F. Espitalier

A comparison between bone reconstruction following the use of mesenchymal stem cells and total bone marrow in association with calcium phosphate scaffold in irradiated bone

The purpose of this study was to compare bone reconstruction using either mesenchymal stem cells (MSCs) or total bone marrow (TBM) in association with biphasic calcium phosphate (BCP) granules after irradiation in a rat model. Three weeks after an external irradiation of the hind limbs of rats, four bone defects were created per animal. The defects were filled with either BCP alone, or with a mixture of BCP and TBM, or with a mixture of BCP and MSCs (adipose-derived or bone marrow-derived MSCs). Three weeks after implantations, new-bone formation was assessed. Histological examination showed osteoconductive and osteointegrative properties of BCP in irradiated tissue. The BCP-TBM mixture significantly improved bone ingrowth (p<0.05). The BCP-MSCs mixtures did not provide new-bone formation over and above that induced by BCP alone. This gives grounds for suspecting that there is a link between this result and the cellular and vascular weakness observed in irradiated bone. The BCP-TBM mixture may have induced an increased vascularization of irradiated bone. This could be due to the presence of all components in TBM that were lacking in the BCP-MSCs mixtures. BCP associated with TBM appears to be the most efficient material for bone substitution in irradiated areas.

Reconstruction of circumferential pharyngolaryngectomy using a 'horseshoe-shaped' pectoralis major myocutaneous flap.

Eighteen patients underwent a circumferential pharyngolaryngectomy reconstruction post pharyngolaryngectomy. All tumours showed pharyngo-oesophageal junction invasion or circular involvement of the hypopharynx, requiring total, circumferential pharyngolaryngectomy. A pectoralis major myocutaneous flap was directly sutured to the pre-vertebral fascia. A Montgomery salivary bypass tube was introduced into the oesophagus, and a nasogastric tube was placed within it. No post-operative complications occurred for 14 patients and only minor ones for the other four. Average post-operative stay was 12 days. For 15 patients, feeding returned to normal throughout the follow-up period. No fistulae were noted and neopharyngeal stenosis occurred in three patients (16 per cent). Thirteen had complete resection with normal margins. Thirteen were still alive after one to three years of follow up. The local recurrence rate was 16 per cent. The use of a pectoralis major myocutaneous flap with Sprianos technique provides a simple, reliable method for circumferential hypopharyngeal resection. It has been applied to a wide range of patients, especially elderly ones and those with poor general status, as well as to cases in which widespread involvement was detected during surgery.

Prognostic factors for secondary recurrence of pleomorphic adenoma: a 20-year, retrospective study.

PURPOSE To evaluate the results of treatment of parotid pleomorphic adenoma, and the risk factors for secondary recurrence. MATERIALS AND METHODS Single-centre, retrospective study of 32 patients with pleomorphic adenoma recurrence managed between 1988 and 2008. RESULTS The mean age at diagnosis of primary pleomorphic adenoma recurrence was 43.4 years. Twenty-eight per cent of patients had secondary recurrence; 32 per cent had undergone two or more surgical resections and external adjuvant radiotherapy. An age of less than 25 years was significantly associated with an earlier primary recurrence (p = 0.008). The most significant histopathological risk factor for secondary recurrence was the presence of a multifocal tumour (p = 0.019). Other histopathological criteria (i.e. cellularity and capsule rupture) were not significant. Radiotherapy was not associated with a decrease in recurrence. Nine per cent of patients progressed to malignancy. The main surgical complication was definitive facial palsy (14 per cent). CONCLUSION Pleomorphic adenoma recurrence requires surgery, with greatly increased risk to the facial nerve. Resection with clear surgical margins is required, especially in young patients with multifocal tumours. Radiotherapy may delay second recurrence in cases of multifocal tumour.

Results after u-shaped pectoralis major myocutaneous flap reconstruction of circumferential pharyngeal defects†‡

To evaluate surgical, functional, carcinologic results after circumferential pharyngolaryngectomy and reconstruction with U‐shaped pectoralis major myocutaneous flap.

