In JoVE (1)

Other Publications (11)

Articles by Mai T. Lam in JoVE

Other articles by Mai T. Lam on PubMed

The Effect of Continuous Wavy Micropatterns on Silicone Substrates on the Alignment of Skeletal Muscle Myoblasts and Myotubes

Biomaterials. Aug, 2006  |  Pubmed ID: 16650470

Tissue-engineered muscle is a viable option for tissue repair, though presently technologies are not developed enough to produce tissue in vitro identical to that in vivo. One important step in generating accurate engineered muscle is to mimic natural muscle architecture. Skeletal muscle is composed of fibrils whose organization defines functionality. In musculoskeletal myogenesis, aligning myoblasts in preparation for myotube formation is a crucial step. The ability to efficiently organize myoblasts to form aligned myotubes in vitro would greatly benefit efforts in muscle tissue engineering. This paper reports alignment of prefused and differentiated skeletal muscle cells in vitro by use of continuous micropatterned wavy silicone surfaces, with features sized 3, 6 and 12 microm in periodicity. Wave features with 6 microm periodicity produced the most healthy, aligned myoblasts. Alignment was found to be a function of plating density. Further growth on these substrates with aligned myoblasts promoted fusion, yielding healthy aligned myotubes. This method will be useful for applications in which differentiated myogenic cells need to be aligned unidirectionally as in the development of engineered muscle.

Reversible On-demand Cell Alignment Using Reconfigurable Microtopography

Biomaterials. Apr, 2008  |  Pubmed ID: 18192004

Traditional cell culture substrates consist of static, flat surfaces although in vivo, cells exist on various dynamic topographies. We report development of a reconfigurable microtopographical system compatible with cell culture that is comprised of reversible wavy microfeatures on poly(dimethylsiloxane). Robust reversibility of the wavy micropattern is induced on the cell culture customized substrate by first plasma oxidizing the substrate to create a thin, brittle film on the surface and then applying and releasing compressive strain, to introduce and remove the microfeatures, respectively. The reversible topography was able to align, unalign, and realign C2C12 myogenic cell line cells repeatedly on the same substrate within 24 h intervals, and did not inhibit cell differentiation. The flexibility and simplicity of the materials and methods presented here provide a broadly applicable capability by which to investigate and compare dynamic cellular processes not yet easily studied using conventional in vitro culture substrates.

Microfeature Guided Skeletal Muscle Tissue Engineering for Highly Organized 3-dimensional Free-standing Constructs

Biomaterials. Feb, 2009  |  Pubmed ID: 19064284

Engineering tissue similar in structure to their natural equivalents is a major challenge and crucial to function. Despite attempts to engineer skeletal muscle, it is still difficult to effectively mimic tissue architecture. Rigid scaffolds can guide cell alignment but have the critical drawback of hindering mechanical function of the resultant tissue. We present a method for creating highly ordered tissue-only constructs by using rigid microtopographically patterned surfaces to first guide myoblast alignment, followed by transfer of aligned myotubes into a degradable hydrogel and self-organization of the ordered cells into a functional, 3-dimensional, free-standing construct independent of the initial template substrate. Histology revealed an intracellular organization resembling that of native muscle. Aligned cell constructs exhibited a 2-fold increase in peak force production compared to controls. Effective specific force, or force normalized over cross-sectional area, was increased by 23%. This template, transfer, and self-organization strategy is envisioned to be broadly useful in improving construct function and clinical applicability for highly ordered tissues like muscle.

Bioengineered Three-dimensional Physiological Model of Colonic Longitudinal Smooth Muscle in Vitro

Tissue Engineering. Part C, Methods. Oct, 2010  |  Pubmed ID: 20001822

The objective of this study was to develop a physiological model of longitudinal smooth muscle tissue from isolated longitudinal smooth muscle cells arranged in the longitudinal axis.

