Transforming Growth Factor-β1Accelerates Resorption of a Calcium Carbonate Biomaterial in Periodontal Defects

Percutaneous delivery of self-propelling hemostatic powder for managing non-compressible abdominal hemorrhage: a proof-of-concept study in swine

INTRODUCTION

Non-compressible intra-abdominal hemorrhage (NCIAH) is a major cause of preventable death on the battlefield and in civilian trauma. Currently, it can only be definitively managed with surgery, as there are limited strategies for controlling ongoing NCIAH in the prehospital environment. We hypothesized that a self-propelling thrombin-containing powder (SPTP) could increase survival in a swine model of NCIAH when delivered percutaneously into the closed abdomen using an engineered spray system.

MATERIALS AND METHODS

Nineteen swine underwent surgical laparotomy followed by a Grade V liver injury that created massive hemorrhage, before closing the abdomen with sutures. Animals either received treatment with standard of care fluid resuscitation (n=9) or the SPTP spray system (n=10), which consisted of a spray device and a 14 Fr catheter. Using the spray system, SPTP was delivered into a hemoperitoneum identified using a focused assessment with sonography in trauma (FAST) exam. Lactated Ringer's solution was administered to all animals to maintain a mean arterial pressure (MAP) of >50 mmHg. The primary outcome was percentage of animals surviving at three hours following injury.

RESULTS

In the swine model of NCIAH, a greater percentage of animals receiving SPTP survived to three hours, although differences were not significant. The SPTP spray system increased the median survival of animals from 1.6 hr in the fluid resuscitation group to 4.3 hr. The SPTP spray system delivered a total mass of 18.5 ± 1.0 g of SPTP. The mean change in intra-abdominal pressure following SPTP delivery was 5.2 ± 1.8 mmHg (mean ± SEM). The intervention time was 6.7 ± 1.7 min. No adverse effects related to the SPTP formulation or the spray system were observed. SPTP was especially beneficial in animals that had either severely elevated lactate concentrations or low mean arterial pressure of <35 mmHg shortly after injury.

CONCLUSIONS

This demonstrates proof-of-concept for use of a new minimally invasive procedure for managing NCIAH, which could extend survival time to enable patients to reach definitive surgical care.

Tissue engineering in periodontology: Biological mediators for periodontal regeneration

Teeth and the periodontal tissues represent a highly specialized functional system. When periodontal disease occurs, the periodontal complex, composed by alveolar bone, root cementum, periodontal ligament, and gingiva, can be lost. Periodontal regenerative medicine aims at recovering damaged periodontal tissues and their functions by different means, including the interaction of bioactive molecules, cells, and scaffolds. The application of growth factors, in particular, into periodontal defects has shown encouraging effects, driving the wound healing toward the full, multi-tissue periodontal regeneration, in a precise temporal and spatial order. The aim of the present comprehensive review is to update the state of the art concerning tissue engineering in periodontology, focusing on biological mediators and gene therapy.

β-TCP/HA with or without enamel matrix proteins for maxillary sinus floor augmentation: a histomorphometric analysis of human biopsies

BACKGROUND

It is still unclear whether enamel matrix proteins (EMD) as adjunct to bone grafting enhance bone healing. This study compared histomorphometrically maxillary sinus floor augmentation (MSFA) with β-TCP/HA in combination with or without EMD in humans.

METHODS

In ten systemically healthy patients needing bilateral MSFA, one side was randomly treated using β-TCP/HA mixed with EMD (BC + EMD) and the other side using only β-TCP/HA (BC). After 6 months, biopsies were harvested from grafted areas during implant installation, being histologically and histomorphometrically analyzed. Differences between the groups considering new bone formation, soft tissues, and remaining BC were statistically evaluated.