Determining a Clinically Relevant Strategy for Bone Tissue Engineering: An “All-in-One” Study in Nude Mice

Purpose Autologous bone grafting (BG) remains the standard reconstruction strategy for large craniofacial defects. Calcium phosphate (CaP) biomaterials, such as biphasic calcium phosphate (BCP), do not yield consistent results when used alone and must then be combined with cells through bone tissue engineering (BTE). In this context, total bone marrow (TBM) and bone marrow-derived mesenchymal stem cells (MSC) are the primary sources of cellular material used with biomaterials. However, several other BTE strategies exist, including the use of growth factors, various scaffolds, and MSC isolated from different tissues. Thus, clinicians might be unsure as to which method offers patients the most benefit. For this reason, the aim of this study was to compare eight clinically relevant BTE methods in an “all-in-one” study. Methods We used a transgenic rat strain expressing green fluorescent protein (GFP), from which BG, TBM, and MSC were harvested. Progenitor cells were then mixed with CaP materials and implanted subcutaneously into nude mice. After eight weeks, bone formation was evaluated by histology and scanning electron microscopy, and GFP-expressing cells were tracked with photon fluorescence microscopy. Results/Conclusions Bone formation was observed in only four groups. These included CaP materials mixed with BG or TBM, in which abundant de novo bone was formed, and BCP mixed with committed cells grown in two- and three-dimensions, which yielded limited bone formation. Fluorescence microscopy revealed that only the TBM and BG groups were positive for GFP expressing-cells, suggesting that these donor cells were still present in the host and contributed to the formation of bone. Since the TBM-based procedure does not require bone harvest or cell culture techniques, but provides abundant de novo bone formation, we recommend consideration of this strategy for clinical applications.

Biomaterials for tissue reconstruction and bone substitution of the ear, nose and throat, face and neck

The role of biomaterials has become more important in the last 30 years in otorhinolaryngology. Legal directives for their use and, more importantly, indications have been specified. Biomaterials are medical devices, designed for tissue substitution or reconstruction. Approval labeling is issued in the form of European Community certification and postmarketing medical device safety in Europe – completely independent from the US FDA’s certification. The indications for biomaterials are generally similar to those of autografts. Their main advantage is that they limit the morbidity caused by autograft harvesting. The benefits are aesthetic, functional or both. The main indications are in otology, sinus surgery, cranio–maxillo–facial traumatology, osteosynthesis and orthognatic surgery, skeletal augmentation and anti-aging surgery, facial prosthetic rehabilitation and laryngology. The research fields are extremely varied (e.g., increased therapeutic properties, drug-delivery systems or tissue engineering). Increasingly, biomaterials are implanted and the surgical success of their use is dependent upon strict legal labeling and well-defined indications.

Vascular imaging with contrast agent in hard and soft tissues using microcomputed‐tomography

Vascularization is essential for many tissues and is a main requisite for various tissue‐engineering strategies. Different techniques are used for highlighting vasculature, in vivo and ex vivo, in 2‐D or 3‐D including histological staining, immunohistochemistry, radiography, angiography, microscopy, computed tomography (CT) or micro‐CT, both stand‐alone and synchrotron system. Vascularization can be studied with or without a contrast agent. This paper presents the results obtained with the latest Skyscan micro‐CT (Skyscan 1272, Bruker, Belgium) following barium sulphate injection replacing the bloodstream in comparison with results obtained with a Skyscan In Vivo 1076. Different hard and soft tissues were perfused with contrast agent and were harvested. Samples were analysed using both forms of micro‐CT, and improved results were shown using this new micro‐CT. This study highlights the vasculature using micro‐CT methods. The results obtained with the Skyscan 1272 are clearly defined compared to results obtained with Skyscan 1076. In particular, this instrument highlights the high number of small vessels, which were not seen before at lower resolution. This new micro‐CT opens broader possibilities in detection and characterization of the 3‐D vascular tree to assess vascular tissue engineering strategies.

