Christian Weinand

An Allogenic Cell–Based Implant for Meniscal Lesions

Background Meniscal tears in the avascular zones do not heal. Although tissue-engineering approaches using cells seeded onto scaffolds could expand the indication for meniscal repair, harvesting autologous cells could cause additional trauma to the patient. Allogenic cells, however, could provide an unlimited amount of cells. Hypothesis Allogenic cells from 2 anatomical sources can repair lesions in the avascular region of the meniscus. Study Design Controlled laboratory study. Methods Both autologous and allogenic chondrocytes were seeded onto a Vicryl mesh scaffold and sutured into a bucket-handle lesion created in the medial menisci of 17 swine. Controls consisted of 3 swine knees treated with unseeded implants and controls from a previous experiment in which 4 swine were treated with suture only and 4 with no treatment. Menisci were harvested after 12 weeks and evaluated histologically for new tissue and percentage of interface healing surface; they were also evaluated statistically. Results The lesions were closed in 15 of 17 menisci. None of the control samples demonstrated healing. Histologic analysis of sequential cuts through the lesion showed formation of new scar-like tissue in all experimental samples. One of 8 menisci was completely healed in the allogenic group and 2 of 9 in the autologous group; the remaining samples were partially healed in both groups. No statistically significant differences in the percentage of healing were observed between the autologous and allogenic cell-based implants. Conclusion Use of autologous and allogenic chondrocytes delivered via a biodegradable mesh enhanced healing of avascular meniscal lesions. Clinical Relevance This study demonstrates the potential of a tissue-engineered cellular repair of the meniscus using autologous and allogenic chondrocytes.

Healing potential of transplanted allogeneic chondrocytes of three different sources in lesions of the avascular zone of the meniscus: a pilot study

Successful treatment of tears to the avascular region of the meniscus remains a challenge. Current repair techniques, such as sutures and anchors, are effective in stabilizing the peripheral, vascularized regions of the meniscus, but are not adequate for promoting healing in the avascular region. The purpose of this study was to demonstrate the healing ability of a tissue-engineered repair technique using allogenic chondrocytes from three different sources for the avascular zone of the meniscus. Material and methods: Articular, auricular, and costal chondrocytes were harvested from 3-month-old Yorkshire swine. A 1-cm bucket-handle lesion was created in the avascular zone of each three swine. A cell-scaffold construct, composed of a single chondrocyte cell type and Vicryl mesh, was implanted into the lesion and secured with two vertical mattress sutures. Controls consisted of each three sutured unseeded mesh implants, suture only, and untreated lesions. The swine were allowed immediate post-operative full weight bearing. Menisci and controls were harvested after 12 weeks. Results: In all experimental samples, lesion closure was observed. Gross mechanical testing with two Adson forceps demonstrated bonding of the lesion. Histological analysis showed formation of new tissue in all three experimental samples. None of the control samples demonstrated closure and formation of new matrix. Conclusion: We present preliminary data that demonstrates the potential of a tissue-engineered, allogenic cellular repair to provide successful healing of lesions in the avascular zone in a large animal model.

Conditions affecting cell seeding onto three-dimensional scaffolds for cellular-based biodegradable implants

Seeding cells efficiently and uniformly onto three-dimensional scaffolds is a key element for engineering tissues, particularly when only a low-number of cells is available for tissue repair and regeneration. The aim of this study was to evaluate three seeding techniques on two biocompatible scaffolds in vitro using chondrocytes as follows: (1) static; (2) modified centrifugal cell immobilization (CCI); and (3) dynamic oscillating motion. Five milliliters of media containing 5, 10, or 25 million articular, auricular, or costal chondrocytes were used to seed porous PLGA scaffolds and sections of devitalized cartilage. The dynamic oscillating technique resulted in up to 150% higher cellular load at 7 days than CCI seeding. Cell distribution was more homogeneous throughout the scaffold under dynamic conditions versus more sporadic and dispersed cell concentrations on the scaffolds when using either the static or the modified CCI technique. Cell load and distribution, when using a low numbers of chondrocytes at one and two million cells per milliliter, was comparable to that using the much higher number, especially under dynamic seeding conditions. The seeded scaffolds were used as implants to achieve cellular bonding between two devitalized meniscus discs. The constructs were implanted subcutaneously in nude mice for 12 weeks and analyzed histologically. Implants seeded with auricular chondrocytes showed qualitative more integration into native meniscus tissue than articular and costal cell implants. We conclude the dynamic oscillating seeding technique is an efficient technique for seeding low-cell numbers onto scaffolds resulting in consistent and uniform cell distribution throughout porous PLGA scaffolds.

