Empirical Evaluation of Bone Extraction Protocols

The application of high-resolution analytical techniques to characterize ancient bone proteins requires clean, efficient extraction to obtain high quality data. Here, we evaluated many different protocols from the literature on ostrich cortical bone and moa cortical bone to evaluate their yield and relative purity using the identification of antibody-antigen complexes on enzyme-linked immunosorbent assay and gel electrophoresis. Moa bone provided an ancient comparison for the effectiveness of bone extraction protocols tested on ostrich bone. For the immunological part of this study, we focused on collagen I, osteocalcin, and hemoglobin because collagen and osteocalcin are the most abundant proteins in the mineralized extracellular matrix and hemoglobin is common in the vasculature. Most of these procedures demineralize the bone first, and then the remaining organics are chemically extracted. We found that the use of hydrochloric acid, rather than ethylenediaminetetraacetic acid, for demineralization resulted in the cleanest extractions because the acid was easily removed. In contrast, the use of ethylenediaminetetraacetic acid resulted in smearing upon electrophoretic separation, possibly indicating these samples were not as pure. The denaturing agents sodium dodecyl sulfate, urea, and guanidine HCl have been used extensively for the solubilization of proteins in non-biomineralized tissue, but only the latter has been used on bone. We show that all three denaturing agents are effective for extracting bone proteins. One additional method tested uses ammonium bicarbonate as a solubilizing buffer that is more appropriate for post-extraction analyses (e.g., proteomics) by removing the need for desalting. We found that both guanidine HCl and ammonium bicarbonate were effective for extracting many bone proteins, resulting in similar electrophoretic patterns. With the increasing use of proteomics, a new generation of scientists are now interested in the study of proteins from not only extant bone but also from ancient bone

Wound dressings for a proteolytic-rich environment

Wound dressings have experienced continuous and significant changes over the years based on the knowledge of the biochemical events associated with chronic wounds. The development goes from natural materials used to just cover and conceal the wound to interactive materials that can facilitate the healing process, addressing specific issues in non-healing wounds. These new types of dressings often relate with the proteolytic wound environment and the bacteria load to enhance the healing. Recently, the wound dressing research is focusing on the replacement of synthetic polymers by natural protein materials to delivery bioactive agents to the wounds. This article provides an overview on the novel protein-based wound dressings such as silk fibroin keratin and elastin. The improved properties of these dressings, like the release of antibiotics and growth factors, are discussed. The different types of wounds and the effective parameters of healing process will be reviewed

The Advancement of Biomaterials in Regulating Stem Cell Fate.

Stem cells are well-known to have prominent roles in tissue engineering applications. Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) can differentiate into every cell type in the body while adult stem cells such as mesenchymal stem cells (MSCs) can be isolated from various sources. Nevertheless, an utmost limitation in harnessing stem cells for tissue engineering is the supply of cells. The advances in biomaterial technology allows the establishment of ex vivo expansion systems to overcome this bottleneck. The progress of various scaffold fabrication could direct stem cell fate decisions including cell proliferation and differentiation into specific lineages in vitro. Stem cell biology and biomaterial technology promote synergistic effect on stem cell-based regenerative therapies. Therefore, understanding the interaction of stem cell and biomaterials would allow the designation of new biomaterials for future clinical therapeutic applications for tissue regeneration. This review focuses mainly on the advances of natural and synthetic biomaterials in regulating stem cell fate decisions. We have also briefly discussed how biological and biophysical properties of biomaterials including wettability, chemical functionality, biodegradability and stiffness play their roles

Sustained Postnatal Skin Regeneration upon Prenatal Application of Functionalized Collagen Scaffolds

