No. If any byte has been lost in an M or MAT file, the contents is destroyed and cannot be recreated with a 100% reliability. If the files have been lost due to a crashed hard disk, I would not even trust in files which look fine on first view. To control this, I store an MD5 checksum in each of my M-files.
The solution is to restore the files from the last backup. All changes since the last backup are lost. If you do not have a backup: Sorry. There is no magic way to reinvent the destroyed data. It is hard, but the general rule is:
All files without a current backup are not important.
Sometimes professional services can save data from crashed hard disks. This costs about 500 to 1500 US$ and the success is not guaranteed.