Low back pain is a common ailment that affects millions of individuals each year and is linked to degeneration of the intervertebral discs in the spine. Intervertebral disc degeneration is known to result from an imbalance in anabolic and catabolic activity by disc cells. Due to the avascular nature of the intervertebral disc, oxygen deficiency may occur in the central nucleus pulposus (NP). The resulting hypoxia affects matrix regulation and energy metabolism of disc cells, although the mechanisms are not fully understood. This study investigates in vitro glucose consumption and gene expression by NP cells over time under varying oxygen tensions. Notochordal porcine NP cells were cultured in agarose discs at 21, 5, or 1% oxygen tension for 1, 5, or 10 days. The expression of 10 key matrix genes, as well as Brachyury (T), by NP cells was analyzed using RT-PCR. Glucose consumption was measured using a two-point method. Results show that culture time and oxygen tension significantly affect glucose consumption rates by porcine NP cells. There were also significant changes in T expression based on oxygen level and culture time. The 1% oxygen tension had a significantly higher T expression on day 10 than the other two groups, which may indicate a better maintenance of the notochordal phenotype. MMP 1 and 13 expression increased over time for all groups, while only the 5% group showed an increase over time for MMP 3. TIMP expression followed the direction of MMPs but to a lesser magnitude. Five percent and twenty-one percent oxygen tensions led to decreases in anabolic gene expression while 1% led to increases. Oxygen concentration and culture time significantly impacted glucose consumption rate and the gene expression of matrix regulatory genes with hypoxic conditions most accurately maintaining the proper NP phenotype. This information is valuable not only for understanding disc pathophysiology, but also for harnessing the potential of notochordal NP cells in therapeutic applications.
Articular cartilage degeneration and traumatic cartilage defects are common disorders causing pain and disability. Many strategies were developed throughout years to address these problems. Tissue engineering approaches offer several promising solutions. Articular hyaline cartilage has very complex structure and follows a multi-layer architecture. In this study, we developed a 4-layers scaffold mimicking the fibers orientation observed within the cartilage extra-cellular matrix (ECM). Bone and cartilage microparticles were incorporated in the first and second layers, respectively, to direct the differentiation of stem cells toward subchondral bone and cartilage phenotype. The 2 upper layers were designed with random (layer 3) and aligned (layer 4) electrospun nanofibers in an attempt to mimic hyaline articular cartilage ECM orientation. Histological analysis of the scaffold showed a continuous and homogeneous structure. Moreover, we confirmed the presence of cartilage and bone microparticles in the gelatin foam-based layers (layer 1 and 2). Scanning electron microscope (SEM) confirmed the tubular, vertical, morphology of the first and second layers, thereby mimicking as intended the native hyaline cartilage structure. Water uptake and degradation rate of our scaffold appeared suitable for our application, with many options for tunability. Finally, we demonstrated that the scaffolds were biocompatible, as it promoted the survival and attachment of MIAMI cells in vitro. In this study, we described the first phases of the development of a multi-layered scaffold designed to mimic the native architecture of articular hyaline cartilage. With further refinements and testing, we hope that this strategy will pave the way for potential new advances in the field of osteochondral repair. Keywords: Electrospinning, gelatin, human tissues, hyaline cartilage, MIAMI cells, multi-layered scaffold, nanofibers, tissue engineering.
Regenerative medicine (RM) possesses the ability to repair injured as well as aging cells, tissues and organs. This review discusses the recent advances, future prospects and challenges in the field of RM mainly the stem cell therapy in degenerative retinal diseases such as age related macular degeneration (AMD), retinitis pigmentosa (RP) and Stargardt disease (STGD). Stem cell lines like retinal progenitor cells, induced pluripotent stem cells, mesenchymal stem cells, embryonic stem cells and very small embryonic-like stem cells have potential application in the degenerative retinal diseases where they have the potency to regenerate the injured and damaged photoreceptors and retinal neurons ultimately restoring and enhancing the visual functions. Stem cell transplantation for AMD, RP and STGD is currently transforming from bench side research to bedside which may eventually allow the progress of the more advanced therapies. In future, stem cell therapy could be combined with bioengineered products and small molecules to produce novel therapies in the field of ophthalmology particularly in terms of visual recovery to fight against blindness. Keywords: Age-related macular degeneration, Retinitis Pigmentosa, Regenerative Medicine, Stargardt disease, Stem Cells.
Background: Demineralized bone matrix is used clinically to stimulate bone repair in orthopedics and dentistry. Demineralized bone matrix has osteoconductive and osteoinductive properties that contribute to its efficacy in new bone formation. However, ethylene-oxide sterilization in the clinical setting diminishes this efficacy. Studies using intramuscular implantation of demineralized bone matrix in rats demonstrate deterioration of its osteoconductive properties by ethylene oxide sterilization. Objective: The goal of this study is to investigate whether treatment with chitosan which is osteoconductive will improve the osteoconductivity of ethylene-oxide sterilized demineralized bone matrix and thus restore the original osteogenetic efficacy of demineralized bone matrix. Methods: We implanted normal and modified demineralized bone matrix implants into the abdominal muscles of Sprague-Dawley rats. New bone growth in implants, harvested at 4 weeks, was determined by mineral content, bone alkaline phosphatase activity, and histology. Results: The unmodified demineralized bone matrix implants demonstrated extensive areas of trabecular bone containing osteoblasts and osteocytes. Ethylene-oxide sterilization of demineralized bone matrix resulted in fibrosis, rather than new bone formation, in the intramuscular implantation site in the rat. Treatment of ethylene-oxide sterilized demineralized bone matrix with chitosan restored mineral content and bone alkaline phosphatase activity of these samples to control levels. Conclusion: Treatment of ethylene-oxide sterilized demineralized bone matrix with chitosan restores the osteoconductive properties completely so that new bone formation is comparable to that of nonsterilized demineralized bone matrix. Thus chitosan treatment of ethylene-oxide sterilized demineralized bone matrix may be used to restore the clinical efficacy of demineralized bone matrix after sterilization. Keywords: Bone alkaline phosphatase, bone morphogenetic protein, chitosan, demineralized bone matrix, ethyleneoxide sterilization, mineralization, osteoconductive, osteoinductive.
