If there's one word that ought to sum up the goal of cell therapy today, it's sustainability. Certainly that's the hope of using living cells to restore health and function to diseased tissues so that they perform as the body intended them to. But more to the point, in today's tough financing environment for venture-capital-backed start-ups, sustainability is the watchword for companies facing 15- to 20-year development curves. Tissue-engineered three-dimensional organs are complex, decades-long projects. Embryonic stem cells are much simpler in concept but are far from a commercial reality. Between those two extremes of tissue-engineering, however, there exist some well-defined opportunities, notably in the treatment of blood vessel disease. Start-ups Pervasis and Cytograft are gaining clinical validation in those areas.

Stem-cell-related strategies may predominate these days in tissue engineering, but cell therapy companies know that providing the right microenvironment for nurturing tissue growth remains a difficult and essential challenge. Thus, start-ups remain committed to the developent of cellular matrices that provide the appropriate structure, environment, and bioactivity to encourage tissue growth. The four start-ups profiled in this issue represent a cross-section of strategies.

Medical device investors who have avoided heart failure, because of the long and uncertain development course of ventricular assist devices, should take another look. The minimally invasive revolution in heart failure, to some extent a logical extension of interventional cardiology's migration into other areas of structural heart disease like heart valves and PFOs, is providing new device opportunities, which have the potential to get to market sooner and at the same address an even larger patient population than heart failure devices that came before.