RESULTS

All patients showed uneventful healing after MSFA, and dental implant installation was possible in all patients after 6 months. Histological analysis showed newly formed bone that was primarily woven in nature; it was organized in thin trabeculae, and it was occasionally in contact with residual bone substitute particles, which appeared in various forms and sizes and in advanced stage of degradation. Mean bone area was 43.4% (CI95 38.9; 47.8) for the BC group and 43.0% (CI95 36.6; 49.5) for the BC + EMD group. Mean soft tissue area was 21.3% (CI95 16.5; 26.2) for BC group and 21.5% (CI95 17.7; 25.3) for BC + EMD group, while the remaining biomaterial was 35.3% (CI95 36.6; 49.5) and 35.5% (CI95 29.6; 41.3) for BC and BC + EMD group, respectively.

CONCLUSIONS

MSFA with BC resulted in adequate amounts of new bone formation allowing successful implant installation; adding EMD did not have a significant effect.

Effect of rhTGF-β1 combined with bone grafts on human periodontal cell differentiation

Various techniques and materials have been proposed for the treatment of periodontal defects. In periodontal regeneration, periodontal ligament (PDL) cell differentiation as well as certain growth factors and their delivery system applied are critical. The purpose of this study was to evaluate the in vitro effect of recombinant human transforming growth factor-beta 1 (rhTGF-β1) combined with two different bone grafts on human PDL (hPDL) cell differentiation. The hPDL cells were treated with TGF-β1 alone or in combination with a calcified freeze-dried bone allograft (FDBA) and a porous biphasic calcium phosphate (BC) bone graft. Cell differentiation effect was estimated by measuring alkaline phosphatase (ALPase) activity and osteocalcin secretion. Results demonstrated that rhTGF-β1 alone or in combination with FDBA and BC provoked a significant (p<0.05) increase in ALPase activity as compared with controls. The findings of this study confirmed the beneficial role of rhTGF-β1 combined with FDBA and BC as carriers in periodontal regeneration.

Evaluation of an injectable rhGDF-5/PLGA construct for minimally invasive periodontal regenerative procedures: a histological study in the dog

AIM

To evaluate the injectability, biocompatibility, safety, and periodontal wound healing/regeneration following application of a novel bioresorbable recombinant human growth/differentiation factor-5 (rhGDF-5)/poly(lactic-co-glycolic acid) (PLGA) construct.

MATERIAL AND METHODS

Periodontal pockets (3 x 6 mm, width x depth) were surgically created over the buccal roots of the second and fourth mandibular pre-molars in eight adult Hound Labrador mongrel dogs. Surgeries including injection of the rhGDF-5/PLGA construct into the pockets were sequenced that four animals provided 2-/4-week and four animals 6-/8-week observations of sites receiving rhGDF-5/PLGA or serving as sham-surgery control.

RESULTS

The rhGDF-5/PLGA construct was easy to prepare and apply. Approximately 0.2 ml (93 microg rhGDF-5)/tooth was used. Clinical and radiographic healing was exemplary without adverse events. Healing was characterized by a non-specific connective tissue attachment, acellular/cellular cementum, periodontal ligament (PDL), bone regeneration, and a junctional epithelium. PLGA fragments were observed in 4/7, 2/8, and 1/8 sites at 2, 4, and 6 weeks, respectively. Associated inflammatory reactions exhibited no limiting effect on periodontal wound healing/regeneration. Root resorption/ankylosis was not observed. Bone formation showed apparent increased maturity (lamellar bone) at 6 weeks in sites receiving rhGDF-5/PLGA compared with the control. Both protocols exhibited significant increases in PDL, cementum, and bone regeneration over time, without significant differences between treatments. In time, PDL and cementum regeneration was twofold greater for the control at 4 weeks (p=0.04) while increased bone formation was observed at sites receiving rhGDF-5/PLGA (p<0.01).

CONCLUSIONS

In conclusion, the rhGDF-5/PLGA construct appears to be a safe technology for injectable, ease-of-use application of rhGDF-5-stimulated periodontal wound healing/regeneration. Additional work to optimize the polymer carrier and rhGDF-5 release kinetics/dose might be required before evaluating the efficacy of this technology in clinical settings using minimally invasive approaches.

