Genetic mapping of the athymic nude (RNU) locus in the rat to a region on chromosome 10

Perfusability and immunogenicity of implantable pre-vascularized tissues recapitulating features of native capillary network

Vascularization is a key pre-requisite to engineered anatomical scale three dimensional (3-D) constructs to ensure their nutrient and oxygen supply upon implantation. Presently, engineered pre-vascularized 3-D tissues are limited to only micro-scale hydrogels, which meet neither the anatomical scale needs nor the complexity of natural extracellular matrix (ECM) environments. Anatomical scale perfusable constructs are critically needed for translational applications. To overcome this challenge, we previously developed pre-vascularized ECM sheets with long and oriented dense microvascular networks. The present study further evaluated the patency, perfusability and innate immune response toward these pre-vascularized constructs. Macrophage-co-cultured pre-vascularized constructs were evaluated in vitro to confirm micro-vessel patency and perturbations in macrophage metabolism. Subcutaneously implanted pre-vascularized constructs remained viable and formed a functional anastomosis with host vasculature within 3 days of implantation. This completely biological pre-vascularized construct holds great potential as a building block to engineer perfusable anatomical scale tissues.

RNU (Foxn1 RNU-Nude) Rats Demonstrate an Improved Ability to Regenerate Muscle in a Volumetric Muscle Injury Compared to Sprague Dawley Rats

Products developed for skeletal muscle regeneration frequently incorporate allogeneic and xenogeneic materials to elicit a regenerative response to heal skeletal muscle wounds. To avoid graft rejection in preclinical studies, immunodeficient rodents are used. Whether the immunodeficiency alters the host response to the material in skeletal muscle has not been studied. In this study, we hypothesized that an allogeneic acellular skeletal muscle grafts implanted in an immunodeficient rat (RNU, Foxn1-deficient) would exhibit better new muscle fiber formation compared to grafts implanted in immunocompetent Sprague Dawley (SD) rats. Decellularized SD skeletal muscle matrix (DMM) was implanted in the gastrocnemius (N = 8 rats/group). 56 days after surgery, animal gait was examined and animals were euthanized. Muscle force was assessed and fiber number as well as immune cell infiltrate was measured by histomorphometry and immunohistochemistry. Animal gait and percent recovery of muscle force were unchanged in both groups, but newly regenerated muscle fibers increased in RNU rats. Macrophage staining for CD68 was higher in RNU rats than in SD rats. These data show differences in muscle regeneration between animal models using the same biomaterial treatment, but these differences could not be ascribed to the immune response. Overall, our data provide awareness that more studies are needed to understand how host responses to biomaterials differ based on the animal model used.

Evaluation of a cell-based osteogenic formulation compliant with good manufacturing practice for use in tissue engineering

Proper bony tissue regeneration requires mechanical stabilization, an osteogenic biological activity and appropriate scaffolds. The latter two elements can be combined in a hydrogel format for effective delivery, so it can readily adapt to the architecture of the defect. We evaluated a Good Manufacturing Practice-compliant formulation composed of bone marrow-derived mesenchymal stromal cells in combination with bone particles (Ø = 0.25 to 1 µm) and fibrin, which can be readily translated into the clinical setting for the treatment of bone defects, as an alternative to bone tissue autografts. Remarkably, cells survived with unaltered phenotype (CD73⁺, CD90⁺, CD105⁺, CD31^-, CD45^-) and retained their osteogenic capacity up to 48 h after being combined with hydrogel and bone particles, thus demonstrating the stability of their identity and potency. Moreover, in a subchronic toxicity in vivo study, no toxicity was observed upon subcutaneous administration in athymic mice and signs of osteogenesis and vascularization were detected 2 months after administration. The preclinical data gathered in the present work, in compliance with current quality and regulatory requirements, demonstrated the feasibility of formulating an osteogenic cell-based tissue engineering product with a defined profile including identity, purity and potency (in vitro and in vivo), and the stability of these attributes, which complements the preclinical package required prior to move towards its use of prior to its clinical use.

