Growth hormone substitution in growth hormone-deficient adults: effects on collagen type I synthesis and skin thickness

Development of nano-liposomal human growth hormone as a topical formulation for preventing uvb-induced skin damage

Due to its involvement in skin maintenance and repair, topical administration of recombinant human growth hormone (rhGH) is an interesting strategy for therapeutic purposes. We have formulated and characterized a topical rhGH-loaded liposomal formulation (rhGH-Lip) and evaluated its safety, biological activity, and preventive role against UVB-induced skin damage. The rhGH-Lip had an average size and zeta potential of 63 nm and -33 mV, respectively, with 70 % encapsulation efficiency. The formulation was stable at 4 °C for at least one year. The SDS-PAGE and circular dichroism results showed no structural alterations in rhGH upon encapsulation. In vitro, studies in HaCaT, HFFF-2, and Ba/F3-rhGHR cell lines confirmed the safety and biological activity of rhGH-Lip. Franz diffusion cell study showed increased rhGH skin permeation compared to free rhGH. Animal studies in nude mice showed that liposomal rhGH prevented UVB-induced epidermal hyperplasia, angiogenesis, wrinkle formation, and collagen loss, as well as improving skin moisture. The results of this study show that rhGH-Lip is a stable, safe, and effective skin delivery system and has potential as an anti-wrinkle formulation for topical application. This study also provides a new method for the topical delivery of proteins and merits further investigation.

Association of COLIA1 Sp1 polymorphism with the effect of subcutaneously injected recombinant hGH in GH-deficient adults

Objective: Collagen type I is a common structural protein in bone and skin. Similar to its association with the mechanical properties of the skeleton and, thus, bone-fracture risk, the collagen type I α (COLIA)-1 specific protein (Sp)-1 polymorphism may be related to variations in the collagen type I-containing subcutaneous tissue and its biological properties. In this study, we analyzed a possible influence of the COLIA1 Sp1 polymorphism on the effect of subcutaneously injected recombinant human growth hormone (hGH) in GH-deficient adults. Materials & methods: We determined the COLIA1 Sp1 polymorphism in 122 adults with GH deficiency of different origin, who were derived from the prospective Pfizer International Growth Database (KIMS) Pharmacogenetics Study. Inclusion criteria were subcutaneous applied treatment with hGH for over 12 months, finished dose titration of hGH by following serum IGF-1 concentrations until desired levels were achieved, and centralized, standardized IGF-1 measurements. The genotypes (GG/GT/TT) were statistically related to clinical data from the KIMS database. Results: The dose of injected hGH was significantly related to the COLIA1 Sp1 genotypes (p = 0.049), whereby the GG homozygotes were treated with a significantly higher dose of hGH than TT homozygotes (p = 0.03). Accordingly, the IGF-1:GH ratios were significantly lower in GG compared with TT homozygotes (p = 0.04). Both groups showed no significant differences in their IGF-1 serum concentrations (p = 0.98) and IGF-1 SDS (p = 0.79). Conclusion: The COLIA1 Sp1 polymorphism is related to the dose of individually required, subcutaneous injected hGH in GH-deficient adults, probably because of an alteration of the subcutaneous collagen type I structure, content and/or biological/biomechanical properties. GG homozygotism, which is related to a more stable bone structure and decreased fracture risk, may impact skin resistance to subcutaneous injected protein-based drugs, as shown for hGH in this study.

Alterations in the mechanical properties and composition of skin in human growth hormone transgenic mice

Growth hormone is known to stimulate connective tissue, but the degree to which it influences skin biomechanical properties is unclear. This study tested the hypothesis that human growth hormone transgene expression changes the material properties and structural composition of adult mouse skin. Fracture toughness and elastic modulus were measured on freshly dissected dorsal skin and fixed samples were analyzed histologically. Transgenics had higher elastic moduli than their sex-matched non transgenic littermates, and male transgenics demonstrated increased fracture toughness. Male transgenics also had thicker skin than controls with a selectively increased dermis. In contrast, female transgenics had thinner skin than controls due to a reduced hypodermis. Biomechanical and histological variables were strongly correlated. Significant sex differences were present in nearly all comparisons indicating a dimorphic response to growth hormone in the skin. These data demonstrate that constant low-level growth hormone expression in marrow differentially affects skin layer thickness and concomitantly alters its biomechanical properties.

Abnormal bone collagen morphology and decreased bone strength in growth hormone-deficient rats

Patients with growth hormone deficiency (GHD) have an increased risk of bone fractures. In these patients, the well-described decrease in bone mineral density (BMD) and content (BMC) may, however, not alone explain the increase in fracture rate. Accordingly, the aim of this study was to evaluate collagen morphology and bone mineralisation in cortical bone as well as bone strength in GHD rats to try to clarify the explanation for the increased fracture rate. The Dw-4 rat was used as a model for GHD. This strain of rats has an autosomal recessive disorder, reducing GH synthesis to approximately 10% and growth rate to approximately 40-50% when compared to normal control rats. Five male Dw-4 rats were examined at age 12 weeks and five healthy Lewis rats served as age-matched controls. The animals were examined for (1) bone mineral status by dual energy X-ray absorptometry (DXA) and ash weight/bone volume, (2) biomechanical properties, (3) serum insulin-like growth factor I (IGF-I) and IGF binding protein 3 (IGFBP-3), and (4) collagen morphology of cortical bone from the right femurs was examined by scanning and transmission electron microscopy. A significant decrease was found in serum IGF-I, IGFBP-3 and biomechanical properties in GHD rats compared to controls (P < 0.009). While DXA-derived BMD was decreased, no significant difference was found in ash weight/bone volume. Electron microscopy showed a significant decrease in the number and a significant increase in the diameter of collagen microfibrils in GHD rats as compared to their controls (P < 0.009). In conclusion, we report for the first time that collagen morphology in bone is markedly altered in rats with isolated GHD. Whether similar conditions are present in GHD patients need further investigations. The changes described, however, may provide a co-explanation for the increased fracture rate in GHD.

Dorsal skin responses to topical application with hydrogen peroxide in Mini and Wistar rats

Mini rats (Jcl: WistarTGN(ARGHGEN) 1Nts) (MRs) are Wistar rat (WR)-derived transgenic rats in which the expression of growth hormone (GH) gene is suppressed under the presence of antisense RNA transgene. In order to evaluate the effects of GH-deficiency on the acute injury by external stimuli, the dorsal skin responses to a single topical application with 20% hydrogen peroxide (HPO), one of the environmental oxidative stressors, were histologically compared between male MRs and WRs of 8 weeks old, whose hair cycle was under the telogen phase. As a result, formation of granulation tissues, reepithelialization and regrowth of hair follicles were delayed in MRs compared with WRs. While hair follicles of MRs of this age are under a long-lasting telogen phase after their 2nd cycle, a new hair cycle started not only in the HPO-applied area but also in the solvent-applied area with a little time lag. These findings suggest that GH-deficiency may influence the skin responses to the external chemical stimuli.