Iris Leinhase

Inhibition of the alternative complement activation pathway in traumatic brain injury by a monoclonal anti-factor B antibody: a randomized placebo-controlled study in mice

BackgroundThe posttraumatic response to traumatic brain injury (TBI) is characterized, in part, by activation of the innate immune response, including the complement system. We have recently shown that mice devoid of a functional alternative pathway of complement activation (factor B-/- mice) are protected from complement-mediated neuroinflammation and neuropathology after TBI. In the present study, we extrapolated this knowledge from studies in genetically engineered mice to a pharmacological approach using a monoclonal anti-factor B antibody. This neutralizing antibody represents a specific and potent inhibitor of the alternative complement pathway in mice.MethodsA focal trauma was applied to the left hemisphere of C57BL/6 mice (n = 89) using a standardized electric weight-drop model. Animals were randomly assigned to two treatment groups: (1) Systemic injection of 1 mg monoclonal anti-factor B antibody (mAb 1379) in 400 μl phosphate-buffered saline (PBS) at 1 hour and 24 hours after trauma; (2) Systemic injection of vehicle only (400 μl PBS), as placebo control, at identical time-points after trauma. Sham-operated and untreated mice served as additional negative controls. Evaluation of neurological scores and analysis of brain tissue specimens and serum samples was performed at defined time-points for up to 1 week. Complement activation in serum was assessed by zymosan assay and by murine C5a ELISA. Brain samples were analyzed by immunohistochemistry, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) histochemistry, and real-time RT-PCR.ResultsThe mAb 1379 leads to a significant inhibition of alternative pathway complement activity and to significantly attenuated C5a levels in serum, as compared to head-injured placebo-treated control mice. TBI induced histomorphological signs of neuroinflammation and neuronal apoptosis in the injured brain hemisphere of placebo-treated control mice for up to 7 days. In contrast, the systemic administration of an inhibitory anti-factor B antibody led to a substantial attenuation of cerebral tissue damage and neuronal cell death. In addition, the posttraumatic administration of the mAb 1379 induced a neuroprotective pattern of intracerebral gene expression.ConclusionInhibition of the alternative complement pathway by posttraumatic administration of a neutralizing anti-factor B antibody appears to represent a new promising avenue for pharmacological attenuation of the complement-mediated neuroinflammatory response after head injury.

Human periosteum-derived progenitor cells express distinct chemokine receptors and migrate upon stimulation with CCL2, CCL25, CXCL8, CXCL12, and CXCL13

For bone repair, transplantation of periosteal progenitor cells (PCs), which had been amplified within supportive scaffolds, is applied clinically. More innovative bone tissue engineering approaches focus on the in situ recruitment of stem and progenitor cells to defective sites and their subsequent use for guided tissue repair. Chemokines are known to induce the directed migration of bone marrow CD34(-) mesenchymal stem cells (MSCs). The aim of our study was to determine the chemokine receptor expression profile of human CD34(-) PCs and to demonstrate that these cells migrate upon stimulation with selected chemokines. PCs were isolated from periosteum of the mastoid bone and displayed a homogenous cell population presenting an MSC-related cell-surface antigen profile (ALCAM(+), SH2(+), SH3(+), CD14(-), CD34(-), CD44(+), CD45(-), CD90(+)). The expression profile of chemokine receptors was determined by real-time PCR and immunohistochemistry. Both methods consistently demonstrated that PCs express receptors of all four chemokine subfamilies CC, CXC, CX(3)C, and C. Migration of PCs and a dose-dependent migratory effect of the chemokines CCL2 (MCP1), CCL25 (TECK), CXCL8 (IL8), CXCL12 (SDF1alpha), and CXCL13 (BCA1), but not CCL22 (MDC) were demonstrated using a 96-multiwell chemotaxis assay. In conclusion, for the first time, here we report that human PCs express chemokine receptors, present their profile, and demonstrate a dose-dependent migratory effect of distinct chemokines on these cells. These results are promising towards in situ bone repair therapies based on guiding PCs to bone defects, and encourage further in vivo studies.