Accelerated Maturation of Human Stem Cell-Derived Pancreatic Progenitor Cells into Insulin-Secreting Cells in Immunodeficient Rats Relative to Mice

Pluripotent human embryonic stem cells (hESCs) are a potential source of transplantable cells for treating patients with diabetes. To investigate the impact of the host recipient on hESC-derived pancreatic progenitor cell maturation, cells were transplanted into immunodeficient SCID-beige mice or nude rats. Following the transplant, basal human C-peptide levels were consistently higher in mice compared with rats, but only rats showed robust meal- and glucose-responsive human C-peptide secretion by 19–21 weeks. Grafts from rats contained a higher proportion of insulin:glucagon immunoreactivity, fewer exocrine cells, and improved expression of mature β cell markers compared with mice. Moreover, ECM-related genes were enriched, the collagen network was denser, and blood vessels were more intricately integrated into the engrafted endocrine tissue in rats relative to mice. Overall, hESC-derived pancreatic progenitor cells matured faster in nude rats compared with SCID-beige mice, indicating that the host recipient can greatly influence the fate of immature pancreatic progenitor cells post-transplantation.

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hESC-derived pancreatic progenitor cells matured faster in nude rats than in SCID-bg mice

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Human C-peptide secretion was meal-regulated in rats but not in mice at 19 weeks

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Grafts from rats expressed more mature β cell markers compared with mice

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Grafts from rats had a denser ECM and greater vasculature than grafts from mice

T cell deficiency in spinal cord injury: altered locomotor recovery and whole-genome transcriptional analysis

BACKGROUND

T cells undergo autoimmunization following spinal cord injury (SCI) and play both protective and destructive roles during the recovery process. T cell-deficient athymic nude (AN) rats exhibit improved functional recovery when compared to immunocompetent Sprague-Dawley (SD) rats following spinal cord transection.

METHODS

In the present study, we evaluated locomotor recovery in SD and AN rats following moderate spinal cord contusion. To explain variable locomotor outcome, we assessed whole-genome expression using RNA sequencing, in the acute (1 week post-injury) and chronic (8 weeks post-injury) phases of recovery.

RESULTS

Athymic nude rats demonstrated greater locomotor function than SD rats only at 1 week post-injury, coinciding with peak T cell infiltration in immunocompetent rats. Genetic markers for T cells and helper T cells were acutely enriched in SD rats, while AN rats expressed genes for T(h)2 cells, cytotoxic T cells, NK cells, mast cells, IL-1a, and IL-6 at higher levels. Acute enrichment of cell death-related genes suggested that SD rats undergo secondary tissue damage from T cells. Additionally, SD rats exhibited increased acute expression of voltage-gated potassium (Kv) channel-related genes. However, AN rats demonstrated greater chronic expression of cell death-associated genes and less expression of axon-related genes. Immunostaining for macrophage markers revealed no T cell-dependent difference in the acute macrophage infiltrate.

CONCLUSIONS

We put forth a model in which T cells facilitate early tissue damage, demyelination, and Kv channel dysregulation in SD rats following contusion SCI. However, compensatory features of the immune response in AN rats cause delayed tissue death and limit long-term recovery. T cell inhibition combined with other neuroprotective treatment may thus be a promising therapeutic avenue.

A deletion in FOXN1 is associated with a syndrome characterized by congenital hypotrichosis and short life expectancy in Birman cats

