Evaluation of osteoinduction properties of the demineralized bovine foetal growth plate powder as a new xenogenic biomaterial in rat

Histopathological and radiographical evaluation of caprine demineralized bone matrix in a critical ulnar defect in a rabbit model

BACKGROUND

Caprine species satisfy the conditions of an ideal donor animal when compared to bovine species that has been extensively studied and commercialized for bone xenograft. Histopathological and radiological evaluations of caprine demineralized bone matrix (CDBM) were therefore carried out for fracture healing properties for its possible use in bone grafting procedures.

MATERIALS AND METHODS

Twenty-four rabbits were used for this study and were divided randomly into three groups of eight (n = 8) rabbits each. Critical bone defect was created on the ulnar diaphysis under xylazine-ketamine anaesthesia for autogenous bone graft (ABG) group, CDBM group and the last group was left unfilled as negative control (NC). Immediate post-grafting radiograph was taken and repeated on days 14, 28, 42 and 56 to monitor the evidence of radiographic healing. The animals were euthanized on day 56 and defect sites were harvested for histopathology.

RESULTS

There was a progressive evidence of radiographic healing and bone formation in all the groups with significance difference (P = 0.0064). When compared with ABG, NC differ significantly (P < 0.0001) whereas the CDBM did not differ significantly (P = 0.6765). The histopathology sections of ABG and CDBM showed normal bone tissue while the NC section was predominated by fibrous connective tissue. There was therefore an overall significant difference (P = 0.0001) in which CDBM did not differ from ABG (P = 0.2946) while NC did (P = 0.0005).

CONCLUSION

The ABG and CDBM groups showed a similar healing effect in the critical bone defect. Therefore, CDBM could be used as an effective alternative to ABG in orthopaedics to circumvent the limitations and complications associated with it.

LEVEL OF EVIDENCE

Not applicable.

Alterações hematológicas após implante de matriz óssea desmineralizada caprina em modelo de defeito ulnar crítico em coelhos

Objetivo Diversos modelos animais têm sido usados em estudos sobre enxertos ósseos e o tratamento de fraturas, mas as respostas hematológicas são raramente relatadas. Este estudo descreveu as alterações hematológicas observadas em coelhos submetidos a xenoenxertos de matriz óssea desmineralizada caprina (MODC).

Métodos Vinte e quatro (24) coelhos machos (2,5 ± 0,5 kg) foram adquiridos para este estudo e divididos aleatoriamente em três grupos: enxerto ósseo autólogo (EOA); controle negativo sem preenchimento (SP) e matriz óssea desmineralizada caprina (MODC). Amostras de sangue foram coletadas por punção cardíaca sob anestesia com xilazina-quetamina no dia 0 (para estabelecimento dos valores basais) e aos dias 28 e 56 após a cirurgia; essas amostras foram submetidas à análise manual em até 2 horas após a coleta. A análise estatística foi composta por análise de variância (ANOVA) de dois fatores com medidas repetidas, e o valor de p < 0,05 foi considerado significativo.

Resultados Houve uma diferença geral significativa nos números de leucócitos totais (p = 0,0043), neutrófilos (p < 0,0001), monócitos (p = 0,0184) e hemácias (p = 0,003), na concentração de hemoglobina (p < 0,0001) e no hematócrito (p < 0,0001) ao longo dos dias e entre os grupos de tratamento. No entanto, não houve diferença global significativa no número de linfócitos (p = 0,4923), basófilos (p = 0,4183) e eosinófilos (p = 0,4806) entre os dias.

Conclusão A resposta ao enxerto de MODC em coelhos é, portanto, caracterizada por leucocitose intensa com neutrofilia, linfocitose e monocitose no 28° dia após o procedimento. Esses dados podem basear a utilização da hematologia no monitoramento da resposta corporal em modelos animais de enxerto ósseo.

