIONS

COL1A1::PDGFB fusion-associated uterine fibrosarcoma is an extremely rare mesenchymal neoplasm. In a case we present herein, we treated a patient with imatinib as first-line medical therapy. The patient is currently in complete remission after 37 months from treatment start. To the best of our knowledge, this represents a unique observation. We also provide a detailed literature review of the published cases so far. Prospective case series are needed to further understand the natural history of these tumors and optimize treatment strategies.

Anorganic Bovine Bone Plus Recombinant Human Platelet-Derived Growth Factor-BB in Ridge Preservation: A Pilot Study

PURPOSE

To determine clinical parameters, histologic features, and radiographic linear bone width changes of regenerated bone using different biomaterials for ridge preservation following tooth extraction.

MATERIALS AND METHODS

For this pilot study, five patients were grafted with anorganic bovine bone and collagen plus recombinant human platelet-derived growth factor-BB (rhPDGF-BB), five patients were grafted with anorganic bovine bone and collagen alone, and five patients did not receive any biomaterial (control) after tooth extraction. Clinical, histologic, and radiographic evaluations were carried out 4 months postextraction.

RESULTS

Differences in terms of buccolingual width were found when comparing the control group to the group grafted with anorganic bovine bone and collagen plus rhPDGF-BB (P = .012). No statistical differences were observed between the groups in terms of mineralized or nonmineralized tissue formation or in terms of the number of osteoblasts or osteocytes per mm2 after 4 months of healing. Interestingly, the number of vessels in the grafted area was found to be significantly different among the three groups (P = .005). The number of Musashi-1 positive cells was also different among groups, both in the mineralized and the nonmineralized areas of the grafted bone (P = .024 and .005, respectively).

CONCLUSION

Anorganic bovine bone with bovine collagen is an efficient biomaterial to avoid postextraction resorption of the alveolar ridge. The addition of rhPDGF-BB appears to improve the biologic features of the newly formed bone and decrease bone resorption; further studies are needed for confirmation.

Effect of Aerosol Inhalation Combined With a Vibration Expectoration Machine on Sputum Volume, IGF-1, α1-AT and PDGF-B in Patients With Chronic Obstructive Pulmonary Emphysema

OBJECTIVE

Aerosol inhalation is commonly used in the treatment of chronic obstructive pulmonary emphysema (COPE). This study aimed to evaluate the effectiveness of aerosol inhalation combined with a vibration expectoration machine on COPE.

METHODS

From June 2019 to June 2020, 110 patients receiving COPE treatment in Linyi Central Hospital in China were included in this randomized controlled trial. All patients were randomly assigned into one of two groups using the random number table. A total of 55 patients were given aerosol inhalation combined with the use of a vibration expectoration machine in the study group, and 55 patients were given aerosol inhalation alone in the control group. The general data, clinical efficacy arterial blood gas index, pulmonary function index and serum levels of insulin-like growth factor 1 (IGF-1), alpha 1 antitrypsin (α1-AT) and platelet-derived growth factor-B (PDGF-B) were compared.

RESULTS

There was no difference in baseline characteristics between the 2 groups (P > .05). After treatment, the clinical efficacy in the study group was significantly higher than in the control group (96.36% vs 81.82%, respectively; P = .023), daily sputum production in the study group was significantly higher compared with the control group (80.92 ± 10.29 vs 58.63 ± 9.02 ml, respectively; P < .001) and hospitalization time was significantly reduced in the study group (11.87 ± 1.76 vs 17.62 ± 1.92 days, respectively; P < .001). In addition, the respiratory rate was significantly lower in the study group (17.43 ± 1.61 vs 22.08 ± 3.25, respectively; P < .001). Partial pressure of oxygen (P[O2]) was significantly higher (76.29 ± 7.34 vs 66.81 ± 7.93 mmHg, respectively; P < .001) and partial pressure of carbon dioxide (P[CO2]) was significantly lower (34.82 ± 6.02 vs 39.83 ± 6.01 mmHg respectively; P < .001) in the study group compared with the control group. In addition, forced expiratory volume in the first second (FEV1) (1.79 ± 0.36 vs 1.66 ± 0.28 L, respectively), forced vital capacity (FVC) (2.58 ± 0.28 vs 2.42 ± 0.11 L, respectively), forced expiratory volume in the first second as a percentage of the predicted value (FEV1%pred) (65.32 ± 4.03 vs 59.83 ± 4.76 L, respectively) and maximal mid-expiratory flow (MMEF) (1.51 ± 0.27% vs 1.36 ± 0.12%, respectively) were all significantly increased after treatment in the study group compared with the control group (all P < .001). The IGF-1 (104.92 ± 11.27 vs 137.83 ± 11.02 ng/mL, respectively) and PDGF-B (124.39 ± 14.29 vs 249.93 ± 33.49 ng/L, respectively) were significantly reduced in the study group after treatment (all P < .001). The α1-AT (2.82 ± 0.38 vs 2.17 ± 0.22 g/L, respectively) were significantly increased after treatment in the study group compared with the control group.

