Use of Xenopus laevis oocytes a microincubators

Patent Number: 7,135,336

The concept of "de-differentiation" of cells is very attractive from a therapeutic perspective since it offers the possibility of generating autologous stem cells from somatic tissue. If one could devise a method for generating even minute numbers of totipotent stem cells from autologous tissue, these cells could be expanded and used to treat almost any illness.

The use of nuclear transfer for "reprogramming" an adult nucleus has previously been demonstrated however, this technology is still in the embryonic phases (no pun intended). Other ways of reprogramming cells include fusing adult cells with more primitive stem cells, as well as transferring cytoplasm from undifferentiated cells into adult cells. All of these technologies have limitations.

A paper in 2003 (Byrne et al. Nuclei of adult mammalian somatic cells are directly reprogrammed to oct-4 stem cell gene expression by amphibian oocytes. Curr Biol. 2003 Jul 15;13(14):1206-13) described that injection of adult human lymphocyte nuclei into Xenopus eggs causes expression of pluripotency markers such as Oct-4, due presumably to reprogramming of the donor nucleus.

In the current patent, the inventor teaches instead of injecting the isolated nucleus, that one should inject the whole cell that needs to be reprogrammed !!

The patent has 2 independent claims. The first covers a "microincubator" made of a xenopus oocyte with bone marrow stromal cell(s) inserted inside of the oocyte, the second covers a method for producing such a "microincubator".

The dependent claims cover human, mouse, and genetically modified bone marrow stromal cells to be injected.

This technology seems very promising from the perspective that xenopus oocytes are readily available and techniques for injecting cells into said oocytes are established. The drawback is that the data presented in the patent appears relatively limited in terms of showing "de-differentiation".

If this technology can be made to "de-differentiate" somatic cells into cells having pluripotency, this may be a very interesting first step towards the generation of individualized "embryonic-like" stem cells for personalized use.

There are numerous complimentary technologies that could be used for enhancing the efficacy of the procedures disclosed in this patent. For example, US Patent # 7053264 discloses the use of several chromatin remodeling proteins that could be genetically engineered into the recipient oocytes in order to augment de-differentiation activity.

Additionally, US Patent # 7064245 teaches that heating of donor genetic material enhances its ability to be de-differentiated during nuclear transfer. It would be interesting to see if this patent can be used in combination with the xenopus oocyte microincubator for enhanced reprogramming.

We at StemCellPatents.com propose the following experiment: Take the current patent and perform transfer of bone marrow cells into the Xenopus oocyte that have been previously semi-permeabilized using the methods disclosed by Collas in US Patent Application # 20050014258. This semipermeabilization will increase the amount of oocyte factors that enter the cell, thereby increasing the rate of reprogramming.

View this patent on the USPTO website.