Human mastoid periosteum‐derived stem cells: promising candidates for skeletal tissue engineering

Currently, mesenchymal stem cells (MSCs) are considered as the most eligible cells for skeletal tissue engineering. However, factors such as difficult stimulation and control of differentiation in vivo hamper their clinical use. In contrast, periosteum or periosteum‐derived cells (PCs) are routinely clinically applied for bone and cartilage repair. PCs have often been named MSCs but, although cells of osteochondrogenic lineages arise from MSCs, it is unclear whether periosteum really contains MSCs. Our aim was to investigate the MSC‐like character of PCs derived from the periosteum of mastoid bone. Harvesting of periosteum from mastoid bone is easy, so mastoid represents a good source for the isolation of PCs. Therefore, we analysed the MSC‐like growth behaviour and the expression of embryonic, ectodermal, endodermal and mesodermal markers by microarray and FACS technology, and the multilineage developmental capacity of human PCs. Regarding clinical relevance, experiments were performed in human serum‐supplemented medium. We show that PCs do not express early embryonic stem cell markers such as Oct4 and Nanog, or the marker of haematopoietic stem cells CD34, but express some other MSC markers. Osteogenesis resulted in the formation of calcified matrix, increased alkaline phosphatase activity, and induction of the osteogenic marker gene osteocalcin. Staining of proteoglycans and deposition of type II collagen documented chondrogenic development. As shown for the first time, adipogenic stimulation of mastoid‐derived PCs resulted in the formation of lipid droplets and expression of the adipogenic marker genes aP2 and APM1. These results suggest MSC‐like PCs from mastoid as candidates for therapy of complex skeletal defects. Copyright

Absence of the complement regulatory molecule CD59a leads to exacerbated neuropathology after traumatic brain injury in mice

BackgroundComplement represents a crucial mediator of neuroinflammation and neurodegeneration after traumatic brain injury. The role of the terminal complement activation pathway, leading to generation of the membrane attack complex (MAC), has not been thoroughly investigated. CD59 is the major regulator of MAC formation and represents an essential protector from homologous cell injury after complement activation in the injured brain.MethodsMice deleted in the Cd59a gene (CD59a-/-) and wild-type littermates (n = 60) were subjected to focal closed head injury. Sham-operated (n = 60) and normal untreated mice (n = 14) served as negative controls. The posttraumatic neurological impairment was assessed for up to one week after trauma, using a standardized Neurological Severity Score (NSS). The extent of neuronal cell death was determined by serum levels of neuron-specific enolase (NSE) and by staining of brain tissue sections in TUNEL technique. The expression profiles of pro-apoptotic (Fas, FasL, Bax) and anti-apoptotic (Bcl-2) mediators were determined at the gene and protein level by real-time RT-PCR and Western blot, respectively.ResultsClinically, the brain-injured CD59a-/- mice showed a significantly impaired neurological outcome within 7 days, as determined by a higher NSS, compared to wild-type controls. The NSE serum levels, an indirect marker of neuronal cell death, were significantly elevated in CD59a-/- mice at 4 h and 24 h after trauma, compared to wild-type littermates. At the tissue level, increased neuronal cell death and brain tissue destruction was detected by TUNEL histochemistry in CD59a-/- mice within 24 hours to 7 days after head trauma. The analysis of brain homogenates for potential mediators and regulators of cell death other than the complement MAC (Fas, FasL, Bax, Bcl-2) revealed no difference in gene expression and protein levels between CD59a-/- and wild-type mice.ConclusionThese data emphasize an important role of CD59 in mediating protection from secondary neuronal cell death and further underscore the key role of the terminal complement pathway in the pathophysiology of traumatic brain injury. The exact mechanisms of complement MAC-induced secondary neuronal cell death after head injury require further investigation.

Tracheal remodeling: comparison of different composite cultures consisting of human respiratory epithelial cells and human chondrocytes.

