Cyclic Tensile Strain Enhances Osteogenesis and Angiogenesis in Mesenchymal Stem Cells from Osteoporotic Donors

We have shown that the uniaxial cyclic tensile strain of magnitude 10% promotes and enhances osteogenesis of human mesenchymal stem cells (hMSC) and human adipose-derived stem cells (hASC) from normal, nonosteoporotic donors. In the present study, MSC from osteoporotic donors were analyzed for changes in mRNA expression in response to 10% uniaxial tensile strain to identify potential mechanisms underlying the use of this mechanical loading paradigm for prevention and treatment of osteoporosis. Human MSC isolated from three female, postmenopausal osteoporotic donors were analyzed for their responses to mechanical loading using microarray analysis of over 47,000 gene probes. Human MSC were seeded in three-dimensional collagen type I constructs to mimic the organic extracellular matrix of bone and 10% uniaxial cyclic tensile strain was applied to promote osteogenesis. Seventy-nine genes were shown to be regulated within hMSC from osteoporotic donors in response to 10% cyclic tensile strain. Upregulation of six genes were further confirmed with real-time RT-PCR: jun D proto-oncogene (JUND) and plasminogen activator, urokinase receptor (PLAUR), two genes identified as potential key molecules from network analysis; phosphoinositide-3-kinase, catalytic, delta polypeptide (PIK3CD) and wingless-type MMTV integration site family, member 5B (WNT5B), two genes with known importance in bone biology; and, PDZ and LIM domain 4 (PDLIM4) and vascular endothelial growth factor A (VEGFA), two genes that we have previously shown are significantly regulated in hASC in response to this mechanical stimulus. Function analysis indicated that 10% cyclic tensile strain induced expression of genes associated with cell movement, cell proliferation, and tissue development, including development in musculoskeletal and cardiovascular systems. Our results demonstrate that hMSC from aged, osteoporotic donors are capable of enhanced osteogenic differentiation in response to 10% cyclic tensile strain with significant increases in the expression of genes associated with enhanced cell proliferation, musculoskeletal development, and angiogenesis. Surprisingly, cyclic tensile strain of magnitude 10% not only enhanced osteogenesis in hMSC from osteoporotic donors, but also enhanced expression of angiogenic factors. Better understanding and methodologies to promote osteogenesis in hMSC from elderly, osteoporotic donors may greatly facilitate achieving long-term success in bone regeneration and functional bone tissue engineering for this ever-growing patient population

Translation of remote control regenerative technologies for bone repair

The role of biomechanical stimuli, or mechanotransduction, in normal bone homeostasis and repair is understood to facilitate effective osteogenesis of mesenchymal stem cells (MSCs) in vitro. Mechanotransduction has been integrated into a multitude of in vitro bone tissue engineering strategies and provides an effective means of controlling cell behaviour towards therapeutic outcomes. However, the delivery of mechanical stimuli to exogenous MSC populations, post implantation, poses a significant translational hurdle. Here, we describe an innovative bio-magnetic strategy, MICA, where magnetic nanoparticles (MNPs) are used to remotely deliver mechanical stimuli to the mechano-receptor, TREK-1, resulting in activation and downstream signalling via an external magnetic array. In these studies, we have translated MICA to a pre-clinical ovine model of bone injury to evaluate functional bone repair. We describe the development of a magnetic array capable of in vivo MNP manipulation and subsequent osteogenesis at equivalent field strengths in vitro. We further demonstrate that the viability of MICA-activated MSCs in vivo is unaffected 48 hrs post implantation. We present evidence to support early accelerated repair and preliminary enhanced bone growth in MICA-activated defects within individuals compared to internal controls. The variability in donor responses to MICA-activation was evaluated in vitro revealing that donors with poor osteogenic potential were most improved by MICA-activation. Our results demonstrate a clear relationship between responders to MICA in vitro and in vivo. These unique experiments offer exciting clinical applications for cell-based therapies as a practical in vivo source of dynamic loading, in real-time, in the absence of pharmacological agents

Hybrid learning of vessel segmentation in retinal images

© 2021, ECTI Association. All rights reserved. In this paper, a novel technique of vessel segmentation in retinal images using a hybrid learning based approach is proposed. Unlike most other existing methods, a double-layer segmentation technique combining supervised and instance learning steps is introduced to enhance a sensitivity score of segmenting retinal blood vessels. The supervised learning based approach alone may not cope with unseen patterns caused by intrinsic variations in shapes, sizes, and color intensities of blood vessels across different retinal images. Thus, in the proposed hybrid learning solution, the supervised learning part is adopted to compute initial seeds of segmented vessels. They are then fed into the instance learning part as an initial foreground to further learn specific characteristics of vessels in each individual image. In the supervised learning step, the support vector machine (SVM) is applied on three types of features including green intensity, line operators, and Gabor filters. An iterative graph cut is adopted in the instance learning step, together with the pre-processing of morphological operations and the watershed algorithm. The proposed method is evaluated using two well-known datasets, DRIVE and STARE. It shows promising sensitivity scores of 82.6% and 82.0% on the DRIVE and STARE datasets respectively, and outperforms other existing methods in the literature

