Erasmus University Medical Center Rotterdam Research Articles

Manfred Kayser

Manfred Kayser

The Authors’ Reply: Mesenchymal Stem Cells and Immunosuppressive Drug Interactions

The findings by Buron et al. confirm our earlier results demonstrating that mesenchymal stem cells (MSCs) act synergistically with mycophenolic acid on peripheral blood mononuclear cell (PBMC) proliferation, but counteract the effect of calcineurin inhibitors (CNIs) and mammalian target of rapamycin inhibition (rapamycin) (1, 2). To explain these results, Buron et al. propose that the CNI inhibits the production of proinflammatory cytokines by immune cells, which are necessary to induce the immunosuppressive activity of MSC. CNI would thereby prevent an additive immunosuppressive effect of MSC. They support this hypothesis by showing that delayed addition of the CNI to alloactivated PBMC allows the MSC activation and thereby induce additive immunosuppression by MSC. An alternative approach to demonstrate the requirement for MSC activation would be to pre-expose MSC to proinflammatory cytokines and add them together with CNI to alloactivated PBMC and measure proliferation. We support the idea that prevention of MSC activation by CNI plays an important role in the lack of synergism between MSC and CNI. The decreased efficacy of the CNI in the presence of MSC, however, needs further explanation. Buron et al. and our group showed that the MSC increase the proliferation of alloactivated PBMC in the presence of CNI, which we think relates to the secretion of growth factors by the MSC under noninflammatory conditions. These factors include tumor necrosis factor-α, interleukin-6, and fibroblast growth factors, which stimulate the PBMC proliferation independently of calcineurin or mammalian target of rapamycin. Mycophenolic acid treatment is insensitive to the effects of trophic factors produced by the MSC, as it blocks the basis of cell proliferation, namely nucleotide synthesis. It would therefore seem that under inflammatory conditions, so in the absence of immunosuppressive drugs, the secretion of anti-inflammatory factors by MSC outweighs the secretion of growth factors, whereas under noninflammatory conditions, the balance shifts the other way. In conclusion, the recent studies on the interactions between MSC and immunosuppressive drugs demonstrate that the choice of drug will be of great importance for the outcome of clinical trials with the MSC. Martin J. Hoogduijn Meindert J. Crop Carla C. Baan Department of Internal Medicine Transplantation laboratory Erasmus University Medical Center Rotterdam, The Netherlands

Is the time right for translation research in genomics?

Genome-wide association studies are rapidly unraveling genetic susceptibility variants that are implicated in the etiology of common multifactorial diseases such as coronary heart disease, type 2 diabetes, non-familial forms of breast cancer and age-related macular degeneration [1]. Expectations about the future impact of these discoveries on preventive and clinical health care practice are high [2, 3]. Future use of genetic tests is foreseen for the prediction of disease susceptibility, targeting pharmacotherapy and tailoring lifestyle and health behavior recommendations. Fueled by the enormous progress in gene discovery, many researchers are already investigating the prediction of common diseases based on genetic profiling, the simultaneous testing of multiple susceptibility variants [4], and an increasing number of companies already offer personalized lifestyle health recommendations and nutritional supplements based on clients’ genetic profiles [5]. Despite the current euphoria, the predictive value of genetic profiling is still limited for most disorders, with only some promising exceptions. [4, 6–9] The major limitation to date is that only a fraction of the genetic factors involved have been identified, for most disorders less than 20 [1], explaining not more than a few percentages of the heritability. While we may expect that a large number of genetic variants will be discovered in the next few years, establishing a solid evidence base for genomics applications in clinical and public health care may take longer given the number of steps to be taken. Khoury and colleagues have described a framework for the continuum of translation research that is required to move genomics research findings to clinical and public health applications that benefit population health [10]. The four phases of translation researches include (1) translation of basic genomics research into a potential health care application; (2) evaluation of the application for the development of evidencebased guidelines; (3) evaluation of the implementation and use of the application in health care practice; and (4) evaluation of the achieved population health impact [10]. Translation research in genomics starts after gene discovery [10]. In common diseases, where numerous genetic factors may be implicated, genes are discovered by demonstrating robust genetic association, not in a single study but in meta-analyses or pooled analyses of large-scale studies [11–13]. A major challenge in common diseases is to decide when we have discovered sufficient genetic variants to begin translation research. One may argue that now the time is right because the studies so far likely have identified the common variants with the strongest effects and that further studies will only add weak susceptibility variants. For instance the complement factor H gene was the first common gene discovered to be involved in agerelated macular degeneration (AMD) using not more than 100 patients and 50 controls [14]. Typical gene discovery studies include 1,000s of patients and are able to detect variants with odds ratios as low as 1.05–1.10. Yet, also a very large number of weak susceptibility variants may further improve risk prediction [15]. Furthermore, stronger genetic effects may still be found for gene-gene and gene– environment interactions. Many groups of researchers are currently pooling their data in large consortia, which together will have sufficient power to model and detect interactions. Another avenue to pursue is to target more rare variants with strong genetic effects in specific populations. Genetic associations may not only differ between A. C. J. W. Janssens (&) Department of Epidemiology, Erasmus University Medical Center Rotterdam, P.O. Box 2040, 3000 CA, Rotterdam, The Netherlands e-mail: a.janssens@erasmusmc.nl