The reconstruction of extensive tracheal defects is still an unsolved challenge for thoracic surgery. Tissue engineering is a promising possibility to solve this problem through the generation of an autologous tracheal replacement from patients’ own tissue. Therefore, this study investigated the potential of three different coculture systems, combining human respiratory epithelial cells and human chondrocytes. The coculture systems were analyzed by histological staining with alcian blue, immunohistochemical staining with the antibodies, 34betaE12 and CD44v6, and scanning electron microscopy. The first composite culture consisted of human respiratory epithelial cells seeded on human high-density chondrocyte pellets. For the second system, we used native articular cartilage chips as base for the respiratory epithelial cells. The third system consisted of a collagen membrane, seeded with respiratory epithelial cells and human chondrocytes onto different sides of the membrane, which achieved the most promising results. In combination with an air–liquid interface system and fibroblast-conditioned medium, an extended epithelial multilayer with differentiated epithelial cells could be generated. Our results suggest that at least three factors are necessary for the development towards a tracheal replacement: (1) a basal lamina equivalent, consisting of collagen fibers for cell–cell interaction and cell polarization, (2) extracellular factors of mesenchymal fibroblasts, and (3) the presence of an air–liquid interface system for proliferation and differentiation of the epithelial cells.

Changes in the gene expression pattern of cytokeratins in human respiratory epithelial cells during culture

The replacement of extensive tracheal defects resulting from intensive care medicine, trauma or large resections is still challenged by the re-epithelialization of an autologous or alloplastic trachea replacement. Therefore, this study was performed to investigate the potential of culture-expanded human respiratory epithelial cells (hREC) to regenerate a functional epithelium for tracheal tissue engineering. hREC from seven male nasal turbinates were freshly isolated, expanded on a collagenous matrix and subsequently cultured in high-density multi-layers to allow epithelial differentiation. The composition of epithelial cells in native respiratory epithelial tissue and culture-expanded hREC was analyzed by histological staining with Alcian blue and by immunohistochemical staining of cytokeratin pairs CK1/10 and CK5/14 with the antibodies 34βE12 and CD44v6. Differentiation of culture-expanded hREC was further characterized by gene expression analysis of cytokeratins CK5, CK13, CK14 and CK18 using semi-quantitative real-time RT-PCR technique. Histological and immunohistochemical staining of culture-expanded hREC demonstrated basal cells covering the collagenous matrix. These cells formed a cellular multi-layer, which was composed of a basal layer of undifferentiated basal cells and an upper layer of cells differentiating along the squamous metaplasia and ciliated cell lineage. Lineage development of culture-expanded hREC was further documented by the induction of cytokeratins CK13 and CK18. Our results suggest that culture-expanded hREC have the potential to colonize collagen-coated biomaterials and to regenerate epithelial cell types for tracheal tissue engineering.

Die pharmakologische Inhibition der intrazerebralen Entzündungsreaktion durch systemische Administration des rekombinanten Komplement-Inhibitors Crry-Ig vermittelt eine Neuroprotektion im experimentellen Schädel-Hirn-Trauma in der Maus

Activation of complement plays a central role in the pathogenesis of neuroinflammation leading to secondary brain injury following a traumatic insult to the brain. In a previous study, we were able to show improved neurological recovery in brain-injured transgenic mice with central nervous system-targeted overexpression of the soluble inhibitor of complement C3 convertases, sCrry. Here, we present the first data on systemic administration of recombinant Crry-Ig in a model of closed-head injury (CHI). Thirty-seven C57BL/6 mice were randomized into 4 cohorts: group 1 — normal mice without CHI; group 2 — sham-operated mice without CHI; group 3 — CHI with posttraumatic i.p. injection of 0.4 ml PBS (vehicle); group 4 — CHI with posttraumatic i.p. injection of recombinant Crry-Ig (1mg in 0.4 ml PBS). Vehicle-injected mice with experimental CHI (group 3) showed massive histomorphological signs of neuroinflammation associated with neuronal apoptosis. Western-Blot analysis of homogenized mouse brains revealed significant mismatch of mitochondrial anti- and pro-apoptotic proteins (Bcl-2, Bax, Bcl-Xs) favouring programmed cell death up to one week post trauma. In contrast, administration of Crry-Ig (group 4) induced a decrease of pro- and an increase of anti-apoptotic protein levels, with as- sociated attenuation of histomorphological tissue damage and improved neurological recovery.