Tissue engineering cartilage with aged articular chondrocytes in vivo.

Background: Tissue engineering has the potential to repair cartilage structures in middle-aged and elderly patients using their own “aged” cartilage tissue as a source of reparative chondrocytes. However, most studies on tissue-engineered cartilage have used chondrocytes from postfetal or very young donors. The authors hypothesized that articular chondrocytes isolated from old animals could produce neocartilage in vivo as well as articular chondrocytes from young donors. Methods: Articular chondrocytes from 8-year-old sheep (old donors) and 3- to 6-month-old sheep (young donors) were isolated. Cells were mixed in fibrin gel polymer at 40 × 106 cells/ml until polymerization. Cell-polymer constructs were implanted into the subcutaneous tissue of nude mice and harvested at 7 and 12 weeks. Results: Samples and native articular cartilage controls were examined histologically and assessed biochemically for total DNA, glycosaminoglycan, and hydroxyproline content. Histological analysis showed that samples made with chondrocytes from old donors accumulated basophilic extracellular matrix and sulfated glycosaminoglycans around the cells in a manner similar to that seen in samples made with chondrocytes from young donors at 7 and 12 weeks. Biochemical analysis revealed that DNA, glycosaminoglycan, and hydroxyproline content increased in chondrocytes from old donors over time in a pattern similar to that seen with chondrocytes from young donors. Conclusions: This study demonstrates that chondrocytes from old donors can be rejuvenated and can produce neocartilage just as chondrocytes from young donors do when encapsulated in fibrin gel polymer in vivo. This study suggests that middle-aged and elderly patients could benefit from cartilage tissue-engineering repair using their own “aged” articular cartilage as a source of reparative chondrocytes.

Incidence and treatment of burns: A twenty-year experience from a single center in Germany

OBJECTIVE To analyze trends in incidence and treatment of thermal injuries over the last two decades. METHODS We retrospectively reviewed our local single center database of patients with thermal injuries admitted to the burn intensive care unit (BICU) of the Cologne-Merheim Medical Center (University Hospital of Witten/Herdecke). The cohort was divided into two groups according to the decade of admission and the epidemiology and clinical course of the patient sample admitted during the period 1991-2000 (n=911) was compared to that of 2001-2010 (n=695). RESULTS The following variables were significantly different in the bivariate analysis: mean age (39.8 years vs. 44.0 years), burn size of total body surface area (23.2% vs. 18.0%) and size of 3rd degree burns (9.6% vs. 14.9%). The incidence of inhalation injury was significantly lower in the last decade (33.3% vs. 13.7%) and was associated with a shorter duration of mechanical ventilation (10.8 days vs. 8.5 days). The ABSI-score as an indicator of burn severity declined in the second period (6.3 vs. 6.0) contributing partially to the decline of BICU length of stay (19.1 days vs. 18.8 days) and to the mortality rate decrease (18.6% vs. 15.0%). CONCLUSION The severity of burn injuries during the last two decades declined, probably reflecting the success of prevention campaigns. Concerning mortality, the chance of dying for a given severity of injury has decreased.

