Regenerative repair of the mandible using a collagen sponge containing TGF-beta1

Intra-articular implantation of collagen scaffold carriers is safe in both native and arthrofibrotic rabbit knee joints

Objectives

Sustained intra-articular delivery of pharmacological agents is an attractive modality but requires use of a safe carrier that would not induce cartilage damage or fibrosis. Collagen scaffolds are widely available and could be used intra-articularly, but no investigation has looked at the safety of collagen scaffolds within synovial joints. The aim of this study was to determine the safety of collagen scaffold implantation in a validated in vivo animal model of knee arthrofibrosis.

Materials and Methods

A total of 96 rabbits were randomly and equally assigned to four different groups: arthrotomy alone; arthrotomy and collagen scaffold placement; contracture surgery; and contracture surgery and collagen scaffold placement. Animals were killed in equal numbers at 72 hours, two weeks, eight weeks, and 24 weeks. Joint contracture was measured, and cartilage and synovial samples underwent histological analysis.

Results

Animals that underwent arthrotomy had equivalent joint contractures regardless of scaffold implantation (-13.9° versus -10.9°, equivalence limit 15°). Animals that underwent surgery to induce contracture did not demonstrate equivalent joint contractures with (41.8°) or without (53.9°) collagen scaffold implantation. Chondral damage occurred in similar rates with (11 of 48) and without (nine of 48) scaffold implantation. No significant difference in synovitis was noted between groups. Absorption of the collagen scaffold occurred within eight weeks in all animals

Conclusion

Our data suggest that intra-articular implantation of a collagen sponge does not induce synovitis or cartilage damage. Implantation in a native joint does not seem to induce contracture. Implantation of the collagen sponge in a rabbit knee model of contracture may decrease the severity of the contracture.

Cite this article: J. A. Walker, T. J. Ewald, E. Lewallen, A. Van Wijnen, A. D. Hanssen, B. F. Morrey, M. E. Morrey, M. P. Abdel, J. Sanchez-Sotelo. Intra-articular implantation of collagen scaffold carriers is safe in both native and arthrofibrotic rabbit knee joints. Bone Joint Res 2016;6:162–171. DOI: 10.1302/2046-3758.63.BJR-2016-0193.

Prospective potency of TGF-β1 on maintenance and regeneration of periodontal tissue

Periodontal ligament (PDL) tissue, central in the periodontium, plays crucial roles in sustaining tooth in the bone socket. Irreparable damages of this tissue provoke tooth loss, causing a decreased quality of life. The question arises as to how PDL tissue is maintained or how the lost PDL tissue can be regenerated. Stem cells included in PDL tissue (PDLSCs) are widely accepted to have the potential to maintain or regenerate the periodontium, but PDLSCs are very few in number. In recent studies, undifferentiated clonal human PDL cell lines were developed to elucidate the applicable potentials of PDLSCs for the periodontal regenerative medicine based on cell-based tissue engineering. In addition, it has been suggested that transforming growth factor-beta 1 is an eligible factor for the maintenance and regeneration of PDL tissue.

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.

The design and use of animal models for translational research in bone tissue engineering and regenerative medicine

This review provides an overview of animal models for the evaluation, comparison, and systematic optimization of tissue engineering and regenerative medicine strategies related to bone tissue. This review includes an overview of major factors that influence the rational design and selection of an animal model. A comparison is provided of the 10 mammalian species that are most commonly used in bone research, and existing guidelines and standards are discussed. This review also identifies gaps in the availability of animal models: (1) the need for assessment of the predictive value of preclinical models for relative clinical efficacy, (2) the need for models that more effectively mimic the wound healing environment and mass transport conditions in the most challenging clinical settings (e.g., bone repair involving large bone and soft tissue defects and sites of prior surgery), and (3) the need for models that allow more effective measurement and detection of cell trafficking events and ultimate cell fate during the processes of bone modeling, remodeling, and regeneration. The ongoing need for both continued innovation and refinement in animal model systems, and the need and value of more effective standardization are reinforced.

