Analysis of Rat Calvaria Defects Implanted With a Platelet-Rich Plasma Preparation: Radiographic Observations

Which substances loaded onto collagen scaffolds influence oral tissue regeneration?-an overview of the last 15 years

BACKGROUND

Collagen scaffolds are widely used for guided bone or tissue regeneration. Aiming to enhance their regenerative properties, studies have loaded various substances onto these scaffolds. This review aims to provide an overview of existing literature which conducted in vitro, in vivo, and clinical testing of drug-loaded collagen scaffolds and analyze their outcome of promoting oral regeneration.

MATERIALS AND METHODS

PubMed, Scopus, and Ovid Medline® were systematically searched for publications from 2005 to 2019. Journal articles assessing the effect of substances on oral hard or soft tissue regeneration, while using collagen carriers, were screened and qualitatively analyzed. Studies were grouped according to their used substance type-biological medical products, pharmaceuticals, and tissue-, cell-, and matrix-derived products.

RESULTS

A total of 77 publications, applying 36 different substances, were included. Collagen scaffolds were demonstrating favorable adsorption behavior and release kinetics which could even be modified. BMP-2 was investigated most frequently, showing positive effects on oral tissue regeneration. BMP-9 showed comparable results at lower concentrations. Also, FGF2 enhanced bone and periodontal healing. Antibiotics improved the scaffold's anti-microbial activity and reduced the penetrability for bacteria.

CONCLUSION

Growth factors showed promising results for oral tissue regeneration, while other substances were investigated less frequently. Found effects of investigated substances as well as adsorption and release properties of collagen scaffolds should be considered for further investigation.

CLINICAL RELEVANCE

Collagen scaffolds are reliable carriers for any of the applied substances. BMP-2, BMP-9, and FGF2 showed enhanced bone and periodontal healing. Antibiotics improved anti-microbial properties of the scaffolds.

Type 2 diabetes impairs angiogenesis and osteogenesis in calvarial defects: MicroCT study in ZDF rats

OBJECTIVES

The present study was motivated by the fact that bone regeneration in the compromised vascular microenvironment of T2DM is challenging and the factors that determine the adverse bone regeneration outcomes are poorly understood. For this purpose the effect of T2DM on osteogenic and angiogenic healing potential of calvarial bone, was evaluated in Zucker diabetic fatty (ZDF) rats, an established rat model for obese T2DM.

MATERIALS AND METHODS

The study used 16-week-old ZDF rats and their age-matched controls, Zucker Lean (ZL). Circular defects of different sizes were created on the animal calvaria, either a single 8-mm-diameter (n = 6) defect, or 6-4-2-mm-diameter multidefects (n = 6). Bone regeneration was evaluated at 0, 4, 6 and 8 weeks post surgery using in vivo micro-CT and after animal sacrifice using ex vivo micro-CT. Vascular network parameters within the defects, were quantified by perfusing the animal vasculature with microfil® and scanning it after decalcification.

RESULTS

Compared to results obtained from the ZL rats, defects of 8-mm-diameter in ZDF rats displayed impaired healing kinetics and significantly reduced newly formed bone volume (p < 0.01) and surface area (p < 0.01), 8 weeks post surgery. Defects of 6-4-2-mm-diameter exhibited bone formation, which was independent of either the size or the diabetic condition. Compared to results from the ZL, in the ZDF rats, vasculature volume and surface area were significantly (p < 0.05) reduced in all size-defects.

CONCLUSION

The present study provided evidence that T2DM impairs bone formation in critical-size calvarial defects and markedly reduces angiogenesis in all defects regardless of the defect size tested.

Effect of Resorbable Collagen Plug on Bone Regeneration in Rat Critical-Size Defect Model

OBJECTIVE

The purpose of this investigation was to examine the effect of resorbable collagen plug (RCP) on bone regeneration in rat calvarial critical-size defects.

METHODS

About 5-mm-diameter calvarial defects were created in forty 12-week-old male Sprague-Dawley rats and implanted with or without RCP. Animals were killed at 1, 2, 4, and 8 weeks postoperatively. After being killed, specimens were collected and subjected to micro-computed tomography (μCT) and histological analysis.

