Nanofiber-hydrogel composite-mediated angiogenesis for soft tissue reconstruction.

Soft tissue losses from tumor removal, trauma, aging, and congenital malformation affect millions of people each year. Existing options for soft tissue restoration have several drawbacks: Surgical options such as the use of autologous tissue flaps lead to donor site defects, prosthetic implants are prone to foreign body response leading to fibrosis, and fat grafting and dermal fillers are limited to small-volume defects and only provide transient volume restoration. In addition, large-volume fat grafting and other tissue-engineering attempts are hampered by poor vascular ingrowth. Currently, there are no off-the-shelf materials that can fill the volume lost in soft tissue defects while promoting early angiogenesis. Here, we report a nanofiber-hydrogel composite that addresses these issues. By incorporating interfacial bonding between electrospun poly(ε-caprolactone) fibers and a hyaluronic acid hydrogel network, we generated a composite that mimics the microarchitecture and mechanical properties of soft tissue extracellular matrix. Upon subcutaneous injection in a rat model, this composite permitted infiltration of host macrophages and conditioned them into the pro-regenerative phenotype. By secreting pro-angiogenic cytokines and growth factors, these polarized macrophages enabled gradual remodeling and replacement of the composite with vascularized soft tissue. Such host cell infiltration and angiogenesis were also observed in a rabbit model for repairing a soft tissue defect filled with the composite. This injectable nanofiber-hydrogel composite augments native tissue regenerative responses, thus enabling durable soft tissue restoration outcomes.

Myogenic Differentiation of ASCs Using Biochemical and Biophysical Induction.

Adipose-derived stem/stromal cells (ASCs) constitute a very promising source for cell therapy and tissue engineering approaches as they can be easily obtained in large quantities with comparatively minimal patient discomfort. Moreover, ASCs have multilineage differentiation capacity. Among these, differentiation capacity along the myogenic lineage is of particular interest since myogenic precursors are scarce and obtaining a large number of cells from skeletal muscle biopsies is difficult. Here, we describe a method to effectively induce ASC myogenesis through the combination of biochemical (cocktail including 5-azacytidine and horse serum) and biophysical (dynamic culture via uniaxial cyclic strain) stimulation. This method results in multinucleated cells that are positive in myogenic markers including Pax 3/7, desmin, myoD, and myosin heavy chain.

Adipose-derived perivascular mesenchymal stromal/stem cells promote functional vascular tissue engineering for cardiac regenerative purposes.

Cardiac tissue engineering approaches have the potential to regenerate functional myocardium with intrinsic vascular networks. This study compared the relative effects of human adipose-derived stem/stromal cells (hASCs) and human dermal fibroblasts (hDFs) in cocultures with neonatal rat ventricular cardiomyocytes (NRVCMs) and human umbilical vein endothelial cells (HUVECs). At the same ratios of NRVCM:hASC and NRVCM:hDF, the hASC cocultures displayed shorter action potentials and maintained capture at faster pacing rates. Similarly, in coculture with HUVECs, hASC:HUVEC exhibited superior ability to support vascular capillary network formation relative to hDF:HUVEC. Based on these studies, a range of suitable cell ratios were determined to develop a triculture system. Six seeding ratios of NRVCM:hASC:HUVEC were tested and it was found that a ratio of 500:50:25 cells (i.e. 250,000:25,000:12,500 cells/cm2 ) resulted in the formation of robust vascular networks while retaining action potential durations and propagation similar to pure NRVCM cultures. Tricultures in this ratio exhibited an average conduction velocity of 20 ± 2 cm/s, action potential durations at 80% repolarization (APD80 ) and APD30 of 122 ± 5 ms and 59 ± 4 ms, respectively, and maximum capture rate of 7.4 ± 0.6 Hz. The NRVCM control groups had APD80 and APD30 of 120 ± 9 ms and 51 ± 5 ms, with a maximum capture rate of 7.3 ± 0.2 Hz. In summary, the combination of hASCs in the appropriate ratios with NRVCMs and HUVECs can facilitate the formation of densely vascularized cardiac tissues that appear not to impact the electrophysiological function of cardiomyocytes negatively. Copyright © 2017 John Wiley & Sons, Ltd.

Pharmacological, Physiochemical, and Drug-Relevant Biological Properties of Short Chain Fatty Acid Hexosamine Analogues Used in Metabolic Glycoengineering.

In this study, we catalog structure activity relationships (SAR) of several short chain fatty acid (SCFA)-modified hexosamine analogues used in metabolic glycoengineering (MGE) by comparing in silico and experimental measurements of physiochemical properties important in drug design. We then describe the impact of these compounds on selected biological parameters that influence the pharmacological properties and safety of drug candidates by monitoring P-glycoprotein (Pgp) efflux, inhibition of cytochrome P450 3A4 (CYP3A4), hERG channel inhibition, and cardiomyocyte cytotoxicity. These parameters are influenced by length of the SCFAs (e.g., acetate vs n-butyrate), which are added to MGE analogues to increase the efficiency of cellular uptake, the regioisomeric arrangement of the SCFAs on the core sugar, the structure of the core sugar itself, and by the type of N-acyl modification (e.g., N-acetyl vs N-azido). By cataloging the influence of these SAR on pharmacological properties of MGE analogues, this study outlines design considerations for tuning the pharmacological, physiochemical, and the toxicological parameters of this emerging class of small molecule drug candidates.

Oxygen delivery from hyperbarically loaded microtanks extends cell viability in anoxic environments.

Oxygen diffusion limitations within nascent tissue engineered (TE) grafts lead to the development of hypoxic regions, cell death, and graft failure. Previous efforts have been made to deliver oxygen within TE scaffolds, including peroxide-doping, perfluorocarbons, and hyperbaric oxygen therapy, to mitigate these effects and help maintain post transplantation cell viability, but these have suffered from significant drawbacks. Here we present a novel approach utilizing polymeric hollow-core microspheres that can be hyperbarically loaded with oxygen and subsequently provide prolonged oxygen delivery. These oxygen carriers are termed, microtanks. With an interest in orthopedic applications, we combined microtanks within polycaprolactone to form solid phase constructs with oxygen delivery capabilities. The mathematical laws governing oxygen delivery from microtank-loaded constructs are developed along with empirical validation. Constructs achieved periods of oxygen delivery out to 6 days, which was shown to prolong the survival of human adipose derived stem cells (hASCs) and human umbilical vein endothelial cells (HUVECs) as well as to enhance their cellular morphology under anoxic conditions. The results of this study suggest the microtank approach may be a feasible means of maintaining cell viability in TE scaffolds during the critical period of vascularization in vivo.