Day-Old Mice Grow Back New Heart Tissue After Injury

When humans have a heart attack, heart muscles die after being cut off from their blood supply. But what if the heart could grow new muscle to replace the dead tissue?
Some amphibians¹ can regrow body parts, even entire limbs. But humans and other higher animals mostly lack that ability, called regeneration. There are exceptions. Liver tissue, for example, will regrow after part of the organ is removed in surgery. But that's not true with most other organs, including the heart.
In a new study at the University of Texas Southwestern Medical Center, researchers cut off a piece of the heart in tiny, day-old mice. Hesham Sadek explains the procedure.
"We cut off the tip until we see the chamber² of the heart. And amazingly enough, the animals survive and they form a blood clot³ and they don't bleed to death. And within three weeks, that tip grows back."
Grows back as normal, functioning heart muscle, not just closed up with scar tissue.
The mice retain the ability to grow back functioning heart tissue only during their first week of life, and Sadek says it's important to identify exactly when the mouse stops being able to regenerate⁴ heart tissue, to see what other changes happen at that point "so we can identify potential factors that are either on or off at this window that we can reintroduce them or block them and have the heart regain⁵ this capacity again."
What is encouraging, Sadek says, is that the heart - or at least the mouse heart - is born with this ability to regenerate.
"We discovered that the heart can do this by itself," he says. "It just forgets how to do that or turns it off for some reason. And the question now is, can we remind the heart to do this again?"
And not just after a week or two - but decades later, when a person suffers a heart attack.
"If we can develop actual therapies from this model, the goal would be to convince the heart, instead of forming a scar, the heart now will basically just fill it back up with contractile cells, cells that will contract and pump blood, and the heart will regain its function again."

1 amphibians   

两栖动物( amphibian的名词复数 )； 水陆两用车； 水旱两生植物； 水陆两用飞行器

参考例句：

• The skin of amphibians is permeable to water. 两栖动物的皮肤是透水的。
• Two amphibians ferry them out over the sands. 两辆水陆两用车把他们渡过沙滩。

2 chamber   

n.房间，寝室；会议厅；议院；会所

参考例句：

• For many,the dentist's surgery remains a torture chamber.对许多人来说，牙医的治疗室一直是间受刑室。
• The chamber was ablaze with light.会议厅里灯火辉煌。

3 clot   

n.凝块；v.使凝成块

参考例句：

• Platelets are one of the components required to make blood clot.血小板是血液凝固的必须成分之一。
• The patient's blood refused to clot.病人的血液无法凝结。

4 regenerate   

vt.使恢复，使新生；vi.恢复，再生；adj.恢复的

参考例句：

• Their aim is to regenerate British industry.他们的目的是复兴英国的工业。
• Although it is not easy,you have the power to regenerate your life.尽管这不容易，但你有使生活重获新生的能力。

5 regain   

vt.重新获得，收复，恢复

参考例句：

• He is making a bid to regain his World No.1 ranking.他正为重登世界排名第一位而努力。
• The government is desperate to regain credibility with the public.政府急于重新获取公众的信任。