An autosomal recessive syndrome characterized by congenital hypotrichosis and short life expectancy has been described in the Birman cat breed (Felis silvestris catus). We hypothesized that a FOXN1 (forkhead box N1) loss-of-function allele, associated with the nude phenotype in humans, mice and rats, may account for the syndrome observed in Birman cats. To the best of our knowledge, spontaneous mutations in FOXN1 have never been described in non-human, non-rodent mammalian species. We identified a recessive c.1030_1033delCTGT deletion in FOXN1 in Birman cats. This 4-bp deletion was associated with the syndrome when present in two copies. Percentage of healthy carriers in our French panel of genotyped Birman cats was estimated to be 3.2%. The deletion led to a frameshift and a premature stop codon at position 547 in the protein. In silico, the truncated FOXN1 protein was predicted to lack the activation domain and critical parts of the forkhead DNA binding domain, both involved in the interaction between FOXN1 and its targets, a mandatory step to promote normal hair and thymic epithelial development. Our results enlarge the panel of recessive FOXN1 loss-of-function alleles described in mammals. A DNA test is available; it will help owners avoid matings at risk and should prevent the dissemination of this morbid mutation in domestic felines.

The human fetal lung xenograft: validation as model of microvascular remodeling in the postglandular lung

BACKGROUND

Coordinated remodeling of epithelium and vasculature is essential for normal postglandular lung development. The value of the human-to-rodent lung xenograft as model of fetal microvascular development remains poorly defined.

AIM

The aim of this study was to determine the fate of the endogenous (human-derived) microvasculature in fetal lung xenografts.

METHODS

Lung tissues were obtained from spontaneous pregnancy losses (14-22 weeks' gestation) and implanted in the renal subcapsular or dorsal subcutaneous space of SCID-beige mice (T, B, and NK-cell-deficient) and/or nude rats (T-cell-deficient). Informed parental consent was obtained. Lung morphogenesis, microvascular angiogenesis, and epithelial differentiation were assessed at 2 and 4 weeks post-transplantation by light microscopy, immunohistochemical, and gene expression studies. Archival age-matched postmortem lungs served as control.

RESULTS

The vascular morphology, density, and proliferation of renal subcapsular grafts in SCID-beige mice were similar to age-matched control lungs, with preservation of the physiologic association between epithelium and vasculature. The microvasculature of subcutaneous grafts in SCID-beige mice was underdeveloped and dysmorphic, associated with significantly lower VEGF, endoglin, and angiopoietin-2 mRNA expression than renal grafts. Grafts at both sites displayed mild airspace dysplasia. Renal subcapsular grafts in nude rats showed frequent infiltration by host lymphocytes and obliterating bronchiolitis-like changes, associated with markedly decreased endogenous angiogenesis.

CONCLUSION

This study demonstrates the critical importance of host and site selection to ensure optimal xenograft development. When transplanted to severely immune suppressed, NK-cell-deficient hosts and engrafted in the renal subcapsular site, the human-to-rodent fetal lung xenograft provides a valid model of postglandular microvascular lung remodeling.

Learning from nudity: lessons from the nude phenotype

In mice, rats, and humans, loss of function of Foxn1, a member of the winged helix/forkhead family of transcription factors, leads to macroscopic nudity and an inborn dysgenesis of the thymus. Nude (Foxn1(nu)/Foxn1(nu)) mice develop largely normal hair follicles and produce hair shafts. However, presumably because of a lack of certain hair keratins, the hair shafts that are generated twist and coil in the hair follicle infundibulum, which becomes dilated. Since hair shafts fail to penetrate the epidermis, macroscopic nudity results and generates the - grossly misleading - impression that nude mice are hairless. Here, we provide an overview of what is known on the role of Foxn1 in mammalian skin biology, its expression patterns in the hair follicle, its influence on hair follicle function, and onychocyte differentiation. We focus on the mechanisms and signaling pathways by which Foxn1 modulates keratinocyte differentiation in the hair follicle and nail apparatus and summarize the current knowledge on the molecular and functional consequences of a loss of function of the Foxn1 protein in skin. Foxn1 target genes, gene regulation of Foxn, and pharmacological manipulation of the nude phenotype (e.g. by cyclosporine A, KGF, and vitamin D3) are discussed, and important open questions as well as promising research strategies in Foxn1 biology are defined. Taken together, this review aims at delineating why enhanced research efforts in this comparatively neglected field of investigative dermatology promise important new insights into the controls of epithelial differentiation in mammalian skin.