Factors of Osteogenesis Influencing Various Human Stem Cells on Third-Generation Gelatin/β-Tricalcium Phosphate Scaffold Material

Human bone marrow-derived stem cells (hBMSCs) and adipose-derived stem cells (hASCs) have been used to regenerate bone. Both sources are claimed to have comparable osteogenic potential, but few comparative studies are available. Third-generation biomaterials have been developed to reduce steps in regenerating tissues. For osteogenesis gelatin/β-tricalcium phosphate (β-TCP) scaffolds with incorporated controlled-release bone morphogenetic protein-2 (BMP-2) as third-generation biomaterials were recently developed. So far, few studies on protein-induced osteogenesis versus chemical-induced osteogenesis have been performed. This study evaluates the osteogenic potential of hBMSCs versus hASCs derived on gelatin/β-TCP scaffolds in vitro under four different conditions. Gelatin/β-TCP scaffolds with and without incorporated controlled-release BMP-2 were seeded with hBMSCs or hASCs under oscillating fluid conditions in osteogenic (OS) medium or growth medium (GM). All were evaluated radiologically (computed tomography [CT] scan), histologically, biomechanically, and for gene expression at 1, 2, 4, and 6 weeks. The highest radiological densities were seen in specimens at 6 weeks with controlled-release BMP-2, close to native bone. HBMSCs, hASCs, OS, and GM conditions resulted in similar bone formation with gelatin/β-TCP scaffolds and incorporated controlled-release BMP-2. This was confirmed histologically by Toluidine Blue and van Kossa staining and biomechanically. Gene expression studies of these specimens showed the presence of preosteoblasts, transitory osteoblasts, and secretory osteoblasts. Specimens comprised of gelatin/β-TCP scaffolds without incorporated controlled release BMP-2 in OS medium showed lesser bone formation. hASCs and hBMSCs have similar osteogenic potential. hASCs are an attractive alternative to hBMSCs for bone regeneration using third-generation gelatin/β-TCP scaffolds with incorporated controlled-release BMP-2.

Suicide by burning : epidemiological and clinical profiles

Self-immolation constitutes a rare form of suicide in developed countries, though it accounts for unique injury characteristics in the burn intensive care unit. The aim of this study was to present the epidemiological and clinical features of patients burned during a suicidal attempt seen in a North Rhine-Westphalia burn intensive care unit (BICU). To address this aim, we undertook a 21-year retrospective study involving patients with thermal injuries admitted to the largest burn unit in Germany. A total of 125 suicide-related burn victims were identified in the study period (9.4%). Comparing the self-immolation group with the rest burn patient cohort, suicide victims were more likely to be single and to act under the influence of alcohol. The suicidal group had a larger extent of burns, higher incidence of inhalation injury, required more surgical procedures, catecholamines, blood transfusions, and a longer BICU stay. Their clinical course was complicated by prolonged intubation period, higher rate of multiple drug-resistant bacteria acquisition and sepsis, leading to a higher mortality rate. Although the proportion of self-immolation victims among all burned patients is not high, the markedly higher severity of their burns and their poorer quality of outcomes makes them an important clinical subgroup for further study.

Human shaped thumb bone tissue engineered by hydrogel-beta-tricalciumphosphate/poly-epsilon-caprolactone scaffolds and magnetically sorted stem cells.

Traumatic amputation of a thumb with bone loss leaves a patient in severe disability. Reconstructive procedures are restricted by limited shape and have the disadvantage of severe donor-site morbidity. To overcome these limitations, we used a tissue engineering approach to create a distal thumb bone phalanx, combining magnetically sorted 133+ human mesenchymal stem cells (hMSCs) suspended in successful tested hydrogels for bone formation and porous 3-dimensionally printed scaffolds (3DP) in the shape of a distal thumb bone phalanx. Collagen I and fibrin glue hydrogels with suspended hMSCs were first histologically evaluated in vitro for bone formation after 6 weeks. Then 3DP scaffolds, made from a mix of osteoinductive and -conductive &bgr;-tricalciumphosphate (&bgr;-TCP) and poly-&egr;-caprolactone (PCL), with hydrogels and suspended hMSCs, were implanted into nude mice subcutaneously for 15 weeks. Histologic evaluation, high-resolution volumetric CT (VCT) scanning, and biomechanical testing confirmed formation of bonelike tissue. Both hydrogels with CD 133+ hMSCs on 3DP scaffolds supported bone formation. Collagen I resulted in radiologically better bone formation. Bone tissue can be successfully tissue engineered with CD 133+ hMSCs, collagen I hydrogels, and porous 3DP &bgr;-TCP/PCL scaffolds.