Induced Periosteum-Mimicking Membrane with Cell Barrier and Multipotential Stromal Cell (MSC) Homing Functionalities

The current management of critical size bone defects (CSBDs) remains challenging and requires multiple surgeries. To reduce the number of surgeries, wrapping a biodegradable fibrous membrane around the defect to contain the graft and carry biological stimulants for repair is highly desirable. Poly(ε-caprolactone) (PCL) can be utilised to realise nonwoven fibrous barrier-like structures through free surface electrospinning (FSE). Human periosteum and induced membrane (IM) samples informed the development of an FSE membrane to support platelet lysate (PL) absorption, multipotential stromal cells (MSC) growth, and the prevention of cell migration. Although thinner than IM, periosteum presented a more mature vascular system with a significantly larger blood vessel diameter. The electrospun membrane (PCL3%-E) exhibited randomly configured nanoscale fibres that were successfully customised to introduce pores of increased diameter, without compromising tensile properties. Additional to the PL absorption and release capabilities needed for MSC attraction and growth, PCL3%-E also provided a favourable surface for the proliferation and alignment of periosteum- and bone marrow derived-MSCs, whilst possessing a barrier function to cell migration. These results demonstrate the development of a promising biodegradable barrier membrane enabling PL release and MSC colonisation, two key functionalities needed for the in situ formation of a transitional periosteum-like structure, enabling movement towards single-surgery CSBD reconstruction.

In vivo studies on osteoinduction: A systematic review on animal models, implant site, and type and postimplantation investigation

Musculoskeletal diseases involving loss of tissue usually require management with bone grafts, among which autografts are still the gold standard. To overcome autograft disadvantages, the development of new scaffolds is constantly increasing, as well as the number of in vivo studies evaluating their osteoinductivity in ectopic sites. The aim of the present systematic review is to evaluate the last 10 years of osteoinduction in vivo studies. The review is focused on: (a) which type of animal model is most suitable for osteoinduction evaluation; (b) what are the most used types of scaffolds; (c) what kind of post-explant evaluation is most used. Through three websites (www.pubmed.com, www.webofknowledge.com and www.embase.com), 77 in vivo studies were included. Fifty-eight studies were conducted in small animal models (rodents) and 19 in animals of medium or large size (rabbits, dogs, goats, sheep, and minipigs). Despite the difficulty in establishing the most suitable animal model for osteoinductivity studies, small animals (in particular mice) are the most utilized. Intramuscular implantation is more frequent than subcutis, especially in large animals, and synthetic scaffolds (especially CaP ceramics) are preferred than natural ones, also in combination with cells and growth factors. Paraffin histology and histomorphometric evaluations are usually employed for postimplantation analyses.

Selection of animal models for pre-clinical strategies in evaluating the fracture healing, bone graft substitutes and bone tissue regeneration and engineering

In vitro assays can be useful in determining biological mechanism and optimizing scaffold parameters, however translation of the in vitro results to clinics is generally hard. Animal experimentation is a better approximation than in vitro tests, and usage of animal models is often essential in extrapolating the experimental results and translating the information in a human clinical setting. In addition, usage of animal models to study fracture healing is useful to answer questions related to the most effective method to treat humans. There are several factors that should be considered when selecting an animal model. These include availability of the animal, cost, ease of handling and care, size of the animal, acceptability to society, resistance to surgery, infection and disease, biological properties analogous to humans, bone structure and composition, as well as bone modeling and remodeling characteristics. Animal experiments on bone healing have been conducted on small and large animals, including mice, rats, rabbits, dogs, pigs, goats and sheep. This review also describes the molecular events during various steps of fracture healing and explains different means of fracture healing evaluation including biomechanical, histopathological and radiological assessments.

Spinal fusion with demineralized calf fetal growth plate as novel biomaterial in rat model: a preliminary study

Background

Spinal fusions are being performed for various pathologies of the spine such as degenerative diseases, deformities, tumors and fractures. Recently, other bone substitutes such as demineralized bone matrix (DBM) have been developed for spinal fusion. Therefore, this study was conducted to evaluate the intertransverse posterolateral fusion with the Bovine fetal growth plate (DCFGP) and compare it with commercial DBM in rat model.

