Ian C. Dickinson

Bone Regeneration Based on Tissue Engineering Conceptions - A 21st Century Perspective.

The role of Bone Tissue Engineering in the field of Regenerative Medicine has been the topic of substantial research over the past two decades. Technological advances have improved orthopaedic implants and surgical techniques for bone reconstruction. However, improvements in surgical techniques to reconstruct bone have been limited by the paucity of autologous materials available and donor site morbidity. Recent advances in the development of biomaterials have provided attractive alternatives to bone grafting expanding the surgical options for restoring the form and function of injured bone. Specifically, novel bioactive (second generation) biomaterials have been developed that are characterised by controlled action and reaction to the host tissue environment, whilst exhibiting controlled chemical breakdown and resorption with an ultimate replacement by regenerating tissue. Future generations of biomaterials (third generation) are designed to be not only osteoconductive but also osteoinductive, i.e. to stimulate regeneration of host tissues by combining tissue engineering and in situ tissue regeneration methods with a focus on novel applications. These techniques will lead to novel possibilities for tissue regeneration and repair. At present, tissue engineered constructs that may find future use as bone grafts for complex skeletal defects, whether from post-traumatic, degenerative, neoplastic or congenital/developmental “origin” require osseous reconstruction to ensure structural and functional integrity. Engineering functional bone using combinations of cells, scaffolds and bioactive factors is a promising strategy and a particular feature for future development in the area of hybrid materials which are able to exhibit suitable biomimetic and mechanical properties. This review will discuss the state of the art in this field and what we can expect from future generations of bone regeneration concepts.

Comprehensive mapping of p53 pathway alterations reveals an apparent role for both SNP309 and MDM2 amplification in sarcomagenesis

Purpose: Reactivation of p53 tumor suppressor activity in diseases such as soft-tissue sarcoma is considered an attractive means of targeted therapy. By systematically assessing alterations affecting the p53 pathway, we aimed to (a) classify sarcoma subtypes, (b) define a potential role in malignancy, and (c) identify potential patient biomarkers in this heterogeneous disease. Experimental Design: We have mapped mutational events in a panel of 192 benign or malignant bone and soft-tissue sarcomas. Analyses included TP53 and CDKN2A mutational and SNP status, MDM2 and MDM4 amplification and MDM2 SNP309 status. Results: We found an inverse relationship between MDM2 amplification and TP53 mutations, with a predominantly wild-type CDKN2A background. A high rate of point mutations in TP53 was observed uniquely in leiomyosarcoma, osteosarcoma, and MFH. Both MDM2 and MDM4 were also amplified in a subtype-specific manner, which was frequently seen as a coamplification event. We have also analyzed the risk allele frequencies for MDM2 SNP309, and show that the G allele was strongly associated with both liposarcomas and MDM2 amplification. Conclusions: Our data emphasize the critical role of p53 inactivation in sarcomagenesis, whereby different pathway alterations may be related to the heterogeneity of the disease. Moreover, we observed a strong association of malignancy with TP53 mutation, or MDM2 amplification and the presence of a G allele in SNP309, especially in lipoma versus liposarcoma. We propose, therefore, that MDM2 markers along with TP53 sequencing should be considered as patient biomarkers in clinical trials of sarcomas using MDM2 antagonists. Clin Cancer Res; 17(3); 416–26. ©2010 AACR.

SURGICAL MARGIN AND ITS INFLUENCE ON SURVIVAL IN SOFT TISSUE SARCOMA

Background:  The goal of surgeons treating soft tissue sarcoma is to gain local control, to avoid risk of local recurrence and to avoid compromise of the patients potential survival. The aim of the investigation was to assess the significance of the extent of surgical margin on the chance of death, metastasis and local recurrence.

