Vascular persistence following precision micropuncture

OBJECTIVE

The success of engineered tissues continues to be limited by time to vascularization and perfusion. Recently, we described a simple microsurgical approach, termed micropuncture (MP), which could be used to rapidly vascularize an adjacently placed scaffold from the recipient macrovasculature. Here we studied the long-term persistence of the MP-induced microvasculature.

METHODS

Segmental 60 μm diameter MPs were created in the recipient rat femoral artery and vein followed by coverage with a simple Type 1 collagen scaffold. The recipient vasculature and scaffold were then wrapped en bloc with a silicone sheet to isolate intrinsic vascularization. Scaffolds were harvested at 28 days post-implantation for detailed analysis, including using a novel artificial intelligence (AI) approach.

RESULTS

MP scaffolds demonstrated a sustained increase of vascular density compared to internal non-MP control scaffolds (p < 0.05) secondary to increases in both vessel diameters (p < 0.05) and branch counts (p < 0.05). MP scaffolds also demonstrated statistically significant increases in red blood cell (RBC) perfused lumens.

CONCLUSIONS

This study further highlights that the intrinsic MP-induced vasculature continues to persist long-term. Its combination of rapid and stable angiogenesis represents a novel surgical platform for engineered scaffold and graft perfusion.

Advanced Nanofiber-Based Scaffolds for Achilles Tendon Regenerative Engineering

The Achilles tendon (AT) is responsible for running, jumping, and standing. The AT injuries are very common in the population. In the adult population (21–60 years), the incidence of AT injuries is approximately 2.35 per 1,000 people. It negatively impacts people’s quality of life and increases the medical burden. Due to its low cellularity and vascular deficiency, AT has a poor healing ability. Therefore, AT injury healing has attracted a lot of attention from researchers. Current AT injury treatment options cannot effectively restore the mechanical structure and function of AT, which promotes the development of AT regenerative tissue engineering. Various nanofiber-based scaffolds are currently being explored due to their structural similarity to natural tendon and their ability to promote tissue regeneration. This review discusses current methods of AT regeneration, recent advances in the fabrication and enhancement of nanofiber-based scaffolds, and the development and use of multiscale nanofiber-based scaffolds for AT regeneration.

Emerging Trends in Information-Driven Engineering of Complex Biological Systems

Synthetic biological systems are used for a myriad of applications, including tissue engineered constructs for in vivo use and microengineered devices for in vitro testing. Recent advances in engineering complex biological systems have been fueled by opportunities arising from the combination of bioinspired materials with biological and computational tools. Driven by the availability of large datasets in the "omics" era of biology, the design of the next generation of tissue equivalents will have to integrate information from single-cell behavior to whole organ architecture. Herein, recent trends in combining multiscale processes to enable the design of the next generation of biomaterials are discussed. Any successful microprocessing pipeline must be able to integrate hierarchical sets of information to capture key aspects of functional tissue equivalents. Micro- and biofabrication techniques that facilitate hierarchical control as well as emerging polymer candidates used in these technologies are also reviewed.

A comprehensive study on donor-matched comparisons of three types of mesenchymal stem cells-containing cells from human dental tissue

BACKGROUND AND OBJECTIVE

Mesenchymal stem cells (MSCs) have been widely used in tissue engineering, such as for regenerating the supporting structures of teeth destroyed by periodontal diseases. In recent decades, dental tissue-derived MSCs have drawn much attention owing to their accessibility, plasticity and applicability. Dental pulp stem cells (DPSCs), periodontal ligament stem cells (PDLSCs) and gingival MSCs (GMSCs) are the most readily available MSCs among all types of dental MSCs. The purpose of this study was to comprehensively compare the characteristics of MSCs from dental pulp (DP), periodontal ligament (PDL) and gingiva (G) in vitro and thus provide insight into optimizing the performance of cells and seed cell selection strategies for tissue regeneration.