Water-soluble Cu²⁺-fluorescent sensor based on core-substituted naphthalene diimide and its application in drinking water analysis and live cell imaging

Water-soluble naphthalene diimide based fluorescent chemosensor, N1, was designed for Cu2+ recognition. The sensor exhibited significant fluorescence modulation and chromogenic change with high Cu2+ sensitivity and selectivity over interfering metal ions. The sensor was able to efficiently monitor Cu2+ in 100% aqueous buffer solution with a low detection limit of 0.7 ppb which is much lower than the recommended value in drinking water by the United States Environmental Protection Agency (U.S. EPA) and the World Health Organization (WHO). The complex formation of N1 with Cu2+ was found to be 1:1 N1-Cu2+ by Job's plot analysis. Furthermore, the sensor was highly tolerant to interference from a matrix of real samples such as drinking water and human liver carcinoma cell line

Water-soluble Cu2+-fluorescent sensor based on core-substituted naphthalene diimide and its application in drinking water analysis and live cell imaging

Water-soluble naphthalene diimide based fluorescent chemosensor, N1, was designed for Cu2+ recognition. The sensor exhibited significant fluorescence modulation and chromogenic change with high Cu2+ sensitivity and selectivity over interfering metal ions. The sensor was able to efficiently monitor Cu2+ in 100% aqueous buffer solution with a low detection limit of 0.7 ppb which is much lower than the recommended value in drinking water by the United States Environmental Protection Agency (U.S. EPA) and the World Health Organization (WHO). The complex formation of N1 with Cu2+ was found to be 1:1 N1-Cu2+ by Job's plot analysis. Furthermore, the sensor was highly tolerant to interference from a matrix of real samples such as drinking water and human liver carcinoma cell line

Cyclic Tensile Strain Enhances Osteogenesis and Angiogenesis in Mesenchymal Stem Cells from Osteoporotic Donors

We have shown that the uniaxial cyclic tensile strain of magnitude 10% promotes and enhances osteogenesis of human mesenchymal stem cells (hMSC) and human adipose-derived stem cells (hASC) from normal, nonosteoporotic donors. In the present study, MSC from osteoporotic donors were analyzed for changes in mRNA expression in response to 10% uniaxial tensile strain to identify potential mechanisms underlying the use of this mechanical loading paradigm for prevention and treatment of osteoporosis. Human MSC isolated from three female, postmenopausal osteoporotic donors were analyzed for their responses to mechanical loading using microarray analysis of over 47,000 gene probes. Human MSC were seeded in three-dimensional collagen type I constructs to mimic the organic extracellular matrix of bone and 10% uniaxial cyclic tensile strain was applied to promote osteogenesis. Seventy-nine genes were shown to be regulated within hMSC from osteoporotic donors in response to 10% cyclic tensile strain. Upregulation of six genes were further confirmed with real-time RT-PCR: jun D proto-oncogene (JUND) and plasminogen activator, urokinase receptor (PLAUR), two genes identified as potential key molecules from network analysis; phosphoinositide-3-kinase, catalytic, delta polypeptide (PIK3CD) and wingless-type MMTV integration site family, member 5B (WNT5B), two genes with known importance in bone biology; and, PDZ and LIM domain 4 (PDLIM4) and vascular endothelial growth factor A (VEGFA), two genes that we have previously shown are significantly regulated in hASC in response to this mechanical stimulus. Function analysis indicated that 10% cyclic tensile strain induced expression of genes associated with cell movement, cell proliferation, and tissue development, including development in musculoskeletal and cardiovascular systems. Our results demonstrate that hMSC from aged, osteoporotic donors are capable of enhanced osteogenic differentiation in response to 10% cyclic tensile strain with significant increases in the expression of genes associated with enhanced cell proliferation, musculoskeletal development, and angiogenesis. Surprisingly, cyclic tensile strain of magnitude 10% not only enhanced osteogenesis in hMSC from osteoporotic donors, but also enhanced expression of angiogenic factors. Better understanding and methodologies to promote osteogenesis in hMSC from elderly, osteoporotic donors may greatly facilitate achieving long-term success in bone regeneration and functional bone tissue engineering for this ever-growing patient population