HOTAIR beyond repression: In protein degradation, inflammation, DNA damage response, and cell signaling.

Long noncoding RNAs (lncRNAs) are pervasively transcribed from the mammalian genome as transcripts that are usually >200 nucleotides long. LncRNAs generally do not encode proteins but are involved in a variety of physiological processes, principally as epigenetic regulators. HOX transcript antisense intergenic RNA (HOTAIR) is a well-characterized lncRNA that has been implicated in several cancers and in various other diseases. HOTAIR is a repressor lncRNA and regulates various repressive chromatin modifications. However, recent studies have revealed additional functions of HOTAIR in regulation of protein degradation, microRNA (miRNA) sponging, NF-κB activation, inflammation, immune signaling, and DNA damage response. Herein, we have summarized the diverse functions and modes of action of HOTAIR in protein degradation, inflammation, DNA repair, and diseases, beyond its established functions in gene silencing.

Selective adhesion and mineral deposition by osteoblasts on carbon nanofiber patterns.

In an effort to develop better orthopedic implants, osteoblast (bone-forming cells) adhesion was determined on microscale patterns (30 microm lines) of carbon nanofibers placed on polymer substrates. Patterns of carbon nanofibers (CNFs) on a model polymer (polycarbonate urethane [PCU]) were developed using an imprinting method that placed CNFs in selected regions. Results showed the selective adhesion and alignment of osteoblasts on CNF patterns placed on PCU. Results also showed greater attraction forces between fibronectin and CNF (compared with PCU) patterns using atomic force microscope force-displacement curves. Because fibronectin is a protein that mediates osteoblast adhesion, these results provide a mechanism of why osteoblast adhesion was directed towards CNF patterns. Lastly, this study showed that the directed osteoblast adhesion on CNF patterns translated to enhanced calcium phosphate mineral deposition along linear patterns of CNFs on PCU. Since CNFs are conductive materials, this study formulated substrates that through electrical stimulation could be used in future investigations to further promote osteoblasts to deposit anisotropic patterns of calcium-containing mineral similar to that observed in long bones.

Increased osteoblast functions on theta + delta nanofiber alumina.

Nanophase materials, or materials with grain sizes less than 100 nm in at least one direction, are promising materials for various implant applications since our tissues are composed of nanometer components (i.e., proteins and/or inorganics). Specifically, bone is comprised of nanostructured hydroxyapatite and collagen fibers which continuously provide an extracellular matrix surface to bone-forming cells (osteoblasts) with a high degree of nanometer roughness. Despite this fact, materials currently utilized for orthopedic implants, whether metallic or ceramic, have constituent grain sizes in the non-biologically inspired micron regime. For this reason, the objective of the present in vitro study was to determine osteoblast functions on one classification of nanomaterials for orthopedic applications: nanofiber alumina. Various crystalline forms of nanofiber alumina were tested in this study. To obtained different crystalline structured nanofiber alumina, boehmite nanofiber alumina was sintered at either 400 degrees C, 600 degrees C, 800 degrees C, 1000 degrees C, or 1200 degrees C for 2 h in air. X-ray diffraction results provided evidence that boehmite nanofiber alumina remained boehmite when sintered at 400 degrees C but changed crystalline phases to gamma, gamma + delta, theta + delta, and alpha when sintered at 600 degrees C, 800 degrees C, 1000 degrees C, and 1200 degrees C, respectively. Moreover, compared to any other alumina formulation tested in this study, osteoblast functions (as measured by alkaline phosphatase activity and calcium deposition) were the greatest on theta + delta crystalline phase nanofiber alumina after 14 days of culture. Boehmite had the next greatest amount of calcium deposition by osteoblasts followed by gamma + delta. Gamma crystalline phase then followed and was greater than alpha crystalline phase nanofiber alumina which promoted osteoblast functions the least of all the compacts with the exception of borosilicate glass (reference substrate). For this reason, this study suggests that theta+delta nanofiber alumina should be further investigated in orthopedic applications.

Nanometer surface roughness increases select osteoblast adhesion on carbon nanofiber compacts.

Carbon nanofibers have exceptional theoretical mechanical properties (such as low weight-to-strength ratios) that, along with possessing nanoscale fiber dimensions similar to crystalline hydroxyapatite found in bone, suggest strong possibilities for use as an orthopedic/dental implant material. To determine, for the first time, cytocompatibility properties pertinent for bone prosthetic applications, osteoblast (bone-forming cells), fibroblast (cells contributing to callus formation and fibrous encapsulation events that result in implant loosening), chondrocyte (cartilage-forming cells), and smooth muscle cell (for comparison purposes) adhesion were determined on carbon nanofibers in the present in vitro study. Results provided evidence that, compared to conventional carbon fibers, nanometer dimension carbon fibers promoted select osteoblast adhesion. Moreover, adhesion of other cells was not influenced by carbon fiber dimensions. In fact, smooth muscle cell, fibroblast, and chondrocyte adhesion decreased with an increase in either carbon nanofiber surface energy or simultaneous change in carbon nanofiber chemistry. To determine properties that selectively enhanced osteoblast adhesion, similar cell adhesion assays were performed on polymer (specifically, poly-lactic-co-glycolic; PLGA) casts of carbon fiber compacts previously tested. Compared to PLGA casts of conventional carbon fibers, results provided the first evidence of enhanced select osteoblast adhesion on PLGA casts of nanophase carbon fibers. The summation of these results demonstrate that due to a high degree of nanometer surface roughness, carbon fibers with nanometer dimensions may be optimal materials to selectively increase osteoblast adhesion necessary for successful orthopedic/dental implant applications.

