Florian Lampert

Effects of endothelial cells on proliferation and survival of human mesenchymal stem cells and primary osteoblasts

Angiogenesis is a fundamental process in bone formation, remodeling, and regeneration. Moreover, for the regeneration of bone in tissue engineering applications, it is essential to support neovascularization. This can be achieved by cell‐based therapies using primary endothelial cells, which are able to form functional blood vessels upon implantation. In bone composite grafts, coimplanted endothelial cells do not only support neovascularization but also support osteogenic differentiation of osteoblasts and osteoprogenitor cells. In this study, we investigated the effect of endothelial cells on proliferation and cell survival of human primary osteoblasts (hOBs) and human mesenchymal stem cells (MSCs). Human umbilical vein endothelial cells (HUVECs) stimulated hOB and MSC proliferation, whereas proliferation of HUVECs was unaffected by cocultured hOBs or MSCs. The effect of HUVEC cocultivation on hOB and MSC proliferation was more pronounced in direct cocultures than in indirect cocultures, indicating that this effect is at least partially dependent on the formation of heterotypic cell contacts between HUVECs and hOBs or MSCs. Furthermore, HUVEC cocultivation reduced low‐serum induced apotosis of hOBs and MSCs by a mechanism involving increased phosphorylation and inactivation of the proapoptotic protein Bad. In summary, our experiments have shown that cocultured HUVECs increase the proliferation and reduce low‐serum induced apoptosis of hOBs and MSCs.

Overexpression of Hif‐1α in Mesenchymal Stem Cells Affects Cell‐Autonomous Angiogenic and Osteogenic Parameters

Reconstruction of large bone defects still represents a major medical challenge. In recent years tissue engineering has developed techniques based on adult mesenchymal stem cells (MSCs) that could represent an attractive therapeutical option to treat large bone defects in the future. It has been demonstrated in various animal models that ex vivo expanded MSCs are capable of promoting the regeneration of skeletal defects after implantation. However, for the efficient regeneration of bone in tissue engineering applications, a rapid vascularization of implanted grafts is essential to ensure the survival of cells in the early post‐implantational phase. A promising strategy to enhance vascularization of MSC‐containing implants could consist of overexpression of the angiogenic master transcription factor Hypoxia‐inducible factor 1 (Hif‐1) in the MSCs in order to induce angiogenesis and support osteogenesis. In the present study, we overexpressed Hif‐1α in MSCs by using recombinant adenoviruses and investigated cell‐autonomous effects. Overexpression of Hif‐1α enhanced proliferation, migration, cell survival and expression of pro‐angiogenic genes. Other parameters such as expression of the osteogenic markers BMP‐2 and RunX2 were decreased. Hif‐1α overexpression had no effect on invasion, senescence and osteogenic differentiation of MSCs. Our experiments revealed multifarious effects of Hif‐1α overexpression on cell‐autonomous parameters. Therefore, Hif‐1α overexpression may represent a therapeutic option to improve cellular functions of MSCs to treat critical sized bone defects. J. Cell. Biochem. 117: 760–768, 2016.

Aesthetic surgery performed by plastic surgery residents: an analysis of safety and patient satisfaction.

BackgroundAesthetic surgery is an integral component of plastic surgery. Despite its importance, adequate training in aesthetic surgery is met with challenges. Although the educational benefit of resident clinics has been demonstrated, such clinics are rarely found outside the United States. The objective of the present study was to assess safety and patient satisfaction associated with aesthetic surgery procedures performed by plastic surgery residents at a German academic medical center. MethodsThe study had 2 components, namely, a retrospective chart review and an administration of a patient satisfaction survey. Only patients who underwent a surgical intervention by a plastic surgery resident between 2003 and 2011 were included in the study. Parameters of interest included age, sex, procedure performed, number of procedures, revenue (in &OV0556;), length of follow-up, revision rate, and postoperative complication rate. Patient satisfaction was assessed by the client satisfaction questionnaire-8. ResultsA total of 273 aesthetic procedures were performed in 206 patients with an increase in recent years. The median follow-up period was 49.5 months. The most frequently performed procedures were liposuction (n = 59), breast augmentation (n = 53), and upper eyelid blepharoplasty (n = 31). One hundred ninety-two (90.3%) patients had an uneventful postoperative course. The client satisfaction questionnaire-8 questionnaire was completed by 110 patients (response rate, 50.2%). The median value of 28 indicates a high degree of patient satisfaction. An association between occurrence of major complications and patient satisfaction was seen. ConclusionsAesthetic surgery performed by plastic surgery residents under supervision by attending physicians is safe and provides for high levels of patient satisfaction postoperatively. Offering these services may be able to bridge the gap between providing high-quality aesthetic surgery training while yet recruiting an increasing number of patients who may appreciate the lower fees associated with these services.