Validation of a Simple Method for Measuring Cranial Deformities (Plagiocephalometry)

Craniofacial measuring is essential for diagnosis or evaluation of growth and therapies. Skull deformities in children are mainly caused by craniosynostosis or by external pressure in positional skull deformations. Traditional anthropometry does not sufficiently analyze craniofacial shape. In computed tomography (CT) scanning, radiation loads are considerable. Both CT and magnetic resonance imaging (MRI) scanning require anaesthesia in children for accurate imaging, due to their long acquisition time. This makes CT and MRI unsuitable for long term follow-up of pediatric patients unless there is a compelling reason. Other noninvasive three-dimensional (3D) surface scanners still have limited practical use. van Vlimmeren et al presented plagiocephalometry (PCM) as a simple and versatile instrument to quantify skull deformities with high intrarater and interrater reliability, but no comparison was made with the actual skull shape. At the Erasmus University Medical Center Rotterdam, Sophia Children's Hospital PCM was compared to 3D-CT scanning in 21 children with craniosynostosis early in life. The PCM ring proved to fit closely to the skin with mean differences less than 1 mm (P < 0.05). The shape of the PCM ring was not significantly changed when taken off the head (P > 0.05). Finally, no significant differences are shown between measurements on the skull (CT-scan) and PCM ring off the head (P > 0.05). This study proves that PCM is a reliable method for analysis of skull deformities. The measurements are in agreement with 3D-CT scanning as golden standard. Although only 2-dimensional measurements are performed by PCM, the combination of simplicity, reliability, and validity make it a promising tool for daily practice.

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Combination therapy for chronic hepatitis B: A one–two knockout punch, or a swing and a miss?

Janssen HLA, van Zonneveld M, Senturk H, Zeuzem S, Akarca US, Cakaloglu Y, Simon C, So TMK, Gerken G, de Man RA, Niesters HGM, Zondervan P, Hansen B, Schalm SW (Erasmus University Medical Center Rotterdam, Rotterdam, The Netherlands; University of Istanbul, Istanbul, Turkey; University Hospital, Homburg am Saar, Germany; Ege University Hospital, Izmir, Turkey; Medical University, Kraclow, Poland; Princess Margaret Hospital, Hong Kong, China; University Hospital, Essen, Germany). Pegylated IFN alfa-2b alone or in combination with lamivudine for HBeAg-positive chronic hepatitis B: a randomised trial.

Pneumococcal vaccination does not affect the genetic diversity of Moraxella catarrhalis isolates in children.

