Christian Horner believes Toyota's demise epitomises the fact Formula One should not be reliant on the manufacturers.

In the space of 11 months Formula One has now lost Honda, BMW and Toyota, with suggestions on Wednesday that Renault held a board meeting to discuss their future in the sport.

Tyre manufacturers Bridgestone also confirmed on Monday they are to pull out at the end of next year, suggesting all is far from rosy in the F1 garden.

There is still the possibility of 13 teams lining up on the grid for 2010, leaving the independents holding sway, as was the case for many years prior to a decade of manufacturer dominance.

"It was with great sadness we learned of Toyota's position," Horner told BBC Sport.

"You have to feel for the employees. I think there's not far off a thousand that are going to be facing a difficult future unless they embark on other programmes.

"For Formula One to lose a name, and the biggest car manufacturer in the world in Toyota, is disappointing.

"But it shows Formula One should not be reliant on manufacturers.

"Independent teams are the heart and soul of Formula One. They don't tend to come and go as manufacturers do.

"We've still a very healthy grid. Toyota's demise gives a chance to the Sauber team - now privately owned - to take their place.

"So we are set for a really competitive year in 2010. We'll have 13 teams - hopefully. But unfortunately without Toyota, which is a shame and a loss."

The FIA, meanwhile, are to revisit the recently imposed cost-cutting measures in the wake of Toyota's exit.

Motor sport's world governing body has expressed "concern" at the announcements made this week by Toyota and Bridgestone.

Whilst the FIA are satisfied Bridgestone at least served notice of its intention to leave, they have made it clear they are far from happy with Toyota.

The Japanese giant recently signed the new Concorde Agreement, so binding themselves to F1 through to 2012.

That was based on a package of cost cuts designed to explicitly avoid decisions such as those made by Toyota Motor Corp.

With legal ramifications possible against Toyota, the FIA have expressed a desire to ensure the cost-cut plans in place are working and that F1 will be safeguarded for the future.

The statement read: "The FIA has repeatedly warned that motor sport cannot outpace the world economic crisis.

"That is why the competing teams have been asked to cut costs and the entry of independent teams has been encouraged.

"The FIA accepted the cost-reduction measures put forward by the teams on the basis they would ensure a long-term commitment to the championship.

"Toyota's announcement demonstrates the importance of the original cost-reduction measures set out by the FIA.

"The FIA will now work to ensure Toyota's departure is managed in the best interests of the championship and will continue to encourage the F1 teams to undertake the necessary cost-cutting measures for the good of the sport.