An official website of the United States government
ObjectiveTo elucidate the role of decorin, a small leucine‐rich proteoglycan, in the degradation of cartilage matrix during the progression of post‐traumatic osteoarthritis (OA). MethodsThree‐month–old decorin‐null (Dcn−/−) and inducible decorin‐knockout (DcniKO) mice were subjected to surgical destabilization of the medial meniscus (DMM) to induce post‐traumaticOA. TheOAphenotype that resulted was evaluated by assessing joint morphology and sulfated glycosaminoglycan (sGAG) staining via histological analysis (n = 6 mice per group), surface collagen fibril nanostructure via scanning electron microscopy (n = 4 mice per group), tissue modulus via atomic force microscopy–nanoindentation (n = 5 or more mice per group) and subchondral bone structure via micro–computed tomography (n = 5 mice per group). Femoral head cartilage explants from wild‐type and Dcn−/−mice were stimulated with the inflammatory cytokine interleukin‐1β (IL‐1β) in vitro (n = 6 mice per group). The resulting chondrocyte response toIL‐1β and release ofsGAGs were quantified. ResultsIn both Dcn−/−and DcniKOmice, the absence of decorin resulted in acceleratedsGAGloss and formation of highly aligned collagen fibrils on the cartilage surface relative to the control (P< 0.05). Also, Dcn−/−mice developed more salient osteophytes, illustrating more severeOA. In cartilage explants treated withIL‐1β, loss of decorin did not alter the expression of either anabolic or catabolic genes. However, a greater proportion ofsGAGs was released to the media from Dcn−/−mouse explants, in both live and devitalized conditions (P< 0.05). ConclusionIn post‐traumaticOA, decorin delays the loss of fragmented aggrecan and fibrillation of cartilage surface, and thus, plays a protective role in ameliorating cartilage degeneration.
more »
« less
Diversity of extracellular matrix morphology in vertebrate skeletal muscle
Abstract Existing data suggest the extracellular matrix (ECM) of vertebrate skeletal muscle consists of several morphologically distinct layers: an endomysium, perimysium, and epimysium surrounding muscle fibers, fascicles, and whole muscles, respectively. These ECM layers are hypothesized to serve important functional roles within muscle, influencing passive mechanics, providing avenues for force transmission, and influencing dynamic shape changes during contraction. The morphology of the skeletal muscle ECM is well described in mammals and birds; however, ECM morphology in other vertebrate groups including amphibians, fish, and reptiles remains largely unexamined. It remains unclear whether a multilayered ECM is a common feature of vertebrate skeletal muscle, and whether functional roles attributed to the ECM should be considered in mechanical analyses of non‐mammalian and non‐avian muscle. To explore the prevalence of a multilayered ECM, we used a cell maceration and scanning electron microscopy technique to visualize the organization of ECM collagen in muscle from six vertebrates: bullfrogs (Lithobates catesbeianus), turkeys (Meleagris gallopavo), alligators (Alligator mississippiensis), cane toads (Rhinella marina), laboratory mice (Mus musculus), and carp (Cyprinus carpio). All muscles studied contained a collagen‐reinforced ECM with multiple morphologically distinct layers. An endomysium surrounding muscle fibers was apparent in all samples. A perimysium surrounding groups of muscle fibers was apparent in all but carp epaxial muscle; a muscle anatomically, functionally, and phylogenetically distinct from the others studied. An epimysium was apparent in all samples taken at the muscle periphery. These findings show that a multilayered ECM is a common feature of vertebrate muscle and suggest that a functionally relevant ECM should be considered in mechanical models of vertebrate muscle generally. It remains unclear whether cross‐species variations in ECM architecture are the result of phylogenetic, anatomical, or functional differences, but understanding the influence of such variation on muscle mechanics may prove a fruitful area for future research.
more »
« less
- Award ID(s):
- 1832795
- PAR ID:
- 10458763
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Morphology
- Volume:
- 281
- Issue:
- 2
- ISSN:
- 0362-2525
- Page Range / eLocation ID:
- p. 160-169
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract BACKGROUNDHaematococcus pluvialis(Hp), a freshwater chlorophyte microalga, is a major natural source of astaxanthin (ASX), a potent antioxidant with anti‐inflammatory, anticarcinogenic and muscle pigmentation properties. However,ASXbioavailability is limited by the rigid cyst wall and, although cell wall rupture improves bioavailability, the free form is unstable under high temperatures,pHextremes, light or oxygen. Encapsulation techniques improveASXstability, making it suitable for functional foods and aquaculture, especially in salmonid feeds where natural pigments are preferred. The present study evaluates the stability of weakenedHp(Hpw) biomass encapsulated in alginate (ALG) via ionic gelation. RESULTSEncapsulation utilizingALGachieved high efficiency (97 ± 2.63%) and loading capacity (32 ± 0.90%), confirming its suitability as a wall material.ALG‐Hpwhydrogels displayed significant color intensity, enhancing potential feed or food hues. Low bulk density (0.59 ± 0.01 g cm−3), moisture content (11.97 ± 0.20%) and water activity (0.28 ± 0.00) suggest minimized oxidation processes. Hydrogels measured 1.30 ± 0.06 mm with a uniform sphericity factor of 0.058 ± 0.03. Confocal laser scanning microscopy confirmed uniformHpwdistribution andscanning electron microscopyrevealed fissure‐free surfaces, ensuring minimal permeability. DPPH (i.e. 2,2‐diphenyl‐1‐picrylhydrazyl) scavenging activity was similar betweenHpwextract (38.32 ± 2.30% to 96.32 ± 0.88%) andALG‐Hpwhydrogels (33.20 ± 1.55% to 93.30 ± 0.44%).ALGIncreasedHpwdecomposition temperature by 40.97 °C. Encapsulation ofHpwinALGsignificantly enhanced the bioaccessibility ofASX. TheALG‐based encapsulation effectively preservedASXstability, retaining over 90% of its content under storage conditions. CONCLUSIONALGis a suitable biopolymer for encapsulatingHpw, preserving antioxidant activity, and enhancing thermal properties, making it valuable for broader applications. © 2025 Society of Chemical Industry.more » « less
-
Summary Steady‐state photosyntheticCO2responses (A/Cicurves) are used to assess environmental responses of photosynthetic traits and to predict future vegetative carbon uptake through modeling. The recent development of rapidA/Cicurves (RACiRs) permits faster assessment of these traits by continuously changing [CO2] around the leaf, and may reveal additional photosynthetic properties beyond what is practical or possible with steady‐state methods.Gas exchange necessarily incorporates photosynthesis and (photo)respiration. Each process was expected to respond on different timescales due to differences in metabolite compartmentation, biochemistry and diffusive pathways. We hypothesized that metabolic lags in photorespiration relative to photosynthesis/respiration andCO2diffusional limitations can be detected by varying the rate of change in [CO2] duringRACiR assays. We tested these hypotheses through modeling and experiments at ambient and 2% oxygen.Our data show that photorespiratory delays cause offsets in predictedCO2compensation points that are dependent on the rate of change in [CO2]. Diffusional limitations may reduce the rate of change in chloroplastic [CO2], causing a reduction in apparentRACiR slopes under highCO2ramp rates.MultirateRACiRs may prove useful in assessing diffusional limitations to gas exchange and photorespiratory rates.more » « less
-
Summary In seed plants, cellulose is synthesized by rosette‐shaped cellulose synthesis complexes (CSCs) that are obligate hetero‐oligomeric, comprising three non‐interchangeable cellulose synthase (CESA) isoforms. The mossPhyscomitrella patenshas rosetteCSCs and sevenCESAs, but its common ancestor with seed plants had rosetteCSCs and a singleCESAgene. Therefore, ifP. patensCSCs are hetero‐oligomeric, thenCSCs of this type evolved convergently in mosses and seed plants. Previous gene knockout and promoter swap experiments showed that PpCESAs from class A (PpCESA3 and PpCESA8) and class B (PpCESA6 and PpCESA7) have non‐redundant functions in secondary cell wall cellulose deposition in leaf midribs, whereas the two members of each class are redundant. Based on these observations, we proposed the hypothesis that the secondary class A and class B PpCESAs associate to form hetero‐oligomericCSCs. Here we show that transcription of secondary class APpCESAs is reduced when secondary class BPpCESAs are knocked out and vice versa, as expected for genes encoding isoforms that occupy distinct positions within the sameCSC. The class A and class B isoforms co‐accumulate in developing gametophores and co‐immunoprecipitate, suggesting that they interact to form a complexin planta. Finally, secondary PpCESAs interact with each other, whereas three of four fail to self‐interact when expressed in two different heterologous systems. These results are consistent with the hypothesis that obligate hetero‐oligomericCSCs evolved independently in mosses and seed plants and we propose the constructive neutral evolution hypothesis as a plausible explanation for convergent evolution of hetero‐oligomericCSCs.more » « less
-
Abstract Copy number variation (CNV) is a major part of the genetic diversity segregating within populations, but remains poorly understood relative to single nucleotide variation. Here, we report on atRNAligase gene (Migut.N02091;RLG1a) exhibiting unprecedented, and fitness‐relevant,CNVwithin an annual population of the yellow monkeyflowerMimulus guttatus.RLG1a variation was associated with multiple traits in pooled population sequencing (PoolSeq) scans of phenotypic and phenological cohorts. Resequencing of inbred lines revealed intermediate‐frequency three‐copy variants ofRLG1a (trip+;5/35 = 14%), andtrip+lines exhibited elevatedRLG1a expression under multiple conditions.trip+carriers, in addition to being over‐represented in late‐flowering and large‐flowered PoolSeq populations, flowered later under stressful conditions in a greenhouse experiment (p < 0.05). In wild population samples, we discovered an additional rareRLG1a variant (high+) that carries 250–300 copies ofRLG1a totalling ~5.7 Mb (20–40% of a chromosome). In the progeny of ahigh+carrier, Mendelian segregation of diagnostic alleles andqPCR‐based copy counts indicate thathigh+is a single tandem array unlinked to the single‐copyRLG1a locus. In the wild,high+carriers had highest fitness in two particularly dry and/or hot years (2015 and 2017; bothp < 0.01), while single‐copy individuals were twice as fecund as eitherCNVtype in a lush year (2016:p < 0.005). Our results demonstrate fluctuating selection onCNVs affecting phenological traits in a wild population, suggest that planttRNAligases mediate stress‐responsive life‐history traits, and introduce a novel system for investigating the molecular mechanisms of gene amplification.more » « less