CONCLUSION

Aerosol inhalation combined with the use of a vibration expectoration machine is worthy of clinical application, and can effectively improve outcomes in patients with COPE.

Subperiosteal Minimally Invasive Aesthetic Ridge Augmentation Technique (SMART): A New Standard for Bone Reconstruction of the Jaws

Traditional guided bone regeneration techniques include flap mobilization and placement of a bone graft, often with the use of space-maintaining devices and cell-occlusive membranes. This approach is associated with frequent complications that negatively affect the outcome of the augmentation and the peri-implant soft tissue esthetics. Although current tunneling techniques have focused on periodontal soft tissue applications, earlier publications described their use for horizontal augmentation of mandibular posterior edentulous ridges in full-denture patients. More recently, the use of recombinant human platelet-derived growth factor (rhPDGF-BB) was tested with different bone matrices to treat maxillary anterior edentulous spans. The present case series reports the use of a subperiosteal minimally invasive aesthetic ridge augmentation technique (SMART) to treat 60 single and multiple edentulous, dentate, and implant sites on 21 patients and five treatment categories with a follow-up period ranging from 4 to 30 months. The technique includes the use of a laparoscopic approach to deliver a growth factor/xenograft combination into a subperiosteal pouch. No flap elevation, cell-occlusive membranes, space-maintaining devices, or decortication procedures were used. The results from this case series demonstrated predictable and consistent bone regeneration. The average gain in ridge width for all treatment categories was 5.11 mm (SD 0.76 mm), which compares favorably with previously published reports. Morbidity and complication rates were consistently reduced as well. Human histology results show xenograft particles surrounded by newly formed bone. The role of the periosteum as a source of pluripotent cells in growth factor–mediated bone regeneration is discussed.

The Use of Recombinant Human Platelet-Derived Growth Factor for Maxillary Sinus Augmentation

The maxillary sinus augmentation procedure has become a predictable treatment to regenerate bone for implant placement. The purpose of this study was to evaluate the effect of recombinant human platelet-derived growth factor BB (rhPDGF-BB) combined with a deproteinized cancellous bovine bone graft for sinus augmentation. The lateral window approach was used for maxillary sinuses with minimal residual bone. After a healing period of 4 months, dental implants were placed and then restored following a 2-month osseointegration period. The result demonstrated increased bone height and ISQ values and a 100% survival rate. This study indicates that the addition of rhPDGF-BB to deproteinized cancellous bovine bone accelerated the healing period in maxillary sinuses with minimal native bone.

Horizontal Guided Bone Regeneration in the Esthetic Area with rhPDGF-BB and Anorganic Bovine Bone Graft: A Case Report

The present article describes the treatment given to a patient who underwent horizontal ridge augmentation surgery in the maxillary anterior area due to the premature loss of the maxillary central incisors. The complete dehiscence of the buccal plate was detected after elevation of mucoperiosteal flaps. The lesion was overfilled with deproteinized bovine xenograft particles combined with recombinant human platelet-derived growth factor BB (rhPDGF-BB) and covered with a porcine collagen barrier hydrated with the same growth factor. The soft tissues healed with no adverse complications. After 12 months, reentry surgery was carried out to place endosseous implants. Complete bone regeneration with the presence of bone-like tissue was observed. Cross-sectional computed tomography scan images confirmed integration of the bone graft and reconstruction of the lost hard tissue volume. The implants were inserted in an optimal three-dimensional position, thus facilitating esthetic restoration. Two years after insertion of final crowns, cone beam computed tomography scans displayed the stability of regenerated hard tissues around the implants. Controlled clinical studies are necessary to determine the benefit of hydrating bovine bone particles and collagen barriers with rhPDGF-BB for predictable bone regeneration of horizontal lesions.

