New and old technologies for organ replacement

Abstract

Purpose of review: The demand for organ transplantation has increased over time, increasingly exceeding the supply of organs. Whether and how new or old technologies separately or together could be applied to replacing organs will thus remain a question of importance.

Recent findings: Estimating how the demand for organ transplantation will evolve over the decades and the need to bring forward and test new technologies will help establish the dimensions of the problem and the priorities for investigation. Pluripotent stem cells can in principle expand to sufficient numbers, differentiate, and assemble complex and functional organs. However, the devising of effective and reliable means to coax the stem cells to do so remains beyond the current grasp.

Summary: Given the time during which novel therapies are devised and applied, which organ transplantation reaches to 2-3 decades, one can anticipate the need for organ replacement will grow dramatically, but advances in science and technology will overcome the hurdles in generating new organs. Whether these advances will address the needs and priorities of society, however, is unclear.

FIGURE 1

The demand for organ transplants and the supply of organs for transplantation. Demand for organ transplants is defined as the number of individuals on waiting lists (those on multiple waiting lists are counted once) in the USA. The supply of organs is defined as the number of transplants performed in the USA. Reproduced with permission from the Annual Report of the Organ Procurement and Transplantation Network and the Scientific Registry of Transplant Recipients [6▪▪].

FIGURE 2

Combining technologies for organ replacement. The figure illustrates a strategy proposed previously by the authors [1,4,18]. The patient needing organ replacement is used either as a source of pluripotent stem cells or of mature cells that are made pluripotent by the nuclear transfer or other manipulation to generate induced pluripotent stem cells. The stem cells are transferred to a developing fetus, where the microenvironment coaxes the cells to become the primordium of the needed organ or a mature organ. The primordium or mature organ is harvested and transplanted into the human patient. Use of the primordium is preferred because it would acquire a vascular supply from the patient rather than from the animal; however, use of primordial might not be feasible for lung and perhaps for heart [18].