An Integrated Therapy Concept for Reduction of Postoperative Complications After Resection of a Panniculus Morbidus

BackgroundPanniculus morbidus is characterized by an edematous, painful hanging abdominal mass, due to laxity and redundancy of the abdominal skin in morbid obesity, particularly after massive weight loss. Panniculectomy, by wedge resection, is a salvage procedure with high satisfaction rates though associated with high complication rates. Here we investigated the effects of perioperative complex decongestive physical therapy (CDP) on outcome and complication rates.MethodsWe retrospectively analyzed the clinical course and outcome of 24 patients receiving panniculectomy between 1998 and 2009 in our department of plastic surgery. Sixteen patients received perioperative CDP, and eight patients did not receive any form of decongestive treatment. We analyzed the incidence of complications, reoperation, blood transfusions, and length of hospital stay based on chart reviews. Complications were categorized as minor or major according to the necessity of readmission or reoperation. CDP was performed for 4–6 weeks preoperatively and 2 weeks postoperatively.ResultsThe incidence of major complications (p = 0.001), the rate of postoperative blood transfusions (p = 0.028), wound healing disorders (p = 0.021), and the incidence for complications (p = 0.001), whether minor or major, were significantly reduced in the CDP group. In summary, 12 of 16 patients within the CDP group had an uneventful course, whereas all non-CDP patients had at least one complication.ConclusionsAdequate perioperative CDP treatment in a lymphological clinic may reduce the rate of early postoperative complications after resection of panniculus morbidus.

Refinements in reconstruction of penile skin loss using intra-operative prostaglandin injections, postoperative tadalafil application and negative pressure dressings

PURPOSE Penile shaft skin defects represent demanding reconstructive tasks because a high degree of flexibility and stability of the skin grafts are essential to allow regular erections and sexual intercourse. METHODS A new concept of tailoring skin grafts to the erect penis by intra-operative application of prostaglandin E1 and postoperative stabilisation by negative-pressure wound therapy and pharmacological expansion by tadalafil was tested on four patients with penile shaft skin defects. Graft take, stability, pliability, softness and aesthetic results were evaluated up to at least 12 months postoperatively. The ratio of the skin transplanted area in the non-erect compared to the erect penis (non-erect/erect ratio) and the ratio of the skin transplanted area in the erect penis at 12 months compared to intra-operatively (Post/Pre ratio) was determined to define the amount of graft contraction and flexibility. International Index of Erectile Function (IIEF)-5 scores were evaluated postoperatively. RESULTS There were no complications. Graft take was 97, 100, 100 and 100%. Stable skin grafts were achieved after 2 weeks. Sexual intercourse was possible at 2-3 months. The Post/Pre ratio was between 81 and 87% and proves comparably mild contracture rates. The non-erect/erect ratio of 50-72% shows how significantly undersized penile shaft skin grafts are when adjusted to the non-erect penis and that an adequate flexibility for erections can be reconstructed. IIEF-5 scores proved regular potency in three patients; one patient was no longer sexually active. CONCLUSIONS With the new concept of tailoring the skin graft to the erect penis, pharmacological expansion and external stabilisation by vacuum-assisted closure (VAC) dressing the difficult task of penile skin reconstruction can be facilitated, accelerated and the functional and aesthetic outcome improved compared to earlier efforts or to results presented in the literature.

Overexpression of hypoxia-inducible factor-1 alpha improves vasculogenesis-related functions of endothelial progenitor cells

Postnatal vasculogenesis is mediated by mobilization of endothelial progenitor cells (EPCs) from bone marrow and homing to ischemic tissues. This feature emphasizes this cell type for cell-based therapies aiming at the improvement of neovascularization in tissue engineering applications and regenerative medicine. In animal models, it was demonstrated that implantation of EPCs from cord blood (cbEPCs) led to the formation of a complex functional neovasculature, whereas EPCs isolated from adult peripheral blood (pbEPCs) showed a limited vasculogenic potential, which may be attributed to age-related dysfunction. Recently, it was demonstrated that activation of hypoxia-inducible factor-1α (Hif-1α) improves cell functions of progenitor cells of mesenchymal and endothelial origin. Thus, we hypothesized that overexpression of Hif-1α may improve the vasculogenesis-related phenotype of pbEPCs. In the present study, we overexpressed Hif-1α in pbEPCs and cbEPCs by using recombinant adenoviruses and investigated effects on stem cell- and vasculogenesis-related cell parameters. Overexpression of Hif-1α enhanced proliferation, invasion, cell survival and in vitro capillary sprout formation of both EPC populations. Migration was increased in cbEPCs upon Hif-1α overexpression, but not in pbEPCs. Cellular senescence was decreased in pbEPCs, while remained in cbEPCs, which showed, as expected, intrinsically a dramatically lower senescent phenotype in relation to pbEPCs. Similarly, the colony-formation capacity was much higher in cbEPCs in comparison to pbEPCs and was further increased by Hif-1α overexpression, whereas Hif-1α transduction exerted no significant influence on colony formation of pbEPCs. In summary, our experiments illustrated multifarious effects of Hif-1α overexpression on stem cell and vasculogenic parameters. Therefore, Hif-1α overexpression may represent a therapeutic option to improve cellular functions of adult as well as postnatal EPCs.