Platelet-derived growth factor-BB attenuates titanium-particle-induced osteolysis in vivo

Inflammation and osteoclastogenesis play critical roles in wear-particle-induced periprosthetic osteolysis (WPO). Platelet-derived growth factor-BB (PDGF-BB) could promote osteogenesis and inhibit inflammatory response. The aim of this study was to investigate the impact of PDGF-BB on WPO. Mice were divided into four groups, namely, sham, vehicle, low-, and high-dose PDGF-BB groups. Mice in the rhPDGF-BB groups were treated with PDGF-BB at 0.25 or 1 mg/ml/kg/day. Mice in the sham and vehicle groups received PBS daily. Two weeks after surgery, calvariae were harvested. Immunohistochemical analysis and μ-CT showed that PDGF-BB significantly reduced osteoclast formation and bone resorption. ELISA showed that rhPDGF-BB decreased the secretion of TNF-α, IL-1β, and IL-6. Western blotting revealed that rhPDGF-BB stimulated the expression of osteocalcin and osteoprotegerin. Furthermore, more VEGF and CD31 proteins were observed due to PDGF-BB by immunofluorescence. In conclusion, these findings suggest that rhPDGF-BB represents a potential treatment for WPO.

Syndecan-4 enhances PDGF-BB activity in diabetic wound healing

Non-healing ulcers are a common consequence of long-term diabetes and severe peripheral vascular disease. These non-healing wounds are a major source of morbidity in patients with diabetes and place a heavy financial burden on the healthcare system. Growth factor therapies are an attractive strategy for enhancing wound closure in non-healing wounds but have only achieved mixed results in clinical trials. Platelet derived growth factor-BB (PDGF-BB) is the only currently approved growth factor therapy for non-healing wounds. However, PDGF-BB therapy is not effective in many patients and requires high doses that increase the potential for side effects. In this work, we demonstrate that syndecan-4 delivered in a proteoliposomal formulation enhances PDGF-BB activity in diabetic wound healing. In particular, syndecan-4 proteoliposomes enhance the migration of keratinocytes derived from patients with diabetes. In addition, syndecan-4 proteoliposomes sensitize keratinocytes to PDGF-BB stimulation, enhancing the intracellular signaling response to PDGF-BB. We further demonstrated that co-therapy with syndecan-4 proteoliposomes enhanced wound closure in diabetic, hyperlipidemic ob/ob mice. Wounds treated with both syndecan-4 proteoliposomes and PDGF-BB had increased re-epithelization and angiogenesis in comparison to wounds treated with PDGF-BB alone. Moreover, the wounds treated with syndecan-4 proteoliposomes and PDGF-BB also had increased M2 macrophages and reduced M1 macrophages, suggesting syndecan-4 delivery induces immunomodulation within the healing wounds. Together our findings support that syndecan-4 proteoliposomes markedly improve PDGF-BB efficacy for wound healing and may be useful in enhancing treatments for non-healing wounds.

STATEMENT OF SIGNIFICANCE

Non-healing wounds are major healthcare issue for patients with diabetes and peripheral vascular disease. Growth factor therapies have potential for healing chronic wounds but have not been effective for many patients. PDGF-BB is currently the only approved growth factor for enhancing wound healing. However, it has not seen widespread adoption due to limited efficacy and high cost. In this work, we have developed an enhancing agent that improves the activity of PDGF-BB in promoting wound healing in animals with diabetes. This co-therapy may be useful in improving the efficacy of PDGFBB and enhance its safety through lowering the dose of growth factor needed to improve wound healing.

A clinical comparison of guided bone regeneration with platelet-derived growth factor-enhanced bone ceramic versus autogenous bone block grafting

PURPOSE

The objective of this study was to evaluate the efficacy of guided bone regeneration (GBR) employing recombinant human platelet-derived growth factor-BB (rhPDGF-BB) incorporated into a beta-tricalcium phosphate (β-TCP)/hydroxyapatite (HA) carrier as a graft material and to compare it to autogenous bone block grafting.

MATERIALS AND METHODS

Adult patients with a site that required bone grafting to increase the thickness of the alveolar bone ridge were treated. After mucoperiosteal flap elevation, experimental bone defects were treated by GBR with rhPDGF incorporated into β-TCP/HA, and control defects were treated with autogenous bone. Primary tension-free wound closure was obtained for all treated sites.

