A Comparison of Electrospun Polymers Reveals Poly(3-Hydroxybutyrate) Fiber as a Superior Scaffold for Cardiac Repair

Despite its long history and some preliminary work in tissue engineering nearly 30 years ago, electrospinning has not gained widespread interest as a potential polymer processing technique for applications in tissue engineering and drug delivery until the last 5-10 years. This renewed interest can be attributed to electrospinning's relative ease of use, adaptability, and the ability to fabricate fibers with diameters on the nanometer size scale. Furthermore, the electrospinning process affords the opportunity to engineer scaffolds with micro to nanoscale topography and high porosity similar to the natural extracellular matrix (ECM). The inherently high surface to volume ratio of electrospun scaffolds can enhance cell attachment, drug loading, and mass transfer properties. Various materials can be electrospun including: biodegradable, non-degradable, and natural materials. Electrospun fibers can be oriented or arranged randomly, giving control over both the bulk mechanical properties and the biological response to the scaffold. Drugs ranging from antibiotics and anticancer agents to proteins, DNA, and RNA can be incorporated into electrospun scaffolds. Suspensions containing living cells have even been electrospun successfully. The applications of electrospinning in tissue engineering and drug delivery are nearly limitless. This review summarizes the most recent and state of the art work in electrospinning and its uses in tissue engineering and drug delivery.

We have derived a cardiac muscle cell line, designated HL-1, from the AT-1 mouse atrial cardiomyocyte tumor lineage. HL-1 cells can be serially passaged, yet they maintain the ability to contract and retain differentiated cardiac morphological, biochemical, and electrophysiological properties. Ultrastructural characteristics typical of embryonic atrial cardiac muscle cells were found consistently in the cultured HL-1 cells. Reverse transcriptase-PCR-based analyses confirmed a pattern of gene expression similar to that of adult atrial myocytes, including expression of alpha-cardiac myosin heavy chain, alpha-cardiac actin, and connexin43. They also express the gene for atrial natriuretic factor. Immunohistochemical staining of the HL-1 cells indicated that the distribution of the cardiac-specific markers desmin, sarcomeric myosin, and atrial natriuretic factor was similar to that of cultured atrial cardiomyocytes. A delayed rectifier potassium current (IKr) was the most prominent outward current in HL-1 cells. The activating currents displayed inward rectification and deactivating current tails were voltage-dependent, saturated at >+20 mV, and were highly sensitive to dofetilide (IC50 of 46.9 nM). Specific binding of [3H]dofetilide was saturable and fit a one-site binding isotherm with a Kd of 140 +/- 60 nM and a Bmax of 118 fmol per 10(5) cells. HL-1 cells represent a cardiac myocyte cell line that can be repeatedly passaged and yet maintain a cardiac-specific phenotype.