Development of mandibular osteoradionecrosis in rats: Importance of dental extraction

OBJECTIVES To develop an animal model of mandibular osteoradionecrosis (ORN) using a high-energy radiation source (as used in human therapeutics) and to assess the role of tooth extraction on ORN development. MATERIALS AND METHODS (STUDY DESIGN) Ten animals were irradiated with a single 35- or 50-Gy dose. Three weeks later, the second left mandibular molar was extracted from three animals in each group. Nine weeks after irradiation, the animals were euthanized, with an injection of contrast agent in the bloodstream to highlight vascularization. Mandibles were harvested and studied using micro-CT, histology, tartrate-resistant acid phosphatase activity and scanning electron microscopy. RESULTS This study demonstrates that a single 50-Gy dose associated with molar extraction is necessary for ORN development. In these conditions, absence of healing of the mucosa and bone, dental effects, fibrosis, an increase in osteoclast activity and a decrease in vascularization were observed. We also determined that molar extraction increases the impact of the cellular effects of radiation. CONCLUSION The mandibular ORN animal model was validated after 50-Gy irradiation and molar extraction. The results of this study therefore support an animal ORN model and tissue engineering strategies will now be developed to regenerate bone for patients with head and neck cancer.

Role of the stromal vascular fraction from adipose tissue in association with a phosphocalcic scaffold in bone regeneration in an irradiated area

BACKGROUND Osteoradionecrosis of the jaw is a major side-effect of radiotherapy used in the treatment of squamous cell carcinomas of the upper aerodigestive tract. The standard reconstruction procedure is a free flap transfer of autogenous bone. A new approach using a tissue engineering strategy has shown that total bone marrow (TBM) associated with biphasic calcium phosphate (BCP) is the best combination for bone regeneration in an irradiated area. Recently, the stromal vascular fraction from adipose tissue (SVF) was described as an alternative to TBM for promoting new bone formation. The aim of this study was to identify the capacity of a freshly isolated SVF to induce new bone formation in an irradiated area. METHODS Four weeks after irradiation of the hind limbs of 15 rats, bone defects were created and filled with either SVF or TBM with and without BCP. RESULTS Three weeks after the implantations, analysis showed that the BCP-TBM mixture improved new bone formation after radiation (p < 0.05). The BCP-SVF association induced significant neoangiogenesis but failed to enhance new bone formation. CONCLUSION The BCP-SVF mixture was insufficient to enhance new bone formation in the irradiated area, suggesting that the role of the environment might be crucial for ossification.

Microarchitecture of irradiated bone: comparison with healthy bone

The squamous cell carcinomas of the upper aero-digestive tract represent about ten percent of cancers. External radiation therapy leads to esthetic and functional consequences, and to a decrease of the bone mechanical abilities. For these patients, the oral prosthetic rehabilitation, including possibilities of dental implant placement, is difficult. The effects of radiotherapy on bone microarchitecture parameters are not well known. Thus, the purpose of this study is to assess the effects of external radiation on bone micro architecture in an experimental model of 25 rats using micro CT. 15 rats were irradiated on the hind limbs by a single dose of 20 Grays, and 10 rats were non irradiated. Images of irradiated and healthy bone were compared. Bone microarchitecture parameters (including trabecular thickness, trabecular number, trabecular separation, connectivity density and tissue and bone volume) between irradiated and non-irradiated bones were calculated and compared using a Mann and Whitney test. After 7 and 12 weeks, images of irradiated and healthy bone are different. Differences on the irradiated and the healthy bone populations exhibit a statistical significance. Trabecular number, connectivity density and closed porosity are less important on irradiated bone. Trabecular thickness and separation increase for irradiated bone. These parameters indicate a decrease of irradiated bone properties. Finally, the external irradiation induces changes on the bone micro architecture. This knowledge is of prime importance for better oral prosthetic rehabilitation, including implant placement.