RESULTS

Thirty patients were treated. No significant differences were observed between the groups for any of the parameters evaluated, including the amount of bone regeneration and a need for additional grafting.

CONCLUSION

A composite bone ceramic graft that incorporated rhPDGF appears to be a suitable substitute for autogenous bone block grafting when employed in conjunction with GBR in humans.

Biologic Agents for Periodontal Regeneration and Implant Site Development

The advancement of molecular mediators or biologic agents has increased tremendously during the last decade in periodontology and dental implantology. Implant site development and reconstruction of the lost periodontium represent main fields in which these molecular mediators have been employed and investigated. Different growth factors trigger different reactions in the tissues of the periodontium at various cellular levels. Proliferation, migration, and differentiation constitute the main target areas of these molecular mediators. It was the purpose of this comprehensive review to describe the origin and rationale, evidence, and the most current understanding of the following biologic agents: Recombinant Human Platelet-Derived Growth Factor-BB (rhPDGF-BB), Enamel Matrix Derivate (EMD), Platelet-Rich Plasma (PRP) and Platelet-Rich Fibrin (PRF), Recombinant Human Fibroblast Growth Factor-2 (rhFGF-2), Bone Morphogenic Proteins (BMPs, BMP-2 and BMP-7), Teriparatide PTH, and Growth Differential Factor-5 (GDF-5).

PDGFB-based stem cell gene therapy increases bone strength in the mouse

Substantial advances have been made in the past two decades in the management of osteoporosis. However, none of the current medications can eliminate the risk of fracture and rejuvenate the skeleton. To this end, we recently reported that transplantation of hematopoietic stem/progenitor cells (HSCs) or Sca1(+) cells engineered to overexpress FGF2 results in a significant increase in lamellar bone matrix formation at the endosteum; but this increase was attended by the development of secondary hyperparathyroidism and severe osteomalacia. Here we switch the therapeutic gene to PDGFB, another potent mitogen for mesenchymal stem cells (MSCs) but potentially safer than FGF2. We found that modest overexpression of PDGFB using a relatively weak phosphoglycerate kinase (PGK) promoter completely avoided osteomalacia and secondary hyperparathyroidism, and simultaneously increased trabecular bone formation and trabecular connectivity, and decreased cortical porosity. These effects led to a 45% increase in the bone strength. Transplantation of PGK-PDGFB-transduced Sca1(+) cells increased MSC proliferation, raising the possibility that PDGF-BB enhances expansion of MSC in the vicinity of the hematopoietic niche where the osteogenic milieu propels the differentiation of MSCs toward an osteogenic destination. Our therapy should have potential clinical applications for patients undergoing HSC transplantation, who are at high risk for osteoporosis and bone fractures after total body irradiation preconditioning. It could eventually have wider application once the therapy can be applied without the preconditioning.

Beneficial effects of platelet-derived growth factor on hemorrhagic shock in rats and the underlying mechanisms

Studies have shown that local application of platelet-derived growth factor (PDGF) can be used for the treatment of acute and chronic wounds. We investigated if systemic application of PDGF has a protective effect on acute hemorrhagic shock in rats in the present study. Using hemorrhagic shock rats and isolated superior mesenteric arteries, the effects of PDGF-BB on hemodynamics, animal survival, and vascular reactivity as well as the roles of the gap junction proteins connexin (Cx)40 and Cx43, PKC, and Rho kinase were observed. PDGF-BB (1–15 μg/kg iv) significantly improved the hemodynamics and blood perfusion to vital organs (liver and kidney) as well as vascular reactivity and improved the animal survival in hemorrhagic shock rats. PDGF recovering shock-induced vascular hyporeactivity depended on the integrity of the endothelium and myoendothelial gap junction. Cx43 antisense oligodeoxynucleotide abolished these improving effects of PDGF, whereas Cx40 oligodeoxynucleotide did not. Further study indicated that PDGF increased the activity of Rho kinase and PKC as well as vascular Ca2+ sensitivity, whereas it did not interfere with the intracellular Ca2+ concentration in hypoxia-treated vascular smooth muscle cells. In conclusion, systemic application of PDGF-BB may exert beneficial effects on hemorrhagic shock, which are closely related to the improvement of vascular reactivity and hemodynamics. The improvement of PDGF-BB in vascular reactivity is vascular endothelium and myoendothelial gap junction dependent. Cx43, Rho kinase, and PKC play very important role in this process. These findings suggest that PDGF may be a potential measure to treat acute clinical critical diseases such as severe trauma, shock, and sepsis.