RESULTS

The μCT showed a significant increase of newly formed bone volume/tissue volume in RCP-implanted defect compared with controls at all designated time points. After 8 weeks, the defects implanted with RCP displayed almost complete closure. Hematoxylin and eosin staining of the decalcified sections confirmed these observations and evidenced active bone regeneration in the RCP group. In addition, Masson's trichrome staining demonstrated that RCP implantation accelerated the process of collagen maturation.

CONCLUSIONS

The RCP enhances bone regeneration in rat critical-size cranial defects, which suggest it might be a desired material for bone defect repair.

Comparison of Effects of Pulsed Electromagnetic Field Stimulation on Platelet-Rich Plasma and Bone Marrow Stromal Stem Cell Using Rat Zygomatic Bone Defect Model

BACKGROUND

Reconstruction of bone defects that occur because of certain reasons has an important place in plastic and reconstructive surgery. The objective of the treatments of these defects was to reinstate the continuity of tissues placed in the area in which the defect has occurred. In this experimental study, the effect of pulsed electromagnetic field stimulation on platelet-rich plasma (PRP) and bone marrow stromal cell, which propounded that they have positive impact on bone regeneration, was evaluated with the bone healing rate in the zygomatic bone defect model enwrapped with superficial temporal fascia.

METHODS

After creating a 4-mm defect on the zygomatic bone of the experiments, the defect was encompassed with a superficial temporal fascial flap and a nonunion model was created. After surgery, different combinations of the PRP, bone marrow stromal cell, and electromagnetic field applications were implemented on the defective area. All the experiments were subjected to bone density measurement.

RESULTS

The result revealed that the PRP and pulsed electromagnetic field implementation were rather a beneficial and an effective combination in terms of bone regeneration.

CONCLUSIONS

It was observed that the superficial temporal fascial flap used in the experiment was a good scaffold choice, providing an ideal bone regeneration area because of its autogenous, vascular, and 3-dimensional structures. As a result, it is presumed that this combination in the nonhealing bone defects is a rather useful treatment choice and can be used in a reliable way in clinical applications.

Platelet-Rich Plasma: A Study of the Variables that May Influence Its Effect on Bone Regeneration

BACKGROUND

Currently, the use of platelet-rich plasma in bone regeneration is a real option, although more than one opinion has alerted us to the absence of clinical benefits.

PURPOSE

Analysis of the factors able to modify the characteristics of the platelet preparation obtained by Curasan, Plasma Rich in Growth Factors (PRGF), Platelet Concentrate Collection System (PCCS) and SmartPrep systems, relating them to the type of clinical application and the final bone regeneration achieved.

MATERIALS AND METHODS

A search was conducted in PubMed using the keywords "platelet-rich plasma," "PRP," "platelet rich growth factors," and "oral bone regeneration." Four widely accepted protocols for the obtention of PRP (above) were analyzed. Any clinical studies with controls, using the four preparation protocols and with a 4 to 6 weeks follow-up period were compared. The protocols were also grouped according to the type of PRP application: PRP-alone, with bone, or with bone substitutes.

RESULTS

Bone regeneration was not achieved in any of the cases using PRP obtained by Curasan and PCCS systems, whereas PRP obtained by SmartPrep achieved it only in one in three published cases and PRGF in one in six.

CONCLUSION

Based on the poor results observed in current literature, the use of PRP in oral surgery cannot be recommended.

Platelet-rich plasma in bone regeneration: engineering the delivery for improved clinical efficacy

Human bone is a tissue with a fairly remarkable inherent capacity for regeneration; however, this regenerative capacity has its limitations, and defects larger than a critical size lack the ability to spontaneously heal. As such, the development and clinical translation of effective bone regeneration modalities are paramount. One regenerative medicine approach that is beginning to gain momentum in the clinical setting is the use of platelet-rich plasma (PRP). PRP therapy is essentially a method for concentrating platelets and their intrinsic growth factors to stimulate and accelerate a healing response. While PRP has shown some efficacy in both in vitro and in vivo scenarios, to date its use and delivery have not been optimized for bone regeneration. Issues remain with the effective delivery of the platelet-derived growth factors to a localized site of injury, the activation and temporal release of the growth factors, and the rate of growth factor clearance. This review will briefly describe the physiological principles behind PRP use and then discuss how engineering its method of delivery may ultimately impact its ability to successfully translate to widespread clinical use.

