The character of gene expression of human periosteum used to form new tissue in allograft bone

Mechanical strain induces ex vivo expansion of periosteum

Segmental bone defects present complex clinical challenges. Nonunion, malunion, and infection are common sequalae of autogenous bone grafts, allografts, and synthetic bone implants due to poor incorporation with the patient's bone. The current project explores the osteogenic properties of periosteum to facilitate graft incorporation. As tissue area is a natural limitation of autografting, mechanical strain was implemented to expand the periosteum. Freshly harvested, porcine periosteum was strained at 5 and 10% per day for 10 days with non-strained and free-floating samples serving as controls. Total tissue size, viability and histologic examination revealed that strain increased area to a maximum of 1.6-fold in the 10% daily strain. No change in tissue anatomy or viability via MTT or Ki67 staining and quantification was observed among groups. The osteogenic potential of the mechanical expanded periosteum was then examined in vivo. Human cancellous allografts were wrapped with 10% per day strained, fresh, free-floating, or no porcine periosteum and implanted subcutaneously into female, athymic mice. Tissue was collected at 8- and 16-weeks. Gene expression analysis revealed a significant increase in alkaline phosphatase and osteocalcin in the fresh periosteum group at 8-weeks post implantation compared to all other groups. Values among all groups were similar at week 16. Additionally, histological assessment with H&E and Masson-Goldner Trichrome staining showed that all periosteal groups outperformed the non-periosteal allograft, with fresh periosteum demonstrating the highest levels of new tissue mineralization at the periosteum-bone interface. Overall, mechanical expansion of the periosteum can provide increased area for segmental healing via autograft strategies, though further studies are needed to explore culture methodology to optimize osteogenic potential.

Periosteal Tissue Engineering: Current Developments and Perspectives

Periosteum, a highly vascularized bilayer connective tissue membrane plays an indispensable role in the repair and regeneration of bone defects. It is involved in blood supply and delivery of progenitor cells and bioactive molecules in the defect area. However, sources of natural periosteum are limited, therefore, there is a need to develop tissue-engineered periosteum (TEP) mimicking the composition, structure, and function of natural periosteum. This review explores TEP construction strategies from the following perspectives: i) different materials for constructing TEP scaffolds; ii) mechanical properties and surface topography in TEP; iii) cell-based strategies for TEP construction; and iv) TEP combined with growth factors. In addition, current challenges and future perspectives for development of TEP are discussed.

Characterization of Tissue-Engineered Human Periosteum and Allograft Bone Constructs: The Potential of Periosteum in Bone Regenerative Medicine

Delayed-union or non-union between a host bone and a graft is problematic in clinical treatment of segmental bone defects in orthopedic cases. Based on a preliminary study of human periosteum allografts from this laboratory, the present work has extensively investigated the use of human cadaveric tissue-engineered periosteum-allograft constructs as an approach to healing such serious orthopedic surgical situations. In this current report, human cadaveric periosteum-wrapped bone allografts and counterpart controls without periosteum were implanted subcutaneously in athymic mice (nu/nu) for 10, 20, and, for the first time, 40 weeks. Specimens were then harvested and assessed by histological and gene expression analyses. Compared to controls, the presence of new bone formation and resorption in periosteum-allograft constructs was indicated in both histology and gene expression results over 40 weeks of implantation. Of several genes also examined for the first time, RANKL and SOST expression levels increased in a statistically significant manner, data suggesting that bone formation and the presence of increasing numbers of osteocytes in bone matrices had increased with time. The tissue-engineering strategy described in this study provides a possible means of improving delayed-union or non-union at the healing sites of segmental bone defects or bone fractures. The potential of periosteum and its resident cells could thereby be utilized effectively in tissue-engineering methods and tissue regenerative medicine.

A Method for the Immunohistochemical Identification and Localization of Osterix in Periosteum-Wrapped Constructs for Tissue Engineering of Bone

A novel immunohistochemistry (IHC) approach has been developed to label and localize osterix, a bone-specific transcription factor, within formalin-fixed, paraffin-embedded, tissue-engineered constructs uniquely containing synthetic polymers and human periosteal tissue. Generally, such specimens consisting in part of polymeric materials and mineral are particularly difficult for IHC identification of proteins. Samples here were fabricated from human periosteum, electrospun poly-l-lactic acid (PLLA) nanofibers, and polycaprolactone/poly-l-lactic acid (PCL/PLLA, 75/25) scaffolds and harvested following 10 weeks of implantation in athymic mice. Heat-induced and protease-induced epitope retrieval methods from selected existing protocols were examined to identify osterix. All such protease-induced techniques were unsuccessful. Heat-induced retrieval gave positive results for osterix immunohistochemical staining in sodium citrate/EDTA/Tween 20 with high heat (120C) and pressure (~30 psi) for 10 min, but the heat and pressure levels resulted in tissue damage and section delamination from slides that limited protocol effectiveness. Heat-induced epitope retrieval led to other osterix-positive staining results achieved with minimal impact on structural integrity of the tissue and polymers in sodium citrate/EDTA/Tween 20 buffer at 60C and normal pressure (14.5 psi) for 72 hr. The latter approach identified osterix-positive cells by IHC within periosteal tissue, layers of electrospun PLLA nanofibers, and underlying PCL/PLLA scaffolds of the tissue-engineered constructs.

