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Mechano-Hypoxia Conditioning of Engineered Human Meniscus

ABSTRACT: Meniscus fibrochondrocytes (MFCs) experience simultaneous hypoxia and mechanical loading in the knee, conditions that have promising applications in human meniscus tissue engineering. We hypothesized that “mechano-hypoxia conditioning,” using mechanical loading such as dynamic compression (DC) and cyclic hydrostatic pressure (CHP), would enhance development of human meniscus fibrocartilage extracellular matrix in vitro. MFCs from inner human meniscus surgical discards were pre-cultured on porous type I collagen scaffolds with TGF-β3 supplementation to form baseline tissues with newly-formed matrix. They were then treated with DC or CHP under hypoxia (HYP, 3% O2) for 5 days. DC was the more effective load regime, and combined HYP/DC enhanced gene expression of fibrocartilage precursors. The individual treatments of DC and HYP regulated thousands of genes and combined in an overwhelmingly additive rather than synergistic manner. Baseline tissues were then treated with a short course of DC (5 vs 60 minutes, 10-20% vs 30-40% strain) with different pre-culture durations (3 vs 6 weeks). Longer courses of loading had diminishing returns in terms of gene regulation. There was a dose-effect for higher DC strains, whereas outcomes were mixed for different MFC donors in pre-culture durations. Finally, baseline tissues were conditioned for 3 weeks with mechano-hypoxia conditioning to assess mechanical and protein-level outcomes. There were 1.8 to 5.1-fold gains in the dynamic modulus relative to baseline in HYP/DC, but matrix outcomes were equal or inferior to static controls. Long-term mechano-hypoxia conditioning was effective in suppressing hypertrophic markers (e.g., COL10A1 10-fold suppression vs static/normoxia). Applied appropriately, mechano-hypoxia conditioning can support meniscus fibrocartilage development in vitro and may be useful as a strategy for developing non-hypertrophic articular cartilage using mesenchymal stem cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE180467 | GEO | 2021/08/23

REPOSITORIES: GEO

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Project description:The pathophysiology of the osteomalacia in X-linked hypophosphatemia is uncertain. In this project, genomic DNA microarrays were used to identify novel genes with abnormal mRNA expression levels in mice with the dominant Hyp mutation of the Phex gene. Femoral shafts from five-week-old C57BL/6J mice, male and female, normal and Hyp (hemizygous male and heterozygous female), were flushed with saline to remove the marrow. RNA was extracted from each bone, pooled between two mice for each array, processed to cRNA, and hybridized to Affymetrix Mouse 430 2.0 GeneChip microarrays with probe sets for 45,101 genes. Twenty microarrays (40 mice) were done with 5 arrays for each treatment group (normal male, Hyp male, normal female and Hyp female). For each gene, factorial analysis of variance was performed for the main effects of genotype (normal vs. Hyp), sex (male vs. female), and genotype-by-sex interaction. The mRNA levels for 54 % of the genes on each array were scored as present. At P < 0.01, 2,635 genes were significant for genotype, 1,488 for sex, and 509 for genotype-by-sex interaction. There were two probes sets for the Phex gene. Probe 1450445, at the 3’ end of the coding sequence, was low in normal samples (246 ± 37 (10), mean ± SEM (n)) and absent in Hyp samples. Probe 1421979, at the far 3’ end of the untranslated region of the cDNA, 3,000 base pairs from the coding sequence, was high in normal mice (3,915 ± 315 (10); 8x brighter than the average gene), undetectable in Hyp males, and 725 ± 93 (5) in Hyp females. Both probe sets were scored as absent in kidney tissue. In Hyp bone, male and female, there was significant down-regulation of markers of osteoblasts and bone matrix synthesis with significant up-regulation of markers of blood vessel formation and cytoskeleton. No prominent skeletal gene was up-regulated in Hyp to attempt to compensate for the low skeletal mineralization. The genes with significant genotype-by-sex interaction did not show a marked fold difference between male and female Hyp mice. In conclusion, male and female Hyp mice showed similar depression of mRNA levels of genes related to bone synthesis in the femoral shaft. There was a high signal level from probes for a sequence in the 3’ untranslated region of the Phex gene of normal, but not Hyp, mice, suggesting the need for further study of the molecular organization of this gene. Keywords: 2x2 factorial design with complete blocks

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Mechano-Hypoxia Conditioning of Engineered Human Meniscus

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