Elastic Properties of Induced Pluripotent Stem Cells

Tissue Engineering. Part A. Feb, 2011  |  Pubmed ID: 20807017

The recent technique of transducing key transcription factors into unipotent cells (fibroblasts) to generate pluripotent stem cells (induced pluripotent stem cells [iPSCs]) has significantly changed the stem cell field. These cells have great promise for many clinical applications, including that of regenerative medicine. Our findings show that iPSCs can be derived from human adipose-derived stromal cells (hASCs), a notable advancement in the clinical applicability of these cells. To investigate differences between two iPS cell lines (fibroblast-iPSC and hASC-iPSC), and also the gold standard human embryonic stem cell, we looked at cell stiffness as a possible indicator of cell differentiation-potential differences. We used atomic force microscopy as a tool to determine stem cell stiffness, and hence differences in material properties between cells. Human fibroblast and hASC stiffness was also ascertained for comparison. Interestingly, cells exhibited a noticeable difference in stiffness. From least to most stiff, the order of cell stiffness was as follows: hASC-iPSC, human embryonic stem cell, fibroblast-iPSC, fibroblasts, and, lastly, as the stiffest cell, hASC. In comparing hASC-iPSCs to their origin cell, the hASC, the reprogrammed cell is significantly less stiff, indicating that greater differentiation potentials may correlate with a lower cellular modulus. The stiffness differences are not dependent on cell culture density; hence, material differences between cells cannot be attributed solely to cell-cell constraints. The change in mechanical properties of the cells in response to reprogramming offers insight into how the cell interacts with its environment and might lend clues to how to efficiently reprogram cell populations as well as how to maintain their pluripotent state.

Comparison of Several Attachment Methods for Human IPS, Embryonic and Adipose-derived Stem Cells for Tissue Engineering

Journal of Tissue Engineering and Regenerative Medicine. May, 2012  |  Pubmed ID: 22610948

As actual stem cell application quickly approaches tissue engineering and regenerative medicine, aspects such as cell attachment to scaffolds and biomaterials become important and are often overlooked. Here, we compare the effects of several attachment proteins on the adhesion, proliferation and stem cell identity of three promising human stem cell types: human adipose-derived stem cells (hASCs), human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs). Traditional tissue culture polystyrene plates (TCPS), Matrigel (Mat), laminin (Lam), fibronectin (FN) and poly-l-lysine (PLL) were investigated as attachment protein surfaces. For hASCs typically cultured on TCPS, laminin resulted in the greatest cell attachment and proliferation with largest cell areas, indicating favourability by cell spreading. However, mesenchymal stem cell markers indicative of hASCs were slightly more expressed on surfaces with lowest cell attachment, corresponding to increased cell roundness, a newly observed attribute in hASCs possibly indicating a more stem cell-like character. hESCs preferred Matrigel as a feeder-free culture surface. Interestingly, hiPSCs favoured laminin over Matrigel for colony expansion, shown by larger cell colony area and perimeter lengths, although cell numbers and stem cell marker expression level remained highest on Matrigel. These data provide a practical reference guide for selecting a suitable attachment method for using human induced pluripotent, embryonic or adipose stem cells in tissue engineering and regenerative medicine applications. Copyright © 2012 John Wiley & Sons, Ltd.

Biomaterial Applications in Cardiovascular Tissue Repair And regeneration

Expert Review of Cardiovascular Therapy. Aug, 2012  |  Pubmed ID: 23030293

Cardiovascular disease physically damages the heart, resulting in loss of cardiac function. Medications can help alleviate symptoms, but it is more beneficial to treat the root cause by repairing injured tissues, which gives patients better outcomes. Besides heart transplants, cardiac surgeons use a variety of methods for repairing different areas of the heart such as the ventricular septal wall and valves. A multitude of biomaterials are used in the repair and replacement of impaired heart tissues. These biomaterials fall into two main categories: synthetic and natural. Synthetic materials used in cardiovascular applications include polymers and metals. Natural materials are derived from biological sources such as human donor or harvested animal tissues. A new class of composite materials has emerged to take advantage of the benefits of the strengths and minimize the weaknesses of both synthetic and natural materials. This article reviews the current and prospective applications of biomaterials in cardiovascular therapies.