Nano-biotechnology: carbon nanofibres as improved neural and orthopaedic implants.

For the continuous monitoring, diagnosis, and treatment of neural tissue, implantable probes are required. However, sometimes such neural probes (usually composed of silicon) become encapsulated with non-conductive, undesirable glial scar tissue. Similarly for orthopaedic implants, biomaterials (usually titanium and/or titanium alloys) often become encapsulated with undesirable soft fibrous, not hard bony, tissue. Although possessing intriguing electrical and mechanical properties for neural and orthopaedic applications, carbon nanofibres/nanotubes have not been widely considered for these applications to date. The present work developed a carbon nanofibre reinforced polycarbonate urethane (PU) composite in an attempt to determine the possibility of using carbon nanofibres (CNs) as either neural or orthopaedic prosthetic devices. Electrical and mechanical characterization studies determined that such composites have properties suitable for neural and orthopaedic applications. More importantly, cell adhesion experiments revealed for the first time the promise these materials have to increase neural (nerve cell) and osteoblast (bone-forming cell) functions. In contrast, functions of cells that contribute to glial scar-tissue formation for neural prostheses (astrocytes) and fibrous-tissue encapsulation events for bone implants (fibroblasts) decreased on PU composites containing increasing amounts of CNs. In this manner, this study provided the first evidence of the future that CN formulations may have towards interacting with neural and bone cells which is important for the design of successful neural probes and orthopaedic implants, respectively.

Osteoblast function on nanophase alumina materials: Influence of chemistry, phase, and topography.

Alumina is a material that has been used in both dental and orthopedic applications. It is with these uses in mind that osteoblast (bone-forming cell) function on alumina of varying particulate size, chemistry, and phase was tested in order to determine what formulation might be the most beneficial for bone regeneration. Specifically, in vitro osteoblast adhesion, proliferation, intracellular alkaline phosphatase activity, and calcium deposition was observed on delta-phase nanospherical, alpha-phase conventional spherical, and boehmite nanofiber alumina. Results showed for the first time increased osteoblast functions on the nanofiber alumina. Specifically, a 16% increase in osteoblast adhesion over nanophase spherical alumina and a 97% increase over conventional spherical alumina were found for nanofiber alumina after 2 h. A 29% increase in cell number after 5 days and up to a 57% greater amount of calcium was found on the surface of the nanofiber alumina compared with other alumina surfaces. Some of the possible explanations for such enhanced osteoblast behavior on nanofiber alumina may be attributed to chemistry, crystalline phase, and topography. Increased osteoblast function on nanofiber alumina suggests that it may be an ideal material for use in orthopedic and dental applications.

Selective bone cell adhesion on formulations containing carbon nanofibers.

Bone cell adhesion on novel carbon nanofibers and polycarbonate urethane/carbon nanofiber (PCU/CNF) composites is investigated in the present in vitro study. Carbon nanofibers have exceptional theoretical mechanical properties (such as high strength to weight ratios) that, along with possessing nanoscale fiber dimensions similar to crystalline hydroxyapatite found in physiological bone, suggest strong possibilities for use as an orthopedic/dental implant material. The effects of select properties of carbon fibers (specifically, dimension, surface energy, and chemistry) on osteoblast, fibroblast, chondrocyte, and smooth muscle cell adhesion were determined in the present in vitro study. Results provided evidence that smaller-scale (i.e., nanometer dimension) carbon fibers promoted osteoblast adhesion. Adhesion of other cells was not influenced by carbon fiber dimensions. Also, smooth muscle cell, fibroblast, and chondrocyte adhesion decreased with an increase in either carbon nanofiber surface energy or simultaneous change in carbon nanofiber chemistry. Moreover, greater weight percentages of high surface energy carbon nanofibers in the PCU/CNF composite increased osteoblast adhesion while at the same time decreased fibroblast adhesion.

Enhanced functions of osteoblasts on nanometer diameter carbon fibers.

The present in vitro study investigated select functions (specifically, proliferation, synthesis of intracellular proteins, alkaline phosphatase activity, and deposition of calcium-containing mineral) of osteoblasts (the bone-forming cells) cultured on carbon fibers with nanometer dimensions. Carbon fiber compacts were synthesized to possess either nanophase (i.e., dimensions 100 nm or less) or conventional (i.e., dimensions larger than 100 nm) fiber diameters. Osteoblast proliferation increased with decreasing carbon fiber diameters after 3 and 7 days of culture. Moreover, compared to larger-diameter carbon fibers, osteoblasts synthesized more alkaline phosphatase and deposited more extracellular calcium on nanometer-diameter carbon fibers after 7, 14, and 21 days of culture. The results of the present study provided the first evidence of enhanced long-term (in the order of days to weeks) functions of osteoblasts cultured on nanometer-diameter carbon fibers; in this manner, carbon nanofibers clearly represent a unique and promising class of orthopedic/dental implant formulations with improved osseointegrative properties.