Human periodontal ligament fibroblast response to rhPDGF-BB application on periodontally diseased root surfaces-in vitro

The aim of the present study was to evaluate the influence of recombinant platelet derived growth factor-BB (rhPDGF-BB) on the cellular proliferation, morphology and adherence of human periodontal ligament fibroblasts (PLFs) to the root surfaces of periodontally diseased and healthy human teeth roots at two different time periods. Primary cell cultures of PLFs were obtained from clinically healthy premolar or mandibular third molar teeth. 11 scaffolds were prepared from healthy teeth for group-1 (Healthy Substrates), 33 scaffolds were prepared from periodontally diseased teeth, which were further divided in Group-2 - Periodontally diseased substrates, Group-3 - Scaled and Root planed (SRP) substrates, Group-4 - SRP + rhPDGF-BB (50 ng/ml). Groups were further subdivided into two groups (n = 5 scaffolds per subgroup) and PLFs were incubated on the scaffolds for three and seven days, topographical assessment was done on the remaining substrate. Cell morphology and counting was assessed under a scanning electron microscope at 350× on day three and seven and statistically compared with the Mann-Whitney U test and the Kruskal-Wallis test. On day three, Group 1 showed least number of cells attached, whereas maximum number of cells were attached on Group 3 (SRP only) substrates. For day 7, Group 1 and Group 4 showed increase in the number of cells from day 3 to 7, while number of cells attached/substrate reduced drastically for Group 2 and 3 substrates. Group 3 and 4 showed better adhesion and proliferation of PLFs as compared to Group 1 and 2. Group-1 and Group-4 showed predominantly spindle cells with flat appearance, Group-3 showed stellate cells and Group-2 showed predominantly distorted spindle shaped cells. The results of this in-vitro study indicates that rhPDGF-BB plays a significant role as an adjunct to periodontal therapy in influencing maturity, attachment and proliferation of PLFs.

Purposeful exposure of a polylactic acid barrier to achieve socket preservation for placement of dental implants: case series report

This retrospective case series reports on the use of a polylactic acid barrier that was left exposed in the process of socket preparation for the placement of dental implants. A retrospective chart review found 43 patients with 48 extraction sockets that were treated in this manner. Teeth were removed and the sockets were thoroughly debrided, with 40 of them receiving a bone replacement graft covered by the polylactic acid barrier and the additional 8 receiving the membrane alone. Suturing left the barrier exposed, and the sites were re-entered on average at 23 weeks for the placement of a dental implant. All sites were able to receive a dental implant, demonstrating the ability to leave a polylactic acid barrier exposed and achieve successful guided bone regeneration (GBR) results. This ultimately helped avoid some of the negative sequelae of trying to achieve primary closure of the flaps at the time of tooth extraction.

Randomized controlled clinical study of rhPDGF-BB + β-TCP versus HA + β-TCP for the treatment of infrabony periodontal defects: clinical and radiographic results

Increased knowledge of specific cellular responses and functions has led to the development of numerous treatment modalities based on the use of growth factors. This controlled clinical and radiographic study aimed to evaluate the effectiveness of recombinant human platelet-derived growth factor BB (rhPDGF-BB) + β-tricalcium phosphate (β-TCP) in the treatment of human infrabony defects and compare it with hydroxyapatite (HA) + β-TCP. A total of 18 interproximal defects in 18 patients with chronic periodontitis were included. The test group was treated by open flap debridement in combination with rhPDGF-BB + β-TCP, while the control group was treated by open flap debridement along with HA + β-TCP. At 12 months, both the test and control groups showed a significant mean probing pocket depth (PPD) reduction and gain in clinical attachment level (CAL). There was a statistically significantly greater PPD reduction in the test group compared to the control. The observed differences between baseline CAL and CAL at 12 months were found to be statistically significant in both groups. The mean CAL gain in the test group was significantly greater than that in the control group. Radiographic linear bone growth was significantly improved in the test group compared to the control group. Percent bone fill was significantly increased at 12 months postsurgery in the test group compared to the control group. The treatment with rh-PDGF-BB + β-TCP resulted in a significantly higher CAL gain and PPD reduction in comparison with HA + β-TCP.

