Michael Schumacher's doctor insists he "does not perform miracles" and slammed the idea he is carrying out "experiments" on the star.
The seven-time Formula One world champion received stem cell therapy in September in the Paris, although little information was released about the procedure.
Schumacher's doctor Philippe Menasche told Italian newspaper La Repubblica: "I do not perform miracles. My team and I are not doing an experiment, an abominable term that is not in line with a serious medical view."
Michael Schumacher through the years
Michael Schumacher through the years
Ferrari's Michael Schumacher sprays the victory champagne in front of an emotional Jean Todt after winning the race and securing his 5th World Driver's Championship
Michael Schumacher of Germany poses during a photo call at the Bongarts Studio in 1991 in Hamburg.
Michael Schumacher poses in a Sauber-Mercedes C291.
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Schumacher’s trademark leap marked another win at Silverstone en route to the drivers’ championship in 2002.
Despite a disqualification, Schumacher went on to win the 1994 Formula One drivers’ title.
The F1 legend is pictured in 1991.
Michael Schumacher is pictured skiing.
File photo dated 12-07-1998 of Michael Schumacher lifts the trophy after winning the British Grand Prix at Silverstone today. Picture Owen Humphries/PA* EDI *
File photo dated 10-07-1994 of Britain's Damon Hill (center) on the winners Rostrum with second placed Michael Schumacher (left) and Jean Alesi after taking his Williams Renault to victory in the British Grand Prix at Silverstone.
File photo dated 09-06-2006 of Ferrari's Michael Schumacher
File photo dated 11-07-2004 of Michael Schumacher
Scuderia Ferrari's Fernando Alonso (centre) after qualifying in pole position with second place Red Bull Racing Renault's Mark Webber (right) and third place Mercedes AMG Petronas' Michael Schumacher during qualifying for the British Grand Prix at Silverstone Circuit, Silverstone.
Mercedes AMG Petronas driver Michael Schumacher in the garage during the third practice session of the British Grand Prix at Silverstone Circuit, Silverstone.
Mercedes Grand Prix driver Michael Schumacher on a bike before the Monaco Grand Prix at the Circuit de Monaco, Monte Carlo.
Mercedes' Michael Schumacher during the Qualifying Day at the Monza Circuit, Italy.
Mercedes' Michael Schumacher during Third Practice Session during Qualifying for the Santander British Grand Prix at Silverstone Circuit, Northampton.
Michael Schumacher, Mercedes GP
Mercedes' Michael Schumacher makes his way down the pit lane after the practice session at the Circuit de Monaco, Monte Carlo.
Mercedes' Michael Schumacher during the driver's parade prior to the start of the Spanish Grand Prix
Mercedes GP driver Michael Schumacher during the Formula One Testing Session at the Circuit de la Comunitat Valenciana Ricardo Tormo, Valencia, Spain.
Michael Schumacher in the pits during practice day at the Circuit Valencia, Spain.
Germany's Michael Schumacher
Motor racing champion Michael Schumacher launches Rally for Safer Roads in central London.
Ferrari's Michael Schumacher at Silverstone ahead of the British Grand Prix which will be held on Sunday.
World F1 Champion Michael Schumacher in the pits during afternoon practise, at Silverstone, prior to Sunday's British Grand Prix in, Northamptonshire.
F1 World Champion, Michael Schumacher at Dublin Castle, where he attended the formal signing of an historic European Charter on Road Safety. The Charter is a key element of the 'European Safety Drive' action programme thats goal is reducing the number of road deaths in Europe by at least 50% by 2010. According to the Irish Department of Transport, 40,000 people die as a result of traffic accidents in the 15 EU countries, with 1.2 million worldwide killed each year on the roads, or over 3,000 every day.
Pele and Michael Schumacher fool around at the Preliminary Draw in Frankfurt for the 2006 World Cup
Ferrari's Michael Schumacher (l) fools around with jockey Frankie Dettori (r) in the pits
Ferrari's Michael Schumacher, Rubens Barrichello and Technical Director Ross Brawn stand with 3rd placed driver Juan Pablo Montoya and celebrate at the top of the podium after another 1-2 finish
Ferrari's Michael Schumacher, relaxing between sessions sips coffee and chats with Sporting Director Jean Todt
Ferrari's Michael Schumacher celebrates at the top of the podium with Jean Todt after winning his 5th World Driver's Championship.McLaren's David Coulthard lifts the arm of team mate Kimi Raikkonen after he came very close to winning the race
Ferrari's Rubens Barrichello stands at the top of the podium, in between team mate Michael Schumacher and McLaren Kimi Raikkonen
Ferrari's Michael Schumacher prepares for the race
Ferrari's Michael Schumacher celebrates victory in the Canadian Grand Prix.
Racing driver Michael Schumacher arrives for the Laureus World Sports Awards at the Forum Grimaldi in Monte Carlo.
Actor Sean Connery (L) and racing driver Michael Schumacher arrive for the Laureus World Sports Awards at the Forum Grimaldi in Monte Carlo.
Michael Schumacher with his Sportsman of the Year award at the Laureus World Sports Awards at the Forum Grimaldi in Monte Carlo.
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The former driver suffered a brain injury in a skiing accident in 2013, with few updates on the Germans condition being issued over the intervening years.
He is believed to have received transfusions of inflammation-reducing stem cells. Menasche, a professor at the University of Alabama, added 'there is still a lot to learn' about the treatment.
It was Schumacher's 50th birthday in January and his family, in a rare social media post, reiterated their wish for privacy.
They wrote on Instagram: "Please understand if we are following Michael's wishes and keeping such a sensitive subject as health, as it has always been, in privacy."
Menasche, a 69-year-old practician, works in the European Georges Pompidou Hospital and leads a team devoted to stem cell therapy for cardiovascular diseases.