Growth factor expression in skin during wool follicle development

Efficacy of a porous-structured titanium subdermal barrier for preventing infection in percutaneous osseointegrated prostheses

Infections of percutaneous osseointegrated prostheses (POP) cause prolonged morbidity and device failure because once established, they are refractory to antibiotic therapy. To date, only limited translational animal studies have investigated the efficacy of POP designs in preventing infections. We developed an animal model to evaluate the efficacy of a porous-coated titanium (Ti) subdermal barrier to achieve skin-implant integration and to prevent periprosthetic infection. In a single-stage "amputation and implantation" surgery, 14 sheep were fitted with percutaneous devices with an attached porous-coated Ti subdermal barrier. Nine sheep were implanted with a smooth Ti subdermal barrier construct and served as controls, with one control sheep removed from the study due to a fractured bone. Clinical, microbiological, and histopathological data showed that the porous Ti barrier prevented superficial and deep tissue infections in all animals (14/14, 100%) at the 9-month endpoint. In contrast, animals with the smooth Ti implant construct had a 25% (2/8) infection rate. Survival analysis indicated a significant difference between the groups (log-rank test, p = 0.018). Data also indicated that although skin marsupialization was evident in both implant types, animals in the control group had a four times greater marsupialization rate. We concluded that osseointegrated implants incorporating porous-coated Ti subdermal barriers may have the ability to prevent infection by maintaining a healthy, biologically attached epithelial barrier at the skin-implant interface in load-bearing animals up to a 9-month terminus.

[A novel polymorphism of IGFBP-3 gene and its relationship with several wool traits in Chinese Merino sheep]

In this study, PCR-SSCP analysis was used to identify genetic variation in IGFBP-3 gene in Chinese Merino and Kazakh sheep. A PCR product of 178 bp corresponding to partial intron1 illustrated three unique binding patterns by SSCP analysis. Frequencies of the genotype AA, AB, BB and allele A, B in Chinese Merino sheep were 0.70, 0.24, 0.06, and 0.82, 0.18 respectively , and they were 0.87, 0.13, 0.00, and 0.93, 0.07 respectively in Kazaka sheep. Sequence analysis revealed a G/T transversion at position 122 of the fragment. This polymorphic locus of IGFBP-3 gene was at Hardy-Weinberg dis-equilibrium (P<0.01) in the two breeds. Different genotypes slightly affected several wool traits of Chinese Merino sheep. The individuals of genotype AA, AB, and BB had no significant difference in post-shearing weight and clean wool rate. Sta-ple length (SL) was decreased with the genotype of AA, AB, and BB, and the difference between AA and AB was significant (P<0.01). Greasy fleece weight (GFW) and follicle density in individuals of genotype AA was significantly lower than that in individuals of genotype AB (P<0.01) and BB (P<0.05); Average fiber diameter (AFD) in individuals of genotype AA was significantly higher than that in individuals of genotype AB (P<0.01) and BB (P<0.05).

Gene expression profiles of BMP4, FGF10 and cognate inhibitors, in the skin of foetal Merino sheep, at the time of secondary follicle branching

The high concentration of secondary branched follicles is a distinctive feature of the Merino sheep. These follicles initiate from 100 days of gestation. Here, we report a transition in abundance of the BMP4 and FGF10 morphogens occurring at this time. At 103 days of gestation, FGF10 gene expression dropped steadily from maximal levels, in a trend that continued until day 143. Conversely, from day 105, BMP4 transcript levels rapidly increased to maximal levels that were maintained until 131 days, before declining. This profile closely matches reported changes in branched follicle numbers, which peak in density at day 134. SPRY4, a known regulator of FGF10, increased to maximal levels concomitant with the fall in FGF10, suggesting a relationship. Levels of the BMP4 inhibitor NOG matched the initial rise of BMP4, with a fivefold spike at 108 days; but consistent with the rise in BMP4, this high level was not sustained.

