Production of human late stage motor neuron progenitor cells

1. A method of preparing a population of viable human motor neuron progenitor cells comprising:

(a) obtaining population of human late stage motor neuron progenitor cells having a purity of greater than about 65% late stage motor neuron progenitor cells, wherein the population is cultured on an adherent substrate and provides a layer of motor neuron progenitor cells;

(b) dissociating the layer of motor neuron progenitor cells cultured on the adherent substrate to provide a cell suspension;

(c) allowing the cell suspension to rest in a non-adherent environment for a period of time sufficient for floating microspheres comprising viable cells to form;

(c) selecting the floating microspheres comprising viable cells; and

(d) collecting the microspheres to provide a population of viable human motor neuron progenitor cells.

2. The method of claim 1 , comprising enzymatically dissociating the layer of motor neuron progenitor cells.

3. The method of claim 2 , further comprising washing the cell suspension after dissociating.

4. The method of claim 1 , wherein the non-adherent environment is a low-adherent material or a material coated for minimal cell adhesion.

5. The method of claim 1 , wherein the cell suspension is allowed to rest for between at 6 hours and about 20 hours.

6. The method of claim 1 , comprising selecting the floating microspheres comprising viable cells by gravitational sedimentation of the cell suspension comprising floating microspheres, wherein the floating microspheres comprising viable cells remain in the supernatant and the nonviable cells form a pellet.

7. The method of claim 6 , comprising collecting the microspheres to provide a population of viable human motor neuron progenitor cells by collecting the supernatant.

8. The method of claim 6 , comprising a plurality of selecting steps, wherein the first selecting step comprises gravitational sedimentation of the cell suspension followed by collecting the supernatant of the sedimentation is repeated one or multiple times, a second selecting step comprises sedimentation of the supernatant collected from the first sedimentation followed by collecting the supernatant of the second sedimentation, and wherein optional subsequent selecting steps comprise sedimentation of the supernatant collected from the previous selecting step followed by collecting the supernatant.

9. The method of claim 8 , comprising three selecting steps.

10. The method of claim 1 , further comprising determining the number of viable and nonviable cells present per unit volume of solution after at least one step.

11. The method of claim 1 , wherein population of viable human motor neuron progenitor cells comprises greater than 95% viable cells.

12. A method for preparing a population of viable motor neuron progenitor cells prepared according to the method of claim 1 , for transplantation into a subject, comprising,

(a) determining the number of cells to be transplanted;

(b) determining the volume of supernatant needed to supply the number of cells to be transplanted by measuring the number of viable and nonviable cells in a sample of the cell suspension to determine the total number of viable and nonviable cells in the cell suspension; measuring the number of cells in a sample of discarded material after each step, to determine the total number of discarded viable and nonviable cells; and determining the total number of viable cells in the supernatant containing floating microspheres, by subtracting the total number of discarded viable cells from the total number of viable cells in the cell suspension, further comprising determining the number of viable cells per unit volume of the supernatant;

(c) determining the total volume to be transplanted;

(d) mixing the volume of supernatant needed to supply the number of cells to be transplanted with a volume of transplant vehicle needed to achieve the total volume to be transplanted.