Effect of platelet-rich plasma on bone regeneration after removal of cysts and benign tumours of the jaws

INTRODUCTION

Platelets are involved in regeneration at sites of pathology, apart from their role in clotting. A preparation composed mainly of platelets (platelet-rich plasma gel) applied to sites of bony pathology, after surgical treatment of lesions, may hasten bone regeneration.

MATERIALS AND METHODS

An autologous platelet-rich plasma (PRP) gel was prepared using a standardized technique, without using thrombin clot accelerator, and applied to surgical site in six patients of study group. Five patients were enrolled as controls, in whom PRP gel was not used. The differences in the occurrence of radiographic changes between the study and control group at 6, 12, 18 and 24 weeks after surgery were analysed with chi-square test. Intragroup radiographic changes, i.e. within the study and control groups occurring over the 24 weeks of follow-up, were analysed with Friedman test.

RESULTS

A trend towards more rapid healing was observed in the study group at 6, 12, 18 and 24 weeks. However, these differences between the study and control group were not statistically significant. Both the study and control group demonstrated significant healing changes over the 24 weeks of follow-up.

CONCLUSIONS

It is possible to prepare platelet-rich plasma gel without using thrombin clot accelerator. PRP, as prepared and applied to surgical sites in this study, was not observed to significantly enhance bone regeneration. All surgical sites, both in the PRP and control group, showed significant healing changes over 6 months.

Histologic Evaluation of Osseous Regeneration Following Combination Therapy With Platelet-Rich Plasma and Bio-Oss in a Rat Calvarial Critical-Size Defect Model

Platelet-rich plasma (PRP) is an autogenous source of growth factors shown to facilitate human bone growth. Bio-Oss, an osteoconductive xenograft, is used clinically to regenerate periodontal defects, restore dental alveolar ridges, and facilitate sinus-lift procedures. The purpose of this study was to analyze whether a combination of PRP and Bio-Oss would enhance bone regeneration better than either material alone. PRP and/or Bio-Oss were administered in an 8-mm critical-size defect (CSD) rat calvarial model of bone defect between 2 polytetrafluoroethylene membranes to prevent soft tissue incursion. Eight weeks after the induction of the CSD, histologic sections were stained with hematoxylin and eosin stain and analyzed via light microscopy. Qualitative analyses revealed new bone regeneration in all 4 groups. The Bio-Oss and PRP plus Bio-Oss groups demonstrated greater areas of closure in the defects than the control or PRP-only groups because of the space-maintaining ability of Bio-Oss. The groups grafted with Bio-Oss showed close contact with new bone growth throughout the defects, suggesting a stronger graft. The use of PRP alone or in combination with Bio-Oss, however, did not appear to enhance osseous regeneration at 8 weeks. Areas grafted with Bio-Oss demonstrated greater space-maintaining capacity than controls, and PRP was an effective vehicle for placement of the Bio-Oss. However, at 8 weeks this study was unable to demonstrate a significant advantage of using PRP plus Bio-Oss over using Bio-Oss alone.

Reduction of bone resorption by the application of platelet-rich plasma (PRP) in bone grafting of the alveolar cleft

OBJECTIVE

We evaluated the effectiveness of platelet-rich plasma (PRP) on the regeneration of autogenous cancellous bone and marrow grafted in the alveolar cleft.

DESIGN

Twenty patients with alveolar clefts were examined; 6 were the control group and received cancellous bone and marrow grafts without PRP, while the remaining 14 comprised the PRP group and received grafts with PRP. Prior to surgery, 50 ml of blood was withdrawn and 5 ml of PRP gel produced through centrifugal separation. The bone graft mixed with PRP was then packed into the alveolar cleft. Postoperative bone density was assessed as the aluminium-equivalent value on occlusal X-ray films in a qualitative analysis. Quantitative evaluation of regenerated bone was made with computed tomography and panoramic radiographs at 1 month, 6 months and 1 year after surgery.