Methods

A total of 16 mature male rats (aged 4 months and weighing 200-300 g) were randomly divided in two groups. After a skin incision on posterolateral site, two separate fascial incisions were made 3 mm from the midline. A muscle-splitting approach was used to expose the transverse processes of L4 and L5. Group I (n = 8) underwent with implanted Bovine fetal growth plate among decorticated transverse processes. In group II (n = 8) commercial DBM was placed in the same manner. Fusion was evaluated by manual palpation, radiographical, gross and histopathological analysis.

Results

The manual palpation, radiological, gross and histopathological findings indicate high potential of the DCFGP in spinal fusion. At the 42nd postoperative day, new bone formation as evidenced by a bridge between L4 and L5 was visualized in all rats implanted with DCFGP and commercial DBM. The newly formed bone tissue was observed in all implanted areas on the 42nd day after operation in the two groups.

Conclusions

The spinal fusion of the animals of both groups demonstrated more advanced osteogenic potential and resulted in proper fusion of the transverse process of lumbar vertebra.

Hydroxyapatite and demineralized calf fetal growth plate effects on bone healing in rabbit model

Background

Synthetic hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP) and their composite are promising biomaterials, specifically in the orthopedic and dental fields, as their chemical composition is similar to that of bone. Due to the need for safer bone graft applications, these bone graft substitutes are gradually gaining increased acceptability. To stimulate the process of bone healing, several methods have been used previously, including ultrasound, electrical stimulation, exposure to electromagnetic fields, bone grafts, interporous hydroxyapatite (as a bone graft substitute) and bone growth factors. The following study was designed to evaluate the effects of the concurrent usage of hydroxyapatite with demineralized calf fetal growth plate (DCFGP) on the bone healing process.

Materials and methods

Fifteen female New Zealand white rabbits were used in this study. A mid-radius bone defect was created and in the first group (n = 5) was filled with hydroxyapatite, in the second group (n = 5) with hydroxyapatite and DCFGP, and finally in the third group (n = 5) with DCFGP alone. Radiological and histopathological evaluations were performed blindly and the results scored and analyzed statistically.

Results

There was a significant difference for bone formation and remodeling at the 8th post-operative week radiographic assessment (P< 0.05), when the hydroxyapatite–DCFGP group was superior to other groups. On the contrary, macroscopical and histopathological evaluation did not revealed significant differences between the three groups

Conclusion

Given the contrasting results of the radiographic assessment and the macro-/microscopic analysis of the healing response, further studies are needed before considering DCFGP-HA as a feasible alternative to HA alone, especially considering the potential hazards and costs of animal-derived biomaterials.

Level of evidence

Not applicable.

Basic concepts regarding fracture healing and the current options and future directions in managing bone fractures

Fracture healing is a complex physiological process, which involves a well-orchestrated series of biological events. Repair of large bone defects resulting from trauma, tumours, osteitis, delayed unions, non-unions, osteotomies, arthrodesis and multifragmentary fractures is a current challenge of surgeons and investigators. Different therapeutic modalities have been developed to enhance the healing response and fill the bone defects. Different types of growth factors, stem cells, natural grafts (autografts, allografts or xenografts) and biologic- and synthetic-based tissue-engineered scaffolds are some of the examples. Nevertheless, these organic and synthetic materials and therapeutic agents have some significant limitations, and there are still no well-approved treatment modalities to meet all the expected requirements. Bone tissue engineering is a newer option than the traditional grafts and may overcome many limitations of the bone graft. To select an appropriate treatment strategy in achieving a successful and secure healing, more information concerning injuries of bones, their healing process and knowledge of the factors involved are required. The main goals of this work are to present different treatment modalities of the fractured bones and to explain how fractures normally heal and what factors interfere with fracture healing. This study provides an overview of the processes of fracture healing and discusses the current therapeutic strategies that have been claimed to be effective in accelerating fracture healing.