E2F7 Can Regulate Proliferation, Differentiation, and Apoptotic Responses in Human Keratinocytes: Implications for Cutaneous Squamous Cell Carcinoma Formation

The E2F family of transcription factors plays a crucial role in the regulation of genes involved in cell proliferation, differentiation, and apoptosis. In keratinocytes, the inhibition of E2F is a key step in the control and initiation of squamous differentiation. Because the product of the recently identified E2F7a/E2F7b gene has been shown to repress E2F-regulated promoters, and to be abundant in skin, we examined its role in the epidermis. Our results indicate that E2F7b mRNA expression is selectively associated with proliferation-competent keratinocytes. Moreover, E2F7 was able to antagonize E2F1-induced proliferation and apoptosis. In contrast, although E2F7 was able to inhibit proliferation and initiate differentiation, it was unable to antagonize the differentiation suppression induced by E2F1. These data indicate that E2F7-mediated suppression of proliferation and apoptosis acts through E2F1-dependent pathways, whereas E2F7-induced differentiation acts through an E2F1-independent pathway. These data also suggest that proliferation, differentiation, and survival of primary human keratinocytes can be controlled by the relative ratio of E2F1 to E2F7. Because deregulated proliferation, differentiation, and apoptosis are hallmarks of cancer, we examined the expression levels of E2F1 and E2F7 in cutaneous squamous cell carcinomas (CSCC). We found that both genes were overexpressed in CSCCs compared with normal epidermis. Furthermore, inhibition of E2F7 in a SCC cell line sensitized the cells to UV-induced apoptosis and doxorubicin-induced apoptosis. Combined, these data suggest that the selected disruption of E2F1 and E2F7 in keratinocytes is likely to contribute to CSCC formation and may prove to be a viable therapeutic target.

Loss of Osteoclasts Contributes to Development of Osteosarcoma Pulmonary Metastases

We conducted a transcriptomic screen of osteosarcoma (OS) biopsies and found that expression of osteoclast-specific tartrate-resistant acid phosphatase 5 (ACP5/TRAP) is significantly downregulated in OS compared with nonmalignant bone (P < 0.0001). Moreover, lesions from OS patients with pulmonary metastases had 2-fold less ACP5/TRAP expression (P < 0.018) than lesions from patients without metastases. In addition, we found a direct correlation (P = 0.0166) between ACP5/TRAP expression and time to metastasis. Therefore, we examined whether metastasis-competent (MC) OS cells could induce loss of ACP5(+) osteoclasts and contribute to metastasis. We found that MC OS cell lines can inhibit osteoclastogenesis in vitro and in vivo. In addition, osteoclasts can inhibit the migration of MC OS cells in vitro. Finally, ablation of osteoclasts with zoledronic acid increases the number of metastatic lung lesions in an orthotopic OS model, whereas fulvestrant treatment increases osteoclast numbers and reduces metastatic lesions. These data indicate that the metastatic potential of OS is determined early in tumor development and that loss of osteoclasts in the primary lesion enhances OS metastasis.

Treatment of long bone defects and non-unions: from research to clinical practice

The treatment of long bone defects and non-unions is still a major clinical and socio-economical problem. In addition to the non-operative therapeutic options, such as the application of various forms of electricity, extracorporeal shock wave therapy and ultrasound therapy, which are still in clinical use, several operative treatment methods are available. No consensus guidelines are available and the treatments of such defects differ greatly. Therefore, clinicians and researchers are presently investigating ways to treat large bone defects based on tissue engineering approaches. Tissue engineering strategies for bone regeneration seem to be a promising option in regenerative medicine. Several in vitro and in vivo studies in small and large animal models have been conducted to establish the efficiency of various tissue engineering approaches. Neverthelsss, the literature still lacks controlled studies that compare the different clinical treatment strategies currently in use. However, based on the results obtained so far in diverse animal studies, bone tissue engineering approaches need further validation in more clinically relevant animal models and in clinical pilot studies for the translation of bone tissue engineering approaches into clinical practice.