The nude gene and the skin

The nude mutation has been known for a long time. Nevertheless, the gene responsible for the defect has been identified only recently. It encodes a transcriptional activator of the family of forkhead proteins mainly expressed in thymic epithelium and distinct keratinocyte populations in the epidermis and hair follicles. The present review focuses on the molecular and functional characterization of the nude gene and its product and gives an overview as to its role in skin biology and the first identified target genes in the skin. In addition, evolutionary aspects are highlighted stressing the importance of such investigations for a comprehensive understanding of the nude gene product and the regulation of its expression. Furthermore, these studies give a hint as to when the nude gene has occurred first and how it has developed in molecular and functional terms since then.

Congenital thymic aplasia in a Holstein-Israeli female calf

An unusual case of congenital thymic aplasia in a Holstein-Israeli female calf is described. The most prominent clinical findings were diarrhoea and weakness. At necropsy, the only significant pathological finding was the marked decrease in thymus size. Histologically, this organ was composed of loose connective tissue in which a few lymphocytes were scattered randomly.

Genetic typing of the mouse and rat nude mutations by PCR and restriction enzyme analysis

A genetic typing method for the mouse and rat nude mutations by PCR and restriction fragment length polymorphism (RFLP) analysis was developed. Since restriction sites useful for RFLP analysis do not exist in the mouse nu and rat rnu mutations, artificial restriction sites were introduced by PCR with modified primers. Three genotypes in the mouse (nu/nu, nu/+ and +/+) or rat (rnu/rnu, rnu/+ and +/+) are rapidly differentiated with the PCR-RFLP assay. In addition, congenic nude strains can be efficiently established by using this assay. Finally, genetic mapping of the rnu locus was performed with microsatellite markers. The locus order on rat chromosome 10 was D10Mgh14-(2.0cM)-D10Mit2-(1.4cM)-rnu-(0.7cM++ +)-D10Mgh6-(2.7cM)-D10Mit8.

Genetic mapping of genes regulating the thymus size in back-cross rats between the laboratory BUF/Mna strain and the MITE strain derived from the wild rat, Rattus norvegicus

The thymoma prone BUF/Mna (B) rat is a useful model for studying the genes responsible for thymus enlargement during the stage of young growth. Among the strains of rats, B rats have the largest thymuses at all stages of life. A locus, Ten-1, which contributes to thymus enlargement in back-cross (BC) rats between the B and WKY/NCrj (W) strains, was mapped on chromosome 1. To determine the precise location of the locus, ¿B x(B x MITE)F1¿ BC rats were generated by crossing the B strain with the inbred MITE (M) strain, which was established from captured, Japanese wild rats, and were examined by linkage study using polymerase chain reaction with 67 microsatellite markers. Linkages with thymus enlargement were found in genotypes of seven markers, BSIS, LSN, MYL2, IGF2, PBPC2, D1Mgh11, and D1MIt6, by chi2-test and Student's t-test, which confirmed the presence of the genetic locus associated with thymus enlargement, Ten-1, in this region. Paradoxically, a suppressive locus, Tsu-1, to thymus enlargement was also found on chromosome 3, showing linkages of phenotype of the small thymus with genotypes of SCN2A, CAT, D3MIt16, and D3MIt13. By analyses of MAPMAKER/EXP and MAPMAKER/QTL, Ten-1 was mapped at 4.6 cM proximal from IGF2 locus on chromosome 1 and Tsu-1 at 4.0 cM proximal from CAT locus on chromosome 3, respectively.