Moraxella catarrhalis is an acknowledged pathogen of the respiratory tract in both adults and children [1], occupying a similar niche to that of Streptococcus pneumoniae and Haemophilus influenzae. In a recent study, Veenhoven et al. [2] showed that toddlers and older children who had previously experienced episodes of acute otitis media (AOM) did not experience a reduction of AOM episodes when vaccinated with a conjugate pneumococcal vaccine followed by a polysaccharide pneumococcal vaccine. Moreover, the incidence of M. catarrhalis isolation did not differ between the two groups, while Staphylococcus aureus was isolated more often from children in the vaccinated group than from children in the control group vaccinated against hepatitis A or B (P=0.02). It was also noted that an “immediate and complete” replacement of S. pneumoniae vaccine serotypes by non-vaccine serotypes tended to occur within the vaccinated group. Since bacterial interference of M. catarrhalis by competing streptococcal species has been demonstrated in vitro [3], the present study was conducted to determine whether vaccination against S. pneumoniae (and its subsequent removal from the M. catarrhalis niche) had an effect in altering the genetic diversity of M. catarrhalis isolates compared to a control vaccinated group. During the course of the study, children were followed for a total of 18 months, with routine microbiological and clinical investigations occurring at 1, 7, 14, 20 and 26 months after vaccination as well as during any episode of AOM. Bacterial cultures were obtained from nasopharyngeal swabs collected at routine visits as well as from middle ear fluids during episodes of AOM. In total, 41 M. catarrhalis isolates obtained from 13 children vaccinated with pneumococcal vaccine and 21 M. catarrhalis isolates obtained from six children vaccinated with a control (hepatitis A or B) vaccine were genotyped using pulsedfield gel electrophoresis (PFGE) as described by Verduin et al. [4]. The results of PFGE analysis are presented as a dendrogram in Fig. 1. As an indication of pathogenic potential, all isolates were also tested for the phenotypic expression of complement resistance using the “culture and spot” test [5]. PFGE analysis of the isolates indicated the presence of four clusters comprising a wide range of genotypes. The high degree of diversity within the M. catarrhalis species has already been documented in several publications [6, 7]. No pattern could be observed between PFGE cluster and vaccination status, or PFGE cluster and the isolation of other (co-colonizing) bacteria. M. catarrhalis PFGE types belonging to different clusters were found to occur within the same patient overtime (e.g. patient 1001), an observation that also held true for PFGE types associated with episodes of AOM (e.g. patient 4025). The vast majority of isolates (56/62) were found to be resistant to the effect of complement in human serum, and there was no difference between the isolation of complement-resistant and complement-sensitive phenotypes between the two vaccinated groups (Fisher’s exact test, P=1). The percentage of complement-resistant M. catarrhalis strains isolated appears to be relatively high compared to some studies involving healthy children (90% vs 30–60% [8], respectively), though other studies have yielded results similar to ours [9]. The percentage of complementresistant isolates could have been influenced by the fact that the children enrolled in the study had previously experienced episodes of AOM disease, possibly resulting in an enhanced immune response (including complementmediated responses) against potential bacterial pathogens. J. P. Hays (*) . K. Eadie . C. M. Verduin . H. Verbrugh . A. van Belkum Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center Rotterdam (EMCR), Dr Molewaterplein 40, 3015 GD Rotterdam, The Netherlands e-mail: j.hays@erasmusmc.nl Tel.: +31-10-4633668 Fax: +31-10-4633875

Incisional Hernia after Repair of Wound Dehiscence: Incidence and Risk Factors

The true incidence of incisional hernia after wound dehiscence repair remains unclear because thorough long-term follow-up studies are not available. Medical records of all patients who had undergone wound dehiscence repair between January 1985 and January 1999 at the Erasmus University Medical Center Rotterdam were reviewed. Long-term follow-up was performed by physical examination of all patients in February 2001. One hundred sixty-eight patients underwent wound dehiscence repair. Of those, 42 patients (25%) died within 60 days after surgery. During a median follow-up of 37 months (range, 3-146 months), 55 of the remaining 126 patients developed an incisional hernia. The cumulative incidence of incisional hernia was 69 per cent at 10 years. Significant independent risk factors were aneurysm of the abdominal aorta (10-year cumulative incidence of 84%, P = 0.02) and severe dehiscence with evisceration (10-year cumulative incidence of 78%, P = 0.01). Wound dehiscence repair by interrupted sutures had no better outcome than repair by continuous sutures. Suture material did not influence incidence of incisional hernia. Incisional hernia develops in the majority of patients after wound dehiscence repair, regardless of suture material or technique. Aneurysm of the abdominal aorta and severe dehiscence with evisceration predispose to incisional hernia.

Dynamics of Ovarian Function in an Adult Woman with McCune-Albright Syndrome

Division of Reproductive Medicine, Department of Obstetrics and Gynecology (J.S.E.L., B.C.J.M.F.), Erasmus University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands; Department of Hormonology (S.L.), University Hospital Montpellier, 34295 Montpellier, France; Department of Hormonology and Unit of Pediatric Endocrinology and Gynecology, Department of Pediatrics (C.S.), University Hospital Montpellier, 34295 Montpellier, France