Periodontal wound healing/regeneration following the application of rhGDF-5 in a beta-TCP/PLGA carrier in critical-size supra-alveolar periodontal defects in dogs

AIM

The objective of this study was to evaluate the effect of a novel recombinant human GDF-5 (rhGDF-5) construct intended for onlay and inlay indications on periodontal wound healing/regeneration.

METHODS

Contralateral, surgically created, critical-size, 6-mm, supra-alveolar periodontal defects in five adult Hound Labrador mongrel dogs received rhGDF-5 coated onto beta-tricalcium phosphate (beta-TCP) particles and immersed in a bioresorbable poly(lactic-co-glycolic acid) (PLGA) composite or the beta-TCP/PLGA carrier alone (control). The rhGDF-5 and control constructs were moulded around the teeth and allowed to set. The gingival flaps were then advanced; flap margins were adapted 3-4 mm coronal to the teeth and sutured. The animals were euthanized at 8 weeks post-surgery when block biopsies were collected for histometric analysis.

RESULTS

Healing was generally uneventful. A few sites exhibited minor exposures. Three control sites and one rhGDF-5 site (in separate animals) experienced more extensive wound dehiscencies. The rhGDF-5 and control constructs were easy to apply and exhibited adequate structural integrity to support the mucoperiosteal flaps in this challenging onlay model. Limited residual beta-TCP particles were observed at 8 weeks for both rhGDF-5/beta-TCP/PLGA and beta-TCP/PLGA control sites. The rhGDF-5/beta-TCP/PLGA sites showed significantly greater cementum (2.34 +/- 0.44 versus 1.13 +/- 0.25 mm, p=0.02) and bone (2.92 +/- 0.66 versus 1.21 +/- 0.30 mm, p=0.02) formation compared with the carrier control. Limited ankylosis was observed in four of five rhGDF-5/beta-TCP/PLGA sites but not in control sites.

CONCLUSIONS

Within the limitations of this study, the results suggest that rhGDF-5 is a promising candidate technology in support of periodontal wound healing/regeneration. Carrier and rhGDF-5 dose optimization are necessary before further advancement of the technology towards clinical evaluation.

Periodontal regeneration: focus on growth and differentiation factors

Several growth and differentiation factors have shown potential as therapeutic agents to support periodontal wound healing/regeneration, although optimal dosage, release kinetics, and suitable delivery systems are still unknown. Experimental variables, including delivery systems, dose, and the common use of poorly characterized preclinical models, make it difficult to discern the genuine efficacy of each of these factors. Only a few growth and differentiation factors have reached clinical evaluation. It appears that well-defined discriminating preclinical models followed by well-designed clinical trials are needed to further investigate the true potential of these and other candidate factors. Thus, current research is focused on finding relevant growth and differentiation factors, optimal dosages, and the best approaches for delivery to develop clinically meaningful therapies in patient-centered settings.

Biological effects of rinsing morsellised bone grafts before and after impaction

Rinsing bone grafts before or both before and after impaction might have different effects on the incorporation of the graft. Rinsing again after impaction might negatively influence bone induction if growth factors released by impaction are washed away. We studied if transforming growth factor-betas (TGF-betas) and bone morphogenetic proteins (BMPs) are released from the mineralised matrix by impaction and if these released growth factors induce osteogenic differentiation in human mesenchymal stem cells (hMSCs). Rinsed morsellised bone allografts were impacted in a cylinder and the escaping fluid was collected. The fluid was analysed for the presence of TGF-betas and BMPs, and the osteoinductive capacity was tested on hMSCs. Abundant TGF-beta was present in the fluid. No BMPs could be detected. Osteogenic differentiation of hMSCs was inhibited by the fluid. Results from our study leave us only able to speculate whether rinsing grafts again after impaction has a beneficial effect on the incorporation process or not.