Role of growth factors on periodontal repair

Regeneration of periodontal structures lost during periodontal diseases constitutes a complex biological process regulated among others by interactions between cells and growth factors. Growth factors are biologically active polypeptides affecting the proliferation, chemotaxis and differentiation of cells from epithelium, bone and connective tissue. They express their action by binding to specific cell-surface receptors present on various target cells including osteoblasts, cementoblasts and periodontal ligament fibroblasts. The observation that growth factors participate in all cell functions led to exogenous application during periodontal tissue repair aiming to their use as an alternative therapeutic approach to periodontal therapy. Cell types and cultures conditions, dose, carrier materials, application requirements are of critical importance in the outcome of periodontal repair. The purpose of this article is to review the literature with respect to the biological actions of PDGF, TGF, FGF, IGF and EGF on periodontal cells and tissues, which are involved in periodontal regeneration.

Local delivery of angiotensin receptor blocker into the kidney ameliorates progression of experimental glomerulonephritis

Intrarenally synthesized angiotensin II (Ang II) may be involved in the progression of glomerulonephritis, leading to irreversible glomerulosclerosis. There is increasing evidence that systemic angiotensin receptor blocker (ARB) treatment has beneficial effect on the prognosis of progressive glomerulonephritis and diabetic nephropathy. However, the cellular and molecular mechanisms behind this therapeutic effect of ARB remain unclear. In this study, we used a novel strategy of local ARB delivery via type-1 collagen sponge, to treat progressive glomerulonephritis that would result in irreversible glomerulosclerosis in our previously established rat model. At days 9 and 14 after disease induction, mild proteinuria, 20.7+/-4.7 and 10+/-1.3 mg/day, was found. Local ARB treatment reduced proteinuria significantly to 3.19+/-3.2 and 5.25+/-0.95 mg/day (P < 0.01), respectively. Scoring of glomerular matrix expansion and sclerotic index revealed that local ARB treatment significantly ameliorated glomerular pathology. Ang II type 1 receptor mRNA expression was remarkably enhanced in the Ang II group and ARB treatment reversed this effect at 14 days. Local delivery of ARB significantly improved glomerular blood flow levels, compared to the untreated disease control group, from 710+/-18.25 to 859.44+/-22.86 microm/s, respectively. Local delivery of ARB into the kidney affected local RAS and thus improved the renal injury and function in the potentially progressive glomerulosclerosis of rat model.

Transforming growth factor-beta1 to the bone

TGF-beta1 is a ubiquitous growth factor that is implicated in the control of proliferation, migration, differentiation, and survival of many different cell types. It influences such diverse processes as embryogenesis, angiogenesis, inflammation, and wound healing. In skeletal tissue, TGF-beta1 plays a major role in development and maintenance, affecting both cartilage and bone metabolism, the latter being the subject of this review. Because it affects both cells of the osteoblast and osteoclast lineage, TGF-beta1 is one of the most important factors in the bone environment, helping to retain the balance between the dynamic processes of bone resorption and bone formation. Many seemingly contradictory reports have been published on the exact functioning of TGF-beta1 in the bone milieu. This review provides an overall picture of the bone-specific actions of TGF-beta1 and reconciles experimental discrepancies that have been reported for this multifunctional cytokine.

In vivo experimental study on bone regeneration in critical bone defects using an injectable biodegradable PLA/PGA copolymer

OBJECTIVES

An assessment was done of the bone-healing rate after implantation of a polylactide/polyglycolide copolymer (PLA-PGA) 50/50 dispersed in aqueous solution of PGA and dextran, used as bone substitutes in an animal model.

STUDY DESIGN

Two groups of 5 rabbits each were used. In both the femoral condyles, a critical size defect of 6x10 mm was made. On the right side PLA/PGA was inserted; the left side remained empty. Thirty and 90 days after surgery the animals were killed.

RESULTS

Defects left unfilled showed no spontaneous healing after 30 and 90 days. Sites filled with experimental materials showed new bone ranging between 11.46% and 76.82% after 30 days, and 75.98% and 95.34% after 90 days. Histomorphometry showed an increase in bone maturation between day 30 and 90 in experimental sites. At day 90, no statistical difference was seen as compared to normal bone.

CONCLUSION

PLA/PGA copolymer dispersed in hydrosoluble matrix seems to be suitable as osteoconductive material in critical size defects.