Engineering biomimetic periosteum with β-TCP scaffolds to promote bone formation in calvarial defects of rats

Background

There is a critical need for the management of large bone defects. The purpose of this study was to engineer a biomimetic periosteum and to combine this with a macroporous β-tricalcium phosphate (β-TCP) scaffold for bone tissue regeneration.

Methods

Rat bone marrow-derived mesenchymal stem cells (rBMSCs) were harvested and cultured in different culture media to form undifferentiated rBMSC sheets (undifferentiated medium (UM)) and osteogenic cell sheets (osteogenic medium (OM)). Simultaneously, rBMSCs were differentiated to induced endothelial-like cells (iECs), and the iECs were further cultured on a UM to form a vascularized cell sheet. At the same time, flow cytometry was used to detect the conversion rates of rBMSCs to iECs. The pre-vascularized cell sheet (iECs/UM) and the osteogenic cell sheet (OM) were stacked together to form a biomimetic periosteum with two distinct layers, which mimicked the fibrous layer and cambium layer of native periosteum. The biomimetic periostea were wrapped onto porous β-TCP scaffolds (BP/β-TCP) and implanted in the calvarial bone defects of rats. As controls, autologous periostea with β-TCP (AP/β-TCP) and β-TCP alone were implanted in the calvarial defects of rats, with a no implantation group as another control. At 2, 4, and 8 weeks post-surgery, implants were retrieved and X-ray, microcomputed tomography (micro-CT), histology, and immunohistochemistry staining analyses were performed.

Results

Flow cytometry results showed that rBMSCs were partially differentiated into iECs with a 35.1% conversion rate in terms of CD31. There were still 20.97% rBMSCs expressing CD90. Scanning electron microscopy (SEM) results indicated that cells from the wrapped cell sheet on the β-TCP scaffold apparently migrated into the pores of the β-TCP scaffold. The histology and immunohistochemistry staining results from in vivo implantation indicated that the BP/β-TCP and AP/β-TCP groups promoted the formation of blood vessels and new bone tissues in the bone defects more than the other two control groups. In addition, micro-CT showed that more new bone tissue formed in the BP/β-TCP and AP/β-TCP groups than the other groups.

Conclusions

Inducing rBMSCs to iECs could be a good strategy to obtain an endothelial cell source for prevascularization. Our findings indicate that the biomimetic periosteum with porous β-TCP scaffold has a similar ability to promote osteogenesis and angiogenesis in vivo compared to the autologous periosteum. This function could result from the double layers of biomimetic periosteum. The prevascularized cell sheet served a mimetic fibrous layer and the osteogenic cell sheet served a cambium layer of native periosteum. The biomimetic periosteum with a porous ceramic scaffold provides a new promising method for bone healing.

Tissue engineering a human phalanx

A principal purpose of tissue engineering is the augmentation, repair or replacement of diseased or injured human tissue. This study was undertaken to determine whether human biopsies as a cell source could be utilized for successful engineering of human phalanges consisting of both bone and cartilage. This paper reports the use of cadaveric human chondrocytes and periosteum as a model for the development of phalanx constructs. Two factors, osteogenic protein-1 [OP-1/bone morphogenetic protein-7 (BMP7)], alone or combined with insulin-like growth factor (IGF-1), were examined for their potential enhancement of chondrocytes and their secreted extracellular matrices. Design of the study included culture of chondrocytes and periosteum on biodegradable polyglycolic acid (PGA) and poly-l-lactic acid (PLLA)-poly-ε-caprolactone (PCL) scaffolds and subsequent implantation in athymic nu/nu (nude) mice for 5, 20, 40 and 60 weeks. Engineered constructs retrieved from mice were characterized with regard to genotype and phenotype as a function of developmental (implantation) time. Assessments included gross observation, X-ray radiography or microcomputed tomography, histology and gene expression. The resulting data showed that human cell-scaffold constructs could be successfully developed over 60 weeks, despite variability in donor age. Cartilage formation of the distal phalanx models enhanced with both OP-1 and IGF-1 yielded more cells and extracellular matrix (collagen and proteoglycans) than control chondrocytes without added factors. Summary data demonstrated that human distal phalanx models utilizing cadaveric chondrocytes and periosteum were successfully fabricated and OP-1 and OP-1/IGF-1 accelerated construct development and mineralization. The results suggest that similar engineering and transplantation of human autologous tissues in patients are clinically feasible. Copyright © 2016 John Wiley & Sons, Ltd.