Complex sentence: This group found that adult stem cells from the spleen did play a role in regeneration and also that Faustman's protocol could be used to reverse a second autoimmune disease, called Sjögren's syndrome, in mice.
Split into simpler sentences: This group found that adult stem cells from the spleen did play a role in regeneration. They also observed that Faustman's protocol could be used to reverse a second autoimmune disease, called Sjögren's syndrome, in mice.