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Background Effective ART is crucial for combating the HIV pandemic. Clinically, plasma viral load monitoring to achieve virological suppression is the guide for an optimal ART. The presence of low-level viraemia (LLV) below the definition level of virological failure is a risk factor for ART failure. However, there is no treatment consensus over LLV yet, mainly due to the limitation of standard HIV-RNA genotyping and the resultant insufficient understanding of LLV characteristics. Objectives To better profile drug resistance mutations (DRMs) and the associated factors in cases experiencing LLV. Methods A prospective observational study was conducted from 2017 to 2019. HIV-DNA was used as an alternative to HIV-RNA for HIV genotyping coupled with deep sequencing for ART-naive and ART-failure cases, as well as those with LLV. Results Eighty-one ART-naive, 18 ART-failure and 16 LLV cases received HIV genotyping in the study. Three-quarters (12/16) of cases experiencing LLV harboured DRMs. Cases with LLV had higher prevalence of DRMs to NNRTIs than the ART-naive group (69% versus 20%, P Conclusions HIV DRM profiles in LLV cases were significantly different to those in ART-naive and ART-failure cases. Approaches to consolidate ART compliance and early exploration of potential ART resistance may be needed for cases experiencing LLV episodes.

The regeneration capacity of knee cartilage can be enhanced by applying periosteal grafts, but this effect varies depending on the different sources of the periosteal grafts applied for cartilage formation. Tibia periosteum can be used to enhance cartilage repair. However, long-term analysis has not been conducted. The endochondral ossification capacity of tibia periosteum during cartilage repair also needs to be investigated. In this study, both vascularized and non-vascularized tibia periosteum grafts were studied to understand the relationship between tissue perfusion of the periosteum graft and the effects on cartilage regeneration and bone formation. Furthermore, anti-ossification reagents were added to evaluate the efficacy of the prevention of bone formation along with cartilage regeneration. A critical-size cartilage defect (4 × 4 mm) was created and was covered with an autologous tibia vascularized periosteal flap or with a non-vascularized tibia periosteum patch on the knee in the rabbit model. A portion of the vascularized periosteum group was also treated with the anti-osteogenic reagents Fulvestrant and IL1β to inhibit unwanted bone formation. Our results indicated that the vascularized periosteum significantly enhanced cartilage regeneration in the cartilage defect region in long-term treatment compared to the non-vascularized group. Furthermore, the addition of anti-osteogenic reagents to the vascularized periosteum group suppressed bone formation but also reduced the cartilage regeneration rate. Our study using vascularized autologous tissue to repair cartilage defects of the knee may lead to the modification of current treatment in regard to osteoarthritis knee repair.

Background Cell-seeded biomaterial scaffolds have been proposed as a future option for reconstruction of bone tissue. The ability to generate larger, functional volumes of bone has been a challenge that may be addressed through the use of perfusion bioreactors. In this study, the authors investigated use of a tubular perfusion bioreactor system for the growth and differentiation of bone marrow stromal (mesenchymal stem) cells seeded onto fibrin, a highly angiogenic biomaterial. Methods Cells were encapsulated within fibrin beads and cultured either within a tubular perfusion bioreactor system or statically for up to 14 days. Scaffolds were analyzed for osteogenic differentiation. A rodent cranial defect model (8-mm diameter) was used to assess the bone regeneration of scaffolds cultured in the bioreactor, statically, or used immediately after formation. Immunohistochemistry was used to visualize CD31 vessel density. Micro-computed tomographic imaging was used to visualize mineral formation within the defect volume. Results Tubular perfusion bioreactor system-cultured samples showed significantly greater osteodifferentiation, indicated by an increase in VEGF expression and mineral deposition, compared with statically cultured samples. Increased expression of OPN, RUNX2, VEGF, and CD90 was seen over time in both culture methods. After implantation, bioreactor samples exhibited greater bone formation and vessel density compared with all other groups. Analysis of micro-computed tomographic images showed full union formation through the greatest diameter of the defect in all bioreactor samples and the highest levels of mineralized volume after 8 weeks. Conclusion Mesenchymal stem cells encapsulated in fibrin beads and cultured in the tubular perfusion bioreactor system resulted in increased vascularization and mineralized tissue formation in vivo relative to static culture.

