The Musculoskeletal Transplant Foundation, an organization that deals with bone, ligament and cartilage transplantation, said it has offered to buy Osteotech ( OSTE) at a premium to its last close, but the company rejected the bid. The foundation said it sent a letter to Osteotech's board on July 12 proposing to buy the company for $6.25 a share in cash. On Aug. 19, Osteotech said its board had rejected the proposal, according to the foundation. In a press release Monday, the foundation said it remained interested in acquiring Osteotech. Osteotech, based in Eatontown, N.J., provides human bone and bone connective tissue for transplantation. After news of the takeover offer became known, shares of Osteotech jumped $1.16, or 26%, to $5.62. The stock has a 52-week range of $2.45 to $5.83. "At the core of our charitable mission is an obligation to donor families and tissue recipients to make the best use we possibly can of these precious donated tissues and to do so in the most cost-effective manner," the foundation said. "However, our ability to accomplish this is severely compromised by our current relationship with Osteotech. Therefore, we believe we can better fulfill our mission by merging the Osteotech and MTF operations."