Rat Hindlimb Cryopreservation and Transplantation: A Step Toward "Organ Banking"

In 2016, over 5 million reconstructive procedures were performed in the United States. The recent successes of clinical vascularized composite allotransplantations, hand and face transplantations included, established the tremendous potential of these life-enhancing reconstructions. Nevertheless, due to limited availability and lifelong immunosuppression, application is limited. Long-term banking of composite transplants may increase the availability of esthetically compatible parts with partial or complete HLA matching, reducing the risk of rejection and the immunosuppressive burden. The study purpose was to develop efficient protocols for the cryopreservation and transplantation of a complete rodent limb. Directional freezing is a method in which a sample is cooled at a constant-velocity linear temperature gradient, enabling precise control of the process and ice crystal formation. Vitrification is an alternative cryopreservation method in which the sample solidifies without the formation of ice crystals. Testing both methods on a rat hindlimb composite tissue transplantation model, we found reliable, reproducible, and stable ways to preserve composite tissue. We believe that with further research and development, cryopreservation may lead to composite tissue "banks." This may lead to a paradigm shift from few and far apart emergent surgeries to wide-scale, well-planned, and better-controlled elective surgeries.

NOX1-induced accumulation of reactive oxygen species in abdominal fat-derived mesenchymal stromal cells impinges on long-term proliferation

Mesenchymal stromal cells (MSCs) are multipotent and can be derived from different adult tissues including fat. Our repeated attempts to produce long-term proliferative cultures of rat abdominal adipose stem cells (aASCs) under normal oxygen concentration (21%) were unsuccessful. We set to examine the events controlling this cytostasis of aASCs and found that it resulted from overproduction of reactive oxygen species (ROS) that led to apoptosis. ROS overproduction in aASCs was accompanied by increased expression of NOX1 but not of NOX2 or NOX4. NOX family members are an important source of intracellular ROS pointing to NOX1 involvement in ROS accumulation. This was verified when aASCs that were grown under 3% oxygen conditions expanded long term, displaying reduced NOX1 expression and decreased ROS accumulation. NOX1 involvement in aASC cytostasis was reaffirmed when cells that were expanded under normoxic conditions in the presence of a specific NOX1 inhibitor, ML171, demonstrated reduced ROS accumulation, reduced apoptosis and long-term expansion. aASC expansion arrest was accompanied also by a weak fat differentiation and migratory potential, which was enhanced by NOX1 inhibition. This suggests an inhibitory role for NOX1-induced ROS overproduction on aASCs, their fat differentiation and migratory potential. In contrast to aASCs, similar cells produced from subcutaneous fat were easily expanded in normoxic cultures, exhibiting low ROS concentrations, a low number of apoptotic cells and improved fat differentiation and migration. Taken together, our results show, for the first time, that NOX1-induced ROS accumulation halts ASC expansion and reduces their differentiation and migratory potential under normoxic conditions. Importantly, this phenotype comprises a tissue-specific signature as it was evident in aASCs but not in subcutaneous ASCs. NOX-induced ROS accumulation and cytokine production by fat are part of the metabolic syndrome. The similarity of this phenomenon to aASC phenotype may indicate that they arise from similar molecular mechanisms.

Disrupting mitochondrial-nuclear coevolution affects OXPHOS complex I integrity and impacts human health

The mutation rate of the mitochondrial DNA (mtDNA), which is higher by an order of magnitude as compared with the nuclear genome, enforces tight mitonuclear coevolution to maintain mitochondrial activities. Interruption of such coevolution plays a role in interpopulation hybrid breakdown, speciation events, and disease susceptibility. Previously, we found an elevated amino acid replacement rate and positive selection in the nuclear DNA-encoded oxidative phosphorylation (OXPHOS) complex I subunit NDUFC2, a phenomenon important for the direct interaction of NDUFC2 with the mtDNA-encoded complex I subunit ND4. This finding underlines the importance of mitonuclear coevolution to physical interactions between mtDNA and nuclear DNA-encoded factors. Nevertheless, it remains unclear whether this interaction is important for the stability and activity of complex I. Here, we show that siRNA silencing of NDUFC2 reduced growth of human D-407 retinal pigment epithelial cells, significantly diminished mitochondrial membrane potential, and interfered with complex I integrity. Moreover, site-directed mutagenesis of a positively selected amino acid in NDUFC2 significantly interfered with the interaction of NDUFC2 with its mtDNA-encoded partner ND4. Finally, we show that a genotype combination involving this amino acid (NDUFC2 residue 46) and the mtDNA haplogroup HV likely altered susceptibility to type 2 diabetes mellitus in Ashkenazi Jews. Therefore, mitonuclear coevolution is important for maintaining mitonuclear factor interactions, OXPHOS, and for human health.

Coevolution predicts direct interactions between mtDNA-encoded and nDNA-encoded subunits of oxidative phosphorylation complex i

Despite years of research, the structure of the largest mammalian oxidative phosphorylation (OXPHOS) complex, NADH-ubiquinone oxidoreductase (complex I), and the interactions among its 45 subunits are not fully understood. Since complex I harbors subunits encoded by mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) genomes, with the former evolving ∼10 times faster than the latter, tight cytonuclear coevolution is expected and observed. Recently, we identified three nDNA-encoded complex I subunits that underwent accelerated amino acid replacement, suggesting their adjustment to the elevated mtDNA rate of change. Hence, they constitute excellent candidates for binding mtDNA-encoded subunits. Here, we further disentangle the network of physical cytonuclear interactions within complex I by analyzing subunits coevolution. Firstly, relying on the bioinformatic analysis of 10 protein complexes possessing solved structures, we show that signals of coevolution identified physically interacting subunits with nearly 90% accuracy, thus lending support to our approach. When applying this approach to cytonuclear interaction within complex I, we predict that the 'rate-accelerated' nDNA-encoded subunits of complex I, NDUFC2 and NDUFA1, likely interact with the mtDNA-encoded subunits ND5/ND4 and ND5/ND4/ND1, respectively. Furthermore, we predicted interactions among mtDNA-encoded complex I subunits. Using the yeast two-hybrid system, we experimentally confirmed the predicted interactions of human NDUFC2 with ND4, the interactions of human NDUFA1 with ND1 and ND4, and the lack of interaction of NDUFC2 with ND3 and NDUFA1, thus providing a proof of concept for our approach. Our study shows, for the first time, evidence for direct interactions between nDNA-encoded and mtDNA-encoded subunits of human OXPHOS complex I and paves the path towards deciphering subunit interactions within complexes lacking three-dimensional structures. Our subunit-interactions-predicting method, ComplexCorr, is available at http://webclu.bio.wzw.tum.de/complexcorr.

Uniquely conserved non-translated regions are involved in generation of the two major transcripts of protein phosphatase 2Cbeta

Partial cDNAs of different isoforms of protein phosphatase 2Cbeta (PP2Cbeta or PPM1B) have been characterized in mammals. We disclose here the full cDNAs of two major PP2Cbeta isoforms from human, rat and mouse. These cDNAs (2.6 and 3.3 kb) are able to encode 53 kDa (PP2Cbetal) and 43 kDa (PP2Cbetas) polypeptides, respectively. The isoforms are co-expressed ubiquitously with the highest level in skeletal muscle, as assessed by Northern-blot analysis. Western and in situ analyses using monoclonal antibodies against PP2Cbeta confirmed the existence of two isoforms in the cytoplasm. Comparative sequence analysis revealed that both cDNAs consist of six exons with an alternate usage of the 3' exons that underlies the differences between them. The genomic structure of PP2Cbeta is similar to that of other PP2C paralogs and includes a non-coding first exon followed by a large intron and a large second exon that encoded most of the catalytic domain. Both variants of the ending exon include large non-coding regions. All non-translated regions (NTRs) are highly conserved between the orthologous genes, indicating their regulatory function. The 5'-NTR is long (379 bp), includes upstream start codons and is predicted to contain stable secondary structures. Such features inhibit translation initiation by the scanning mechanism. Introduction of this NTR element into a bi-luciferase expression-cassette enabled expression of the second cistron, suggesting that it might serve as an internal ribosome entry site, or it contains a cryptic promoter. Overexpression of PP2Cbeta under CMV-promoter in 293 cells led to cell-growth arrest or cell death.

Identification of a fourth half ABC transporter in the human peroxisomal membrane

Three half ATP-binding cassette transporters (ALDP, ALDR, PMP70) are known to be present in the human peroxisome membrane. Mutations in the gene encoding ALDP cause X-linked adrenoleukodystrophy; the role of ALDR and PMP70 in human disease is unclear. We report the cloning and characterization of a fourth human gene encoding a peroxisomal half ABC transporter. The gene, designated P70R, maps to chromosome 14q24, encodes a 73 kDa transporter most similar to PMP70, and is expressed in all human tissues examined. Because half ABC transporters heterodimerize to form functional transporters, the identification of a fourth member of this family in the peroxisome membrane has implications for our understanding of mammalian peroxisomes and the genetic disorders of peroxisomal function.

Posttraumatic stress disorder, tenderness and fibromyalgia

The aims of the present study were to inquire into the prevalence of fibromyalgia syndrome, to assess nonarticular tenderness, to measure fibromyalgia syndrome-related symptoms, quality of life, and functional impairment among posttraumatic stress disorder (PTSD) patients as compared with control subjects. Furthermore, the differences between the PTSD patients with and without fibromyalgia syndrome were studied. Twenty-nine PTSD patients and 37 control subjects were assessed as to the diagnosis of fibromyalgia syndrome according to the American College of Rheumatology. Tenderness was assessed manually and with a dolorimeter. Fibromyalgia syndrome-related symptoms, quality of life, physical functioning, PTSD symptomatology, and psychiatric features were assessed by valid and reliable self-report inventories. Results showed that the prevalence of fibromyalgia syndrome in the PTSD group was 21% vs. 0% in the control group. Furthermore, the PTSD group was more tender than the control group. PTSD subjects suffering from fibromyalgia syndrome were more tender, reported more pain, lower quality of life, higher functional impairment and suffered more psychological distress than the PTSD patients not having fibromyalgia syndrome. It is suggested that previous reports on diffuse pain in PTSD in fact described undiagnosed fibromyalgia syndrome. The link between psychological stress and pain syndromes is emphasized.

A Saccharomyces cerevisiae homolog of the human adrenoleukodystrophy transporter is a heterodimer of two half ATP-binding cassette transporters

The adrenoleukodystrophy protein (ALDP) and the 70-kDa peroxisomal membrane protein (PMP70) are half ATP-binding cassette (ABC) transporters in the human peroxisome membrane. ALDP and PMP70 share sequence homology and both are implicated in genetic diseases. PXA1 and YKL741 are Saccharomyces cerevisiae genes that encode homologs of ALDP and PMP70. Pxa1p, a putative ortholog of ALDP, is involved in peroxisomal beta-oxidation of fatty acids while YKL741 is an open reading frame found by the yeast genome sequencing project. Here we designate YKL741 as PXA2 and show that its protein product, Pxa2p, like Pxa1p, is associated with peroxisomes but not required for their assembly. Yeast strains carrying gene disruption of PXA1, PXA2, or both have similar and, in the case of the latter, nonadditive phenotypes. We also find that the stability of Pxa1p, but not Pxa2p, is markedly reduced in the absence of the other. Finally, we find that Pxa1p and Pxa2p coimmuno-precipitate. These genetic and physical data suggest that Pxa1p and Pxa2p heterodimerize to form a complete peroxisomal ABC transporter involved in fatty acid beta-oxidation. This result predicts the presence of similar heterodimeric ABC transporters in the mammalian peroxisome membrane.

Characterization and analysis of conserved motifs in a peroxisomal ATP-binding cassette transporter

The adrenoleukodystrophy protein (ALDP) and the 70-kDa peroxisomal membrane protein are half ATP-binding cassette (ABC) transporters in the human peroxisome membrane. Both are implicated in genetic disorders of peroxisome biogenesis and function. Proteins homologous to ALDP and the 70-kDa peroxisomal membrane protein have been discovered in other eukaryotic organisms and form a growing group of peroxisomal half ABC transporters. Amino acid sequence alignment of these and other ABC transporters reveals several protein motifs that are highly conserved both in sequence and location. Here we characterize two of these, designated the EAA-like and the loop1 motifs. We study them by introducing missense mutations in Pxa1p, a Saccharomyces cerevisiae ortholog of ALDP, and show that both motifs are important for Pxa1p function. Interestingly, missense mutations in corresponding amino acids in ALDP cause adrenoleukodystrophy in humans. We conclude that these motifs are important for ABC transporter function and that the yeast protein Pxa1p is a useful system for understanding the molecular basis of adrenoleukodystrophy.

PXA1, a possible Saccharomyces cerevisiae ortholog of the human adrenoleukodystrophy gene

The adrenoleukodystrophy protein (ALDp) is an ATP-binding cassette (ABC) transporter in the human peroxisome membrane. It is defective in X chromosome-linked adrenoleukodystrophy (ALD), a neurodegenerative disorder with impaired peroxisomal oxidation of very long chain fatty acids. We report cloning and characterization of PXA1, a yeast gene encoding a protein (Pxa1p) exhibiting high similarity to ALDp. Disruption of PXA1 results in impaired growth on oleic acid and reduced ability to oxidize oleate. Pxa1p is peroxisome associated; however, in the PXA1 mutant yeast, as in ALD cells, peroxisomes are morphologically intact. Disruption of a second yeast gene, YKL741, which encodes a more distantly related ALDp homolog (Yk174p), in either wild-type or PXA1 mutant yeast, results in a growth phenotype identical to that of the PXA1 mutant. This result suggests that Yk1741p and Pxa1p may be subunits of the same transporter. Sequence analysis of Pxa1p, ALDp, and related ABC transporters reveals a possible fatty acid binding domain and a 14-amino acid EAA-like motif, previously described only in prokaryotes. Because of the similarities in sequence and function, we propose that Pxa1p is the Saccharomyces cerevisiae ortholog of ALDp.

Mechanisms of assembly of wheat high molecular weight glutenins inferred from expression of wild-type and mutant subunits in transgenic tobacco

Following sequestration into the endoplasmic reticulum, wheat high molecular weight glutenin subunits (HMW-GS) assemble into polymers through intermolecular disulfide bond formation. These polymers, which also include low molecular weight glutenin subunits (LMW-GS), have a broad distribution of molecular mass reaching up to several million daltons. To study the mechanism of assembly of the HMW-GS, we have expressed x- and y-type HMW-GS in transgenic tobacco plants. Both types, when expressed individually or in combination, were incorporated into polymers. Partial reduction of polymers formed by different subunits resulted in different patterns of release of homodimers, heterodimers, and monomers. This suggested different arrangements of intermolecular disulfide bonds or different peptide conformations in the vicinity of the disulfide bonds linking x-x, y-y, and x-y type HMW-GS. A mutant of the x-type subunit, lacking a conserved cysteine in the C-terminal domain, assembled into oligomers linked by intermolecular disulfide bonds, but not into large polymers. This mutant was deposited, however, in dense protein bodies, similar to those formed by the native HMW-GS, suggesting that polymer formation and packaging into protein bodies may be the result of different types of interactions. Pulse-chase labeling of proteins in wheat endosperm showed that the assembly of the HMW-GS into insoluble polymers occurs by a slow process which apparently continues after the initiation of protein body formation.

Role of the amino- and carboxy-terminal regions in the folding and oligomerization of wheat high molecular weight glutenin subunits

The high molecular weight glutenin subunits are considered one of the most important components of wheat (Triticum aestivum) gluten, but their structure and interactions with other gluten proteins are still unknown. Understanding the role of these proteins in gluten formation may be aided by analyses of the conformation and interactions of individual wild-type and modified subunits expressed in heterologous systems. In the present report, the bacterium Escherichia coli was used to synthesize four naturally occurring X- and Y-type wheat high molecular weight glutenin subunits of the Glu-1D locus, as well as four bipartite chimeras of these proteins. Naturally occurring subunits synthesized in the bacteria exhibited sodium dodecyl sulfate-polyacrylamide gel electrophoresis migration properties identical to those of high molecular weight glutenin subunits extracted from wheat grains. Wild-type and chimeric subunits migrated in sodium dodecyl sulfate gels differently than expected based on their molecular weights due to conformational properties of their N- and C-terminal regions. Results from cycles of reductive cleavage and oxidative reformation were consistent with the formation of both inter- and intramolecular disulfide bonds in patterns and proportions that differed among specific high molecular weight glutenin species. Comparison of the chimeric and wild-type proteins indicated that the two C-terminal cysteines of the Y-type subunits are linked by intramolecular disulfide bonds, suggesting that the role of these cysteines in glutenin polymerization may be limited.

Airway resistance measurements throughout the respiratory cycle in infants

Using a constant-volume infant whole-body plethysmograph containing a heated rebreathing bag, we have been able to measure airway resistance (Raw) throughout the respiratory cycle using a computer-based technique. Data from the plethysmograph transducers are sampled at 60 Hz for the calculations and Raw is calculated at each point sampled during the breath, with appropriate corrections for absolute lung volume. It was found that in most cases Raw varied less with respect to tidal volume than to tidal flow. Various patterns of Raw change in relation to tidal volume were found. These included an elevated but relatively constant resistance, a progressively rising expiratory resistance, and in 3 infants with laryngomalacia, a progressively rising inspiratory resistance. It was also found that the dynamic performance of the rebreathing bag was such that considerable errors would occur if apparatus resistance was assumed to be constant and so the actual apparatus resistance at each point was subtracted from the total resistance to give Raw. In conclusion, Raw is not constant throughout the respiratory cycle in infants and the pattern of change conveys additional information.

Clinical significance of sinusoidal fetal heart rate pattern

Sinusoidal fetal heart rate pattern has been regarded as a sign of fetal jeopardy and 92 instances of this pattern were analysed. The morphologically different major and minor sinusoidal patterns were assessed with regard to their clinical significance as predictors of fetal compromise. There were 83 instances of minor sinusoidal pattern (amplitude of oscillation less than 25 beats/min) with only one antepartum fetal death. Major sinusoidal pattern (amplitude of oscillation greater than 25 beats/min) was diagnosed in nine patients and in six of them the fetus died before, during or after delivery. It is concluded that patients with minor sinusoidal heart rate patterns may be managed expectantly, whereas on the rare occasion when a major sinusoidal pattern is seen expeditious delivery is justified.

Is end-stage deceleration of the fetal heart ominous?

End-stage deceleration (ESD) defined as deep and sustained fetal bradycardia during the second stage of labour was observed in 55 patients. Fetal well-being and neonatal outcome were assessed with fetal-scalp pH, umbilical-vein pH and 1-min Apgar score values. Only six infants with pathological fetal heart-rate patterns before ESD had a 1-min Apgar score of less than 7 and an acidotic umbilical-vein pH. The remaining 49 babies were born in excellent condition, although when ESD persisted for more than 15 min umbilical-vein pH decreased.