Periosteum is a promising tissue engineering scaffold in research of cartilage repair; so far however, periosteum transfers have not been realized successfully because of insufficient nourishment of the graft. In a translational approach we, for the first time, designed a vascularized periosteum flap as ‘independent’ biomaterial with its own blood supply to address this problem and to reconstruct circumscript cartilage defects. In six 3-month-old New Zealand rabbits, a critical size cartilage defect of the medial femur condyle was created and covered by a vascularized periosteum flap pedicled on the saphenous vessels. After 28 days, formation of newly built cartilage was assessed macroscopically, histologically and qualitatively via biomechanical compression testing, as well as on molecular biological level via immunohistochemistry. All wounds healed completely, all joints were stable and had full range of motion. All flaps survived and were perfused through their pulsating pedicles. They showed a stable attachment to the bone, although partially incomplete adherence. Hyaline cartilage with typical columnar cell distribution and positive Collagen II staining was formed in the transferred flaps. Biomechanical testing revealed a significantly higher maximum load than the positive control, but a low elasticity. This study proved that vascularization of the periosteum flap is the essential step for flap survival and enables the flap to transform into cartilage. Reconstruction of circumscript cartilage defects seems to be possible. Although these are the first results out of a pilot project, this technique, we believe, can have a wide range of potential applications and high relevance in the clinical field.

Engineered vascularized adipose tissue could serve as an alternative to traditional tissue reconstruction procedures. Adipose formation occurs in a coordinated fashion with neovascularization. Previous studies have shown that extracellular matrix-based materials supplemented with factors that stimulate neovascularization promote adipogenesis in a number of animal models. The present study examines the ability of fibroblast growth factor (FGF-1) delivered from alginate microbeads to induce neovascularization and adipogenesis in type I collagen gels in a vascular pedicle model of adipose tissue engineering. FGF-1 loaded microbeads stimulated greater vascular network formation in an in vitro 3D co-culture model compared than a single bolus of FGF-1. In in vivo studies, FGF-1 loaded beads suspended in collagen and implanted in a chamber surrounding the exposed femoral pedicle of a rat resulted in a significant increase in vascular density at 1 and 6 weeks in comparison to bolus administration of FGF-1. Staining for smooth muscle actin showed that over 48% of vessels had associated mural cells. While an increase in neovascularization was achieved, there was less than 3% adipose under any condition. These results show that delivery of FGF-1 from alginate beads stimulated a more persistent neovascularization response than bolus FGF-1 both in vitro and in vivo. However, unlike previous studies, this increased neovascularization did not result in adipogenesis. Future studies need to provide a better understanding of the relationship between neovascularization and adipogenesis in order to design advanced tissue engineering therapies.

Background: Wound healing and skin tissue engineering are mediated, in part, by interactions between cells and the extracellular matrix (ECM). A subset of the ECM, basement membranes (BM), plays a vital role in regulating proper skin healing and function. Methods: ECM-rich, tissue-specific hydrogels were extracted and assembled from dermis samples. These hydrogels contain BM proteins vital to skin regeneration, including laminin β3, collagen IV, and collagen VII. The extracts could be assembled to form hydrogels by either temperature or pH mechanism, with the mechanical properties and structure varying with the mechanism of assembly. A wound healing model was developed to investigate the ability of these hydrogels to enhance healing with a single application in vivo. Results: The pH, but not temperature gels were easily applied to the wounds. There were no signs of increased inflammation due to the application of the hydrogels. The width of granulation tissue at the first week was reduced ( p = 0.064) relative to controls with the application of hydrogel. There were no changes in wound closure rates or vessel density. Conclusions: Dermis-derived hydrogels contain BM proteins important for skin regeneration. They can be easily applied, but their poor mechanical strength and rapid degradation may hinder their biological effects.

Vascularization is influenced by the physical architecture of a biomaterial. The relationship between pore size and vascularization has been examined for hydrophobic polymer foams, but there has been little research on tissue response in porous hydrogels. The goal of this study was to examine the role of pore size on vessel invasion in porous poly(ethylene glycol) (PEG) hydrogels. Vascularized tissue ingrowth was examined using three-dimensional cell culture and rodent models. In culture, all porous gels supported vascular invasion with the rate increasing with pore size. Following subfascial implantation, porous gels rapidly absorbed wound fluid, which promoted tissue ingrowth even in the absence of exogenous growth factors. Pore size influenced neovascularization, within the scaffolds and also the overall tissue response. Cell and vessel invasion into gels with pores 25-50 μm in size was limited to the external surface, while gels with pores larger pores (50-100 and 100-150 μm) permitted mature vascularized tissue formation throughout the entire material volume. A thin layer of inflammatory tissue was present at all PEG-tissue interfaces, effectively reducing the area available for tissue growth. These results show that porous PEG hydrogels can support extensive vascularized tissue formation, but the nature of the response depends on the pore size.