Mapping of two genetic loci, Ten-1 and Ten-2, associated with thymus enlargement in BUF/Mna rats

The thymoma-prone BUF/Mna rat is a useful model for human thymoma. Thymoma develops spontaneously in these rats at an incidence of nearly 100%. At pre-thymoma age, BUF/Mna rats have extremely large thymuses when compared with those of rats of the other strains, suggesting the presence of genes that regulate the thymus enlargement. We performed linkage study to identify the genetic loci associated with thymus enlargement in {(WKY/NCrj x BUF/Mna) F1 x BUF/Mna} backcross rats. Linkage study showed the significant associations between thymus size and markers on Chromosomes (Chrs) 1 and 13, suggesting the presence of two genes, Ten-1 and Ten-2, which regulate the thymus enlargement. Ten-1 was located between myosin light chain, muscle 2 (MYL2) and D1Mgh11 loci on Chr 1, and Ten-2 was located between synaptotagmin II (SYT2) and D13N2 loci on Chr 13.

A genetic, physical, and comparative map of rat chromosome 10

A map of rat Chromosome (Chr) 10 was generated from 21 markers, mostly of conserved structural genes, by linkage analysis and fluorescence in situ hybridization. The study emphasizes the proximal third of the chromosome which, until now, has been relatively devoid of markers. Based on comparative analysis, our data suggest that genes on rat Chr 10 are conserved on mouse Chr 11, 16, 17 and human Chr 16, 5, and 17.

Linkage of the athymic nude locus with the myeloperoxidase locus in the rat

In rats of the BUF/Mna strain epithelial thymoma development is regulated by a single autosomal susceptible gene, Tsr-1. In pre-thymoma stage, BUF/Mna rats have extremely large thymuses, when compared with those of other strains of rats. The large thymus size of this strain is contributed by a thymus-enlargement gene, Ten-1. On the other hand, reduced thymus size and suppression of thymoma development were found in heterozygous BUF/Mna-rnu/+ rats. Linkage studies between RNU and microsatellite and restriction fragment length polymorphism markers in ([BUF/Mna-rnu/rnu x WKY/NCrj] F1 x WKY/NCrj)- and (WKY/NCrj x [BUF/Mna-rnu/rnu x WKY/NCrj] F1)- backcross rats have led to the localization of RNU on chromosome 10. The rat homolog of mouse Mpo (myeloperoxidase) was also assigned to the chromosome 10. The gene order on the chromosome was MYHSE (myosin heavy chain of embryonic skeletal muscle)--(1.0 centimorgan [cM])--SHBG (sex hormone-binding globulin)--(4.0 cM)--RNU (Rowett rat nude)--(10.0 cM)--MPO--(13.0 cM)--AEP (anion exchange protein). Conserved linkage of homologous loci mapped to rat chromosome 10 and mouse chromosome 11 supports the hypothesis that the RNU and MPO loci are rat homologs of the mouse nu and Mpo loci.

New member of the winged-helix protein family disrupted in mouse and rat nude mutations

Mutations at the nude locus of mice and rats disrupt normal hair growth and thymus development, causing nude mice and rats to be immune-deficient. The mouse nude locus has been localized on chromosome 11 (refs 3, 4) within a region of < 1 megabase. Here we show that one of the genes from this critical region, designated whn, encodes a new member of the winged-helix domain family of transcription factors, and that it is disrupted on mouse nu and rat rnuN alleles. Mutant transcripts do not encode the characteristic DNA-binding domain, strongly suggesting that the whn gene is the nude gene. Mutations in winged-helix domain genes cause homeotic transformations in Drosophila and distort cell-fate decisions during vulval development in Caenorhabditis elegans. The whn gene is thus the first member of this class of genes to be implicated in a specific developmental defect in vertebrates.

Autonomic function in systemic lupus erythematosus

A controlled study with paired analysis of data was performed in 34 patients with systemic lupus erythematosus (SLE) and 34 age and sex-matched healthy controls. Autonomic function was not affected significantly in SLE patients as judged by standardised cardiovascular tests. Pancreatic polypeptide (PP) response to meal stimulation, which is impaired in parasympathetic failure, was for unknown reasons found to be significantly increased in SLE patients both in unstimulated and stimulated states. Neither cardiovascular nor serological tests could thus reveal significant autonomic dysfunction in SLE. Drugs with cardiovascular effects highly influenced autonomic function and could thus be misinterpreted as autonomic dysfunction caused by SLE itself.