Interplay between local versus soluble transforming growth factor-beta and fibrin scaffolds: role of cells and impact on human mesenchymal stem cell chondrogenesis

Structural extracellular matrix molecules gain increasing attention as scaffolds for cartilage tissue engineering owing to their natural role as a growth factor repository. We recently observed that a collagen-type I/III (Col-I/III) matrix, human recombinant transforming growth factor-beta (TGF-β) protein, and fibrin hydrogel (FG) combined to a biphasic construct provided sufficient long-term TGF-β support to drive in vitro chondrogenesis of human mesenchymal stem cells (hMSC). Here we ask whether FG and Col-I/III can both retain TGF-β, describe the influence of cell seeding on TGF-β release, and compare the molecular path of hMSC chondrogenic differentiation under soluble versus local TGF-β supply. Release of growth factor from scaffolds augmented with increasing amounts of TGF-β was analyzed over 7 days and chondrogenesis was assessed over 42 days. Low TGF-β release rates from Col-I/III as opposed to higher release from FG indicated that both molecules retained TGF-β, with Col-I/III being the superior storage component. Cell seeding enhanced TGF-β retention in FG by about threefold and almost stopped release beyond 24?h. TGF-β remained bioactive and supported MSC chondrogenesis without impairing the amount of proteoglycan and collagen-type II deposition per cell and per construct compared to standard scaffold-free MSC pellets supplied with soluble TGF-β. Local TGF-β, however, mediated lower cell content, less collagen-type X relative to collagen-type II deposition and no matrix metalloproteinase-13 up-regulation. In conclusion, cells quickly halted release of local TGF-β from FG, turning FG and Col-I/III into attractive TGF-β repositories capable to drive full hMSC chondrogenesis, but via a modulated differentiation pathway. Since only part of the changes was reproduced by transient soluble TGF-β supply, release kinetics alone could not explain the molecular differences, suggesting that local TGF-β acts distinct from its soluble counterpart.     

Copolythiophenes with Hydrophilic and Hydrophobic Side Chains: Synthesis,Characterization, and Performance in Organic Field Effect Transistors

Statistical copolymers of regioregular polythiophene with hydrophobic hexyl side chains (P3HT) and hydrophilic 3,6‐dioxaheptyl side chains (P3DOHT) are synthesized by the GRIM method. A comparable study on the different polymers has been accomplished regarding solubility, thin film structure, and performance in organic field effect transistors (OFETs). DSC and XRD measurements are done to investigate the crystallinity of the copolymers. The novel functionalized fully π‐conjugated copolymers P(3HT‐co‐3DOHT) with feed molar ratios of 1:1, 2:1, and 1:2 show hole mobilities in the range of 10^?2 cm² V^?1 s^?1. Using poly(methyl methacrylate) as the dielectric layer in a top gate device architecture leads to air stable transistors without significant losses in the OFET performance over several months.     

12/15-lipoxygenase orchestrates the clearance of apoptotic cells and maintains immunologic tolerance

Noninflammatory clearance of apoptotic cells (ACs) is crucial to maintain self-tolerance. Here, we have reported a role for the enzyme 12/15-lipoxygenase (12/15-LO) as a central factor governing the sorting of ACs into differentially activated monocyte subpopulations. During inflammation, uptake of ACs was confined to a population of 12/15-LO-expressing, alternatively activated resident macrophages (resMΦ), which blocked uptake of ACs into freshly recruited inflammatory Ly6C(hi) monocytes in a 12/15-LO-dependent manner. ResMΦ exposed 12/15-LO-derived oxidation products of phosphatidylethanolamine (oxPE) on their plasma membranes and thereby generated a sink for distinct soluble receptors for ACs such as milk fat globule-EGF factor 8, which were essential for the uptake of ACs into inflammatory monocytes. Loss of 12/15-LO activity, in turn, resulted in an aberrant phagocytosis of ACs by inflammatory monocytes, subsequent antigen presentation of AC-derived antigens, and a lupus-like autoimmune disease. Our data reveal an unexpected key role for enzymatic lipid oxidation during the maintenance of self-tolerance.     

Real-time temperature determination during retinal photocoagulation on patients

The induced thermal damage in retinal photocoagulation depends on the temperature increase and the time of irradiation. The temperature rise is unknown due to intraocular variations in light transmission, scattering and grade of absorption in the retinal pigment epithelium (RPE) and the choroid. Thus, in clinical practice, often stronger and deeper coagulations are applied than therapeutically needed, which can lead to extended neuroretinal damage and strong pain perception. This work focuses on an optoacoustic (OA) method to determine the temperature rise in real-time during photocoagulation by repetitively exciting thermoelastic pressure transients with nanosecond probe laser pulses, which are simultaneously applied to the treatment radiation. The temperature-dependent pressure amplitudes are non-invasively detected at the cornea with an ultrasonic transducer embedded in the contact lens. During clinical treatment, temperature courses as predicted by heat diffusion theory are observed in most cases. For laser spot diameters of 100 and 300 μm, and irradiation times of 100 and 200 ms, respectively, peak temperatures range between 70°C and 85°C for mild coagulations. The obtained data look very promising for the realization of a feedback-controlled treatment, which automatically generates preselected and reproducible coagulation strengths, unburdens the ophthalmologist from manual laser dosage, and minimizes adverse effects and pain for the patient.     

Conditional DC depletion does not affect priming of encephalitogenic Th cells in EAE

EAE, an animal model for multiple sclerosis, is a Th17‐ and Th1‐cell‐mediated auto‐immune disease, but the mechanisms leading to priming of encephalitogenicTcells in autoimmune neuroinflammation are poorly understood. To investigate the role of dendritic cells (DCs) in the initiation of autoimmuneTh17‐ andTh1‐cell responses andEAE, we used mice transgenic for a simian diphtheria toxin receptor (DTR) expressed under the control of the murineCD11c promoter (CD11c‐DTRmice onC57BL/6 background).EAEwas induced by immunization with myelin oligodendrocyte glycoprotein (MOG) protein in CFA. DCs were depleted on the day before and 8 days afterMOG immunization. The mean clinicalEAEscore was only mildly reduced inDC‐depleted mice when DCs were ablated beforeEAEinduction. The frequency of activatedTh cells was not altered, andMOG‐inducedTh17 orTh1‐cell responses were not altered, in the spleens ofDC‐depleted mice. Similar results were obtained ifDCswere ablated the first 10 days afterMOGimmunization with repeatedDCdepletions. Unexpectedly, transient depletion of DCs did not affect priming or differentiation of MOG‐inducedTh17 andTh1‐cell responses or the incidence ofEAE. Thus, the mechansim of priming ofTh cells inEAEremains to be elucidated.