Transcriptomic Changes in Osteoblasts Following Endothelial Cell‐Cocultivation Suggest a Role of Extracellular Matrix in Cellular Interaction

Vascularization is important for bone development, fracture healing and engineering of artificial bone tissue. In the context of bone tissue engineering, it was shown that coimplantation of human primary umbilical vein endothelial cells (HUVECs) and human osteoblasts (hOBs) results in the formation of functional blood vessels and enhanced bone regeneration. Implanted endothelial cells do not only contribute to blood vessel formation, but also support proliferation, cell survival and osteogenic differentiation of coimplanted hOBs. These effects are partially mediated by direct heterotypic cell contacts. In a previous report we could show that cocultivated hOBs strongly increase the expression of genes involved in extracellular matrix (ECM) formation in HUVECs, suggesting that ECM may be involved in the intercellular communication between hOBs and HUVECs. The present study aimed at investigating whether comparable changes occur in hOBs. We therefore performed a microarray analysis of hOBs cultivated in direct contact with HUVECs, revealing 1,004 differentially expressed genes. The differentially expressed genes could be assigned to the functional clusters ECM, proliferation, apoptosis and osteogenic differentiation. The microarray data could be confirmed by performing quantitative real time RT‐PCR on selected genes. Furthermore, we could show that the ECM produced by HUVECs increased the expression of the osteogenic differentiation marker alkaline phosphatase (ALP) in hOBs. In summary, our data demonstrate that HUVECs provoke complex changes in gene expression patterns in cocultivated hOBs and that ECM plays and important role in this interaction. J. Cell. Biochem. 117: 1869–1879, 2016.

Comparison of Multidetector Computed Tomography and Flat-Panel Computed Tomography Regarding Visualization of Cortical Fractures, Cortical Defects, and Orthopedic Screws: A Phantom Study.

Abstract To compare the visualization of cortical fractures, cortical defects, and orthopedic screws in a dedicated extremity flat-panel computed tomography (FPCT) scanner and a multidetector computed tomography (MDCT) scanner. We used feet of European roe deer as phantoms for cortical fractures, cortical defects, and implanted orthopedic screws. FPCT and MDCT scans were performed with equivalent dose settings. Six observers rated the scans according to number of fragments, size of defects, size of defects opposite orthopedic screws, and the length of different screws. The image quality regarding depiction of the cortical bone was assessed. The gold standard (real number of fragments) was evaluated by autopsy. The correlation of reader assessment of fragments, cortical defects, and screws with the gold standard was similar for FPCT and MDCT. Three readers rated the subjective image quality of the MDCT to be higher, whereas the others showed no preferences. Although the image quality was rated higher in the MDCT than in the FPCT by 3 out of 6 observers, both modalities proved to be comparable regarding the visualization of cortical fractures, cortical defects, and orthopedic screws and of use to musculoskeletal radiology regarding fracture detection and postsurgical evaluation in our experimental setting.

Utilization of a genetically modified muscle flap for local BMP-2 production and its effects on bone healing: a histomorphometric and radiological study in a rat model

Aim of the studyWe developed an experimental rat model to explore the possibility of enhancing the healing of critical-size bone defects. The aim of this study was to demonstrate the feasibility of this concept by achieving high local BMP-2 expression via a transduced muscle flap that would facilitate bony union while minimizing systemic sequelae.MethodsThe transduction potential of the adenoviral vector encoding for BMP-2 was tested in different cell lines in vitro. In vivo experiments consisted of harvesting a pedicled quadriceps femoris muscle flap with subsequent creation of a critical-size defect in the left femur in Sprague-Dawley rats. Next, the pedicled muscle flap was perfused with high titers of Ad.BMP-2 and Ad.GFP virus, respectively. Twelve animals were divided into three groups comparing the effects of Ad.BMP-2 transduction to Ad.GFP and placebo. Bone healing was monitored radiologically with subsequent histological analysis post-mortem.ResultsThe feasibility of this concept was demonstrated by successful transduction in vitro and in vivo as evidenced by a marked increase of BMP-2 expression. The three examined groups only showed minor difference regarding bone regeneration; however, one complete bridging of the defect was observed in the Ad.BMP-2 group. No evidence of systemic viral contamination was noted.ConclusionsA marked increase of local BMP-2 expression (without untoward systemic sequelae) was detected. However, bone healing was not found to be significantly enhanced, possibly due to the small sample size of the study.

The RESTORE-2 trial: proof of safety and efficacy of "regenerative-cell enriched" fat-grafting?

With great interest we have read the publication of P erez-Cano et al. reporting on the use of so-called “Regenerative Cells” for fat-grafting procedures to the female breast after partial mastectomy. We very much appreciate the author’s commitment to evaluate the highly potential possibilities of combining the more than 100-year old technology of autologous fat grafting with recent findings from stem cell research. However, at least in our opinion, the findings leading to the study’s final evaluation, deserve complementary consideration in rather relevant aspects: