Injectable biomaterials as minimal invasive strategy towards soft tissue regeneration-an overview

Soft tissue engineering has been gaining increasing interest as an approach to overcome the limitations posed by current clinical procedures such as invasiveness of the surgery, post-operative complications and volume loss. Soft tissue damage occurs either due to congenital malformation, trauma/disease or surgical resection. Through the use of autologous cells, such as mesenchymal stem cells, combined with a biomaterial acting as a support, biological substitutes can be developed. A promising pathway in terms of delivery of these engineered constructs is the use of an injectable system, able to provide a minimally invasive approach. Advances have been made in the development of biocompatible biomaterials able to induce soft tissue regeneration. The present review provides an overview of fillers used in the clinic as well as a non-exhaustive overview of all injectable systems reported for soft tissue engineering. A particular focus is placed on the benefits and drawbacks of the biomaterials and the underlying polymerisation strategy. Furthermore, focus is placed on the mechanical properties of the systems

Indirect versus direct 3D printing of hydrogel scaffolds for adipose tissue regeneration

There exists a need for an innovative reconstructive approach for breast reconstruction, tackling current drawbacks and limitations present in the clinic. In this respect, adipose tissue engineering could offer a promising alternative. We have previously shown that methacrylamide-functionalized gelatin scaffolds are suitable to support the adhesion of adipose tissue-derived stem cells as well as their subsequent differentiation into the adipogenic lineage. The current paper aims to compare different techniques to produce such scaffolds including direct versus indirect 3D printing. Extrusion-based (direct) 3D printing was compared to indirect 3D printing exploiting a polylactic acid (PLA) sacrificial mould, thereby focussing on the physico-chemical characteristics of the obtained scaffolds. The results indicate that similar properties can be achieved irrespective of the technique applied. It can therefore be concluded that indirect 3D printing could offer some benefits over direct additive manufacturing (AM) as a more complex design can be created while materials that were previously unsuited for direct printing because of limitations associated with their characteristics (e.g. low viscosity), could potentially be applied as starting materials for indirect 3D printing to generate porous constructs with full control over their design

NEK1 variants confer susceptibility to amyotrophic lateral sclerosis

To identify genetic factors contributing to amyotrophic lateral sclerosis (ALS), we conducted whole-exome analyses of 1,022 index familial ALS (FALS) cases and 7,315 controls. In a new screening strategy, we performed gene-burden analyses trained with established ALS genes and identified a significant association between loss-of-function (LOF) NEK1 variants and FALS risk. Independently, autozygosity mapping for an isolated community in the Netherlands identified a NEK1 p.Arg261His variant as a candidate risk factor. Replication analyses of sporadic ALS (SALS) cases and independent control cohorts confirmed significant disease association for both p.Arg261His (10,589 samples analyzed) and NEK1 LOF variants (3,362 samples analyzed). In total, we observed NEK1 risk variants in nearly 3% of ALS cases. NEK1 has been linked to several cellular functions, including cilia formation, DNA-damage response, microtubule stability, neuronal morphology and axonal polarity. Our results provide new and important insights into ALS etiopathogenesis and genetic etiology

A Novel Classification of Lung Cancer into Molecular Subtypes

The remarkably heterogeneous nature of lung cancer has become more apparent over the last decade. In general, advanced lung cancer is an aggressive malignancy with a poor prognosis. The discovery of multiple molecular mechanisms underlying the development, progression, and prognosis of lung cancer, however, has created new opportunities for targeted therapy and improved outcome. In this paper, we define “molecular subtypes” of lung cancer based on specific actionable genetic aberrations. Each subtype is associated with molecular tests that define the subtype and drugs that may potentially treat it. We hope this paper will be a useful guide to clinicians and researchers alike by assisting in therapy decision making and acting as a platform for further study. In this new era of cancer treatment, the ‘one-size-fits-all’ paradigm is being forcibly pushed aside—allowing for more effective, personalized oncologic care to emerge

Identification of Serpinb6b as a species-specific mouse granzyme A inhibitor suggests functional divergence between human and mouse granzyme A

Background: There are conflicting reports on the ability of granzyme A (GzmA) to kill cells. Results: Substrate specificity mapping of human and mouse GzmA was used to identify Serpinb6b as a mouse-specific GzmA inhibitor. Conclusion: Mouse but not human GzmA is controlled by an intracellular inhibitor. Significance: The GzmA debate is partly explained by species-specific divergence in cytotoxicity. The granzyme family serine proteases are key effector molecules expressed by cytotoxic lymphocytes. The physiological role of granzyme (Gzm) A is controversial, with significant debate over its ability to induce death in target cells. Here, we investigate the natural inhibitors of GzmA. We employed substrate phage display and positional proteomics to compare substrate specificities of mouse (m) and human (h) GzmA at the peptide and proteome-wide levels and we used the resulting substrate specificity profiles to search for potential inhibitors from the intracellular serpin family. We identified Serpinb6b as a potent inhibitor of mGzmA. Serpinb6b interacts with mGzmA, but not hGzmA, with an association constant of 1.9 +/- 0.8 x 10(5) m(-1) s(-1) and a stoichiometry of inhibition of 1.8. Mouse GzmA is over five times more cytotoxic than hGzmA when delivered into P815 target cells with streptolysin O, whereas transfection of target cells with a Serpinb6b cDNA increases the EC50 value of mGzmA 13-fold, without affecting hGzmA cytotoxicity. Unexpectedly, we also found that Serpinb6b employs an exosite to specifically inhibit dimeric but not monomeric mGzmA. The identification of an intracellular inhibitor specific for mGzmA only indicates that a lineage-specific increase in GzmA cytotoxic potential has driven cognate inhibitor evolution

Additive manufacturing of photo-crosslinked gelatin scaffolds for adipose tissue engineering

There exists a clear clinical need for adipose tissue reconstruction strategies to repair soft tissue defects which outperform the currently available approaches. In this respect, additive manufacturing has shown to be a promising alternative for the development of larger constructs able to support adipose tissue engineering. In the present work, a thiol-ene photo-click crosslinkable gelatin hydrogel was developed which allowed extrusion-based additive manufacturing into porous scaffolds. To this end, norbornenefunctionalized gelatin (Gel-NB) was combined with thiolated gelatin (Gel-SH). The application of a macromolecular gelatin-based thiolated crosslinker holds several advantages over conventional crosslinkers including cell-interactivity, less chance at phase separation between scaffold material and crosslinker and the formation of a more homogeneous network. Throughout the paper, these photo click scaffolds were benchmarked to the conventional methacrylamide-modified gelatin (Gel-MA). The results indicated that stable scaffolds could be realized which were further characterized physicochemically by performing swelling, mechanical and in vitro biodegradability assays. Furthermore, the seeded adipose tissue-derived stem cells (ASCs) remained viable (>90%) up to 14 days and were able to proliferate. In addition, the cells could be differentiated into the adipogenic lineage on the photo click crosslinked scaffolds, thereby performing better than the cells supported by the frequently reported Gel-MA scaffolds. As a result, the developed photo-click crosslinked scaffolds can be considered a promising candidate towards adipose tissue engineering and a valuable alternative for the omnipresent Gel-MA. Statement of Significance The field of adipose tissue engineering has emerged as a promising strategy to repair soft tissue defects. Herein, Gel-NB/Gel-SH gelatin-based hydrogel scaffolds were produced using extrusion-based additive manufacturing. Using a cell-interactive, thiolated gelatin crosslinker, a homogeneous network was formed and the risk of phase separation between norbornene-modified gelatin and macromolecular crosslinkers was reduced. UV-induced crosslinking of these materials is based on step growth polymerization which requires less free radicals to enable polymerization. Our results demonstrated the potential of the developed scaffolds, due to their favourable physico-chemical characteristics as well as their adipogenic differentiation potential when benchmarked to Gel-MA scaffolds. Hence, the hydrogels could be of great interest towards future development of adipose tissue constructs and tissue engineering in general