Increased vibrissa growth in transgenic mice expressing insulin-like growth factor 1

Insulin-like growth factor 1 (IGF-1) mediates many of the actions of growth hormone. Overexpression of IGF-1 has been reported to have endocrine and paracrine/autocrine effects on somatic growth in transgenic mice. To study the paracrine/autocrine effects of IGF-1 in hair follicles, transgenic mice were produced by pronuclear microinjection of a construct containing a mouse ultra-high sulfur keratin (UHS-KER) promoter linked to an ovine IGF-1 cDNA. This UHS-KER promoter has previously been shown to direct expression of a reporter gene to the hair follicles of transgenic mice. Four transgenic mouse lines were established as a result of microinjection of 435 embryos. Transgene expression was found in skin at day 8 and day 15 of age in three of the lines. Progeny tests were carried out by mating two of the transgenic expressing males to nontransgenic females. Mice from one line were all nonexpressors while four of the 12 mice from the other showed integration of the transgene and three expressed transgene IGF-1 mRNA in the skin. Vibrissa growth at 11-21 d of age was significantly greater in transgenic expressors than in their nontransgenic littermates. Specifically, the increase in vibrissa length for transgenics at days 11-16 (20.5%) is approximately 2-fold compared with days 16-21 (11.9%). These results demonstrate that local overexpression of IGF-1 in transgenic mice is capable of stimulating vibrissa growth during the first neonatal hair cycle.

Detection of growth factors and proto-oncogene mRNA in the growing tip of red deer (Cervus elaphus) antler using reverse-transcriptase polymerase chain reaction (RT-PCR)

Deer antler is a unique mammalian organ that has an annual cycle of regeneration. The antler grows very rapidly from the tip at up to 1 cm/day in red deer for a 90- to 120-day period. It is hypothesised that locally produced growth factors are required to control and stimulate this growth. The tip of the growing antler from animals whose antlers had been growing for 30, 60, or 90 days was dissected into four zones: epidermis/dermis, reserve mesenchyme, precartilaginous, and cartilaginous. Total RNA was extracted, and the presence of various growth factors and proto-oncogenes was detected using RT-PCR, IGF-I, IGF-II, TGF beta 1, TGF beta 2, c-fos, c-myc, and beta-actin were all present as single bands of the expected molecular weight in the four zones of the antler at each stage of growth. There were higher levels of IGF-I, TGF beta 2, and c-myc relative to beta-actin in the epidermis/dermis layer than in the other three zones. There were no differences in the expression of any of the genes between the three stages of growth. The presence of TGF beta 3 cannot be confirmed since multiple bands were seen in all antler tissues. A single band of the expected size for TGF alpha was seen only in the epidermal/dermal layer of the antler, with multiple bands of different molecular weight being detected in the other zones of the antler. This work has demonstrated the presence of multiple growth factors in the growing deer antler and supports the hypothesis that paracrine/autocrine stimulation is important for regulating antler growth.

Cysteines 153 and 154 of transmembrane transforming growth factor-alpha are palmitoylated and mediate cytoplasmic protein association

Transforming growth factor-alpha (TGF-alpha) is synthesized as a transmembrane protein with a highly conserved, short cytoplasmic domain that is rich in cysteines. TGF-alpha is a prototype of a large family of growth factors involved in cell-cell communication. We have shown previously that transmembrane TGF-alpha associates with a kinase activity and two proteins of 106 and 86 kDa. In this study, we have used site-directed mutagenesis of the cytoplasmic domain of TGF-alpha to define the structural requirements for these protein interactions. Whereas the cytoplasmic domain of TGF-alpha was not essential for association with transmembrane p106, deletion of the C-terminal 8 amino acids, including a cysteine pair, abolished the interaction with p86 and greatly reduced the kinase activity associated with transmembrane TGF-alpha. Replacement of these 2 cysteines by serines similarly reduced the association of p86 with transmembrane TGF-alpha. Using a combination of mutational analysis and direct microsequencing, we have determined that this cysteine pair was palmitoylated. We therefore conclude that these cysteines play a critical role in the interaction of TGF-alpha with associated proteins and in the function of this protein complex. The palmitoylation of these cysteines suggests a possibly dynamic role of fatty acid modification in the integrity and function of the transmembrane TGF-alpha complex.