Two stem cell researchers at the Harvard-affiliated Brigham and Women’s Hospital have filed a lawsuit against the hospital and Harvard Medical School alleging that an investigation into the researchers’ practices by the Medical School and the Brigham is unlawful and damaging to their reputations.

Piero Anversa and Annarosa Leri, a professor and associate professor at the Medical School, respectively, who also work at the Brigham, filed the suit against the hospital and the Medical School in federal court on Dec. 16. The researchers alleged that an investigation into their findings on stem cells is damaging to them and should be aimed at their collaborator, Jan Kajstura, formerly an associate professor at the Medical School.

The lawsuit also names Brigham president Elizabeth G. Nabel and Medical School Dean for Faculty and Research Integrity Gretchen A. Brodnicki as defendants in the case.

The investigation against the plaintiffs, conducted by the Brigham and the Medical School and led by Nabel, picked up in early April after Anversa’s 2011 paper on the regenerative potential of heart stem cells published in journal The Lancet came under fire for alleged scientific misconduct. Since then, two of his papers have come under heavy scrutiny. One, published by Circulation in 2012, has been retracted. Another, published by the Lancet in 2011, was flagged this spring by the journal’s editors when the Medical School disclosed the launch of the investigation.

According to their complaint, Anversa and Leri claim that the Brigham and the Medical School’s investigation into their research was not impartial and unbiased, took place with undue delay, and negatively reflected on the researchers’ careers.

“[The defendants] have caused and are causing ongoing harm to Plaintiffs Dr. Piero Anversa and Dr. Annarosa Leri’s...reputations and careers by conducting a procedurally and legally flawed investigation into alleged research misconduct at a Brigham laboratory,” the complaint says.

The complaint presents what the plaintiffs claim is evidence of misconduct by their collaborator Kajstura, who they allege is solely responsible for problems with data included in their research. Specifically, the complaint accuses Kajstura of doctoring spreadsheet data and altering images in the published papers and claims that neither Anversa nor Leri saw the raw data that ultimately informed the 2012 Circulation paper.

The lawsuit, among other points, also alleges that the investigation into the researchers’ work is itself unlawful. According to the complaint, after finding “substantial evidence” that Kajstura alone may have been responsible for research misconduct, the inquiry panel recommended to continue the investigation “on the theory that Dr. Anversa should be held responsible for arguably negligent failure to investigate Dr. Kajstura’s research misconduct.”

The complaint argues that such a recommendation is “contrary to law” because research misconduct must be “be committed intentionally, knowingly, or recklessly” according to federal law.

Harvard has not yet responded publicly to the lawsuit. But in an emailed statement, Medical School spokesperson David J. Cameron wrote that the Medical School is “fully committed to upholding the highest standards of ethics and to the integrity of our research, and we have full confidence in the rigor of the review process conducted in accordance with applicable regulations and policies.”

Neither Anversa and Leri’s attorney nor Kajstura could be reached for comment.

—Staff writer Jiwon Joung contributed to the reporting of this story.

—Staff writer Melanie Y. Fu can be reached at mfu@college.harvard.edu.