Treatment of a large postextraction buccal wall defect with mineralized allograft, β-TCP, and rhPDGF-BB: a growth factor-mediated bone regenerative approach

Buccal wall defects following tooth removal are frequent in the anterior portions of the mandible and maxilla. Common reasons for such defects include thin buccal bone, preexisting periodontal disease, bundle bone resorption, difficult orthodontic movement, and traumatic extractions. Regeneration of the postextraction defect with vital, well-vascularized, dense bone is critical to a successful implant-supported restoration. This case report examines the effectiveness of using a composite graft of freeze-dried bone allograft and β-tricalcium phosphate plus recombinant human platelet-derived growth factor BB to regenerate healthy, dense bone in a large mandibular anterior buccal wall defect. The importance of access to the overlying periosteum as a readily available source of osteogenic cells in growth factor-mediated bone regenerative procedures is emphasized.

Growth factor-mediated combination therapy to treat large local human alveolar ridge defects

The purpose of this case report is to demonstrate the effectiveness of a matrix consisting of recombinant human platelet-derived growth factor BB (rhPDGF-BB)-hydrated cancellous allogenic block graft in the reconstruction of large local human alveolar ridge defects. The results suggest improved bone regeneration when combining rhPDGF-BB with the allogenic block graft. The clinical and histologic evidence of new bone formation as well as bone remodeling supports the clinical potency of this growth factor-mediated therapy.

Evaluation of a resorbable collagen matrix infused with rhPDGF-BB in peri-implant soft tissue augmentation: a preliminary report with 3.5 years of observation

Soft tissue augmentation around dental implants in the esthetic region remains a challenging and unpredictable procedure. The ideal surgical technique would include of an off-the-shelf product to minimize morbidity after autogenous grafting procedures. The aim of this study was to use a resorbable collagen matrix (Mucograft) to serve as a scaffold to recombinant human platelet-derived growth factor BB (rhPDGF-BB) to increase peri-implant soft tissue volume in anterior maxillary sites. A total of six patients who had previously undergone a bone regeneration procedure were included in this study. The collagen matrix was applied during stage-two surgery (expanded polytetrafluoroethylene membrane removal and implant placement). Measurements were performed through customized stents by means of endodontic files, and at abutment connection, a soft tissue biopsy specimen was harvested for histologic examination. The healing period was uneventful in all six patients. Measurements were taken apically, centrally, and occlusally for each site. The mean gains in volume from baseline to the 4-month measurement at the apical, central, and occlusal aspects were 0.87 ± 2.13 mm, 2.14 ± 3.27 mm, and 0.35 ± 3.20 mm, respectively. The results showed a moderate increase in the soft tissue volume in esthetic peri-implant sites when applying a collagen matrix infused with rhPDGF-BB. However, the measuring techniques available need to be further improved to record exact changes in the soft tissue volume.

Impact of recombinant platelet-derived growth factor BB on bone regeneration: a study in rabbits

The aim of this study was to test whether recombinant human platelet-derived growth factor BB (rhPDGF-BB) enhances bone regeneration in combination with Β-tricalcium phosphate (Β-TCP) granules or deproteinized bovine bone mineral (DBBM) compared to empty defects and Β-TCP granules alone. Four titanium cylinders were placed on the external cortical plates of seven rabbits' calvaria and randomly allocated to one of four groups: (1) empty, (2) Β-TCP, (3) Β-TCP + rhPDGF-BB, and (4) DBBM + rhPDGF-BB. The mean area of bone regeneration was 13.9% ± 8.4% (empty), 24.0% ± 14.8% (Β-TCP), 37.1% ± 8.9% (Β-TCP + rhPDGF-BB), and 64.4% ± 5.4% (DBBM + rhPDGF-BB), with the greatest bone regeneration noted for DBBM + rhPDGF-BB (P < .01). The fraction of bone substitute material varied between 48.3% ± 9.3% (DBBM + rhPDGF-BB), 53.1% ± 10.6% (Β-TCP + rhPDGF-BB), and 58.0% ± 14.8% (Β-TCP). rhPDGF-BB combined with DBBM showed the greatest potential to enhance bone regeneration.