Primary closure of fetal skin in spina bifida protects the spinal cord and improves clinical outcome, but is also associated with postnatal growth malformations and spinal cord tethering. In this study, we evaluated the postnatal effects of prenatally closed full-Thickness skin defects in sheep applying collagen scaffolds with and without heparin/vascular endothelial growth factor/fibroblast growth factor 2, focusing on skin regeneration and growth. At 6 months, collagen scaffold functionalized with heparin, VEGF, and FGF2 (COL-HEP/GF) resulted in a 6.9-fold increase of the surface area of the regenerated skin opposed to 1.7 × for collagen only. Epidermal thickness increased 5.7-fold at 1 month, in line with high gene expression of S100 proteins, and decreased to 2.1 at 6 months. Increased adipose tissue and reduced scaffold degradation and number of myofibroblasts were observed for COL-HEP/GF. Gene ontology terms related to extracellular matrix (ECM) organization were enriched for both scaffold treatments. In COL-HEP/GF, ECM gene expression resembled native skin. Expression of hair follicle-related genes in COL-HEP/GF was comparable to native skin, and de novo hair follicle generation was indicated. In conclusion, in utero closure of skin defects using functionalized collagen scaffolds resulted in long-Term skin regeneration and growth. Functionalized collagen scaffolds that grow with the child may be useful for prenatal treatment of closure defects like spina bifida

Collagen-Vicryl scaffolds for reconstruction of the diaphragm in a large animal model

Current methods for closure of congenital diaphragmatic hernia using patches are unsatisfactory, and novel collagen-based scaffolds have been developed, and successfully applied in a rat model. However, for translation to the human situation constructs must be evaluated in larger animal models. We developed collagen scaffolds enforced with Vicryl, loaded either with or without the muscle stimulatory growth factor insulin-like growth factor 1 (IGF1). We describe our steps to a surgical method to implant these scaffolds into a diaphragmatic defect in 1.5-3 week old lambs, and evaluate the scaffolds 6 months after implantation. Omentum was attached to the scaffold. At sacrifice, eventration of the implantation site was observed in all animals with a thin layer of tissue separating the abdomen from the thorax. Histologically, no scaffold remnants could be observed. Fatty tissue surrounded by fibrous tissue was seen, resembling encapsulated omentum, with collagen-rich tissue present between this tissue and the original diaphragmatic muscle. Outcomes were not different for scaffolds with or without IGF1. In conclusion, the scaffolds integrated well into the surrounding tissue, but slower degrading materials are needed to prevent eventrations. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 102B: 756-763, 2014

Bladder Regeneration Using a Smart Acellular Collagen Scaffold with Growth Factors VEGF, FGF2 and HB-EGF

Tissue engineering may become an alternative to current bladder augmentation techniques. Large scaffolds are needed for clinically significant augmentation, but can result in fibrosis and graft shrinkage. The purpose of this study was to investigate whether smart acellular collagen-heparin scaffolds with growth factors (GFs) VEGF, FGF2, and HB-EGF enhance bladder tissue regeneration and bladder capacity in a large animal model of diseased bladder. Scaffolds of bovine type I collagen with heparin and VEGF, FGF2, and HB-EGF measuring 3.2cm in diameter were prepared. In 23 fetal sheep, a bladder exstrophy was surgically created at 79 days of gestation. One week after birth (at full term), the bladder was reconstructed by primary closure (PC group) or using a collagen-heparin scaffold with GFs (COLGF group) and compared to a historical group reconstructed with a collagen scaffold without GFs (COL group). Functional (video urodynamics) and histological evaluation was performed 1 and 6 months after bladder repair. The overall survival rate was 57%. Cystograms were normal in all animals, except for low-grade reflux in all groups. Urodynamics showed no statistically significant differences in bladder capacity and compliance between groups. Histological evaluation at 1 month revealed increased urothelium formation, improved angiogenesis, and enhanced ingrowth of smooth muscle cells (SMCs) in the COLGF group compared to the COL group. At 6 months, improved SMC ingrowth was found in the COLGF group compared to the COL group; both scaffold groups showed normal urothelial lining and standard extracellular matrix development. Bladder regeneration using a collagen-heparin scaffold with VEGF, FGF2, and HB-EGF improved bladder tissue regeneration in a large animal model of diseased bladder. Larger GF-loaded constructs need to be tested to reach clinically significant augmentation