Five American Saddlebreds injected with an unknown caustic substance several weeks ago continue to recover from their injuries under the care of several practitioners. Hyperbaric oxygen chamber therapy continues for the animals, and a medication that promotes tissue restoration has been added to the treatment regimen.Carol McLeod, DVM, MS, a practitioner with the practice of John R. Cummins, DVM, in Lexington, Ky., has been involved in the treatment of these horses since their injuries were discovered on June 30."I think that all of them at the moment are stable," said McLeod. "Wild Eyed and Wicked is still in serious condition--the other three are in good condition, and we're continuing to treat the wounds themselves. The injuries to their legs will take several months to heal." (Last week, Ric Redden, DVM, founder of the International Equine Podiatry Center in Versailles, Ky., a treating veterinarian for the horses, said that the injuries sustained by the fifth injured horse, a filly, were less complicated than those of the other four animals.)According to McLeod, the holes in the back of the horses' left pasterns range from the size of a quarter to three or four inches in diameter.The horses are being treated in the hyperbaric (oxygen) chamber once a day "at pressure for about an hour," says McLeod, making their total time in the chamber 1.5-1.75 hours. A hyperbaric chamber is designed to increase the levels of oxygen in the bloodstream to a level where oxygen can more easily diffuse into the tissues to improve healing. Within the chamber, pressure can be raised to between two and three "atmospheres"--an atmospheric pressure roughly equivalent to the pressure experienced 66 to 99 feet (20-30 meters) underwater.Use of the Lacerum (a topical growth factor medication) has been discontinued in their treatment for the moment. McLeod says that the Saddlebreds are now being treated with another drug, ACell. "It's just a little bit of a different product," said McLeod. "The ACell provides a framework or a matrix for the development of granulation tissue, and we have such a big defect that we decided to use the ACell for a little while and will go back and forth between the two as needed. The Lacerum gave us a head start, giving a place for the granulation tissue to grow."According to the ACell web site (www.acell.com), the veterinary product is derived from the urinary bladder of specific pathogen-free (SPF) pigs. The product "is an innovative tissue-engineered resorbable bioscaffold that promotes the restoration of damaged or injured tissue. It consists of a naturally occurring extracellular matrix (ECM) scaffold that promotes the repair and replacement of tissues. Acting as a template, this biological scaffold repairs damaged tissues by promoting the body's own wound healing capabilities."The ACell Vet bioscaffold is acellular. That means the cell markers that might cause an adverse immune response are removed," according to the company. "What remains is an acellular matrix that appears to provide signals to the host immune system that stimulates an adaptive or accommodative response. This is ideal for both wound healing and three-dimensional growth of various cell types."Additionally, the horses are being treated with systemic antibiotics and anti-inflammatory medications. The reward for information leading to the prosecution of the perpetrators has grown to $100,000 (see article #4532 on www.thehorse.com). This morning (July 16), a representative of the Kentucky State Police in Frankfort, Ky., said that the investigation is ongoing, but no further information is available to the public at this time.