Minimally invasive treatment of maxillary anterior gingival recession defects by vestibular incision subperiosteal tunnel access and platelet-derived growth factor BB

An array of therapeutic options are available for treatment of gingival recession defects, though many of these are better suited for treatment of isolated defects. Some of the limitations of current techniques include the need for harvesting of autogenous donor tissues and their associated morbidity, as well as scar formation at the recipient site resulting from surface incisions. Moreover, muscle pull during healing often leads to incomplete root coverage or relapse of the recession. The current case reports introduce a novel, minimally invasive approach applicable for both isolated recession defects as well as multiple contiguous defects in the maxillary anterior region. Access to the surgical site is obtained by means of an approach referred to as vestibular incision subperiosteal tunnel access (VISTA). This entails making an access incision in the maxillary anterior frenum, followed by elevation of a subperiosteal tunnel. VISTA allows for both access as well as an opportunity to coronally reposition the gingival margins of all involved teeth. In this approach, recombinant human platelet-derived growth factor BB saturated onto a matrix of beta-tricalcium phosphate is introduced using VISTA over root dehiscences to enhance periodontal healing. A novel method of stabilization of the gingival margins is also introduced, referred to as coronally anchored suturing, designed to maintain the coronal positioning during healing. The current report describes the technique and two clinical case documentations for treatment of Miller Class I and II defects, demonstrating stable, long-term outcomes. Although VISTA has been applied in other regions, its application is most advantageous in the esthetic zone.

Human buccal plate extraction socket regeneration with recombinant human platelet-derived growth factor BB or enamel matrix derivative

The objective of this study was to assess the osseous healing of buccal plate extraction socket defects. There were four cohorts: group A (mineral collagen bone substitute [MCBS] scaffold alone), group B (MCBS with recombinant human platelet-derived growth factor BB [rhPDGF-BB; 0.3 mg/mL]), group C (MCBS with enamel matrix derivative [EMD]), and group D (combination of EMD with bone ceramic). The primary outcome of bone quality was evaluated using light microscopy, backscatter scanning electron microscopy, and histomorphometrics. Reentry surgery provided an opportunity for clinical observation of the healed ridge morphology. Sixteen patients with buccal wall extraction socket defects were randomized into four treatment groups of equal size. Grafting was provided at the time of extraction with advancement of the buccal flap for primary closure. A trephine core biopsy of the implant site preparation was performed after 5 months for implant placement. Histologic examination identified new bone healing around the biomaterial scaffolds. Statistically significant differences in new bone formation were not observed among the treatment groups. There was a histomorphometric trend toward more new bone for the rhPDGF-BB-treated group (group B). This group had the most favorable ridge morphology for optimal implant placement.

A retrospective consecutive case series using mineralized allograft combined with recombinant human platelet-derived growth factor BB to treat moderate to severe osseous lesions

This retrospective case series reports on the use of freeze-dried bone allograft (FDBA) combined with a purified recombinant protein of platelet-derived growth factor BB (PDGF-BB) for the treatment of periodontal intraosseous defects in 50 consecutive patients. The mean pretreatment measurements for clinical attachment level and probing depth were 7.9 ± 1.6 mm and 7.8 ± 1.4 mm, respectively. At 6 months, mean clinical attachment level was 3.9 ± 1.4 mm, reflecting an improvement of 4.1 ± 1.3 mm, whereas mean probing depth was reduced to 3.0 ± 1.2 mm, corresponding to a reduction of 4.8 ± 1.4 mm. These clinical results indicate that the combined use of FDBA and PDGF-BB can lead to substantial improvements in clinical parameters.

Lateral ridge augmentation using an equine flex bone block infused with recombinant human platelet-derived growth factor BB: a clinical and histologic study

This paper reports on a patient who underwent horizontal ridge augmentation using recombinant human platelet-derived growth factor BB (rhPDGF-BB) in combination with a collagenate equine block. Ninety days after the first surgery, 8 mm of new bone was noted on a computed tomography scan, and three 5-mm implants were placed. Histology, performed using confocal laser scanning microscopy, showed a large amount of newly formed bone well characterized with osteon and resorption lacunae, which demonstrated the intense bone remodeling. This study supports the use of rhPDGF-BB in combination with allograft blocks.