RESULTS

Satisfactory bone bridging formation was observed in all patients without any complications. The bone density of the PRP group was lower than that of the control group at 1 week, but the same after 1 month. The added PRP reduced the resorption of regenerated bone postoperatively.

CONCLUSION

Autogenous cancellous bone grafting with PRP, which significantly reduces postoperative bone resorption, is a reliable technique for alveolar bone grafting of cleft patients.

Platelet-rich plasma diminishes calvarial bone repair associated with alterations in collagen matrix composition and elevated CD34+ cell prevalence

The interaction between platelets and both type I and III collagens plays an important role in modulating platelet adhesion and aggregation, also contributing to the chemotaxis of CD34+ cells. The interaction with type III collagen can maintain high levels of collagen and alter the biology of bone repair when the PRP is used. The aim of this study was to evaluate the effect of platelet-rich plasma (PRP) and autograft on the presence of type III and type I collagens, the ratio between them, as well as the presence of CD34+ progenitor cells, while comparing these results by means of a histomorphometric analysis of the bone tissue. Four bone defects (8.0mm in diameter and 2.0mm in depth) were produced on the calvarium of 23 rabbits. The surgical defects were treated with either autogenous bone grafts, autogenous bone grafts with PRP and PRP alone. Animals were euthanized at 2, 4 or 6 weeks post-surgery. Histological, histomorphometric and immunohistochemical analyses were performed to assess repair time, as well as the expression of type I and III collagens, and number of progenitor CD34+ cells. Data were analyzed using the ANOVA and Student-Newman-Keuls test (alpha=5%). An enlarged granulation and medullary tissue areas in the PRP groups were observed. The use of PRP in this study hindered bone deposition, also enhanced type III to type I collagen ratio and the chemotaxis of CD34+ progenitor cells, similarly to a thrombogenic effect.

Cages augmented with mineralized collagen and platelet-rich plasma as an osteoconductive/inductive combination for interbody fusion

STUDY DESIGN

After anterior cervical discectomy, fusion was radiologically, biomechanically, and histologically assessed in a sheep spine fusion model.

OBJECTIVE

To evaluate the efficacy of a platelet-rich plasma (PRP) application combined with a mineralized collagen matrix (MCM) as an alternative to autologous cancellous iliac crest bone grafts in a spine fusion model.

SUMMARY OF BACKGROUND DATA

PRP has the ability to stimulate bone and tissue healing. MCM is a recently developed osteoconductive material. Up to now, no comparative evaluation of PRP in combination with a MCM at the cervical spine has been performed in vivo.

METHODS

Twenty-four sheep (N = 8/group) underwent C3/4 discectomy and fusion: group 1, titanium cage filled with autologous cancellous iliac crest bone graft; group 2, titanium cage filled with MCM; and group 3, titanium cage filled with MCM and PRP. Radiographic evaluation was performed before surgery and after 1, 2, 4, 8, and 12 weeks, respectively. After 12 weeks, fusion sites were evaluated using functional radiographic views and quantitative computed tomographic scans to assess bone mineral density. Furthermore, histomorphologic and histomorphometrical analyses were performed to evaluate fusion.

RESULTS

In comparison with the titanium cage group filled with autologous cancellous iliac crest bone grafts representing the control group, MCM-alone group showed a slightly lower fusion rate in the radiographic and the histomorphometrical analysis. The addition of PRP could not enhance this finding. There was no significant difference between MCM and MCM + PRP group in radiologic and histologic findings.

CONCLUSION

The MCM alone is not able to replace autologous bone grafts. Early activation of the platelets by calcium, which is released from mineralized collagen, could be the reason for the insufficient osteoinductive effect of PRP. In consequence, the combined application of mineralized collagen and PRP had no significant osteoinductive effect in this model.