Effective Delivery of Stem Cells Using an Extracellular Matrix Patch Results in Increased Cell Survival and Proliferation and Reduced Scarring in Skin Wound Healing

Tissue Engineering. Part A. Mar, 2013  |  Pubmed ID: 23072446

Wound healing is one of the most complex biological processes and occurs in all tissues and organs of the body. In humans, fibrotic tissue, or scar, hinders function and is aesthetically unappealing. Stem cell therapy offers a promising new technique for aiding in wound healing; however, current findings show that stem cells typically die and/or migrate from the wound site, greatly decreasing efficacy of the treatment. Here, we demonstrate effectiveness of a stem cell therapy for improving wound healing in the skin and reducing scarring by introducing stem cells using a natural patch material. Adipose-derived stromal cells were introduced to excisional wounds created in mice using a nonimmunogenic extracellular matrix (ECM) patch material derived from porcine small-intestine submucosa (SIS). The SIS served as an attractive delivery vehicle because of its natural ECM components, including its collagen fiber network, providing the stem cells with a familiar structure. Experimental groups consisted of wounds with stem cell-seeded patches removed at different time points after wounding to determine an optimal treatment protocol. Stem cells delivered alone to skin wounds did not survive post-transplantation as evidenced by bioluminescence in vivo imaging. In contrast, delivery with the patch enabled a significant increase in stem cell proliferation and survival. Wound healing rates were moderately improved by treatment with stem cells on the patch; however, areas of fibrosis, indicating scarring, were significantly reduced in wounds treated with the stem cells on the patch compared to untreated wounds.

Customizable Engineered Blood Vessels Using 3D Printed Inserts

Methods (San Diego, Calif.). Apr, 2016  |  Pubmed ID: 26732049

Current techniques for tissue engineering blood vessels are not customizable for vascular size variation and vessel wall thickness. These critical parameters vary widely between the different arteries in the human body, and the ability to engineer vessels of varying sizes could increase capabilities for disease modeling and treatment options. We present an innovative method for producing customizable, tissue engineered, self-organizing vascular constructs by replicating a major structural component of blood vessels - the smooth muscle layer, or tunica media. We utilize a unique system combining 3D printed plate inserts to control construct size and shape, and cell sheets supported by a temporary fibrin hydrogel to encourage cellular self-organization into a tubular form resembling a natural artery. To form the vascular construct, 3D printed inserts are adhered to tissue culture plates, fibrin hydrogel is deposited around the inserts, and human aortic smooth muscle cells are then seeded atop the fibrin hydrogel. The gel, aided by the innate contractile properties of the smooth muscle cells, aggregates towards the center post insert, creating a tissue ring of smooth muscle cells. These rings are then stacked into the final tubular construct. Our methodology is robust, easily repeatable and allows for customization of cellular composition, vessel wall thickness, and length of the vessel construct merely by varying the size of the 3D printed inserts. This platform has potential for facilitating more accurate modeling of vascular pathology, serving as a drug discovery tool, or for vessel repair in disease treatment.


Biomedical Engineering and Computational Biology. 2016  |  Pubmed ID: 27346948

Mechanical Stimulation Increases Knee Meniscus Gene RNA-level Expression in Adipose-derived Stromal Cells

Plastic and Reconstructive Surgery. Global Open. Sep, 2016  |  Pubmed ID: 27757329

Efforts have been made to engineer knee meniscus tissue for injury repair, yet most attempts have been unsuccessful. Creating a cell source that resembles the complex, heterogeneous phenotype of the meniscus cell remains difficult. Stem cell differentiation has been investigated, mainly using bone marrow mesenchymal cells and biochemical means for differentiation, resulting in no solution. Mechanical stimulation has been investigated to an extent with no conclusion. Here, we explore the potential for and effectiveness of mechanical stimulation to induce the meniscal phenotype in adipose-derived stromal cells.

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