Tendon healing in vitro: genetic modification of tenocytes with exogenous PDGF gene and promotion of collagen gene expression

PURPOSE

Promotion of collagen production can increase tendon healing strength and reduce repair ruptures. Transfer of an exogenous growth factor gene to tenocytes of intrasynovial tendons may enhance the capacity of cells to produce collagen. We transferred the platelet-derived growth factor B (PDGF-B) gene to tenocytes and investigated its effects on the expression of the PDGF gene and the type I collagen gene in an in vitro tenocyte culture model.

METHODS

Tenocytes obtained from explant cultures of rat intrasynovial tendons were treated for 12 hours with the plasmid containing the PDGF complementary deoxyribonucleic acid (cDNA) with liposome and were then cultured for 6 additional days. The control tenocytes did not receive the exogenous gene and liposome. Efficiency of the gene transfer was evaluated by using reverse transcription polymerase chain reactions (RT-PCR) to detect the presence of the transferred gene in the tenocytes. Enhancement of the expression of the target gene was assessed by RT-PCR with primers effective to amplify both internal and transferred genes. Expression of the type I collagen gene was determined by quantitative analysis of the products of RT-PCR.

RESULTS

Levels of expression of the type I collagen gene by tenocytes were increased significantly by transfer of the exogenous PDGF gene to the tenocytes. Efficiency of the gene transfer was confirmed by the presence of exogenous PDGF cDNA in the tenocytes receiving the transferred gene. Expression of the PDGF gene increased significantly in the cells treated with exogenous PDGF cDNA.

CONCLUSIONS

Exogenous PDGF genes can be transferred effectively into intrasynovial tenocytes and the transfer increases significantly the expression of genes for PDGF and type I collagen. Transfer of the PDGF gene may offer a novel way of effectively promoting healing of intrasynovial flexor tendons. The findings warrant future in vivo study to test the effectiveness of gene therapy to promote flexor tendon healing.

Matrix immobilization enhances the tissue repair activity of growth factor gene therapy vectors

Although growth factor proteins display potent tissue repair activities, difficulty in sustaining localized therapeutic concentrations limits their therapeutic activity. We reasoned that enhanced histogenesis might be achieved by combining growth factor genes with biocompatible matrices capable of immobilizing vectors at delivery sites. When delivered to subcutaneously implanted sponges, a platelet-derived growth factor B-encoding adenovirus (AdPDGF-B) formulated in a collagen matrix enhanced granulation tissue deposition 3- to 4-fold (p < or = 0.0002), whereas vectors encoding fibroblast growth factor 2 or vascular endothelial growth factor promoted primarily angiogenic responses. By day 8 posttreatment of ischemic excisional wounds, collagen-formulated AdPDGF-B enhanced granulation tissue and epithelial areas up to 13- and 6-fold (p < 0.009), respectively, and wound closure up to 2-fold (p < 0.05). At longer times, complete healing without excessive scar formation was achieved. Collagen matrices were shown to retain both vector and transgene products within delivery sites, enabling the transduction and stimulation of infiltrating repair cells. Quantitative PCR and RT-PCR demonstrated both vector DNA and transgene mRNA within wound beds as late as 28 days posttreatment. By contrast, aqueous formulations allowed vector seepage from application sites, leading to PDGF-induced hyperplasia in surrounding tissues but not wound beds. Finally, repeated applications of PDGF-BB protein were required for neotissue induction approaching equivalence to a single application of collagen-immobilized AdPDGF-B, confirming the utility of this gene transfer approach. Overall, these studies demonstrate that immobilizing matrices enable the controlled delivery and activity of tissue promoting genes for the effective regeneration of injured tissues.

Growth factors in clinical practice

Wound repair consists of a complex interaction of cellular and biochemical events. Several growth factors have been identified as regulatory polypeptides co-ordinating the healing process. Although it is not known precisely why chronic wounds do not follow the normal pattern of healing, diminished growth factor content and accelerated growth factor degradation may contribute to poor healing. Topical application of different factors exert stimulatory effects on wounds in animal models. Human data are limited but the most investigated compound is recombinant human platelet-derived growth factor-BB (rhPDGF-BB). PDGF-BB enhances granulation tissue formation and facilitates epithelialisation. Clinical trials in patients with 'hard to heal' diabetic foot ulcers demonstrated significant improvement in the 'healing rate' and the 'time to healing' compared with controls. Refinement of therapeutic strategies with growth factors will take place in the future.