The management of extra-abdominal desmoid tumours

We performed a retrospective analysis of 35 cases of desmoid tumours (aggressive fibromatoses) that underwent treatment at our institutions between 1987 and 2002. The purpose was to evaluate the rate of local recurrence of desmoid tumours treated with surgical excision, to assess the impact of surgical margins on local recurrence and to define the role of radiotherapy in the treatment. Nine patients experienced a recurrence at an average of 16 months after initial treatment. Seven of the 15 patients with a less-than-wide margin had a local recurrence. Comparatively, only two of the 20 patients with a wide margin had a local recurrence. Thirty-three of the 35 patients were disease free at the last follow-up. We recommend wide excision with clear margins whenever possible. Marginal resections are appropriate when wide excision would severely compromise the function of the limb. Surgical resections and selective supplementation of adjuvant radiotherapy give excellent control rates.RésuméNous avons exécuté une analyse rétrospective de 35 cas de tumeurs desmoides (fibromatose agressive) traitées dans notre institution entre 1987 et 2002. Le but était d’évaluer le taux de récidive locale après traitement par excision chirurgicale, d’étudier le rôle des marges chirurgicales sur la récidive et de définir le rôle de la radiothérapie dans le traitement. Neuf malades ont eu une récidive à une moyenne de 16 mois après le traitement initial. Sept des 15 malades opérés avec une marge qui n’était pas large, avait une récidive locale. Comparativement, seulement 2 des 20 malades avec une marge large avaient une récidive locale. Trente trois des 35 malades étaient sans maladie au dernier suivi. Nous recommandons l’excision large avec des marges claires toutes les fois que possible. Les résections marginales sont appropriées quand l’excision large compromettrait sévèrement la fonction du membre. Les résections chirurgicales avec, sélectivement, un traitement adjuvant par radiothérapie donnent d’excellents taux de contrôle de la maladie.

Guide to the Assessment of Competence and Performance in Practising Surgeons

Surgical performance is increasingly under public scrutiny and non‐technical behavioural issues are more frequently the focus of complaints. Currently, there is a lack of a suitable framework or template to assist surgeons in the assessment of their own performance or that of their colleagues. A Royal Australasian College of Surgeons (RACS) Working Party considered the methods currently available to define and assess surgical performance. The scope included assessment tools, resources available, and support for surgeons. The Non‐Technical Skills for Surgeons (NOTSS) programme developed by the Royal College of Surgeons, Edinburgh and the School of Psychology, University of Aberdeen was of particular interest. This programme was reviewed, adapted and expanded. The nine RACS competencies were used as the foundation for developing a set of three behavioural patterns within each competency domain. Each behavioural pattern was then described by a set of eight behavioural markers – describing four good and four poor behaviours. A variety of resources were identified to assist surgeons, including College and other similar courses and guidelines, publications covering professionalism‐and health issues and support through various agencies. It was recognized that the College has a role to support its Fellows and to ensure any review of performance is conducted impartially, competently and confidentially. The resulting guide was approved by College Council in June 2008 and later distributed to Fellows and hospitals throughout Australia and New Zealand. It is intended to be used for self‐reflection and self‐assessment, although it could equally be used as a template for the review of an individual surgeon’s performance by a clinical director of surgery or other agency. Considerable progress has been made in the assessment of performance of practising surgeons. This guide has been published to address performance issues across all RACS competencies. It also outlines a variety of assessment methods and strategies to support surgeons.

Osteosarcoma is characterised by reduced expression of markers of osteoclastogenesis and antigen presentation compared with normal bone.

Background:Osteosarcoma (OS) is the most common primary bone tumour in children and adolescents. Patients who respond poorly to chemotherapy have a higher risk of metastatic disease and 5-year survival rates of only 10–20%. Therefore, identifying molecular targets that are specific for OS, or more specifically, metastatic OS, will be critical to the development of new treatment strategies to improve patient outcomes.Methods:We performed a transcriptomic analysis of chemo-naive OS biopsies and non-malignant bone biopsies to identify differentially expressed genes specific to OS, which could provide insight into OS biology and chemoresistance.Results:Statistical analysis of the OS transcriptomes found differential expression of several metallothionein family members, as well as deregulation of genes involved in antigen presentation. Tumours also exhibited significantly increased expression of ID1 and profound down-regulation of S100A8, highlighting their potential as therapeutic targets for OS. Finally, we found a significant correlation between OS and impaired osteoclastogenesis and antigen-presenting activity. The reduced osteoclastogenesis and antigen-presenting activity were more profound in the chemoresistant OS samples.Conclusion:Our results indicate that OS displays gene signatures consistent with decreased antigen-presenting activity, enhanced chemoresistance, and impaired osteoclastogenesis. Moreover, these alterations are more pronounced in chemoresistant OS tumour samples.

Systematic review of the impact of volume of oesophagectomy on patient outcome

Purpose:  This systematic review aims to assess whether overall survival, mortality, morbidity, length of stay and cost of performing oesophagectomy are related to surgical volume.