RANCHO CORDOVA, Calif. (AP) — ThermoGenesis and TotipotentRx will combine to become a single company that will focus on regenerative technology, used to replace or regenerate human tissues and cells that have been damaged or are not functioning properly.

ThermoGenesis will issue about 12.5 million shares of its common stock to TotipotentRx worth about $18.6 million, based on ThermoGenesis' closing stock price Monday.

While the deal has been approved by the boards of both companies, it remains subject to approval of shareholders who sent the stock of ThermoGenesis tumbling 18 percent Tuesday in midday trading.

TotipotentRx Corp. is a privately held company.

The tie-up must also be approved by government regulators.

The combined company would operate under the name Cesca Therapeutics. Shares would to trade on the Nasdaq stock market under the ThermoGenesis ticker symbol, "KOOL."

ThermoGenesis, based in Rancho Cordova, Calif., develops and manufactures automated blood and bone marrow processing systems, along with affiliated disposable products that allow the separation, processing and preservation of cell and tissue therapy products.

TotipotentRx develops cell-based therapies for regenerative medicine. It also has an established cord blood banking business.

ThermoGenesis CEO Matthew Plavan will serve as CEO, while TotipotentRx Chairman and CEO Kenneth Harris will become president. Harris also have a seat on the company board.

In morning trading, shares of ThermoGenesis Corp. fell 27 cents to $1.22,

The combination, if approved, is expected to close in the final quarter of 2013.