**Core Concept**
The supporting cells of the testes play a crucial role in the maintenance of spermatogenesis by providing structural and nutritional support to the developing sperm cells. These cells are essential for the normal functioning of the testicular tissue.

**Why the Correct Answer is Right**
The correct answer is Leydig cells. Leydig cells, also known as interstitial cells of Leydig, are located between the seminiferous tubules in the testicular interstitium. They are responsible for producing and secreting testosterone, a hormone essential for the development and maturation of sperm cells. Testosterone stimulates the growth and differentiation of spermatogonia into spermatocytes and further into spermatozoa. The Leydig cells receive their blood supply from the testicular arteries and are innervated by the sympathetic nervous system.

**Why Each Wrong Option is Incorrect**
* **Option A:** Sertoli cells are not the supporting cells of the testes, but rather the nurse cells that support and nourish the developing sperm cells. They play a crucial role in the regulation of spermatogenesis, but they are not responsible for testosterone production.
* **Option B:** Peritubular cells are not the correct answer, as they are a type of smooth muscle cell that surrounds the seminiferous tubules and helps to move the sperm cells through the tubules.
* **Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Leydig cells are the primary source of testosterone in the testes, and their dysfunction can lead to hypogonadism and infertility.

**Correct Answer:** C. Leydig cells are the supporting cells of the testes.