Bone regenerative properties of rat, goat and human platelet-rich plasma

To explore the reported contradictory osteogenic capacity of platelet-rich plasma (PRP), the aim of the study was to examine and compare the bone regenerative effect of: PRPs of different species (rat, goat, human); human bone graft (HB) vs. HB combined with human PRP (HB+hPRP); and HB+hPRP vs. synthetic hydroxyapatite-tricalcium phosphate bone substitute combined with hPRP (HA/TCP+hPRP). For this purpose, 72 implants, divided into 6 groups (n=6) were inserted in critical-sized defects of immunodeficient rats. After 2 and 4 weeks, descriptive and quantitative histological, and micro-CT analyses were performed on the specimens. Rat and goat PRP combined with HA/TCP did not enhance bone regeneration compared with HA/TCP. In contrast, human PRP combined with HA/TCP resulted in significantly increased bone fill compared to HA/TCP. The addition of human PRP to human bone graft increased significantly the amount of newly formed bone after 2 weeks. HB+hPRP demonstrated enhanced bone healing compared to HA/TCP+hPRP. In conclusion, rat and goat PRP had no effect on bone formation. Human PRP improved the initial osteogenic response of human bone graft. Human PRP combined with human bone graft had better osteogenic capacity than human PRP combined with synthetic bone substitute.

Activation of human platelet-rich plasmas: effect on growth factors release, cell division and in vivo bone formation

OBJECTIVES

Aims of this controlled study were to determine the effects of activated human platelet-rich plasmas (PRPs) on early and mature bone formation in vivo, and to characterize the effect of PRP activation on growth factors release and endothelial cell division in vitro.

MATERIAL AND METHODS

PRPs were prepared from four volunteers with the platelet concentrate collector system (PCCS) system and activated with three concentrations of calcium and thrombin. Platelet-derived growth factor (PDGF)-BB, vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF-beta) and interleukin-1beta (IL-1beta) levels released in supernatants were measured by ELISA, at time 0, 1h, 24h and 6 days following PRP activation. Mitogenic potential of PRP supernatants were tested on endothelial cells in vitro, and the effects of activated human PRPs on bone formation in vivo were measured in athymic rats by micro-CT analyses.

RESULTS

Activation of PRPs with calcium and thrombin triggered an immediate release of VEGF, PDGF-BB and TGF-beta and a delayed release of IL-1beta in PRP supernatants. Higher endothelial cell division was observed with supernatants from activated PRPs than from non-activated PRPs. Positive correlations were observed between VEGF levels and endothelial cell division and bone formation. A negative correlation was also found between PDGF-BB concentration and bone formation. However, early and mature bone formations with activated PRPs did not significantly differ from the ones obtained in the control group.

CONCLUSIONS

Activation of PRPs with calcium and thrombin regulates growth factors release and endothelial cell division in vitro. However, activated PRPs does not improve the early or mature bone formations in vivo in this athymic rat model.

Validity of radiographic evaluations of bone formation in a rat calvaria osteotomy defect model

OBJECTIVE

The objective of this study was to evaluate the validity of radiographic evaluations of bone formation in a critical-size rat calvaria osteotomy defect model.

METHODS

Bilateral, critical-size ( [symbol in text] 6 mm) calvaria osteotomy defects in 30 adult Sprague-Dawley rats treated with a rat platelet-rich plasma preparation or control treatments were evaluated by radiographic and histometric measures following a 4- or 8-week healing interval. Standardized radiographic images of the rat calvaria gross specimens were used to assess bone formation within the defect sites by visual evaluation of the grey scale by three masked examiners. The most central portion of each defect site was subject to histometric analysis using a PC-based image analysis system. Kappa statistics and percentage agreement between the radiographic and histometric analysis were estimated.

RESULTS

Radiographic evaluations of bone formation are associated with significant weaknesses poorly representing actual healing events; kappa statistics (0.17) denoting slight agreement beyond chance. Perfect agreement between the histologic and radiographic analysis for defect sites showing complete and partial histologic bone fill was achieved 63% and 50% of the time, respectively. Agreement reached only 20% for sites with no/limited bone fill. When no/limited and partial bone fill occurred, the radiographic analysis tended to overestimate bone fill and underestimate bone fill when complete closure of the defect sites was observed in the histologic analysis.

CONCLUSION

Low accuracy was observed when radiographic evaluations were employed in identifying and characterizing bone fill in the rat calvaria osteotomy defects. Assessment of bone healing in animal models aiming at treatment recommendations for clinical application must not solely be based on radiographic analysis, but should be confirmed using histologic observations.