MATERIALS AND METHODS

In this study, patient-matched (n = 5) cells derived from DP, PDL and G which, respectively, contained DPSCs, PDLSCs and GMSCs were evaluated using multiple methods in terms of their proliferation, senescence, apoptosis, multilineage differentiation and stemness maintenance after long-term passage.

RESULTS

Mesenchymal stem cells-containing cells from G (MSCs/GCs) showed superior proliferation capability, whereas patient-matched MSCs-containing cells from PDL (MSCs/PDLCs) exhibited excellent osteogenic and adipogenic differentiation ability; MSCs-containing cells from DP (MSCs/DPCs) achieved mediocre results in both aspects. In addition, MSCs/GCs were the least susceptible to senescence, while MSCs/PDLCs were the most prone to ageing. Furthermore, the biological properties of these three types of cells were all affected after long-term in vitro culture.

CONCLUSION

These three types of dental MSCs showed different biological characteristics. MSCs/PDLCs are the best candidate cells for bone regeneration, but the application of MSCs/PDLCs might be limited to certain number of passages. Improving the differentiation of MSCs/GCs remains the key issue regarding their application in tissue engineering.

Evaluation of a novel poly(amidoamine) with pendant aminobutyl group on the cellular properties of transfected bone marrow mesenchymal stem cells

Stem cell-based gene therapy has been considered in the treatment of many degenerative diseases. Gene-modified stem cells should maintain its reproductive activity without losing stem cell properties, including genetic phenotype and differentiation potential. In the study, a novel poly (amidoamine) with pendant aminobutyl group (PAA-BA) designed by our group was used in the transfection of bone marrow mesenchymal stromal cells (BMSCs) and the cellular properties post-transfection were evaluated, including DNA content, colony forming capacity, genetic phenotype, and multi-directional differentiation. Two classical non-viral gene delivery vectors, polyethylenimine (PEI) and Lipofectamine 2000 (LP2000) were also used. Compared to non-transfected group, PAA-BA showed minor decreased DNA content but maintained BMSCs' phenotype, reproductive activity and multi-differentiation potential (osteogenic, chondrogenic, adipogenic, and neurogenic differentiation). Both PAA-BA and PEI transfected BMSCs demonstrated improved osteogenic differentiation ability at late stage but suppressed adipogenic as well as mature neural differentiation in vitro. LP2000 and PEI transfected BMSCs displayed significantly lower DNA content and reproductive activity. These findings suggest that PAA-BA is one of safe gene delivery vectors in BMSCs transfection and plays a role in stem cell's osteogenic and neurogenic differentiation. This study proposes the potential application of PAA-BA in BMSCs based gene therapy, in particular bone and nerve relative diseases. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 686-697, 2018.

Silicone Substrate with Collagen and Carbon Nanotubes Exposed to Pulsed Current for MSC Osteodifferentiation

Autologous human adipose tissue-derived mesenchymal stem cells (MSCs) have the potential for clinical translation through their induction into osteoblasts for regeneration. Bone healing can be driven by biophysical stimulation using electricity for activating quiescent adult stem cells. It is hypothesized that application of electric current will enhance their osteogenic differentiation, and addition of conductive carbon nanotubes (CNTs) to the cell substrate will provide increased efficiency in current transmission. Cultured MSCs were seeded and grown onto fabricated silicone-based composites containing collagen and CNT fibers. Chemical inducers, namely, glycerol phosphate, dexamethasone, and vitamin C, were then added to the medium, and pulsatile submilliampere electrical currents (about half mA for 5 cycles at 4 mHz, twice a week) were applied for two weeks. Calcium deposition indicative of MSC differentiation and osteoblastic activity was quantified through Alizarin Red S and spectroscopy. It was found that pulsed current significantly increased osteodifferentiation on silicone-collagen films without CNTs. Under no external current, the presence of 10% (m/m) CNTs led to a significant and almost triple upregulation of calcium deposition. Both CNTs and current parameters did not appear to be synergistic. These conditions of enhanced osteoblastic activities may further be explored ultimately towards future therapeutic use of MSCs.