Failure of secondary wound closure after sternal wound infection following failed initial operative treatment: causes and treatment.

BackgroundPatients transferred to Plastic Surgery Departments for sternum osteomyelitis have a high morbidity of about 3%. Despite several known options for sternal wound coverage and salvage operations, wound dehiscence or wound necrosis can occur, increasing patient morbidity. Patients and MethodsOne hundred thirty-five patients admitted between January 2007 and December 2010 were evaluated in a retrospective study for wound dehiscence after salvage wound coverage at our institution. Various flaps were applied, such as pectoralis major myocutaneous pedicled flaps, pectoralis major muscle pedicled flaps, latissimus dorsi pedicled flaps, greater omental flaps, and vertical rectus abdominis muscle and transverse rectus abdominis muscle flaps. Inclusion criteria were sternal wound infection, bacterial wound infection, previous wound debridement outside our institution, vacuum-assisted closure device wound treatment at our institution, and secondary flap closure of the sternal defect at our institution. A multivariate regression analysis was performed. ResultsOne hundred thirty patients met the inclusion criteria. In all patients, bacterial wound colonization was shown. Forty patients showed wound dehiscence after closure at our institution. Reasons for wound dehiscence were attributed to wound size, >4 different species of bacteria colonizing the wound, gram-negative bacteria, Candida albicans, intensive care unit stay, and female gender. Interestingly, wound dehiscence was not significant correlated to obesity, smoking, atherosclerosis, renal insufficiency or type of closure influenced significantly, or necrosis. ConclusionsFemale patients after CABG, with large sternal wounds infected with gram-negative bacteria and candida, have an 85% risk of wound dehiscence after flap coverage for sternal wound infection.

Optimizing Biomaterials for Tissue Engineering Human Bone Using Mesenchymal Stem Cells.

Background: Adequate biomaterials for tissue engineering bone and replacement of bone in clinical settings are still being developed. Previously, the combination of mesenchymal stem cells in hydrogels and calcium-based biomaterials in both in vitro and in vivo experiments has shown promising results. However, results may be optimized by careful selection of the material combination. Methods: &bgr;-Tricalcium phosphate scaffolds were three-dimensionally printed with five different hydrogels: collagen I, gelatin, fibrin glue, alginate, and Pluronic F-127. The scaffolds had eight channels, running throughout the entire scaffold, and macropores. Mesenchymal stem cells (2 × 106) were mixed with each hydrogel, and cell/hydrogel mixes were dispersed onto the corresponding &bgr;-tricalcium phosphate/hydrogel scaffold and cultured under dynamic-oscillating conditions for 6 weeks. Specimens were harvested at 1, 2, 4, and 6 weeks and evaluated histologically, radiologically, biomechanically and, at 6 weeks, for expression of bone-specific proteins by reverse-transcriptase polymerase chain reaction. Statistical correlation analysis was performed between radiologic densities in Hounsfield units and biomechanical stiffness. Results: Collagen I samples had superior bone formation at 6 weeks as demonstrated by volume computed tomographic scanning, with densities of 300 HU, similar to native bone, and the highest compression values. Bone specificity of new tissue was confirmed histologically and by the expression of alkaline phosphatase, osteonectin, osteopontin, and osteocalcin. The bone density correlated closely with histologic and biomechanical testing results. Conclusion: Bone formation is supported best by &bgr;-tricalcium phosphate/collagen I hydrogel and mesenchymal stem cells in collagen I hydrogel. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.