Triggering the activation of Activin A type II receptor in human adipose stem cells towards tenogenic commitment using mechanomagnetic stimulation.

Stem cell therapies hold potential to stimulate tendon regeneration and homeostasis, which is maintained in response to the native mechanical environment. Activins are members of the mechano-responsive TGF-ß superfamily that participates in the regulation of several downstream biological processes. Mechanosensitive membrane receptors such as activin can be activated in different types of stem cells via magnetic nanoparticles (MNPs) through remote magnetic actuation resulting in cell differentiation. In this work, we target the Activin receptor type IIA (ActRIIA) in human adipose stem cells (hASCs), using anti-ActRIIA functionalized MNPs, externally activated through a oscillating magnetic bioreactor. Upon activation, the phosphorylation of Smad2/3 is induced allowing translocation of the complex to the nucleus, regulating tenogenic transcriptional responses. Our study demonstrates the potential remote activation of MNPs tagged hASCs to trigger the Activin receptor leading to tenogenic differentiation. These results may provide insights toward tendon regeneration therapies.

Magnetic responsive materials modulate the inflammatory profile of IL-1ß conditioned tendon cells.

Tendinopathies represent half of all musculoskeletal injuries worldwide. Inflammatory events contribute to both tendon healing and to tendinopathy conditions but the cellular triggers leading to one or the other are unknown. In previous studies, we showed that magnetic field actuation modulates human tendon cells (hTDCs) behavior in pro-inflammatory environments, and that magnetic responsive membranes could positively influence inflammation responses in a rat ectopic model. Herein, we propose to investigate the potential synergistic action of the magnetic responsive membranes, made of a polymer blend of starch with polycaprolactone incorporating magnetic nanoparticles (magSPCL), and the actuation of pulsed electromagnetic field (PEMF): 5 Hz, 4mT of intensity and 50% of duty cycle, in IL-1ß-treated-hTDCs, and in the immunomodulatory response of macrophages. It was found that the expression of pro-inflammatory (TNFα, IL-6, IL-8, COX-2) and ECM remodeling (MMP-1,-2,-3) markers tend to decrease in cells cultured onto magSPCL membranes under PEMF, while the expression of TIMP-1 and anti-inflammatory genes (IL-4, IL-10) increases. Also, CD16++ and CD206+ macrophages were only found on magSPCL membranes with PEMF application. Magnetic responsive membranes show a modulatory effect on the inflammatory profile of hTDCs favoring anti-inflammatory cues which is also supported by the anti-inflammatory/repair markers expressed in macrophages. These results suggest that magnetic responsive magSPCL membranes can contribute for inflammation resolution acting on both resident cell populations and inflammatory cells, and thus significantly contribute to tendon regenerative strategies. Statement of significance Magnetically-assisted strategies have received great attention in recent years to remotely trigger and guide cell responses. Inflammation plays a key role in tendon healing but persistent pro-inflammatory molecules can contribute to tendon disorders, and therefore provide a therapeutic target for advanced treatments. We have previously reported that magnetic fields modulate the response of human tendon cells (hTDCs) conditioned to pro-inflammatory environments (IL-1ß-treated-hTDCs), and that magnetic responsive membranes positively influence immune responses. In the present work, we combined pulsed electromagnetic field (PEMF) and magnetic responsive membranes to guide the inflammatory profile of IL-1ß-treated-hTDCs and of macrophages. The results showed that the synergistic action of PEMF and magnetic membranes supports the applicability of magnetically actuated systems to regulate inflammatory events and stimulate tendon regeneration.

Human adipose tissue-derived tenomodulin positive subpopulation of stem cells: A promising source of tendon progenitor cells.

Cell-based therapies are of particular interest for tendon and ligament regeneration given the low regenerative potential of these tissues. Adipose tissue is an abundant source of stem cells, which may be employed for the healing of tendon lesions. However, human adult multipotent adipose-derived stem cells (hASCs) isolated from the stromal vascular fraction of adipose tissue originate highly heterogeneous cell populations that hinder their use in specific tissue-oriented applications. In this study, distinct subpopulations of hASCs were immunomagnetic separated and their tenogenic differentiation capacity evaluated in the presence of several growth factors (GFs), namely endothelial GF, basic-fibroblast GF, transforming GF-ß1 and platelet-derived GF-BB, which are well-known regulators of tendon development, growth and healing. Among the screened hASCs subpopulations, tenomodulin-positive cells were shown to be more promising for tenogenic applications and therefore this subpopulation was further studied, assessing tendon-related markers (scleraxis, tenomodulin, tenascin C and decorin) both at gene and protein level. Additionally, the ability for depositing collagen type I and III forming extracellular matrix structures were weekly assessed up to 28 days. The results obtained indicated that tenomodulin-positive cells exhibit phenotypical features of tendon progenitor cells and can be biochemically induced towards tenogenic lineage, demonstrating that this subset of hASCs can provide a reliable source of progenitor cells for therapies targeting tendon regeneration.

[Burns. A retrospective study of the Burn Unit of the Hospital de Santa Maria]. / Queimaduras. Estudo retrospectivo da Unidade de Queimados do Hospital de Santa Maria.

A retrospective analysis was made concerning 291 admissions to the Burn Care Unit from June 1987 to March 1992, due to acute burns. Within that considered period of time there was a progressive increase in the number of admissions. Of the patients admitted, patients 177 men were and 144 women. The average age was 33.7 years. The main etiology was thermal injury. The average time of admission was 24.3 days. The mortality rate was 18%. The observer complications were mainly cutaneous and were seen on patients who were lately debrided.

Optimization of a chromatographic stationary phase based on gellan gum using central composite design.

To develop a new stationary phase of easy production, low cost, biocompatible, biodegradable and low unspecific adsorption, a three-dimensional network was prepared by combining the natural polysaccharide of gellan with divalent cations. The stability of this cation exchange chromatographic matrix was optimized by using an experimental design tool. The optimal conditions proposed for the gellan gel formulation were 48mM ZnSO4, 0% DMF, 25°C, 0.75% gellan and 0.5h. The applicability of gellan matrix was tested by chromatographic assays with three model proteins (bovine serum albumin (BSA), α-chymotripsin and lysozyme). The results showed that the retention occurred in function of the net charge of each protein in MES buffer pH 6.2 and the elution was performed by increase of ionic strength to 750mM NaCl in MES buffer pH 6.2. Lysozyme was the more retained protein due to its positive charge more effective than α-chymotripsin, while BSA did not interact with the matrix due to its negative charge at these conditions. Dynamic binding capacity assays were accomplished to characterize this matrix and to compare with commercial resins. The values of dynamic binding capacity from gellan gel were 3.9mg/mL and 17.4mg/mL, at 10% and 50% of breakthrough, respectively. In this way, gellan gel might be a promising chromatographic matrix to explore ionic interactions and to be applied in different purification strategies, getting the best benefit from its use at low cost.